Team Run Amok receives a lot of email asking about the design and operation of combat robots. My son and team member Aaron Joerger (age 15) requested a question and answer page to document our responses. Aaron answers most of the questions, but I'll step in for very technical questions.

This page is the archive of older questions and answers categorized by topic. To see the most recent questions or to ask a new question, go to the Ask Aaron main page.

Q: Can you tell me how to build a combat robot?

A: There's way too much to cover here! Support your local public library -- there are some great books on building robots. Look on the shelves in section 629.892 for a good selection. You can check the (Team Run Amok webpage) for some specific book recommendations.

• You can get a step-by-step construction lesson from the 'Build a Robot' page at coolrobots.com.
• For ideas on smaller (antweight) robots, try www.sozbots.com.
• Take a look at the Toy Hacks and Kits section of this page to get some more ideas.

A: 'Cheap' and 'combat robot' don't go together. You're going to spend a lot of time and effort building your 'bot and going to a tournament. When some component fails in combat and puts you out of the competition, you're gonna wish you hadn't gone cheap. In particular, don't scrimp on electronics! With experience you'll learn where you can save money, but it's not gonna be on key components like speed controllers and wheel hubs.

A: Check the Robot Fighting League Events Calendar and the Builders Database for events in the US. For British events, try The Fighting Robot Association.

A: A good place to start is robotmarketplace.com. If you can't find it there, you probably don't need it. Other sources:

A: A remote control transmitter sends variable control signals for several `channels' based on stick, switch, and knob positions on the transmitter. The receiver deciphers the signal and sends separate signals to the channel ports. You can plug various devices into channel ports that read the signals and turn them into mechanical action (servos), variable current flow (electronic speed controllers), or on/off switches (R/C switches). Connect drive motors to the speed controllers, a lifter to the servo, and a weapon to the R/C switch and you've got control of your robot. For more on robot control systems, see: 4QD Robot Control website.

A: Radio System Requirements from the RFL 2006 Rules.
Check with the event organizer for any variation in these requirements.

Robots with passive weapons	Minumum Radio Requirement	Fail-Safe Required
		Drivetrain	Weapon
1 pound & under	AM or Toy OK	NO	---
3 and 6 pound	AM or Toy OK	NO	---
Hobbyweight	AM or Toy OK	NO	---
30 pound & up	Coded FM Required	YES	---

Robots with active weapons	Minumum Radio Requirement	Fail-Safe Required
		Drivetrain	Weapon
1 pound & under	FM Required	NO	YES
3 and 6 pound	FM Required	YES	YES
Hobbyweight	Coded FM Required	YES	YES
30 pound & up	Coded FM Required	YES	YES

A: If there was one type of weapon that was 'best', everyone would be using it. Although the highest ranked combat robots generally use high-powered spinning weapons, those teams are very experienced builders. Overall, you might be surprized by what weapons win the most matches.

A: Check the current Robot Fighting League rules for details on allowable weapons.

A: See our Armor Guide.

A: Tech question, Mark J. here: very briefly, with a number of assumptions:

• The power input pads for drive ESC, weapon ESC, and power indicator light connect in parallel to the battery via a plug so you can disconnect the battery to charge it. Get the polarity correct! If you want to add a charging plug, see the charging jack post.
• Drive motors connect to the motor output tabs on the drive ESC -- weapon motor to the power output tabs on the weapon ESC.
• Two three-wire R/C input cables attach to the drive ESC signal inputs, and one R/C cable for the weapon ESC. They may already be attached. If not, double check the correct connection of the three wires (power+, power-, and signal) -- if you get it wrong you'll fry something.
• Drive ESC R/C cables plug into whichever channel ports you'll be using on the receiver: typically 1 and 2 if you're mixing, 2 and 3 if you're not. The weapon ESC R/C cable plugs into a spare channel of your choice.
• The crystals for receiver and transmitter are different -- plug the correct crystals into the receiver and transmitter

A: My best robot tip is to make sure the basics of the chassis and drivetrain are really well built. I see lots of 'bots lose matches because something really simple wasn't designed well: wheels fall off, battery packs break free, unsecured wires come loose. The most insane weapon is no use at all if the chassis or drive fails.

A: I'll replace it when I win a bigger trophy.

Q: How do I rubber-mount armor?

A: You rubber-mount armor by running the mounting bolts thru a large rubber grommit in the chassis. Be sure to use a 'fender washer' on the back side of the grommit, and self-locking nuts. Don't tighten the mounting nuts down very tight -- leave room for the rubber to flex and absorb impact. Rubber mounting is particularly useful for polycarbonate armor, which tends to crack at high-stress mounting points.

A: Thanks!

Omnibots are way cool to watch! The can move forward and back and turn like a regular 'bot, but they can also move sideways without turning and even rotate while moving in a straight line! Check out the videos of the flamethrowing superheavyweight omnibot Alcoholic Stepfather.

Omnibots use some variant of an omniwheel or mecanum wheel with built-in rollers that allow it to provide thrust in one axis and slip without resistance in another direction. By applying power selectively to different wheels you can get the 'bot to perform its tricks. You can view a detailed description of a robot using mecanum wheels here.

Omnibots may have three or four wheels. Each wheel needs it's own speed controller and dedicated radio channel. Check the earlier post on omnibots in the Ask Aaron Archive for more videos, and search the web for 'mecanum'. I think you'll pick up the idea after you see a few examples.

You actually have two challenges in running an omnibot: building the drivetrain, and programming the R/C transmitter to make the 'bot controllable. You'll need a computerized R/C system with multiple user programmable mixes or some double-fancy helicopter swashplate settings. If you get the 'bot built and need help with the programming, write back and we'll put our heads together!

Q: Could I make an omni-bot in the 'Robot Arena' simulation game?

A: Hmmm... There aren't any omniwheels or macanum wheels available in the Robot Arena parts box, and the control options don't offer channel mixing for proper omnibot control. If you did manage to cobble one together, it would be a poor representation of the real thing.

A: Twist three wires together, solder, and insulate with heat-shrink tubing. Do not use 'bullet crimp' or 'twist' connectors on a combat robot -- they can fail under impact and vibration. Use stranded wire instead of solid-core for the same reason.

Q: Could I make a 'Y' shape in my wire with 3 ring terminal conectors held together with a nut and bolt?

Don't do that! You'd have three 'crimp' connections each subject to failure, plus a nut and bolt that could vibrate loose. It would also be heavy and bulky. Even though I don't like them, you'd be better off using a 'wire nut' twist connector to hold your three wires together. Best solution: learn to solder.

A: Mark J. here: a battery charging jack is a very useful addition to your 'bot. It will minimize charging mistakes in the pits and save critical time between matches.

Select a power plug and wires rated for at least the maximum output of your charger. Find a mounting spot protected from damage but with easy access. The jack will be 'live' to the main battery power, so protect it from accidental shorting!

The jack is wired into the main power cables, between the battery disconnect plug (optional, but handy) and the master power switch. See the diagram at right for details. Check the event rules to determine what type of master power switch is required for your weight class -- a 'removeable link' disconnect may be required.

With this set-up, the battery may be charged with the master power switch 'off' for safety, and the battery may be quickly removed or replaced while the charging jack remains with the 'bot.

Q: What type of power plug do you recommend for a heavyweight 'bot charging jack?

A: I use Anderson PowerPole connectors for charger plugs on our larger 'bots. They are available in 15/30/45 amp ratings, have no exposed metal, may be crimped or soldered in place, and require no 'heat shrink' insulation. The PowerPole connectors are available at many hobby shops. Pre-assembled wire sets with PowerPole connectors are available thru Team Delta.

A: The tutorial files included on the program disk have the information you're asking about. For additional help with Robot Arena 2, visit the Robot Arena Forum and post your questions there.

A: Take away its bus pass. [Sorry - couldn't resist the bad joke.]

Walking robots are for advanced robot builders and are much too complicated to talk about here. See earlier posts about walkers for some information sources.

Q: Do you have any more bad robot jokes?

A: Yes, but I don't want to drive people away from my website.

A: Check the diagram at the right to see what gets connected to what. Solder the connections with rosin core solder and a non-acid flux. Watch out for sharp points on your connections that could poke thru insulation -- file smooth any rough edges. Large diameter 'heat shrink' plastic tubes are available at R/C hobby shops that will insulate the pack and hold it all together. Smaller diameter heat shrink does a great job of insulating the connector terminals.

A: Carbon fiber should not be bent - it seriously weakens or breaks. Angled or curved carbon fiber was formed to shape when made, not bent afterward. The whole point of CF is how stiff it is.

A: I'm not sure what you mean by 'trim'. If you're reducing the outer diameter of the bushing, it should ideally be done on a small lathe. Small adjustments may be made with a jeweler's file. Bushings should be a snug fit -- they should not rotate in their mounting.

A: You'll need a narrow two-wheel high-speed drive and a long sturdy boom with a sharp pick or blunt heavy weapon on the end. The rest of the 'bot is much like any other 'bot. Search down the page for 'thwackbot' for more tips.

Thwackbots are not currently popular. The RFL Judging Guidelines demand constant aggression to score well, and a simple thwackbot cannot spin and move toward an opponent at the same time.

A: Flame weapons are allowed at the discretion of the event organizer. Check with the specific event you plan to enter for eligibility and special rules.

Note that flamethrowers are not effective robot weapons. They are for very experienced builders who just want to show off. I'm not going to encourage anyone to attempt dangerous construction beyond their skill level -- build something else.

A: Servos are way too slow to directly power a flipper. I suppose you could use a servo converted to continuous rotation as a winch to wind a spring for a flipper, but that's too complicated to write about here.

You can use a servo to power a small lifter for an insect-class 'bot. You can simply connect an arm directly to the servo output wheel, but you'll have more interesting leverage options if you connect the servo to the lifter with either a rod link or a full 4-bar linkage. Search down the page for "4-bar" for tips. Your local hobby shop will have everything you need.

Q: What should I look for in a servo that's gonna power an antweight lifter? How powerful should it be (in/oz)? Are there any successful antweight lifters?

A: Mark J. here: I've looked around at ant lifters and the only things their servos have in common is high torque. The drive gears are usually well protected so metal gears are not needed. Speed isn't really an issue either. You don't need to spend a lot of money here.

Assuming that you're using the servo on one end of a simple lifter arm, you need to have enough power at the end of the arm to lift 16 ounces. Example: if you have a 3 inch long lifting arm, you need 3 in. X 16 oz. = 48 in/oz torque, plus about 25% to keep it from stalling. More torque will lift faster. There are other factors to consider, but that will get you in the ballpark.

My favorite (and very successful) antweight lifter is Adam Conus' Mission Control. Technically it's a clamp-bot since it has a second servo on the lift arm that clamps the other 'bot in place. Adam uses a Hitec high-torque standard servo with 76 in/oz of torque for the lifter and a Hitec mini servo for the clamp.

../pic2/winch.gif" align="right" width="200" height="81" hspace="10" vspace="0" alt="Servo winch layout."> A: I also mentioned in that post that the winch was too complicated to write about here. I guess you didn't believe me!

The servo must be converted to continuous rotation and a small bobbin added to wind in string. The string passes around a pulley and attaches to the front edge of a mousetrap bar to pull it down. The complicated part is disengaging the bobbin so that it will spin free when the trap is released and re-engage when you're ready to reset the flipper. That requires a second servo and a better drawing than I can make. A pneumatic flipper would be less trouble.

A: Mark J. here: Modeling the physics of a motor/pulley/rotary weapon system requires more information than the motor type and the weight of the weapon. An approximate solution requires:

• A calculation of the rotational inertia of the weapon, which changes not only with weapon mass but with shape and dimensions (brush up on your calculus for this);
• An integration of the instantaneous torque available from the motor, which changes with the RPM, voltage, and available amperage (more calculus).

A: Mark J. here: Chris Sherwood has been building robots in England for a long time. He was able to build his 150-gram pneumatic 'bot out of odd bits and pieces because of his extensive building experience. You can find pictures of 'Flipper': here. I don't believe his design would be legal (or competitive) in the U.S. under current RFL rules.

Very briefly, Chris uses a plastic egg for an air pressure reservoir and syringes for pneumatic cylinders. The system fires the 3-way pneumatic valve when a robot hits the microswitch on the flipper. Take a look at the Inertia Labs Micro Pneumatics FAQ and read the Micro Pneumatics PDF for info on building a similar system that would be safe and legal.

You might also be interested in using Lego Mindstorm Pneumatics parts for a low-budget flipper 'bot.

A: Mark J. here: The more precisely a weapon is made, the better the balance is likely to be. If the weapon was hand drilled and cut, it isn't going to be anywhere close. Assuming the mounting bearings spin freely, you can 'static balance' the weapon:

• Remove the connection to the weapon motor (belt, chain, friction drive...) so that the weapon spins free.
• Position the robot so the weapon shaft is horizontal (parallel to the floor) and the weapon has room to spin.
• Give the weapon a spin with your hand and let it coast to a stop.
• Mark the part of the weapon that is at the bottom, closest to the floor.
• Repeat the spinning and marking about a dozen times. The part of the weapon that has the most marks on it is too heavy.
• Remove some material from the heavy part of the weapon, or add some weight to the opposite (light) side.
• Repeat the spinning, marking, and weight adjustment until there is not an obvious heavy spot.

You need a 'hub' to connect a thin weapon to a small diameter shaft -- a precision machined connector that will hold the weapon in correct alignment and provide sufficient depth to allow a stable and snug fit onto the motor shaft. This hub will be the most highly stressed part of your weapon system, so don't try to bodge this.

Note that it's generally not a good idea to connect a weapon directly to a small motor. It is difficult to attach a hub securely enough to a small shaft to be able to transmit large weapon loads. Search this page for tips on belt drives that can give better weapon performance. Hubs and belt drives smaller than 3mm bore are hard to find.

A: NiCad or NiMHd cells come with or without metal tabs welded to either end. You can solder your wires to the tabs or directly to the cells. If you're soldering directly to the cell, you'll need a soldering iron with enough power to do the job quickly without heating up the whole cell -- maybe 25 watts. Use rosin core solder and a little non-acid flux.

A: That depends on what you call a 'walker'. Shufflebots can be very fast -- Dave Hall's 'Drillzilla' claimed a top speed in excess of 30 MPH, but shufflebots are no longer considered to be 'true walkers' in the rules. In the British TV series 'Technogames' the walking sprint race winner 'Scuttle' covered the 25 meter course in just over 7 seconds, about a 7 MPH average speed. Scuttle doesn't qualify as a walker under the current rules either.

Building a true walking robot is very challenging. You might get some tips from looking at designs in Servo magazine.

A: Instead of wheels, shufflebots have two or more long 'feet' on each side of the 'bot that are operated by crankshafts. Each 'foot' is lifted and set down again as the crankshaft turns to move it a little forward or back. The motion is bouncy and makes maneuvering tricky. Shufflebots once got a weight bonus as 'walkers', but a few years ago they changed the rules and sufflebots now don't get that extra weight.

A shufflebot requires a complex drivetrain and custom made parts to make a slower and less maneuverable 'bot than you'd have if you used wheels. Don't bother!

Note: Dear Aaron, the 2006 draft of RFL rules offer a weight bonus to non-wheeled robots including shufflers. [Ted J.]

Not true, Ted. Section 2 of the RFL 2006 rules says, "There is no weight bonus for shufflers or other forms of locomotion which are predicated on rolling." Shufflebots are dead.

A: I don't know of anyone currently building true walkers for combat. I'd suggest getting a copy of Servo magazine and looking thru the ads for walker kits. The makers of these kits may be able to supply parts and design ideas for your combat walker.

A: The basic shape of the robot body doesn't have to be a rectangular box. The first step in chassis layout sets the size and shape of the base plate. Click on 'Step 2' to set the top plate, click on a front corner, and pull it toward the rear to make it smaller than the bottom plate. Repeat with the other front corner. Instant wedge!

A: I guess you found our Virtual Run Amok for Robot Arena 2. The mechanical components available in the game are not well suited for building an accurate model of the chain-driven 'paddlewheel' spinner weapon on Run Away or the multi-pivot pneumatic platform on The Gap. You might get it to work, but it wouldn't look right.

A: For info on Robot Arena 2, visit the Robot Arena Forum.

A: Critter Crunch has been fighting robots for a long time. Their first tournament was years before the first Robot Wars, but their rules are, ummmm... different. They do allow both 2 pound and 20 pound robots to operate with a wire cable instead of radio control. The circuit for each motor and weapon runs from the battery thru a long cable to a control box then back thru the cable to the motor/weapon. The control box has switches and maybe rheostats to control the motors. The cable wires have to be heavy enough to carry the motor current, and the robot has to drag the long, heavy cable behind it.

Critter Crunch also allows R/C robots, so why not build a 'bot that can enter other contests?

A: Not a toggle switch -- some very early robots used an R/C servo to close microswitch contacts to turn motors on and off. It was unreliable, and suitable only for very slow robots. Also, some early R/C dune buggies used a servo to rotate a mechanical speed controller based on power resistors - both heavy and unreliable. If you really need cheap, you'll be better off to hack a radio/controller module out of an R/C toy or pull the low-power speed controller out of a low-end servo.

A: It doesn't take a whole hand to control a R/C channel -- you can easily control two with one finger. R/C airplane guys have to balance throttle, rudder, elevator, aileron, flaps, and landing gear controls. We've got it easy!

For a 'bot, throttle and steering take two sticks if you use simple tank-steer, but you can electronically 'mix' two channels and put both throttle and steering on a single stick operated by one thumb. The on/off control for the weapon can be assigned to a toggle switch that you can flip with an index finger. That leaves seven fingers and a thumb that aren't doing anything except holding the transmitter.

Different manufacturers have slightly different control layouts, but you can see a diagram of a typical Futaba transmitter and get more radio tips at my dad's page: Programming the Futaba 6XAPs for Combat Robotics. I usually run the weapon from the channel 5 toggle switch.

A: Soldering is a very good skill to develop for making all sorts of things. A soldered electrcal connection is strong and unlikely to fail in combat. Some speed controllers do come with either pre-soldered or screw-type connectors, so you can build a 'bot without soldering. It would limit your choices of components.

Maybe you could find a team-mate who can solder?

A: Making custom gears requires machining skills and special equipment. It's much better to find gears that will work, but that can be difficult as well. Try a local hobby shop, or sift thru a surplus supply store. Old toys can yield valuable parts, too. Try a web search for 'slot car gears'.

A: Sure! Get hold of a copy of Robot Combat: Weapons by Chris Hannold, or Kickin' 'Bot by Grant Imahara. They both cover basic weapon construction materials, design, and technique.

A: We don't build robots for sumo type events. There are plenty of websites that give detailed information on autonomous sumo 'bots -- try Dave's Sumo Robot Project Page for a start.

A: Two great questions! Start out small -- it's a lot less expensive to learn from mistakes you make on a 12 pound robot than on a 220 pound monster. You can find a list of local competitions at www.robotcombat.com -- if you're lucky, there will be a competition close to where you live. Study their rules, watch a live competition, learn what you can from the internet, and ask specific questions of the builders. Check out the library and bookstores for help on building robots, too. Amazon.com has lots of robot books.

Second question: 'bot builders design and build 'bots all different ways. Some use computer drawing software to design every last detail before they buy parts. Some build exact models from cardboard to see how things fit. Some just buy lots of parts and see if they can fit them together like a jigsaw puzzle. I like to list all the parts I think I'll need, sketch a drawing, and add up the weights of the parts to make sure I'm under the weight limit. If you stick with proven parts that other builders use, you won't get into too much trouble.

Q: What motors would you recommend for a beetleweight thwackbot?

A: Thwackbots are not popular in the insect weight classes. They need time and a clear area to spin up that just doesn't exist in a small insect class arena. If you really wanna try a beetleweight thwackbot, the B16 High Speed Gearmotor at RobotMarketplace might be worthwhile.

A: Magnetic wheels are extremely effective -- if you happen to be fighting in an arena with a steel floor. I've only seen them used on insect-class bots. See Team Nightmare's beetle page for some good photos of the 2004 beetleweight national champion 'Wallop' with its magnet wheels.

The wheels are simply round rare-earth neodymium magnets with a hole in the center. These can be very expensive, unless you happen to find a suitable set at a surplus outlet.

Don't leave magnet wheels exposed. Put them under your armor or use side guards to keep them from clamping onto steel rails or other vertical structures. It would be embarrassing to end up stuck to a railing. Also, be sure to check with your local event organizer to see if magnet wheels are even allowed!

A: First, find another hobby shop - one that knows something about 'bots. Second, servos make poor 'bot drive trains. Save up your money and buy a real speed controller and drive motors. See the servo discussion for more info.

A: I like to fight big 'bots! The bigger the 'bot the better -- but even tiny 'bots rock.

A: The sidewheel spinner design on Run Away is unique and showy, but a pivot steer 'bot like Run Away would be very difficult to maneuver in a small arena.

A: Mark J. here: an insect class FBS has a disadvantage -- it has to spin-up really fast because of the small arena it will fight in. That's why you don't see many beetle FBS designs. A pair of Speed 400s will give you about 150 watts of power -- too little to spin up a heavy shell before your opponent gets to you.

Q: If I still want to build a beetle class FBS, what kind of motors would be adequate?

A: Mark J. here: I've posted before about calculating power requirements for spinning weapons. 'Adequate' power depends on:

• the rotational inertia of the spinning weapon; and
• the amount of time available to spin the weapon up.

The cardinal rule of FBS design is: "There is no such thing as too much power." For a beetleweight friction-drive FBS, there many not even be such a thing as enough power. I'd consider another design.

A: No. Internal Combustion Engines (ICE) are tempting, but getting them to work well and reliably in combat can be a huge problem. Also, not many insect class competitions allow ICE. Check the rules for your competition before you commit.

A: You could do a lot worse than the components used for the Robot Marketplace Basic Antweight Starter Package, Nick. The Tamiya dual-motor gearbox is quick and tough, and the 56 mm 'sports tires' slide right onto the shafts of the gearbox. The Ant 100 ESC is reliable, but I'd upgrade to the Ant 150 ESC for a weapon control channel that could come in handy on a later 'bot.

Radio and battery/charger are up to you. I use inexpensive NiMHd cells for ants because chargers for them are available and cheap -- but LiPoly cells are lighter. Bolt everything down to a simple flat chassis, add your armor and a sturdy wedge. Keep your first 'bot simple and have fun!

A: Servos are slow! The speed of a typical 'fast' servo modified for continuous rotation is about 60 RPM. With a 2" diameter tire that gives you about 32 feet per minute, or less than 0.4 miles per hour. That's not even a crawl!

It is possible to 'speed mod' a servo by locking the first and third reduction gear clusters together and eliminating the second reduction stage altogether. That will improve the speed by a factor of fifteen or more, but will reduce the torque by the same factor. It will make the motor prone to stall and an early death. It isn't worth the trouble -- don't use servos for drive motors.

The Futaba S3110 is a really tiny servo. The gear train is way too fragile to even consider using it as a drive motor in an antweight. It would be slow, weak, and vulnerable.

A: Mark J. here: I can't figure out why a servo would be your only option, but if you wanna do the servo thing right my choice would be the Hitec HS-5996TG.

• The titanium gears are next to indestructable,
• A beefy 111 oz/in stall torque is un-stallable,
• 60 degrees rotation in 0.10 seconds is nasty quick (for a servo),
• Hardened gear pins and intermediate oilite bushings with ball bearings on the output shaft will take serious punishment, and
• The coreless motor shaves the weight down to 63 grams.

Q: Is there a good servo to power a 'bot for less than $40?

A: It's funny how fast a price limit gets set when somebody finds out what 'absolute best' actually costs.

I really don't want to encourage you to build a servo-powered 'bot - they're really slow! For less than the $80 you're willing to pay for a pair of servos you can buy a Tamaya dual-motor gearbox and a good speed controller that will run rings around any servo-bot. Reconsider?

A: 'Cheap' and 'robot combat' really don't go well together. You're gonna spend your time and effort to build something that's going to let you down in battle. Why bother?

If you insist: buy a Futaba '2DR' 2-channel AM R/C setup. It comes with a transmitter, a receiver, two servos, crystals, mounting hardware, and a battery holder for about $40. Hack the two servos for continuous rotation. Find the centers on two plastic mayonnaise jar lids and mount them to the servo horns with self-tapping screws that come with the radio -- instant wheels. Stretch a wide rubber band around the outside of each jar lid for tires. Foam tape the receiver, battery holder, and servos to one of those free AOL CDs that come in the mail. Insert 4 AA cells in the battery holder and 8 more in the transmitter.

Congratulations, you've just built the world's cheapest scratch antweight. Now, throw it away before you embarass yourself.

Q: In a earlier post you mentioned the complete Futaba 2DR AM R/C set for around $40. Where can I buy one?

A: Futaba 2DR at Tower Hobbies. This is a two-channel AM system. Check with your local event rules to make sure they allow AM radios for the weapon type and weight class you plan to build. FM radios are more expensive for a reason: they work better.

A: If you want to go hard-core there are some tiny new brushless outrunner motors like the MSYS-300T that could make you 'King of the Fairys'. Only 20 grams, plus 2 grams for the controller!

On a lower budget, I think I'd try a warmed-up 130 size motor like the 'Hyper Dash 2'. They're light (17 grams), cheap, and put out crazy RPM at low voltage.

A: Rat trap - $1.79.

Q: How can I make the rat trap into a weapon?

A: Don't be too anxious; the rat trap is cheap but I'm not saying it's good. Set the trap and drive toward your opponent -- you get one shot. Check legality with your local event organizer and watch your fingers!

Q: I'm having trouble with my rat trap weapon. Every time I bump something the trap snaps shut. Is there a way to make it less sensitive?

A: Examine the way the trap latches to the trip plate. The bar is held by a very narrow dimple of bent metal. Bend the dimple to make it deeper, and reshape it to hold the bar more firmly.

My dad's antweight has a tiny servo that latches the trap shut 'til he releases it -- but that adds too much expense for it to qualify as the 'cheapest active weapon'.

Q: How did you turn Rat Amok into a flipper 'bot?

A: You must have seen the 'Rat Amok' video. Rat Amok isn't designed to be a flipper, but if an opponent climbs far enough on top they can be thrown forceably upward then the trap is released. Other times, the trap ejects the opponent out the front of the trap at high speed and Rat Amok may flip over backward in reaction (she drives fine upside-down). Only occasionally does the trap actually 'catch' a part of the other 'bot. Teeth or a rubber 'gripper' added to the trap bar would modify the effect of the impact.

Q: What was the total cost of Rat Amok? What servos did it have?

A: Mark J. here: Let's see --

• Rat trap - $1.79
• Futaba T6XAPS R/C system - $229.95
• 2 Futaba S3004 ball bearing servos - $0.00 (came with R/C system)
• Cirrus 'nano' servo trap release - $29.95
• 5 700 mAH NiMHd cells - $9.95
• 2 front wheels from Tamyia R/C dune buggy - $7.95
• Dollar Store knife for front blade - $1.00
• Polypropylene cheese box from thrift store - $0.50
• Assorted hardware - $2.58

A: If this is your first 'bot, keep it simple. An antweight wedge would be a great choice for a first scratch-built 'bot. Search down the page for an antweight parts list and lots of tips. You can get all the supplies you need at Robot Marketplace. I just counted, and that's the 18th plug for Robot Marketplace. Doesn't anybody read the old questions?

A: I'm getting tired of plugging Robot Marketplace, but how about trying their antweight motor section?

A: That's not much of a description. The motor must fit in with all the design elements of the 'bot and work with them as a whole. What's your weapon? How large is the arena you'll be fighting in? What is the arena layout? Is speed more important to you than pushing power? What's your budget? Two wheel drive? Four wheel drive? Wheel size? Are you willing to make custom hubs, or do you want off-the-shelf parts only? Do you plan to use a lithium battery, or NiMH? How much weight allowance is available for the motors?

You can search down the page for 'fairyweight wedge' for a general recommendation of a motor that would make a good starting point for a 'bot.

A: You really have to make sure your wheels are securely fastened to the gearbox shaft. Having a wheel fall off is pretty much the most embarassing thing that can happen in combat, so I really can't advise scrimping on hubs. Robot Marketplace has nice 3mm aluminum hubs to fit Lite Flights and other wheels for about $5 each. If you're really cheap, Tamaya wheels come with 3mm press-on plastic hubs for both round and hex shafts -- but if they shatter or just fall off, don't say I didn't warn you.

A: We used car-style steering on our heavyweight 'bot 'Run Amok'. Car steering is better than tank-style 'differential' steering at holding a straight line course and at making smooth turns, but tank steering gives much greater maneuverability in tight spaces. Car steering can work in a wedge or rammer in any weight class, but it certainly isn't popular.

P.S. - Alex Udanis wrote to tell me he thinks car steering bites. He didn't actually say 'bites', but I don't want to use the word he picked.

A: Mark J. here: just like there are different alloys of metals, there are lots of types of fiberglass. The type of resin used is very important to the properties the material as a whole exhibits. Some resins are hard, but brittle. Others are more resilient. Search down the page for 'garolite'.

A: They're the same size and they weigh about the same, but the Speed-300 spins faster, puts out about 3 times as much power, and consumes about three times as many amps. There's also a Speed T-280, and a Speed S-280 that each have their own specs.

A: The T-280 draws 5 amps at max power output, but much more at stall. If your application makes sure it never stalls because of high gear reduction or slip clutches, and your ESC can really handle 5 amps for as long as you plan to abuse the motor, then maybe - but I woudn't.

A: All sorts of motors are found in R/C cars. Many toys have the 130 or 230 class motors that are popular in antweights. Larger scale hobby R/C racers have motors too heavy for most antweight designs, but they might work well for beetleweight weapons or hobbyweight drives.

A: The 130's are more than enough, but heavy. Take a look at the Sanyo NA5S motor/gearbox at Robot Marketplace. Less than 0.3 ounce each!

A: No 'product' needed -- just solder three ESC wires to each output pin on the battery connector plug. I use Deans Power Plugs for ant and beetle connectors, but any good R/C hobby power connector is fine. Buy them at your local hobby shop. Don't use automotive connectors (bullet connectors) -- they give trouble in robots.

A: Neither SozBots nor RFL rules specify a maximum size for U.S. antweights or fairyweights. It's the British '150 gram' antweights that must fit in a 4" cube.

A: 'Best' depends on your design needs. The 'outrunner' style (Axi, Park) motors are widely used because of their high torque and reasonable RPM. I like the Axi 'cause it's easier to mount.

A: Tech question, Mark J. here: Outrunner style motors are a problem to mount because the entire outside 'can' rotates. Some outrunners (like the AXI) have a shaft that runs thru the rear mounting plate that makes for a simple mount. Others (like the Park) don't have a shaft in the rear and you have to get creative.

Take a look at Team Basenji's antweight 'Bitsy Blade' at the Robot Riots 5 photos page. It's an ant vertical spinner with an outrunner. They simply mounted the rear motor plate to the chassis and left the rest of the motor and pulley drive dangling in the air! It isn't good engineering practice, but it works for them. A better solution would be to add a support to the motor shaft as close to the weapon pully as possible with a bearing on a strong support anchored to the chassis -- kinda the same as their weapon support.

Technical question, Mark J. here:

• Robotmarketplace.com claims that the Park 370 Outrunner has "awesome torque" and that "in most circumstances" the motor can be used direct drive for an antweight weapon. I'm not able to find actual torque figures for the motor to back up those claims.
• The power needed to spin a 7 oz. bar depends on the length of the bar. A short bar has less rotational mass than a longer bar and will require less torque to 'spin up'.
• A spinning bar weapon needs to spin slowly enough for the bar end to grab and catch your opponent. The Park 370 Outrunner has a no-load speed close to 10,000 RPM at 7.2 volts! That's much too fast to spin a bar weapon.

A: You don't see many ant thwackbots! Thwackbots use their high turn-in-place speed to spin an attached hammer or axe up to dangerous velocity. In a small ant arena you'd better be able to spin up quickly. Remember to keep your track width as narrow as possible to maximize spin RPM. More power is better, but I think a pair of hot Speed-280s should be enough to get you some respect.

A: Unless you're running a very powerful weapon motor or a very small drum, you will need some gear reduction to spin the weapon up properly. For a reasonable motor and a mid-sized drum, try a belt drive with about a 3:1 reduction for a starting point.

A: The number of flips you get is dependent on the size of your air storage tank, the volume of your pneumatic actuator, and the pressure of the air in your system. You can design in as many flips as you like.

Antweight flippers are not generally effective at causing damage. They are popular in 'Sozbots' style arenas where a 'bot that leaves the platform looses. Flip 'em over the low arena wall and you win!

A: Lithium polymer battery packs require special chargers that generally run from an external DC power supply. If you want to get off cheap, you can use the battery from your car as that DC power supply. Alternately, you can run NiCad or NiMHd cells that are less picky about charging and buy an inexpensive AC/DC charger from EBay.

If you want cheaper still, run AAA alkaline cells and replace them every few matches.

A: The 'Speed 280' motor is a good choice. It's inexpensive, light weight, and has enough power to be feared! The current trend in weapon motors is 'brushless' -- but these are expensive and require special controllers. Try a Speed 280 for your first spinner! They are used in R/C aircraft, so your local hobby shop may stock them. If not, check out the ant motor selection at The Robot Marketplace

A: A few years ago it was common to see antweight robots that used 'hacked' R/C servos as drive motors. Inexpensive R/C servos contain a small speed controller, a small DC motor, and a reduction gear train. They can be modified to provide rotating output rather than the stock back/forth motion (see: hacking a servo). Bolt on a wheel and you were in business!

Servo drives are nearly extinct now. They are slow and weak compared to other drivetrain options. You can build a robot with them, but you won't win many matches.

A: Flippers are powered by compressed gas. You'll need a cylinder to store the compressed gas, an actuator to move the flipper arm, an electric control valve to release gas into the actuator (and vent the pressure to lower the flipper), an interface to control the valve with your remote control, and hoses/fittings to connect everything up.

Getting all of this equipment small and light enough for an antweight isn't easy. Inertia Labs makes a full pneumatics kit for antweights, and they have a FAQ page that answers a lot of questions about antweight pneumatic systems. Give it a read!

A: Gee, everybody wants to build an antweight! I really like modifying R/C toys for antweights [look in the 'Toy Hacks and Kits section below] but if you want to build from scratch, visit www.sozbots.com and browse their FAQ and Tips page.

For a simple ant you'll need an R/C radio set-up, a two-channel motor controller (three if you want an active weapon), two motors with gearboxes, a small battery pack, a battery charger, and wheels. You'll need to make a chassis to bolt all that stuff onto -- aluminum, Lexan plastic, and carbon fiber panels are popular. Then you'll have to get enough armor together to keep it from being cut in two. This is getting expensive!

There's an antweight discussion forum at forums.delphiforums.com/antweights/start -- dig thru the information there for more tips.

A: The same armor materials used in larger 'bots works great on antweights. Titanium is the top-of-the-line, but is expensive, not easy to find, and can be difficult to work with. Polycarbonate plastic (Lexan) is inexpensive, widely available, and simple to cut and drill. I've used ultra-high molecular weight (UHMW) polyethylene plastic with good results on my beetleweight.

A: Combat robots are usually built to a maximum weight rather than size. Popular weight classes for small 'bots include:

• 1-pound (antweight);
• 3-pound (beetleweight); and
• 12-pound (hobbyweight).

A: Wow -- that's really light! In the U.S. we get a full pound for antweights - 454 grams.

I live near some places that build parts for airplanes and I can get scrap pieces of thin titanium that are great for robots. Titanium is light and very tough, but it's usually expensive and hard to find.

You might want to consider thin carbon composite material instead of metal. Robotcombat.com marketplace sells small sheets of it. It's very stiff and strong.

Some types of plastic make good armor for light robots, too. Polypropylene is used for kitchen storage containers and is very thin, light, and tough.

Q: How can you tell what model motor is in your remote control car?

A: You can compare the motor with photos and dimensions at robotmarketplace.com.

A: I don't think so -- too fragile, wrong gearing, poor traction, and no good weapon mounts.

A: I don't know of any absolutely complete kits. Robot Marketplace offers several partial ant kits, and Inertia Labs has basic ant chassis kits and will supply radio gear and battery packs.

Robot combat is all about design and mechanical skill. Showing up with an antweight kitbot won't get you much respect in the pits.

A: Rat traps really don't make good combat robot weapons. They are dangerous to handle, may not be legal for your local event, and are probably too heavy to add to a 'Fly Wheels' and stay under weight. A good wedge would be a better choice.

I don't have a 'Fly Wheels' yet. Has anybody weighed one?

A: Putting armor on a micro R/C car is only a good idea if you're trying to be underpowered target practice for the other fairyweight 'bots. Have you considered building an antweight? It's cheaper and you'll find more tournaments to enter.

A: The 'toy' radio system is the problem. The Robot Fighting League rules allow 'toy' radio systems to compete in all weight classes up to 12 pounds (hobbyweight) if the 'bot has no active weapon. Check the RFL rule set for other restrictions. The local event organizer can overrule this, so check with them, too.

A: For $50, the Fly Wheels is a good start. The rest is up to your imagination and how good you are at making things. I think I'd start with a sturdy front wedge.

A: The short answer is 'no'. R/C toys don't have interchangeable frequency crystals like hobby R/C components, and changing from 27 MHz to 49 MHz is completely out of the question -- it would require extensive modification and tuning reserved for electronic tech specialists.

A: So many Fly Wheels questions -- I'm gonna have to get one just to keep up!

Robot builders love to overvolt motors to get more power! The trick is to stop before you smoke something. I'm guessing the Fly Wheels toys have some version of the 130 size motor. That motor in the BattleBots toys could take a lot of voltage -- for short periods. How much voltage the rest of the toy will take is another question. I'm guessing 9 volts would be do-able, but more power always comes with reduced lifespan.

I'll buy a Fly Wheels and do some experimenting.

A: I don't have a 'Fly Wheels' here to look at. I suspect you can drill a small hole thru the center of the wheel into the hub and insert a small self-tapping screw and washer. Anybody have one handy to look at and tell me if this will work?

A: Neither tape nor glue will work.

A: EBay.

A: Technical question - Mark J. here: Don't increase your radio voltage! Batteries aren't your problem, as long as they're fresh. Range problems are often a result of too short a receiver antenna, or not having the antenna wire stretched straight.

Different radio frequencies have different optimum antenna lengths for both the transmitter and receiver. Try a nice straight receiver antenna first, then try doubling it's length.

A: The BattleBots pro-series toys weigh about two pounds stripped down and make a pretty good platform for a beetleweight. I'd stop there. The tiny 130-size motors are awfully small to be pushing 12 pounds of robot around a combat arena, and toy radio systems are not allowed in hobbyweight 'bots with an active weapon. By the time you replace all that, you might just as well have started from scratch.

A: There isn't much to learn, and there isn't much to hack. Trace the wires -- you'll have two power leads (+ and -), an antenna wire, and a pair of leads to each motor.

Toy receiver/controllers don't come with specifications, so you'll have to guess how much power they'll handle. It's probably not smart to use motors much more powerful than the ones that came with the toy.

Also, check with the organizer of the event you plan to enter. Some don't allow toy radio systems, and others place restrictions on their use.

A: There was a really good description of how to hack the BattleBot R/C toy at the Robot Dojo site, but the site is down. Fortunately, the Web Archive has a pretty good copy! Try: How to Hack a BattleBots Toy [archived].

A: Mark J. here: Inexpensive toy R/C cars do not have standard servos -- most just slide a magnet back and forth with wire coils. There is no rotary steering servo motor in a toy R/C car.

A: The only toys I've seen hacked for beetleweight competition are the larger BattleBots Pro Series R/C toys -- Diesector and Biohazard. Like the smaller custom series toys, they are no longer available in stores. Your best bet on finding one is at EBay.

A: Technical question - Mark J. here: Most people build their combat robots from scratch, but four different robot kits are available from Battlekits.com. They may be used to construct 'bots ranging from the 30-pound feather weight class to the 340-pound super heavy weight class. The featherweight comes fully assembled except for the electrical connections and radio gear. It also has armor and a simple wedge weapon, but the larger kits require you to supply such 'finishing touches'. The price of the featherweight kit is close to $1200 -- plus the radio gear.

There are a few sources for less complete and less expensive kits for lighter weight classes. Check the Robot Kits Page (link down) at the Combat Robot Wiki for an up-to date list.

A: You can learn a lot and have some fun by converting an R/C toy into an antweight combat robot. Lots of small 'bots have been based on the BattleBots R/C toy. Those toys are now hard to find, but if you can find one [try EBay] there is a nice description of how to convert it into a combat robot here: How to Convert a BattleBots Toy [archived].

I've seen a new toy called Fly Wheels that sells for less than $20 and looks like it would make a good starting platform for a combat robot.

Look around your local toy shop for something that turns by changing the speed of one side versus the other [tank steering]. You might find something no one else has used!

A: It's a little like making a statue of an elephant: you start with a big chunk of rock and carve away everything that doesn't look like an elephant.

Seriously -- there are all types of R/C toys. Some have steerable front wheels and some steer by making the wheels on one side turn the opposite direction from the other side. That later type is more maneuverable and might make a better robot, but either type will work. Just start taking off things that don't look like they belong on a robot -- the body, bumpers, wings, roll bars, whatever. Get it stripped down.

The next step is to weigh the stripped-down toy to see how much armor and weapon weight you can add without going over the maximum weight for the class of robot you want. Toys make good 1-pound and 3-pound weight class robots, and larger ones can fight in the 12-pound class. Bolt on your armor to protect the wheels and other delicate stuff. Tough plastic is good, or fairly thin metal. Bolt on a wedge or a couple of spikes and you're a roboteer! You'll learn a lot from the things that go wrong with your first 'bot, and you'll have fun. Be careful with anything sharp, and don't attack your cat/dog/hamster!

The picture at the right is my beetleweight 'Zpatula', a converted BattleBots toy. It works great!

A: There are eight 'custom series' BattleBots toys:

• Blendo
• DoAll
• Dr. Inferno Jr.
• El Diablo
• KillerHurtz
• Minion
• Son of Whyachi
• Vlad the Impailer

'The Gap' has it's own webpage with several pics: The Gap

A: Tank steering takes two motor control channels - one for the motor(s) on each side of the `bot. A toy R/C car has a one motor control channel and a second channel that operates only the steering servo. Find something that already has tank steering, like the `Fly Wheels' R/C toy.

A: Sorry, but I just can't get excited about a combat robot that you could put two stamps on and mail to a competition. Fifty grams is less than two ounces. It would take nine of them to make one US antweight! Check out the Antweight Forum at Delphi for good tips on antweights, fairyweights, and fleaweights.

Q: I need something like a bearing to support a rotating part powered by a servo. I know ball bearings can do the job but are there any other solutions without having to buy a ball bearing?

A: Mark J. here: I could use a little more info on what you're building! The selection of a proper bearing or bushing depends on how long the support needs to last, how precise the alignment needs to be, the type and magnitude of the force that will be applied, the speed of operation, and the depth of your wallet.

Since you're powering this mystery device with a servo, I'm guessing that the force and speed are both pretty low. Since it's in a combat robot, I'll assume it doesn't need to last forever and that extremely precise alignment is not an issue.

You can likely get away with just drilling an appropriately sized hole in a block of strong, slick plastic -- like UHMW polyethylene, polycarbonate, or nylon. If you need to absorb high shock loading, you might want to go with a bronze 'oilite' bushing. Oilite bushings are cheap, durable, and widely available in a variety of sizes.

A: There's a review of "Build your own combat robot" on the Team Run Amok book review page.

A: Sounds like somebody wants me to do their homework for them.

An automobile gets better gas mileage when it travels slower, right? That's because friction and drag increase quickly with greater speed. It's much more efficient to move along at a slow and steady pace than to sprint forward and coast to a stop. A well designed mousetrap car can travel dozens of yards if it keeps speed under control.

Hard, large diameter wheels reduce rolling resistance, and when combined with a low gear ratio will reduce the torque available to accelerate the car and will keep speed down. A typical mousetrap car has one end of a thread wrapped around the drive axle, with the other end pulled by an extension bar from the mousetrap. The number of turns the rear axle makes while the mousetrap unwinds is the equivalent of a 'gear ratio'. A longer extension bar on the trap lowers the effective gear ratio.

Your goal is to keep the car just barely moving along for the entire time the trap unwinds. Tinker with the length of your trap bar extension to get a steady forward crawl -- lengthen it if you're going too fast, and shorten it if the car stalls.

Hey, this question isn't even about combat robots! Why am I answering it?

A: See the Wikipedia differential article.

A: Sorry, no. The hobbyweight class is dominated by passives (wedges, rammers, dustpans), spinning weapons (mostly drums/eggbeaters), and a few lifters. Spinning weapons store power delivered by their motors over several seconds of spin-up time as kinetic energy. A hammer that gains power over a fraction of a second from a similar motor just can't put together enough energy to do any damage.

A: The design of 4-bar systems is very technical and I've never found a good primer on the web. There is a 'Four Bar Front Bar' calculator that could be helpful if you were building an electric lifter.

You can get a very good education in general robot pneumatic systems at the Team Da Vinci Robotics pneumatics page. Remember: high-pressure pneumatic systems are potentially VERY dangerous. Don't get in over your head.

A: Yes, but it has several drawbacks and may not be considered legal under current RFL rules. Not everyone interprets the rules the same way -- check with your event organizer before you build!

You'd need to add a pressure rated 'T' fitting between the tank and the system shutoff valve before the pressure regulator. A second shutoff valve on the other branch of the 'T' connects to a male quick-disconnect refill fitting.

This adds weight, bulk, and complexity to the system. I think it's easier to design the CO2 tank mounts for easy release. You can then carry the tank (instead of the whole robot) over to the refilling station.

A: Mark J. here: some machine shops just don't accept small one-off custom jobs, but a clear explanation of what you want and a friendly smile will improve your chances. Machine shop time isn't cheap -- do as much prep work as you can and listen to their questions and suggestions. Let them know that you appreciate their taking time to work with you.

A: Mark J. here: There are a variety of large-hole making devices that will fit in standard-size drill chucks. Here are some options:

• The proper way to do this is with a Hole Saw. A 3/4" hole saw with arbor and pilot drill bit should run about $15 at your local tool supply shop. Get one with a central 'pilot drill' to guide the saw. You can also buy a hole saw set with several diameters for around $30 - they come in handy!

• You might be tempted to use a wood boring Spade Bit. This is not recommended. Although they are inexpensive (about $3) and will crudely bore thru Lexan, a spade bit is difficult to position and control precisely with a hand drill. If you insist on using one, drill a small (1/8") pilot hole, securely clamp the plastic to scrap wood, and securely clamp the wood to your workbench. Be prepared to ruin a few pieces.

• With a soft material like Lexan, you can always scratch a 3/4" circle in the surface (a penny is 3/4" diameter), drill several small holes to 'rough out' the interior, and finish with a curved hand file. This will get you 'reasonably round' if you have the patience.

A: You make something better by standing on the shoulders of giants.

A: Mark J. here: simple answer first: most hobbyweights I see are built around a hypothetical top speed of around 12 to 15 miles per hour. Hypothetical top speed is calculated by the formula:

For help with motor, gearing, tire, and battery selection, check the Team Tentacle Torque Calculator. Be sure to investigate the 'Acceleration" button.

A: Mark J. here: in designing a combat robot, you have to think about how all the components of the machine will work together. A chassis design that would work well for one design could be a disaster in another design. Since I know nothing about your design, I can't comment on your frame.

You have a number of choices for a heavyweight 'bot. You can use welded tubular steel, bolted steel angle, interlocking aluminum flat panels, a stiffened composite pan, or bonded polycarbonate. You can integrate the armor into the chassis as a stressed component, or have a separate armor shell. Be sure to consider your skill level and experience in working with the materials involved, as well as your budget.

A: Torque reaction overhead blades/spikes are legal and easy enough to build, but they would not be effective under the current damage/aggression scoring system.

For an explanation of the operating principle, see the Toecrusher website.

A: Mark J. here: That's over two pounds worth of motors in a six pound 'bot! How do you plan to use that much power in a small arena? By the time you add in batteries (lots of 'em for those motors), gearboxes, wheels, and a chassis you're not gonna have much weight left over for armor or a weapon. Keep your design elements in balance - go with smaller motors.

A: 'SJ' (it used to be called 'Slam Job') has a classic overhead pneumatic pickaxe -- two pneumatic cylinders acting together on a pivoting arm. Getting a pneumatic system to work over a long weapon arc is tricky. SJ uses one short cylinder to give the weapon an initial 'boost' at an optimum angle until the working angle for the second longer cylinder improves.

A: Mark J. here: Taps are available in diameters up to 4 inches, but they are expensive. You may also consider thread milling for large diameter holes. Unless you're going to be doing a lot of large diameter tapping, give the job to a machine shop.

A: Mark J. here: It would help if I knew what size 'bot you're building. When in doubt, go bigger.

Screws and bolts are designed to take tension stress along their axis and are not ideal for enduring the shear stress that will be imposed when you use them on a spinning drum weapon. Their advantage is that they are inexpensive and easy to replace. Use a coarse thread -- it will be easier to remove when damaged.

A: Drum weapons are most effective when the teeth are spaced far enough around the drum circumference to allow the other 'bot to get close enogh to the drum for the teeth to dig in and get some 'bite'. Don't put on too many teeth!

I don't know if big screws are better than custom teeth, but they're inexpensive and easy to replace! Make sure you have plenty of material depth in the drum to support the threaded shaft of the screw.

A: Mark J. here: It would help if I knew what size 'bot you're building. When in doubt, go bigger.

Screws and bolts are designed to take tension stress along their axis and are not ideal for enduring the shear stress that will be imposed when you use them on a spinning drum weapon. Their advantage is that they are inexpensive and easy to replace. Use a coarse thread -- it will be easier to remove when damaged.

A: Mark J. here: pocketing removes material from low-stress areas of a panel or component by milling away some of the thickness while leaving a border of thicker material. If properly done this results in reduced weight while retaining the majority of the strength of the original panel. The location and depth of pocketing requires extensive stress analysis of the component.

The exterior panels of combat robots don't really have any 'low-stress' areas. They can be exposed large forces from any angle and at any point. I do not recommend pocketing external 'bot panels -- although it looks really cool.

A: Mark J. here: I don't think 'most popular' is a good way to select a weapon controller. The controller should be matched to the specific motor and weapon loading for your 'bot, not just to it's weight class. I've seen a very wide range of weapon motors and designs in hobbyweights. If you can tell me more about the weapon you plan to build, I can be of more help.

I'm planning to use two Mini EVs or HTIs to power a vertical disk weapon.

A full analysis of your weapon system power requirements and energy potential also requires the weight and diameter of your disk, and the speed reduction of your drive system. Assuming an 8" disk weighing 3 pounds and a 3:1 reduction, your twin-mini-EV powered weapon running at 12 volts would spin up to 3780 RPM in about 1.6 seconds with 530 Joules of energy, and will eventually reach over 1000 Joules. Killer for a hobbyweight!

If you have a no-slip drive system for the weapon (chain, gears) and switch power full-on, those twin Mini EVs will pull an average 117 amps during that 1.6 seconds, with a peak inrush of almost 170 amps. That's killer too, but not in a good way.

The easy solution is to use a hefty battery pack, a Victor 883 controller, and a belt drive. You'll be able to feed the power in quickly enough to keep a great spin-up time while avoiding that nasty sudden amp spike you'd get with a solenoid/contactor. A belt drive set-up with a little slippage will help keep you from melting down when the weapon stalls. The 833 is reverseable to allow you to clear the weapon if it jams.

There are other options:

• Use a solenoid/contactor and a separate high-amp battery pack for the weapon. This will keep the big amp surge from glitching the other systems on your 'bot, but adds weight.

• Use a high slipage belt drive with a solenoid/contactor to avoid high amperage draw during spin-up. This will lengthen spin-up time and will be difficult to adjust properly.

• Use a lower capacity motor controller with a Team Delta Digital Servo Slower between your receiver and controller to slowly ramp-up the amperage delivered to the weapon motor during spin-up. This will lengthen spin-up time and you'll still need a high-slip belt drive to keep everything healthy when the weapon stalls.

A: Building a successful combat robot requires experience in mechanical design, construction techniques, material properties, and control systems. See my earlier post on where to get help in these areas.

Robot builders use a variety of methods to design their robots. Some use computer aided design tools, some build detailed cardboard models, and some just design as they build. We like to sketch out the overall design, make a complete parts list - with prices and weights, and jump right in to the build. Our sketches wouldn't be much use to anyone else building a combat robot, and copying someone's exact design isn't as rewarding as designing your own 'bot, anyhow.

Keep your first 'bot simple and make sure the mechanical basics are well covered.

A: Mark J. here: no -- weapon RPM is limited only by bearing friction, transmission loss, and aerodynamic drag. A very heavy weapon will eventually spin-up to the same RPM as a lighter weapon. However, given the information you list, you can calculate the approximate RPM of the weapon after a given number of seconds spin-up time.

Paul Hills has written a very complete guide to the physics of spinning 'bot weapons that covers such calculations. If you're serious about kinetic energy weapons, you'll want to study the contents of his page: Spinning Disk Weapons.

A: Mark J. here: the simple answer is 'all you can manage'. Successful FBS 'bots typically spin a shell representing around 20% of the total robot mass at speeds around 3000 RPM. I'll let you do the math to calculate the KE of such a weapon.

A: Mark J. here: mechanical switching control of brushed weapon motors has a number of drawbacks. Solenoid operated switches are called 'contactors', and a reliable contactor isn't much less expensive than a weapon ESC. If you get a cheap one, the contacts can weld shut under the high current loading encountered when suddenly dumping full voltage to a loaded weapon motor. That high current draw is also hard on your battery pack and may cause a voltage drop that can glitch other 'bot systems. A smooth transfer of current available with an ESC avoids these problems.

A contactor requires an R/C interface to trigger, like the Team Delta solid-state R/C 'D' switch. The R/C switch plugs into your receiver and controls a small current load to activate the coil of the contactor. The contactor then switches the high current load to the weapon motor. You can control as many weapon motors as you like with a single contactor -- as long as the total current draw of the motors does not exceed the capacity of the contactor. This also applies to ESCs.

Oh, and did I mention that contactors are heavy? They are not commonly used in high power sub-light 'bots. I'll say it again, 'cheap' and 'robot combat' don't mix.

A: Mark J. here: yes, milling a Full Body Spinner shell from one big chunk of metal does waste material, but I've seen it done. More commmonly, somebody finds a short section of large diameter pipe at a scrapyard and welds a top onto it. I've also seen a tube formed from thick plate with a set of forming rollers, seam welded, and a top added. The key is precision to keep the finished product well balanced.

A: Combat robots don't have axle hooks. See web articles on mousetrap cars.

A: Technical question - Mark J. here: that depends on how many and what type of motors you use, the gearing, tire diameter, and driving style as well as the weapon motor type, how much you use it, and how heavy the spinning mass is.

Look at 'bots that have a similar set-up to the one you plan and use their experience to help you decide on a battery pack. You can also get some help from the Team Tentacle Torque Calculator which provides an estimate of required battery capacity based on motors and various design factors.

A: Hi, Nick! Since you're asking about windshield wiper motors, I'm guessing you're thinking about a hobbyweight or featherweight class robot? We built a hobbyweight with windshield wiper motors almost five years ago. Even though we were running the 12 volt motors at 24 volts, the gear reduction was so large that they were really slow! They were also very heavy for the power they provided. I'd stay away from them.

Keep your first 'bot simple. Wedges win more matches than 'bots with active weapons, so get some experience before you start showing off with fancy weapons. Cordless drill motors are fast, powerful, simple to mount, and pretty cheap. Fasten them down to a simple flat panel base, armor up, and bolt on a sturdy wedge. Spend some money to buy good speed controllers -- that's the one place you shouldn't scrimp. Check the How Do I... section for some other tips and book references. Best luck!

A: Try: www.shender4.com/thread_chart.htm for pilot and clearance hole sizes.

Once you have the hole, the tool used to put threads on the inside is called a 'tap'. The tool for putting threads on the outside of a rod is called a 'die'. You can purchase an inexpensive Tap and Die set, or you can purchase individual taps and dies at your local tool store. A brief guide to tapping holes with hand tools can be found at www.jjjtrain.com/vms/cutting_tools_hand_tap.html.

A: Interesting question! I figure anything more than 45 degrees isn't a wedge, it's a sloped 'brick'. How much lower than 45 degrees you go is a function of how the wedge is going to be used. A very shallow angle is useful for defense and sneaking in under spinning weapons. A steeper angle is better for ramming attacks. A curved 'scoop' can be effective both for offense and as a 'spinner killer' -- I'd say that's ideal.

Q: What material would you use the create the "curved scoop"?

A: Titanium would be great, or steel if you have enough weight allowance.

A: Very ambitious plans! I would suggest starting with something simpler for your first 'bot. Exotic weapons won't do a lot of good until your basic mechanical systems are up to the task.

The current top-bots have heavy, high-speed rotating 'kinetic energy' weapons that hit like a speeding truck. The preferred armor in the heavyweight class is 1/2" thick titanium. Get to a tournament and see what the competition looks like before you decide on a design.

A: The first step is to carefully read the Robot Fighting League rules. The RFL rules are used by most robot competitions in the US. That will answer your questions about nail guns (not legal) and huge wheels (go crazy - but you're not gonna get thru 'bot armor that easy). Read down the page for suggestions on books for robot construction.

A: Mark J. here: Countersinking forms an angled cut-away around a hole for a flat-top fastener that leaves the fastener top flush with the surface to provide a smooth surface.

Counterboring forms a flat-bottomed recess around a hole to provide fastener clearance and/or offer a flat surface for the fastener on a curved, sloped, or irregular surface.

A: If you don't want to buy hubs, then spend the money for a mask so nobody will know who that guy was that had his wheels fall off. Read my post about hubs in the Ants, Beetles, and Fairys section.

A: Nice choice! Your gear reduction will depend on the size of your undercutter blade. Take a look at Johnson Junior -- a S-280 powered undercutter with a big 8.5" blade and a gearbox. They're running a 5:1 reduction which seems about right for a blade that big. A smaller and lighter blade would use less reduction -- maybe 3:1 for a 5" blade.

Most builders like belt drives over gear drives for weapons because they require less precision, can absorb impact shock loads, and won't 'jam' as easilly. A well designed gearbox can still be effective and rugged.

A: Brushless hobby motors are mostly sold to model aircraft builders. On a model airplane a 'firewall' is the flat panel at the front of the plane where the motor is attached.

Robot weapons put large side-loading forces on the motor shaft. Support the motor by mounting it as close to the weapon drive as possible -- 'behind the firewall' style.

Mark J. here: Engines in early airplanes were prone to catch fire. The 'firewall' was the solid bulkhead behind the engine that prevented flames from entering the cockpit. In that context it wouldn't make much sense to mount an engine behind the firewall, but the term survives.

A: Mark J. here: There are three broad categories of screws: wood, self-tapping, and machine. A 4-40 screw is a machine screw that is should be threaded into a pre-tapped hole. Drill a pilot hole with a #43 drill bit at low speed, then use a 4-40 tap to create the threads. Alternately, you may use self-tapping screws with Lexan. They will also require pilot holes, but will not require pre-tapping the threads. Cramming a machine screw into an untreaded hole is a weak bodge - don't do it.

A: Mark J. here: Motor mount design depends on powertrain layout. If a large motor is being held in critical alignment for an open gear or chain reduction, it must be held very precisely with no wobble or the gear/chain system may fail. Such designs should secure both ends of the motor. Mounts for small motors with attached gearboxes (gearmotors) that do not rely on the mount for alignment of the gear reduction may allow or even encourage a little shock-absorbing 'give' in the mounting design and material.

A popular design for insect-class robots with small gearmotors is the wide circular clamp: a machined hole on a block of aluminum or plastic (UHMW polyethylene or Lexan) with a gap along one side that can be closed down with screws/bolts to clamp the gearmotor in place. The wider the clamp, the more secure the mounting. Remember, 'bots with exposed wheels put more strain on the mount.

I've also seen low-budget mounts made from wood blocks and steel automotive hose clamps that were surprisingly functional. You don't need a full machine shop to build a workable 'bot.

A: For an antweight, that's probably too thick. For a heavyweight, that's probably too thin.

A: Team Inevitable Destruction's 'Cadaver' has simply hard-mounted the can of a brushless outrunner motor inside one end of a drum and put a support bearing in the other end. The force of impact is taken directly by the motor bearings, which is hard on the motor. A belt drive would isolate the motor from impact forces, give a faster spin-up, and would keep the weapon speed down enough to 'grab and toss' an opponent.

A: You think lifters are easy? I guess you can make an antweight lifter out of a servo without much trouble, but a bigger 4-bar linkage lifter is not easy.

A better question might be, "What is the simplest weapon that is effective at winning matches?" The answer might surprise you. My dad looked at the results from 20 recent robot tournaments to see what type of weapons did best. Take a look at the results: What Weapons Win?

A: There are lots of motors you can use in your robot. You can find pictures, descriptions, and specifications for dozens of popular motors at: www.robotmarketplace.com/marketplace_motors.html.

Mark J. here: They aren't thwackbots -- triangular 'bots with an omni wheel at each apex are called 'omnibots'. Yes, they can rotate, but the really cool thing is that by differentially powering the three wheels, they have the ability to move in any direction without turning -- that's called 'holonomic motion'. There's a cool video of a four-wheel holonomic omnibot (same principle as a 3-wheel version): holonomic at www.charmedlabs.com. An R/C omnibot requires a computerized transmitter with programmable mixing to properly do it's tricks.

Autonomous omnibots can be programmed to move (slowly) while spinning (slowly): frisbee at www.charmedlabs.com, but doing it at variable high spin rates and variable directions under radio control is a REAL challenge. It's called 'Melty Brain', 'Tornado Drive' or 'Cyclone Drive' and many builders have spent years trying to get it to work. It requires on-board processors, motion sensors, sophisticated programming, and it still doesn't work reliably. Don't even try to cram all that into an antweight!

A: Small 'bots usually have a skid of slick plastic -- like polyethylene. Bigger 'bots may have a ball caster or an omni wheel. Our heavyweight 'bot 'The Gap' has a wide roller machined out of Teflon in the front so it can slide sideways and roll forward.

A: A drum is just a large diameter metal tube with end plates and a few teeth welded to the outside. It's empty inside except for the shaft. The weapon shaft needs strong support, like any spinning weapon. Spin it with a belt drive from your weapon motor.

A: It's like the difference between a rotating bar and a disk. An eggbeater (like Team Sawzall's 'Switchblade') can't store as much kinetic energy as a drum that weighs the same -- the weapon has less rotational inertia. They're still effective, and more durable than a thin-walled drum.

A: Same as for any other rotating weapon: solid supports, correct RPM, protected drive, good balance, and quick spin-up. Drums are particularly hard to balance, so use extra care in precision construction.

A: Tech question, Mark J. here: the smaller timing belts (MXL series) are rated up to 20,000 RPM, and can transmit as much as 400 watts of power. They're much more effective at power transmission than other belt types. For a full engineering summary of timing belt selection and performance, see: www.roymech.co.uk/Useful_Tables/Drive/Timing_belts.html.

A: Tech question, Mark J. here: The wider the belt, the more power it can transmit. Wider belts also stay in place a little better.

A: The weapon/pulley shaft must be supported so that it remains aligned and does not wobble. This requires two bearing supports at separate locations along the shaft on either side of the pulley and/or the weapon. You'll need to adapt or fabricate bearing mounts strong enough to both support the correct pulley alignment and absorb the weapon loading.

Take a look at Team Basenji's antweight 'Bitsy Blade' at the Robot Riots 5 photos page for an example of a belt driven antweight spinner.

A: Technical question, Mark J. here: Briefly, gear drives require precision alignment and spacing to function properly. They can operate at very high RPM, but are not terribly efficient at transmitting power. Belt and pulley systems can tolerate some misalignment and are capable of absorbing the sudden shock loading a rotary weapon can produce.

Timing belts have small raised teeth along the inner surface of a flat belt that mesh with grooves in the pulley to reduce slippage and increase power capacity. They are very efficient at transmitting power and can operate at higher speed than regular belts.

I like belt drives for rotational weapon systems like bars, disks, and drums. The ratio of the number of grooves on the larger pulley to the number of grooves on the smaller pulley is your gear ratio. You'll probably want to try something around 4 to 1 for a large bar weapon.

Robotcombat.com has a selection of small timing belts and pulleys suitable for antweights in their in their Mechanical and Drive Components section. Their timing belt page has a calculator to help with correct belt length selection. Tower Hobbies has inexpensive, ready-made gearboxes designed for model airplanes that would be useful for an ant weapon. Search for `gearbox' at their site.

A: A tank-steer 'bot steers the same way no matter how many wheels it has: all the drive wheels on one side of the 'bot turn at a different speed and/or direction than the wheels on the other side. Robots with four or more wheels drag their wheels sideways a bit as they turn. That takes a little more power, but it works just fine.

A: Wow - another technical question - Mark J. here: Power is calculated as the product of torque and RPM, so the real answer to your question is that both are equally important. A spinning weapon stores power in the rotating mass of the weapon and unloads it destructively onto your opponent. You need as much spinning mass as possible, enough torque to spin that mass up quickly enough for it to be effective before your opponent can get to you and stop it, and as much speed as possible to store more energy in the weapon. A spinning weapon is all about stored power!

A: Technical question - Mark J. here: Gyroscopic forces can cause odd effects for robots with a spinning mass weapon. Problems come when turning changes the orientation of a line running thru the weapon axle. With a horizontal spinning weapon, the axle points up and down, so turning the robot does not change the direction that line points -- no problem, as long as the weapon is well balanced.

With a vertical spinning weapon, turning the robot does change the orientation of the weapon axle. This results in forces that resist the turning motion and lift one side of the robot. The magnitude of the force is dependent on the speed of rotation, the mass of the weapon, and the radius of gyration. You can get full details on calculating gyroscopic forces at: www.freestudy.co.uk/dynamics/gyroscope.pdf

A: If tracks were a real advantage, lots of winning robots would use them. They don't! I'd go with wheels.

Wheel/tire selection depends on many design factors with which the wheels will have to fit. If your wheels will be exposed to attack, use a solid or foam-filled tire that can't go flat.

For general use, I like the Colson wheels. They have been used on combat robots for many years. They're pretty light, durable, have good traction on arena floors, and are inexpensive to replace when damaged. Team Delta sells Colson wheels in different sizes and will even make wheel hubs to fit your drive shaft.

A: Thanks! How long it takes to build a robot depends on how complicated the design is and how much experience you have working with the tools and materials you need. Getting some friends who have skills you don't have will help a lot! I've seen experienced teams build a heavyweight 'bot in a week, but our larger 'bots take us about two months to put together. That includes time to design, get parts, build, and test.

A: Different builders have different ideas about what's 'best'. It depends on your driving style and your skill as a builder. I see lots of different weapon types winning, but I notice robots with spinning drum weapons doing very well in the 12 to 60 pound classes.

A: Mark J. here: a 4-bar linkage is a simple arrangement of four mechanical links (like rods or beams) with pivot connectors on each end linking them together into a roughly rectangular shape. By careful selection of the relative lengths of the links used, you can create complex movement arcs and gain torque or speed without gear reduction. The Wikipedia has diagrams of 4-bar linkages in their mechanical linkages section.

Robots sometimes use 4-bar links to control and position lifter arms efficiently and allow them to scoop in a sweeping upward and outward arc rather than a simple single-pivot backward rotation. Aaron's beetleweight 'Zpatula' uses a 4-bar linkage in its electric lifter.

A: I like 'bots that have a lot of pushing power and good control. I think the best weapon is to be all over your opponent and don't let up -- hit 'em 'til they break!

A: Thanks, Coleman! Before you start building a 'bot there are a few things to take care of. First, read the rules for the competition you plan to enter very carefully. You don't want to build your 'bot only to find out you aren't legal for the competition! Next, take time to find as many websites from competitors who have been to competitions like the one you want to enter. Read everything they have to say. Finally, draw up a design that you can actually build. The coolest design won't do you any good if you don't have the skills (or money) to build it.

The words 'best' and 'cheap' don't go together in robot building -- especially with speed controllers. You don't want cheap parts that will put you out of the competition if they fail. See what other builders that have been successful use in their 'bots. It won't be cheap speed controllers! For reliable parts, try Team Delta (www.teamdelta.com), and the marketplace at www.robotcombat.com.

Q: How do I attach 1/8" polycarbonate to 1/8" aluminum for armor?

A: Polycarbonate and aluminum can be bonded with a 'Goop' type adhesive, but mixing materials to make a composite armor is tricky. You're trying to get the best properties of both materials, but it's just as easy to end up with the worst properties of each! I don't recommend it.

Q: Would 1/8" polycarbonate plus 1/8" aluminum be adequate heavyweight armor?

A: Heavens, no! You'll need much thicker armor for a heavyweight. Current design favors at least 3/4" high-strength alloy aluminum or 1/2" titanium for protection from heavyweight spinners. Quarter-inch plastic or aluminum is purely sub-light class.

Q: Titanium is expensive! How thick should polycarbonate armor be for a heavyweight robot?

A: Mark J. here: good armor is less expensive than having your opponent punch thru your poor armor, destroy your 'bot, and blow you out of a tournament. Heavyweight 'bots are expensive. If there was a less expensive alternative to exotic metal armor, builders would be using it. The current field of heavyweight spinner 'bots are brutal!

No matter how thick you make the plastic, polycarbonate is not a direct replacement for titanium. They have different strengths and weaknesses. Take a look at the Team Stupid materials page for a listing of suggested uses for different materials and alloys.

A: There are a lot of different types of steel. The properties of the metal vary widely according to the elements alloyed into the mixture, the process that is used to form the steel, and various heat-treating processes that may be applied to the metal after it is formed. A 'high carbon' steel that has been specially heat tempered takes on properties that allow it to bend and 'spring back' rather than permanently deform is called 'spring steel'. The process often leaves the surface of the steel darkened with a blue tint. Spring steel is more resilient than structural steel, but it is not as tough -- it will break rather than dent.

A: Mark J. here: Let me pose another question first -- Is it a good idea to combine Carbon Fiber and UHMW Polyethylene to make composite armor?

Consider the properties of the two materials: carbon fiber is extremely stiff with a fairly hard surface, while UHMW is soft and so pliable that it is considered 'unbreakable'. If the proposed composite was placed under stress, all the force would be placed on the stiff CF with the UHMW simply bending out of the way with little resistance. Only when the CF fails would the properties of the UHMW become useful. Bad combination!

Back to your original question: if you decide to do this anyway, what glue should you use? Polyethylene is almost as slick as Teflon and very difficult to bond. Epoxy, silicone, and cyanoacrylate adhesives won't work. The surface has to be chemically modified to allow an adhesive the chance to get a grip! 3M makes a couple of two-part adhesives that will do this: Scotch-Weld Structural Plastic Adhesive DP8005 and DP8010. They are difficult to find, expensive, and tricky to work with. You can view the product data sheet for DP8005 here: DP8005.pdf.

If you really want to bond CF to something for effective composite armor, try Garolite and an epoxy adhesive. UHMW, like polycarbonate, needs to flex to absorb energy and be useful as armor. Adding a stiff CF layer doesn't make good sense.

Q: My armor is also the chassis side plates. I need to tap holes into the side plates to mount the top and bottom chassis plates. Garolite (like CF) doesn't hold edge taps well. Can I glue CF to Lexan?

A: Lexan is much easier to glue than UHMW polyethylene, but you'll still have the problem of the Lexan flexing a lot more than the CF. You can use a gel cyanoacrylate 'Super Glue' to bond CF to Lexan, but I think I'd use 'Goop' adhesive or silicone sealant for a little 'give' with a countersunk screw thru the CF into the Lexan in each corner for a little mechanical insurance.

A: It's not easy to compare performance figures for the brushless outrunner motors -- manufacturers often don't supply the type of numbers you really need for comparison. Also, there are different versions of the AXI 2208 (2208/34, 2208/26, 2208/20) that have very different performance figures.

Browse around the Aeromicro website. They have what specs are available for AXI, Park, Himax and other outrunner motors. The E-flite Park 370 Outrunner has seen good use in insect class 'bots and would be a good place to start.

A: Mark J. here: check the Frequently Asked Questions section of the Ask Aaron Archive for general comments about cheap robot parts.

Speed controllers are the heart of your 'bot. They are key to the function and useability of the entire machine, and if they fail you're toast. To be useable in your 'bot, speed controllers must:

• Handle the current and voltage requirements of your motors;
• Transition seamlessly from forward to reverse motion;
• Interface with your R/C system; and
• Be small, light, and reliable.

I don't recommend scrimping on robot electronics -- you can bet your opponent hasn't.

A: Inexpensive cordless drills are a very popular source of compact and powerful gearmotors. If you really want to 'salvage' something, permanent magnet DC gearmotors are used in automobile electric seats, windows, and windshield wipers. Your local auto salvage yard can be a good source.

Note that the power and output speed for gearmotors varies widely. You may have some difficulty finding something that meets your needs, so be ready to improvise!

A: Mark J. here: there are a HUGE number of specialized steel alloys, and several different standards for referring to them. There are entire college courses devoted to steel alloys and library shelved filled with books on the topic. Add to this the various heat treatments, casting and milling options available and you're quickly in deep water!

To narrow your search I suggest that you first determine which alloys are available from your supply sources and research their properties. It won't do you much good to find an alloy you want that you simply cannot get in the shapes or quantities you need!

• A good introductory article on steel and aluminum alloy designations: ESPRIT Mechanical Design.

• An overview of the different designation types for carbon steel: Key to Steel.

• General descriptions of commonly available stainless steel alloys: Small Parts, Inc. - Stainless Steel.

• ASTM, ISO and IEC Test Methods: IDES property descriptions.

• Physical and mechanical properties of specific metal alloys and plastics: MatWeb Material Search.

A: Mark J. here: there are a lot of different measures of material strength, some of which are overlapping. Each measure may have several different test procedures that can be difficult to directly compare. Some useful material physical properties to examine include:

• Tensile Strength is a measure of how much pulling force a material can withstand. It is commonly measured as the peak pulling force a material can withstand before it begins to fail (ultimate tensile strength).

• Yield Strength is a measure of a specific attribute of tensile strength: the amount of pulling force required to permanently deform the material. Materials with low yield strengths tend to `smear' when hit with a high energy weapon.

• Impact Strength is a measure of the amount of energy a material absorbs when breaking by impact. This is also known as 'toughness'. Some materials that are very strong are also brittle and can shatter under sharp impact. These make poor armor!

• Modulus of Elasticity is a measure of material stiffness -- now much the material flexes in response to a specific amount of force. Materials with a higher elastic modulus flex less than materials with lower values.

• Hardness is a measure of the resistance of a material to surface penetration. Hard materials do not scratch easily, but may be more brittle than softer material.

• Density is a measure of the weight per unit volume of the material. Tests of material strength are conducted on samples of a specific size, not of a specific weight. A one inch diameter rod of 4130 steel may have twice the tensile strength of a one inch diameter rod of 6061 T6 aluminum, but it weighs three times as much! With a combat robot, you're generally looking for strength per unit weight.

The www.matweb.com site has information on the physical properties of a wide range of metals, plastics, and related materials.

A: I really like recycling useable parts to make something new. You can also learn a few things about mechanical engineering by taking apart an old VCR. You probably won't find anything very useful in the way of drivetrain or electronic components but there are plenty of gears, belts, pulleys, and maybe even motors that could be used for a weapon system on an insect-class 'bot. Be aware that some of the motors in a VCR are likely brushless motors that require special electronic driver circuits to operate.

One problem with recycled parts is replacement spares. Unless you have another identical scrap VCR, it may be difficult and expensive to replace a recycled component damaged in combat.

A: Mark J. here: Your Li-Poly battery is toast! The usual cause of this 'outgassing' is overheating brought on by too high a discharge rate -- you're asking for more amps from the LiPoly than it can provide. Replace it with a larger capacity battery. It's also possible that your charger is providing the wrong charge rate. Never charge Lithium cells with a charger not designed for the purpose.

Whatever the cause, IT IS NOT SAFE TO USE THE BATTERY. Do not attempt to charge or discharge the battery. Drop the battery into a plastic bucket with 1/2 cup of salt dissolved in a gallon of water, cover the bucket, and let it set for at least two weeks. It will then be safe to toss out with the garbage.

Li-Polys are not nearly as robust as NiCad or NiMHd cells, and can be dangerous if abused. Electrifly.com has a good article on Li-Poly care.

A: Mark J. here: A thin layer of silicone rubber does improve the traction of many types of tires and treads. Pure silicone rubber can be found at auto supply stores. It's used for making automotive gaskets ('RTV silicone gasket maker'). Pure silicone kitchen and bathroom caulking from a hardware store is also OK, but do not try to substitute similar products like 'Goop' or 'siliconized latex caulking'. Silicone rubber comes in assorted colors, but they are all about the same for grip.

The trick to aplication is in getting a good bond so the silicone rubber doesn't peel off. Clean the surface of the tire very thoroughly with rubbing alcohol and let dry. Uncured silicone rubber is sticky and messy to work with, so spread out some newspaper and have paper towels handy. Use a popsicle stick or old knife to spread a very thin layer of the gooey silicone evenly onto the tire surface. Apply enough pressure to get the rubber down into the tire pores, Wipe excess off the edges with a towel. Let 'cure' for at least a full day before use. Curing RTV silicone smells like vinegar.

Clean silicone grips better than dirty silicone, so clean your tires before each match. I use a little lighter fluid on a towel, but be very careful with any flamible liquid!

Remember: better traction means less wheel spin, and less wheel spin means higher amperage consumption my the motors. Make sure your speed controllers can take the extra load.

A: Mark J. here: Judging the relative strengths of metals is difficult and sometimes misleading. The tensile and yield strengths of magnesium are more than twice as great as common aluminum alloys, but the shear modulus is four times less, which means that magnesium is brittle; it tends to break rather than bend. This restricts its use in combat robots to internal braces and mounts that are not exposed to high impact. It would be really embarassing to have your armor shatter and fall off!

Also, magnesuim is not that light! Common alloys are about 67% the density of aluminum. You'll save a little weight, but it may not be worth the trouble for small parts.

One last thing - magnesium is flamable! If exposed to a high-energy weapon impact it could ignite, and water or CO² fire extinguishers won't put it out! Your event organizer wouldn't like that.

I know that Biohazard uses some magnesium in its internal components, but in general people use more common materials. My metal suppliers don't stock magnesium, so you're on your own for a source.

Thank you.

A: Mark J. here: The preferred method of cutting carbon fiber is an abrasive cutting disk, but you can use a fine-toothed hacksaw.

Safety precautions when cutting or sanding carbon fiber include a dust mask (always!), safety goggles (always!), and gloves (always!). CF dust is very irritating, and jamming a loose carbon fiber into your flesh is painful, easy to do, and difficult to remove. Don't take shortcuts!

A: Unobtainium:

1. an item so expensive, rare, or otherwise difficult to get that it is effectively unobtainable.

2. a reference to a material with physical properties that do not exist, as in "I broke the titanium hub, so I'll build the next one out of unobtainium to make it stronger and lighter."

A: Bosch makes several motors used in combat robotics:

• The Mini EV Warrior is available at Robot Marketplace. I don't think Bosch actually makes this motor, but it kinda got lumped in with them. Weight is just over one pound with an output of about 1/3 HP at 12 volts.

• The Bosch GPB, also known as the `EV Warrior' is no longer available. It weighed 3.25 pounds and produced just about 1 HP at 24 volts. These motors were on the surplus market for as little as $15 each and became VERY popular.

• Run Amok used the large Bosch GBA 750, purchased from Team Delta. This motor was popular in England and even powered some of the Robot Wars Housebots. The GBA 750 weighs a little over 8 pounds and can produce more than 3 HP when overvolted to 36 volts, but is more often used at 24 volts.

Q: How much Horsepower does a Bosch 750 motor produce at 24 volts?

A: Mark J. here: There's a simple formula to calculate the hosepower of a DC permanent magnet motor at different voltages:

The Bosch 750 makes 3.375 HP at 36 volts, so horsepower at 24 volts = ( 24 / 36 )² X 3.375 = 1.5 horsepower.

A: Mark J. here: I did some research. A free-flowing powder placed inside a hollow cylinder can improve rotating balance. There's a product available for balancing automotive tires called 'Equal' that might be what you saw. Drum weapons are difficult to build precisely enough to be well balanced and can use all the help they can get!

A: They don't buy them, they build them. See the post on flamethowers. They're ineffective and dangerous -- not for novice builders!

A: Mark J. here: One last time: 'Cheap' and 'Robot Combat' don't mix! If you're going to spend your time and effort to design and construct a robot and take it to to a competition, you don't want some crappy component to fail and flush the whole project.

A: Mark J. here: Delrin is an Acetal plastic developed more than 50 years ago by Dupont. It is a little heavier and stiffer than Lexan polycarbonate, but it is not nearly as impact resistant. Delrin makes good machined components (gears, bolts, actuators), but polycarbonate makes better armor.

A: Check the motors, mounts, and gearboxes at Team Delta.

A: Mark J. here: real specification for R/C hobby motors are just not provided by the manufacturers. They offer all sorts of variation in magnets, armature winds, and can designs -- but they won't give real-world numbers on the performance differences. Without figures like amperage draw, torque curves, and real RPM it's a pure guessing game.

How did you decide that two 550 motors are the right number to power your FBS weapon without specs for the motors you want to use?? How are you going to select an ESC for the weapon if you don't know how much amperage the motors draw??

I'd stick with motors that provide real specifications, like the Mini EV. If you go with a hobby 550, try to find a bot that's using something similar and use their experience. Otherwise, you're on your own!

A: Mark J. here: a 'machine wound' motor has the armature windings done quickly by a machine. The windings are not neatly and compactly arranged on the armature. A 'hand wound' motor is wound by a human who can take care with the wire and make the windings more regular and uniform. A hand-wound armature usually starts off better balanced and requires less drilling or grinding in the dynamic balancing process. The more uniform wire winds also result in a little more efficient use of available current. The overall difference is small and is of more interest to an R/C racer than a 'bot builder.

A: You can see a whole bunch of different drive and weapon Electronic Speed Controllers at Robot Marketplace - speedcontrollers page.

A: LiPoly batteries are a good choice for any weight class -- if you can afford them and can maintain them properly. They provide a lot of power for their weight, but they do have limits on their safe output amperage. Be sure to allow for that in your calculations.

Take a look at my dad's previous post about calculating battery capacity. For a starting point, I'd try about 4000 mAH for a hobbyweight with a large weapon.

Most builders use a single large capacity battery rather than multiple smaller batteries for each ESC. Multiple dedicated batteries could leave you with no drive power but plenty of weapon power still available. The single battery will also be better able to survive large amperage surges.

A: I don't know 'Cobra'. The official name database at BotRank.com does not show a 'bot named 'Cobra' in any weight class, and neither does the RFL name search. Sorry.

Most hobbyweight (12 pound) and featherweight (30 pound) 'bots use cordless drill motors and gearboxes for their drive train. Top of the line is the DeWalt 18 volt drill motor and transmission, but a DeWalt with all drive components will run more than $150. Many builders in these classes use motors and gearboxes from less expensive, lower voltage drills. The 'Handiworks' 7.2 volt drill was once a favorite for this purpose, but they are no longer widely available. Look around your local discount tool store and you should be able to find something for $30.

You might want to reconsider your desire for 'really fast'. Robot combat is not a race and trying to drive a fast 'bot can be a real handfull.

Q: Aaron, this is more of an answer than a question: in an earlier post someone asked for information about a 'bot named 'Cobra'. I have been privileged to see Cobra in action. It's a fast wedge bot from Sydney, Australia -- powered by modified DeWalt drills.

A: Thanks for the info! DeWalt has powered more top flight 'bots than I could possibly name here. Robot Marketplace offers a wide range of DeWalt motors and gearboxes, and Team Delta has the 18 volt DeWalt motors and gearboxes plus special combat mounts and driveshafts.

A: 'Scrapmetal' could be almost any type of material, Chris. Some could be great, some would be useless. I live in an area where I can get exotic scrap titanium from the aerospace industry that makes tremendous armor, but you may not be as lucky. Check my dad's Armor Guide to get some ideas.

A: Mark J. here: Axi brushless outrunner motors are built for the model aircraft market and the specifications they list are designed to make it easy for an airplane builder to pick the best Axi for their purpose. It's not easy to extract robot type specs from the information provided. For example, the 2208/34 spins a larger recommended propeller than the 2208/20, so it would be reasonable to assume that it has more torque -- but this is misleading because the larger prop is called for only because the 2208/34 spins at a slower speed.

The simple answer to your question is no. With an adequate power source the Axi 2208/20 will produce both more torque and more RPM than the Axi 2208/34. It will also pull almost three times the amperage at stall and will require a larger battery and an ESC with greater power handling capability.

A: Garolite is a branded composite fiber/resin material similar in properties but much less expensive than carbon fiber composite. Stick with the woven glass cloth varieties like G10 or G11 for general robotics construction for their high impact resistence. There's a good discussion of Garolite at the Spambutcher Robotics site.

A: Mark J. here: "Best" depends on lots of factors. Various metals, plastics, and composites are all useful for different designs, applications, budgets, and builder skill levels. Commonly used materials include:

• Aluminum: Different alloys vary widely in strength. Don't use the stuff you can buy off the rack at the local home center - it is soft and weak. 6061-T6 alloy is nearly as strong as mild steel and is widely available thru metal dealers. Aircraft alloys like 2024-T3 and 7075-T6 are harder and nearly twice as strong, but more expensive and difficult to find. Aluminum armor has a tendency to `smear' and show damage.

• Steel: There is a huge array of steel types: hot rolled, cold rolled, tool, stainless, high carbon, low carbon, plain carbon, mild, nickel, invar, chromium, tempered, annealed, quenched, ferritic, pearlitic, martensitic, killed, capped, spring, and chrome moly - to name a few. If you want to use steel, do your homework and pick out something suitable. Mild steel (called `1018') and Chrome Moly (`4130') are commonly available. Other materials offer greater strength for the same weight, but mild steel is cheap and you can find it in sheets, angles, and rods at your local hardware store or home center. See also other posts about steel alloys and terminology.

• Titanium: Top of the line `bot armor, titanium is nearly as light as aluminum and nearly as strong as alloy steel. It's also very expensive, tricky to work with, and makes pretty white sparks when hit hard with a rotary weapon. A common alloy used for `bots is 6AL-4V.

• Lexan: Also known as polycarbonate, Lexan is a clear, lightweight plastic with an enormous capacity to absorb impact and pop back to its original shape. Leave room for the material to flex when designing - fastening points are common failure sites. Lexan can also be chemically welded for very strong joints. You can find Lexan at your local glass shop or home center, but make sure you're getting polycarbonate and not clear acrylic plastic - acrylic is useless for `bot armor.

• Polyethylene: Ultra-high molecular weight (UHMW) polyethylene plastic is lightweight, cut resistant, unbreakable, and very easy to machine. It takes huge abuse and bounces back for more. Thin sheets are flexible, but thick plates can be used for motor mounts and main chassis components.

• Carbon Fiber: Amazingly stiff, strong and light -- but when it fails it comes all apart! Great for small `bot chassis plates and top armor. Expensive!

• Fiberglass: A blend of woven glass fiber and a resin media, there are lots of fiberglass formulations. A high performance type called Garolite is popular with some insect-class builders for chassis plates and armor. It is heavier, less strong, and less stiff than carbon fiber composite but much less expensive.

Remember, you don't have to use the most exotic materials to make a winning `bot. I've built two champion robots with wood armor!

A: OK, everyone say it at once: EBay! You should be able to buy standard servos for $10 or less. Your local hobby shop may cut you a deal on some and save you shipping costs.

A: Clear plastic 'Package Tape' is available pretty much anywhere. It might be good enough for your purpose.

If you really want the good stuff, 3M makes a specialty tape that's super strong, very flexible, and so sticky it will even bond to polyethylene. I use it to hinge the side skirts on my beetleweight. It's called 3M #396 Super Bond Film Tape. It's hard to find and it isn't cheap. You can get it here: www.hillas.com.

A: Check with local sources that sell window glass. They often sell polycarbonate as burglar-proof window material. Your local home center may also have polycarbonate, but make sure it's the real stuff -- they may also sell clear acrylic plastic that is not nearly as strong. Check the yellow pages under 'Plastic' as well.

If you can't find what you need locally, www.robotmarketplace.com sells a variety of materials suitable for 'bot armor (Lexan. carbon fiber, titanium). Check their Metals & Materials section.

A: You don't mention how large your robot is going to be. For smaller 'bots, take a look at the 'Rubber Treads' section at www.classictintoy.com. For a medium sized 'bot automotive V-belts or timing belts might do. Big 'bots can use treads from light equipment like snow blowers.

Remember that treads are heavier than wheels, often fail in battle, and are easy to attack. They're also expensive.

A: We get parts from many sources: our local hobby shop, pieces scavenged from toys, stuff we make ourselves, and web stores. Places you might try:

Team Delta
Microbotparts.com
Sozbots
Robot Marketplace

Q: Hi Aaron: My name is Alan. I have purchased all the parts for a tank robot, but I need help hooking everything up. I have: an R/C system, a twin-channel drive motor ESC, a weapon ESC, a master power switch, a 7.2v NiCad battery, and head and tail that should light up when the robot is turned on. Could you please advise me how to hook all this together? Thank you very much.

A: Take a look at the diagram and decription of basic robot wiring, Alan. Wire in your power switch where the removeable power link is in the diagram -- combat robot tournaments often require a removeable link instead of a switch. Your multiple lights will replace the single power indicator light in the diagram.

Q: Thanks for your advice. Just to clarify, do I attach three wires to each battery lead and run one + and one - to each ESC and the lights? Thank you very much for your reply.

A: That's right, Alan -- the ESCs and lights are connected in parallel to the battery. Don't forget to insert your switch between one battery lead and the device connections.

Q: I forgot to ask you this question last time. The different parts for my robot have wires of different gauges. Do I have to replace all the wires in one gauge? Will the robot function with wires in various gauges connecting together? Thanks for your reply.

A: Don't worry about the different wire gauges, Alan. The important thing is that the smallest wire in a given circuit is capable of carrying the largest expected current for that circuit. Bigger wire is OK, but smaller wire can overheat under the load, melt thru the insulation, and short out. As long as your robot components are operating within their rated voltage, you should be able to trust that the manufacturer has provided wire of adequate size. Hook 'em up and run 'em!

A: No -- American Wire Gauge (AWG) sizes measure the conductor only, not counting any insulation. The conductor diameter of 18 gauge wire is about 0.04 inch (1.02 mm).

A: Shortening the antenna that much will certainly reduce reception, but you may still have plenty of range. Give it a test run and see how it does.

If you decide to repair the antenna, you can just solder on a length of similar gauge insulated wire to restore the length. Cover the solder joint with heat shrink tubing or a flap of vinyl tape to prevent accidental grounding of the antenna. If you are comfortable soldering PC boards you can open the receiver case, remove the damaged antenna entirely, and solder on a new wire of the correct length.

Q: What is impedance? I hear that even if I solder on a length of similar gauge insulated wire to restore the length, I need the correct impedance as well.

A: Mark J. here: Impedance is a measure of the opposition of an electrical component (like an antenna) to an alternating current (like a radio signal). A proper antenna must have its impedance match the other elements of the system to maximize signal strength.

The main factor determining the impedance of your simple wire antenna is length. Restoring the antenna length by soldering on a length of similar wire will restore the impedance to that of the original antenna.

A: Mark J. here: How quickly you throw the stick forward shouldn't matter to the radio system, so I don't think your problem is entirely with the transmitter set-up.

First, check the set-up procedure in the manual for your Electronic Speed Control (ESC) to make certain that the unit is correctly adjusted to work with your radio. An ESC requires careful adjustment to assure that the motors will respond correctly throughout the entire range of transmitter stick motion. Make certain that your transmitter trim settings are centered during ESC set-up.

Once the ESC is correctly set, the transmitter trim should be adjusted so that both wheels start turning at the same time when the stick is gently pushed forward or back. If you're still veering to one side, reduce the Adjustable Travel Volume (ATV) transmitter setting for the side of the 'bot that is running too fast.

If rapid acceleration is still a problem, check for equal weight on the drive wheels on both sides of the 'bot. If one side of the 'bot has more weight it will get better traction and can cause a spin under hard acceleration. You may need to move some components on the chassis to equilize weight. Backing up may mask the problem by reducing traction to both drive wheels.

For a 4-wheel 'bot, make sure all four wheels are in good contact when the 'bot is on a level surface. Adjust the chassis or motor mounts to correct if required.

For additional help on transmitter set-up, I suggest reading thru my guide to programming radio systems for combat robots. I wrote it with specific reference to Futaba systems, but the general tips are useful for any computer radio.

A: You probably saw the IFI Isaac Control System that is commonly used at the BattleBots IQ competitions. Some builders use this system at other competitions as well.

The IFI system accepts a variety of analog PC joysticks as external controllers. These are the same joysticks you can buy at your computer store. PC joysticks are not compatible with standard R/C transmitters.

A: Mark J. here: the operating frequency of your radio does not effect the ability of the system to accomodate a lifting servo. However, the 27 MHz band is used by both 'toy' radios and 'hobby-grade' radio systems. Toy radios are not compatible with hobby grade components like servos.

Toy radios in the USA are on either the 27 MHz or 49 MHz bands. Hobby grade radio systems are commonly available in the USA for the 27 MHz, 72 MHz (aircraft only), and 75 MHz (non-aircraft) frequency bands.

A: Mark J. here: We need to be careful not to mix apples and oranges:

AM (amplitude modulation)and FM (frequency modulation) are two methods of adding information onto a radio wave. All hobby radios are either AM or FM. Of those two methods, FM is less susceptable to electrical 'noise' interference.

PPM (pulse position modulation) and PCM (pulse code modulation) are two methods of encoding the information for radio control before it is added to the radio wave.

• PPM is an analog coding system with servo position represented by a time interval between two pulses. It is the standard system used on hobby radios.

• PCM is a digital coding system with servo position represented by a binary number. A computer in the receiver decodes the number and instructs the servo or speed controller. If no signal reaches the receiver, the computer can send a predetermined 'fail safe' position signal to the servo that can stop the robot and turn off weapons.

A: Mark J. here: Is that the middleweight flamethrower from Minnesota? I don't know about their radio, but the homebrew radio systems I've seen from the few other teams to try it were unreliable and had no advantages over off-the-shelf systems. If you just happen to have a degree in electrical engineering and a lot of time to spend designing, building, and de-bugging a radio system -- go for it. If you want something that works, stick with a professionally built system.

A: No functional difference. The only reason Robot Marketplace carries the discontinued Thor 883 is so builders who have a pair and smoke one can get an exact replacement.

A: Sure - as an expensive smoke bomb.

A: It would save time if people would check Robot Marketplace before asking me any question that starts with "Where can I buy a...".

Pretty much any place that sells R/C equipment will offer systems with computerized mixing. For a 'bot, you'll want a system on the 75MHz band. Guess what? Robot Marketplace sells a very nice Hitec Laser 6 FM System for less than $135. Check with your local hobby shop as well.

You can also find Electronic Speed Controllers with built-in mixing at (wait for it...) Robot Marketplace.

A: Mark J. here: the IFI Isaac Control System has long been the mandatory R/C system for the BattleBots IQ competition. However, the system has been discontinued by IFI, and used systems are in short supply. BBIQ now strongly encourages the use of the Isaac system, but approves alternate systems on a case-by-case basis.

The Isaac controller is a 'smart' system that prevents radio interference and the need for frequency control and transmitter impound at tournaments. This makes things run much more smoothly for the tournament director. The Isaac also interfaces to the tournament computer and allows the director to remotely shut down power to all 'bots instantly - a big safety plus!

A: An ESC designed to interface with a hobby R/C receiver should have a plug already installed that will fit directly into the channel output socket of your choice on the receiver. See the 'bot wiring diagram. Ask the manufacturer of your ESC for additional info, if needed.

A: Mark J. here: radio systems are assigned to operate on specific frequency 'bands'. Both of the frequency bands you mention are available for use by R/C toys. MHz refers to how many million times per second the radio 'cycles' -- 27 million cycles per second for the 27 MHz radio.

Within each band are several specific frequencies to which a radio system may be tuned. A radio tuned to a specific frequency will not interfere with a radio operating on another frequency.

See also this earlier post, and the Radio Frequency Chart (link down) at the Combat Robots Wiki.

A: You can scavenge the speed controller out of a toy or servos if you're really cheap, but remember: 'cheap' and 'combat robot' don't mix. If you're going to invest your time and effort, don't allow cheap components to let you down!

A: Mark J. here: The manufacturers don't tell, and the R/C racers don't care. To find out, you'll have to buy one and do your own testing (or find someone who has). A procedure to measure the performance specs of a DC motor, including stall amperage, can be found here.

I dug thru my box of old R/C parts and found a 17 turn hobby R/C motor. A quick test using the 'D-cell method' shows 31 amps stall current at 7.5 volts. That seems a little low. A 19 turn motor would pull less stall current, but I can't say how much less.

A: Mark J. here: there are several methods for determining the maximum current a permanent magnet DC motor will draw at stall. I think the simplest for most builders is the 'D-cell' method. You will need:

• a new, fresh alkaline D-cell; and
• an ammeter capable of reading at least 15 amps;

The reading provided by the ammeter is the stall current at 1.5 volts. Current is proportional to voltage, so the stall current in operation would be this reading times (V / 1.5) where V is the operating voltage of your 'bot. This all assumes that your 'bot battery can actually deliver the calculated amps, and that the resistence of your speed controller and wiring is negligible.

A: I really don't think that there are worthwhile options to a good speed controller, but I have seen some other things tried:

You can use the Team Delta RCE225 dual ended switch. It plugs direct into your R/C receiver and will give forward/off/reverse control for a single motor (rated 24 amps) for $42.50. Works best on slow 'bots.

If you're really hurting for funds, I remember seeing some early 'bots that converted the variable speed trigger that came from the same cordless drill as their motor. They removed the trigger spring and used a servo to move the throttle. Another servo ran the converted forward/reverse switch. Clunky and hard to drive, but it did work.

A: Two-wheeled robots can be difficult to drive in a straight line without veering to one side and they don't turn in a smooth arc. A peizo gyro senses turning motion, compares it the the signal comming from the R/C receiver, and adjusts the signal to the electronic speed controller to keep the robot on the course the driver wants.

My dad has a whole webpage about gyros and combat robots that should answer any additional questions.

A: Sorry -- I've never used either a Jeti or Phoenix. Try asking that question at the Delphi Antweight Forum.

A: You need to be very careful when interpreting motor amperage specifications. Brushless motor specs may list a "maximum loading" which is a recommended amperage over an extended period of time that is much lower than the peak amperage draw! Electronic Speed Controllers are usually rated for the peak amperage they can provide over a very short time period.

It doesn't hurt to use an ESC with a higher amperage rating than you need, and it may keep you from cooking the ESC. When in doubt, use a higher rated ESC.

A: Mark J. here. The message doesn't seem to be getting thru: cheap and robot combat don't mix. You're going to spend a lot of time and effort building your 'bot and going to the tournament. When some component fails in combat and puts you out of the match, you're gonna wish you hadn't gone cheap.

That said, Tower Hobbies has a Hitec 3-channel pistol grip FM system for $69.99. You'll need either an ESC with built-in mixing or a separate elevon mixer to use it with a 'bot. Inertia Labs will sell you a GWS 4-channel twin-stick FM system for $89.90 (transmitter with crystal $59, micro receiver $21.95, receiver crystal $8.95) that does not require a mixer. Best luck.

A: Mark J. here: a piezoelectric crystal can be made to vary its electrical properties at a very precise frequency. When incorporated into a radio ocillator circuit, the crystal controls the frequency 'channel' on which the set operates. Hobby R/C systems have removeable crystals in both the transmitter and receiver that can be replaced with crystals of a slightly different frequency to tune the system to a different channel and avoid interference from other radios.

R/C systems normally come with one set of crystals. Robot tournaments usually require that you have crystals for at least two different channels, so plan to buy a second set. There are different types of crystals for AM, FM single conversion, and FM double conversion -- make sure you get a set that matches your radio.

A: Mark J. here: LiPoly batteries have excellent charge retention and capacity recovery after storage. A LiPoly battery stored for six months at room temperature will recover about 95% of its capacity on the first charge cycle. It's still a good idea to discharge/charge cycle your rechargeable battery (LiPoly, NiCad, NiMHd) a couple of times before a competition to assure full capacity. Always follow the manufacturer's procedure for cycling.

A: Make sure the batteries in the car and the transmitter are fresh. If this doesn't help, as a last resort you might want to open up the car to expose the electronics board. There will be a couple of screw adjustments on the board, sealed with a thick, waxy material. Pick one adjuster, scrape away the wax, mark the starting position of the adjuster, and try turning the adjustment screw a little one way and the other to see if the range improves. If not, return it to the starting position and tweak another adjuster. Do NOT try this with the transmitter!

A: Mark J. here: In the USA the "AM Band" refers to commercial radio broadcast frequencies between 520 kHz and 1720 kHz -- a kilohertz is 1000 cycles per second. 49 MHz (49 million cycles per second) band is a 'public service' frequency range a little below VHF television broadcast. It's shared by older wireless phones, baby monitors, and five toy R/C channels. Other toy R/C systems operate on 27 MHz on six frequencies squeezed in between CB radio channels.

Toy R/C systems on 27 or 49 MHz use interference-prone Amplitude Modulation (AM) signals, but 'hobby grade' R/C gear on 27, 72, and 75 MHz use either AM or FM (Frequency Modulation) signals.

A: The Robot Marketplace and Tower Hobbies are both good on-line sources of 75 MHz 'ground frequency' radio systems, but don't forget to check with your local hobby shop!

It's also possible to have a 72 MHz radio converted to 75 MHz. Tower hobbies offers this service on new systems, and a web search will turn up other specialty shops that will do this.

A: Mark J. here: Micro receivers are 'single conversion' designs that are more sensitive to interference than the 'double conversion' design usually found in standard receivers, but if you're only getting 5 feet of reception distance you have problems other than your receiver. Electric motors create a lot of electrical 'noise' that can be a problem -- try adding anti R.F. capacitors across the motor leads. Position the receiver as far away from the motors and ESC as possible. Stretch out the receiver antenna and get it out in the open air, away from metal or carbon armor.

Check the 'Radio Reception Problems' page at the Combat Robotics Wiki (link down) for more info on the topic.

A: Tech question, Mark J. here: In a brushless motor, each of the three leads is directly attached to different spots in the stationary field windings of the motor -- just as a commutator would be attached to the rotating field windings in a brushed motor. You can see wiring diagrams for brushless motors at: www.megamotorusa.com.

Since brushless motors have no commutator, they require some electronic 'intelligence' to correctly assign the current flow to the field windings of the motor as the armature rotates. This intelligence is built into the motor controller matched to the brushless motor you have selected. The motor controller also acts as speed controller on hobby brushless motors.

A: Tech question, Mark J. here: You'll get a nice puff of smoke followed by a quick trip to the trash bin. Solid state switching controls are rated for a maximum amperage flow. Doubling the voltage to a motor also doubles the maximum amperage, so you've already taken the unit to twice it's design limit. I suspect that if you got into a pushing match you'd fry the controller as is. Bigger motor = more amperage = thermal meltdown. Note that not many R/C receivers can handle 12 volts -- try that at your own peril.

A: Some combat robot ESCs have a short set-up process, but it isn't programming. Some brushless motor controllers have more elaborate programming capability, but most work fine with the default settings. More sophisticated radio systems can be programmed by selecting options from menus for things like channel mixing, but it isn't required to provide basic radio functions. See my dad's page on programming transmitters for details.

A: Tech question, Mark J. here: AWG wire sizes run opposite from the way you'd think, with larger numbers indicating smaller diameter wire. For small wire, amperage capacity approximately doubles with each decrease of three number sizes (thicker wire). A 22 gauge copper wire is conservatively rated to carry 7 amps in conditions found in a combat robot. You might get away with it, but I'd suggest 18 gauge for at least the battery to ESC hookup -- or you could use double strands of 22 gauge if that's what you have.

Always use 'multi-strand' wire in your robot, not solid-core. Solid core can break from repeated flexing and shock.

A: Mark J. here -- You can turn your weapon motor on and off with a simple mechanical relay or contactor, but that puts a really big momentary drain on the battery. The drain can drop the voltage so low that your radio receiver cuts out. A speed controller allows you to feed power smoothly to the weapon and avoid the voltage drop.

With some designs, it's also handy to be able to reverse the weapon direction if you're inverted or if the weapon gets fouled on something.

Also, the new 'brushless' motors require a controller to run at all. You can't just hook them up to a battery -- it won't work!

A: Technical question - Mark J. here: Yes, there are a few:

A: Check with the event organizer before attempting to use any 'cheap' radio system in a 'bot with a spinning weapon. Many combat rules sets require specific safety measures for weapon safety that are not available in inexpensive radios. For robot combat it isn't smart to try to save money on your radio system.

A: Technical question - Mark J. here: The wire colors are different, but the signal and polarity is the same on Futaba, JR, and Hitec radio systems -- they are fully interchangeable. Some Airtronics radio gear has the polarity reversed, so always check before mixing anything with Airtronics. More info on the different connector types can be found here.

A: Technical question - Mark J. here: A twin motor controller can handle two (or more) motors in parallel on each channel (four total) if the total current draw is within the amperage rating of the controller. The specific controller recommendation would depend on the total draw for a pair of the motors you plan to use.

If you want four motors each with independent control, then you'll have to use two, two-channel controllers.

A: Technical question - Mark J. here: NO! Most micro electronics have a very narrow range of operating voltage. Raising the voltage can fry them. Unless you're very sure you know what you're doing, keep the voltage to your electronics at the original specified levels.

Q: What happened in the fight between Ginsu and Mechadon at the 1999 BattleBots event in Las Vegas?

A: I've misplaced my tape of the 1999 pay-per-view event, but I remember that at the end of the match, the true-walker Mechadon had a couple of it's six legs inoperative and it was tangled up against the rail. The saw-wheeled Ginsu was tipped over on it's side and couldn't move. Ginsu had done a lot of damage, but the judges apparently decided that it was incapacitated at the end of the match while Mechadon could still kinda move a little.

The match decision went to Mechadon, but Team Sinister couldn't repair the damage in time for the next match and they had to forfeit.

A: CIRC is a member of the Robot Fighting League, and there is a table of RFL minimum radio requirements on this page. However, the event organizer has the final call on variations to the RFL rules. Try asking CIRC president Bruce Stott: brucestott@yahoo.com.

A: I'm not a big fan of destruction for its own sake. I think destruction is an over-rated factor in robot combat. I'd rather see a fight won by crafty driving and strategy any day. Wouldn't you rather ask about the 'best' fight of all time?

That said, there are plenty of 'bot fights where one machine tears the other a new oil hole (like 'Ultra Violence' vs. 'Tiger Wood' at Robotica III), but not many where both 'bots get really well shredded.

For being both mega destructive and a great overall battle, I'd nominate the heavyweight final of BattleBots 3.0 at Treasure Island. 'Son of Whyachi' and 'Biohazard' beat the bolts out of each other! Armor is ripped away, weaponry is mangled and snapped, systems fail and recover, and still the fight goes the distance.

As an aside, I don't agree with the judges' decision in this fight -- I score it in favor of Biohazard.

Q: OK, so what do you think was the best robot fight of all time?

A: San Francisco, Robot Wars 1995, heavyweight final: 'Thor' vs. 'The Master'. There is a video of the '95 event shot from the stands that circulates in the combat robot underground. Find a copy if you can!

A: Nickelodeon GAS sometimes reruns the Nickelodeon Robot Wars series with kids driving the robots. That's the only current showing of Robot Wars I know about. Check their website for times.

A: There were more than 20 matches at that tournament and they didn't all get recorded. I think you can spot 'Mini Maxbot' in the 'rumble' footage if you look carefully. Most of the 'Rat Amok' fights are included.

A: Mark J. here: I've learned a few things about small-scale events from organizing three Antbotica events:

The most important thing is safety. Make sure your arena and rules provide a safe environment for spectators and participants. The event organizer is going to be very busy, so assign a safety monitor in the pit area to enforce regulations and keep spectators out.

The second most important thing is fun. If everybody, including you, is having fun then it's a successful event. Don't get so hung-up on event details and regulations that you squash the fun.

Finally, make sure that full information on rules, schedule, and event details are available to participants well in advance of the event. Event turn-out will likely be less than you expect -- don't be disappointed.

A: Active weapons must be turned on and off remotely -- no 'turn it on and set it in the arena' allowed. Further, an active weapon must turn itself off automatically if the radio transmitter is turned off. Finally, active weapons are not allowed with toy/AM radios. Sounds like you'd better stick to a passive weapon with your 'bot, or upgrade to a failsafe FM R/C system.

A: We were at that match in London. By the time Sir K got involved, Drillzilla had already lost the match. The housebot operators are carefully instructed to not influence the results of any 'final' match. None of the teams we talked with thought the match was less than fair.

A: Those pics are from the first round of the Tag Team Terror match: 'Run Away' and 'General Chompsalot' vs. 'Falcon' and 'Joker'. General C. is shown fighting Falcon, and you can see Run Away in the background of picture #3. Joker was a full-body 'tuna can' spinner.

A: 'The Speedway' challenge used in the first season of Robotica was a figure-8 race with two robots travelling in opposite directions. Robots scored 10 points for each lap (up to 8) completed within the time limit with a 20 point bonus to the winner of the race.

There never was a tie in 'The Speedway'. If two 'bots had completed the same number of laps, the winner would have been the 'bot that completed their final lap first. The closest finish was between Run Amok and Kritical Mass. Run Amok crossed the line to finish her 6th lap just feet ahead of Kritical Mass and defended the line long enough for the clock to run out, holding Kritical Mass to 5 laps.

A: If I told you, it wouldn't be 'clandestine'.

A: Probably neither. Our library of tournament trees contains major televised tournaments (Robot Wars, BattleBots, Robotica) that developed big followings, and the earlier versions of those same tournaments that weren't televised. Those tournament trees are the most popular feature of our website!

There just isn't enough interest in the BBIQ and RFL tournaments to justify digging up the data needed for the trees.

A: About ten o'clock on each of the first three mornings of the competition, all of the robots on hand would gather and go thru the qualifying tests. The top eight qualifying teams would divide into two groups of four 'bots and film two shows that day.

All eight teams would compete in 'The Speedway', then the big 'Maze' set had to be moved into place. After 'The Maze', that set had to be moved out and and 'The Gauntlet' moved into position. Finally, 'The Gauntlet' could be cleaned up and moved out and the platform for the 'Fight to the Finish' could be rolled in. Every set change took a couple of hours -- longer if there was a mechanical problem. Each day wrapped up about three in the morning.

For the 'Fight to the Finish', each 'bot had to be lifted up onto the entry gantry to drive onto the platform. After the match, the winner had to be lowered back down, if they were still on the platform! Each 'Fight to the Finish' took about 40 minutes, once the platform was ready to go.

A: Opinion: the summaries I sampled were not good reading. I'd rather not check them all against the tapes for accuracy.

A: Last time - NO! We don't hold copyright to the material and cannot legally do anything with it but watch it in our own home. We'd get seriously sued!

A: Robotica presented a number of different challenges. For some of those challenges, weight and bulk were a disadvantage. It was much easier to slip thru the barrier walls in 'The Gauntlet' with a small 'bot than by banging a big 'bot against all those bricks and blocks, and you didn't need to be big to be fast in 'The Speedway'. Run Amok herself was almost 40 pounds under the weight limit to get an edge in maneuverability.

A: No. It was 3:00 AM when we finished the 'Fight to the Finish". Nobody wanted to load up the other 'bots for another fight.

Q: Who do you think would have won the consolation 'Fight to the Finish' at Robotica if it had happened?

A: The 'bots involved would have been 'Kritical Mass', 'Jawbreaker', and 'Viper'. Of the three, Viper had by far the best traction and pushing power. They took 'Panzer Mk I' off the platform in the preliminaries in an incredible pushing match. My vote would go to Viper.

The consolation match in Robotica II would have had 'Deb Bot' against 'Ill Tempered Mutt'. Deb Bot was quick and powerful, but much lighter than ITM. My vote goes to the Mutt.

The third-place fight at Robotica III would have been 'Ultra Violence' (an evolved version of Kritical Mass) versus 'Jawbreaker's Revenge'. Two experienced teams, crushing jaws versus a powerful spinning weapon, too close to call!

A: The Robot Wars Second World Championship in England paid $25,000 to the winner. We were there, but 'Panzer' took us out in the qualifying round.

A: The 2005 event had 3-day adult tickets for $50, kids 7-17 for $40, 6 and under free. Single day tickets were $20/$15/free.

Update: spectator admission to the 2006 national championships in Minneapolis was free!

A: Pictures: here.

A: Mark J. here: Very funny, Alex.

Technically, Robotica may have been the fairest and least-scripted of all the televised competitions. Competitors went thru a qualifying trial to test their maneuverability, precision, and power. The preliminary round match-ups were based entirely on the scores from the qualifying trial, and matches in the championship were based on tournament scores from the preliminary round. Nobody got a 'bye' for the early rounds, and the show producers had no hand in the tournament matches.

The outcome of the first Robotica competition certainly played like a Hollywood script, but none of the interviews or matches were coached or scripted. I once joked that we had to film the final 'Fight to the Finish" three times before it came out right, but I was kidding!

A: Yes, some more than twice. Check the RFL Events Calendar.

A: Sorry - our collection of tournament trees doesn't include the 'extra' events at RWEW. The Robots Rule site lists the robots that fought in the extra events and notes the winners. Both of the events you mention were simple single elimination tournaments with eight 'bots.

A: Yep. Search Google Video for "Robot Combat" and you'll find the first half of the match between 'The Gap' and 'Tricerabot' at the Oregon Clandestine Street Fight.

A: Not exactly. If you win an RFL sanctioned tournament using a full BattleKit within one year of purchase from an authorized dealer, you are elligible for a refund of the cost of the basic BattleKit you purchased. Details are at the BattleKits website.

A: The subscription service www.tvshows.org claims to have entire BattleBots shows for download -- but I can't confirm that. The official BattleBots webpage has battle clips.

A: Some events allow projectile weapons if they have a restraining device to stop the projectile in 8 feet or less. Untethered projectiles are prohibited, so paintball guns are right out. Projectile weapons have never been popular.

Check the current Robot Fighting League rules for details on allowable weapons.

A: Gift certificates from various robotics suppliers are common prizes at tournaments. Robot Marketplace has been a prize sponsor at the BattleBots IQ competitions.

A: We have our own tournament: see www.antbotica.com.

A: Robotica paid the largest top prize in American robot combat: $12,000 cash. Second thru sixth paid $2000 each. DaVinci Days paid out quite a bit less -- about $100.

A: The Run Amok video library has tapes of all five seasons of Comedy Central 'BattleBots', all three seasons of TLC 'Robotica', both seasons of TNN 'Robot Wars Extreme Warriors', and the BBC 'Robot Wars' episodes from the 4th Wars onward. Wish I had the earlier Robot Wars!

Q: Is there any way I can buy stuff from the video libary?

A: Sorry - we don't have rights to sell any of those commercial videos.

Q: Where did you get the robot combat videos for your library?

A: They were recorded off-air, for personal use only.

A: Tillah was built by Oregon's 'Team Tillah', headed by Team JuggerBot weapon designer Ron Ender. The design is essentially the back half of the basic JuggerBot chassis with a large and nasty square drum spinner weapon hanging off the front. The robot was 'entropically retired' at the 'Steel Conflict 4' tournament by the combat robot hall of fame spinner 'Megabyte'.

You can see Tillah in action on the Oregon Clandestine Street Fight video CD.

A: Part of competing at Robot Wars was the challenge of putting on exciting matches. If you had an entertaining 'bot you would be invited to participate in some of the 'extra' events like the House Robot Challenge, the Annihilator, and Tag Team Terror.

As mentioned in a previous post, the American competitor 'Tricerabot' was 'JuggerBot 3.0' in a cardboard disguise. The team had several replacement costumes. The burning costume did no harm to the titanium armor underneath, but added excitement to their matches.

A: The Wikipedia is correct; Growler did have a rear-mounted flamethrower. The flame didn't come from the end of the tail, but from underneath -- more like a flame farter.

A: Mark J. here: I have no connection to the sale of the Robotica videos. They are sold by InetVideo.com. The link appears on our Run Amok webpage only as a service to fans.

I'm told that the video they offer has episodes five and six, plus the double-length final episode. Please contact InetVideo with any further questions. For info in the Robotica competition format, see the Robotica Wikipedia page.

A: Sorry, no. Try Robots Rule - Housebot page for photos and stats.

A: I don't know of any purpose-built American multi-bots, but it is not uncommon for a couple of 'bots from one weight class to 'team up' and enter a higher weight class just to get more arena time. In general, multi-bots don't do very well.

A: Very observant! The TV robot shows didn't want 'bots with the same name or appearance as other shows, so builders often disguised and re-named their 'bots to compete in different televised events. There is actually a relationship between all four of the 'bots you mentioned:

• Tricerabot actually was JuggerBot 3.0 in a cardboard costume.
• Rosie the Riveter 2 was a disguised Logoseye.
• Team Logoseye was a group of builders that split-off from Team JuggerBot after the first Robotica season -- the underlying designs of 'bots from both teams were very similar.

A: Biohazard, hands down. Ziggo and Hazard are tied for second, in my opinion.

A: BattleBots.com has DVDs from the pre-Comedy Central tournaments.

A: Best I remember, the match went to the judges. Voltarc got under the skirts of Biohazard and managed to look more aggressive all thru the match.

A: The very early versions of Biohazard could self-right, but that ability was lost in 1997 when Carlo added the large titanium side skirts. 'Vlad the Impaler' managed to get under those skirts and flip Biohazard at the 1999 BattleBots 'Pay-Per-View' event in Las Vegas and Biohazard couldn't recover. Vlad went on to win the championship at that event.

A: They may have bounced off each other in one or more of the superheavyweight 'rumbles', but they never met 'head-to-head'. Toro and Diesector somehow always ended up on opposite ends of the BattleBots superheavyweight tournament tree and never met in the final:

• Season 2.0 - Toro lost to 'Atomic Wedgie' in a quarter-final match. Diesector beat Atomic Wedgie in the final.
• Season 3.0 - Both 'bots lost in the quarter-finals: Toro to 'Minion', and Diesector to eventual champion 'Vladiator'.
• Season 4.0 - 'New Cruelty' defeated Diesector in the semi-finals, then lost to Toro in the final.
• Season 5.0 - 'Phrizbee Ultimate' took out Toro in the third round. Diesector won the championship.

A: Arenas built to contain heavier robots are very expensive to build, costly to transport and assemble, and big bucks to maintain. Without major sponsorship, big arenas just aren't cost effective. Without big arenas, there isn't anyplace to fight big 'bots.

A: Find out what weight classes are popular at the tournaments you plan to enter. It won't do much good to build a 'bot for a class that isn't supported. Beyond that, it's largely a matter of your budget and level of mechanical experience. Start simple.

A: The standard Robot Fighting League rules allow AM radios in weight classes up to the 12-pound 'hobbyweight' class, with some restrictions on weaponry. Most RFL member tournaments follow these guidelines.

A: MechWars is a member of the Robot Fighting League, but they have modifed the RFL ruleset for their events. Section 4.4.6 of the MechWars ruleset has been altered to require FM radio systems for all weight classes and weapon types. The AM radio in your 'Fly Wheels' wouldn't comply.

I'd suggest emailing Jon Vandervelde (jon@tcmechwars.com) to make sure this applies to antweights. At big events it's common for another organization to handle the insect class competition -- they might have different rules.

A: I think 'Robo Rat' (picture here - scroll down the page) was built just to fight 'Rat Amok', but the match never happened. Rat versus Rat Trap -- who do you think would'a won?

Q: Where is 'da Vinci Days' held?

A: The da Vinci Days technology festival happens each July on the campus of Oregon State University in in Corvallis, Oregon. No robot tournament there this year (2006).

A: We've been to a few 'big' competitions like Robotica and Robot Wars. Robotica had the biggest prize of any robot combat event ever held in the US. Robot Wars Extreme Warriors 2 had more than 50 heavyweights from the U.S. plus quite a few from Europe.

Q: How much was the grand prize at Robotica?

A: $12,000 -- we won!

Q: Where did 'Robotica' take place?

A: All three seasons of Robotica were filmed on a large sound stage at the old ABC studios in Hollywood, California.

A: The show gave the impression that the housebots were autonomous, but each of them had a R/C operator down at arena level that you never got to see.

A: Yep, see www.roboforge.net.

A: For builders, antweights. For spectators, heavyweights.

Q: What is the least popular weight class?

A: The 6-pound 'mantisweight' class is not popular with builders, and the 50-gram 'fleaweight' class isn't getting much action, either.

A: Try the Robot Marketplace Video Store -- I don't think any of the videos there are over $20, and some are under $15.

A: There were races, obstacle courses, barrier destructions, head-to-head push-offs -- all sorts of matches. Take a look at the Robotica page at Wikipedia for a full listing of events in all three seasons of Robotica.

A: I drove my dad's 'bot at Robot Wars when I was ten. Most events don't have an age limit, but they may require adult supervision in the pits. Check with the event organizer.

A: I think the Nickelodeon version of Robot Wars with kids driving the 'bots is still on the Nick Games & Sports network -- watch for me driving 'Run Away' in that series!

A: Yes, Ted. The robot's name was 'Gemini'. It competed in the Fourth and Fifth Wars. It won the 'Best Design' and 'Most Original Entry' awards at the Forth Wars. I think I remember that both halves of the multibot were identical CO2 flippers. It did OK, winning the first round fight both times, but didn't get any farther.

Robot Wars rules said a multibot had to enter the arena as a single unit. Gemini used magnets, but broke apart prior to fighting.

A: Building a robot that can fight and win without an operator is quite a challenge. This is real 'cutting edge' stuff, and you're pretty much on your own trying to build an autonomous navigation and attack system. You might get some help from robotics publications like Servo magazine.

Some tournaments give a weight advantage to autonomous 'bots and let them fight the R/C 'bots. I like to drive my 'bots. Letting them fight with me just standing there sounds like less fun. Besides, the autonomous 'bots I've seen fight weren't very good at it. My dad has offered a $100 prize to the first autonomous 'bot to take him out of a tournament. I think his money is safe.

A: Nope - I was at the RFL nationals last year, but not this time. Must be an impersonator.

A: Literary question - Mark J. here: Brad Stone's Gearheads is a great book on the history and politics of the early days of robot combat. Unfortunately, it is also the only book published on the subject. If you have an interest in the topic, you might enjoy reading thru the archive of the original U.S. Robot Wars forum on the Delphi site: http://forums.delphiforums.com/RobotWars/start

A: I've always liked Dead Metal. His design is cool and the weapon is very effective.

A: Heck yea! I don't know of a competition that hasn't had at least one female competitor. Robotica, Robot Wars, and BattleBots all had female teams, and the local competitions I go to have plenty. Don't let anyone tell you that girls don't build 'bots.

A: I'm sorry to be the one to give you the bad news, but the final season of Robot Wars -- the Seventh Wars -- was filmed in late 2003. The house robots were given to charity, and the arena was sold to the Fighting Robot Association in England. No more Robot Wars.

The good news is that there are plenty of robot combat tournaments both in the U.S. and England. For information on U.S. events, try The Robot Fighting League. For British events, try The Fighting Robot Association.

A: Never seen Robot Wars? It's pretty simple -- two big (220 pound) remote controlled robots enter a sealed box about the size of a basketball court. Destroy the other robot and you win. You can crush, smash, pierce, saw, or flip the other 'bot. You can throw them over the arena rail. You can push them into the pit, or roast them over the flames. Just do NOT turn your back on the 'house robots' that patrol the edges of the arena.

A: I liked being able to see all the other robots close-up. I especially liked the British robots "Tornado" and "Razer". The American robot "Tricerabot" was very impressive at the first Robot Wars Extreme Warriors -- he almost pushed Sir Killalot into the pit! My friend Jerome had an impressive robot named "Unibite" that was pretty strong. It was the first robot to go into the "drop zone". Being in the pits was awesome!

Q: Can I see a picture of your Antbotica robot, Mini Maxbot 2.0?

A: Sure. Mini Max 2.0 uses the drivetrain from a BattleBots custom series 'DoAll' toy. I replaced the radio and speed controllers with hobby-grade equipment, and added a 700 MAH rechargeable battery pack. The treads are silicone rubber coated for added traction, and I added a removeable front polyethylene scoop. The 'bot will run upside down if needed.

Mini Maxbot 2.0 placed second at the 2005 daVinci Days Antbotica event in Corvallis, Oregon.

A: Nobody was gonna beat 'Wallop' at the 2004 RFL National Championships. The magnet wheels gave him a huge advantage on the steel-floored arena. There is more to building a good magnet-bot than just bolting ring magnets onto your hubs, and Jim Smentowski did a great job of it.

On a non-magnetic surface, a 'Zpatula' versus rubber-tired 'Wallop' match would be interesting. I think my narrower lifter might get under his, but Jim is a very experienced driver. Call it a toss-up.

A: Zpatula is based on a BattleBots Pro-Series Biohazard R/C toy that I bought on EBay ($30). We removed the toy radio and installed a SOZBots ESC ($58), a Microbotparts FM micro receiver ($25), and a home-built 7.2 volt 700 mAH NiMHD battery pack ($10). The drive train uses the 130 size electric motors that came with the toy.

The toy gearbox for the lifter was modified to lock the slip clutch and to allow controlled up/down operation with a Team Delta R/C dual-ended switch ($39). We also upgraded the electric lifter motor from a 130 size to a more powerful 180 ($10). The lifter itself is a shortened BBQ spatula ($4).

For protection, we added 1/8" polycarbonate top armor ($3) and 3/16" UHMW polyethylene side/rear skirts ($3). Not counting the radio transmitter, that adds up to well less than $200.

Zpatula won the 2004 daVinci Days tournament and finished 3rd at the 2004 RFL nationals. It's lifetime ranking score is 1277.68, placing it in the top 25 beetles of all time at Botrank.com.

You're Welcome. Your 'bots look great! Happy to hear our advice was helpful.

A: We still have all of our combat 'bots, although hobbyweight 'Nasty Glass of Water' is not operational.

A: I'm not active on the RA board, and did not enter the tournament.

A: Each of our 'bots at Robot Wars had its own driver and support team. We'd just go for it and see who had the better stuff that day. But no senseless destruction after the match was over!

A: I think I mentioned before that I had a grudge with Sir Killalot -- he attacked 'Run Away' without provocation and from behind. Cowardly! Dead Metal was my fave.

A: Yep, I own the game -- very cool! The housebots cannot be bought there, but you can play as a housebot in 'Robot Wars Advanced Destruction' for the Game Boy Advance.

A: Three reasons:

• Run Away was a longer and taller 'bot than Run Amok.
• We wanted to pack a lot of spare parts and tools in the same crate.
• International shipping required a much sturdier crate to ship Run Away to Robot Wars in England than we needed to ship Run Amok to Robotica in California.

A: We don't need anything new at the moment, but we always have a couple things on the drawing board...

A: Didya run outta robot questions? My favorite color is green, my eyes are blue, I'm 6' 2" tall, my favorite musician is Ray Charles, my favorite class is Computer Aided Drafting, I like to eat pizza (no anchovies) and play Yu-Gi-Oh. I have two dogs, three birds, and a fish named 'Alpha'. More robot questions!

A: Tillah was very compact, but the Oregon drum spinner was a 220 pound heavyweight. The weapon was very heavy. You can see Tillah fight on the Oregon Clandestine Street Fight CD.

Q: How heavy is Tillah's drum?

A: Mark J. here: First, Tillah should be referred to in the past tense - Tillah is no more. As noted in an earlier post, Tillah was destroyed in a match against Megabyte at Steel Conflict 4.

I could only guess at the weight of Tillah's drum weapon. It was made from very thick steel plate. Ask Team JuggerBot for a deffinitive answer.

A: Mark J. here: The primary weapon of all the JuggerBots was speed and power. In addition, chief weapons officer Ron Ender developed the 'up-ender' weapon for JB2 -- a small but mighty high-pressure air powered flipper to coordinate with the other atributes of the 'bot.

A: No. We didn't compete in any RFL qualifying events this year; we don't like their scoring system.

A: Yes, and no. Explanation:

The Gap's lifting platform has a max capacity of 1060 pounds, but you'd have to position the load very precisely on the platform to lift that much. The Gap will lift 400 pounds placed anywhere on the platform, and 616 would be very possible if we got well under the weight...

...but, Sir Killalot's true weight was almost double the advertised 616 pounds. Robot Wars didn't want to make it seem too one-sided.

A: Its shift key stuck on and it capitalized itself to death.

Actually, all of the old 'bots from the JuggerBot team are hanging on the wall of Mike Morrow's big workshop in Oregon. They're just bare chassis - all re-useable parts have been removed. The motor units from Tricerabot were used in Mike's full-scale 'Mars Rover' recreation. Cool!

Q: Why did Team JuggerBot's Mike Morrow build a giant mars rover?

A: Not giant, just full sized. The Mars Rover is much bigger than most people think! Mike built it for the 2004 daVinci Days festival in Corvallis, Oregon. He also arranged for truckloads of dirt and rocks to fill one end of a parking lot with a replica Mars crater. Visitors to the festival could drive the rover around the crater. Big fun!

A: Ask Team JuggerBot.

A: Mark J. here: The weapon and electronics changes to turn 'Run Amok' into 'Run Away' for Robot Wars Extreme Warriors cost about $1200. We also had to build a crate to ship Run Away to England.

'The Gap' was built in a big hurry for the second RWEW event, and I never added up all the receipts. I think an exact copy would cost about $4000.

A: About 208 pounds, with an empty CO² tank.

A: Yea, it's a pun. Look up 'mettle'.

Q: I don't understand the 'mettle' pun.

A: Never try to explain a pun.

A: Chris Gattman, former member of Team JuggerBot and captain of Team Logoseye (Robot Wars: Rosie the Riveter, Robotica: Logoseye) is also the frontman for the hard rock band, Logoseye (turn up your speakers and click the link). I hadn't heard that they were giving out a robot trading card with CD purchase. Here's a list of all the robot cards in the series:

• R1 - Team Run Amok: The Gap
• R2 - Team Run Amok: Run Amok
• R3 - Team JuggerBot: JuggerBot 3.0
• R4 - Team Logoseye: Rosie the Riveter
• R5 - Team JuggerBot: TriceraBot 3.0
• R6 - Death by Monkeys: Death by Monkeys
• R6 - Death by Monkeys: Silverback (repeated number)

Q: How can I get the Team Death by Monkeys robot trading cards?

A: Write to them and ask nicely. Contact info is at their website: www.teamdeathbymonkeys.com.

A: On our first trip to Robot Wars we spent a lot of time on the London 'Underground' subway system. There were signs and a voice on the PA system reminding riders to 'mind the gap', which ment to look out for the space between the boarding platform and the train.

When we built our lifterbot for the next Robot Wars, it had a 'gap' between the raised lifter platform and the lower frame that could trap other 'bots. We thought it was only fair to point out that our opponents should mind The Gap.

A: Team Jawbreaker reports that Jawbreaker/General Chompsalot 3 has been ready for some time. Looks about ready to me: Photo.

Q: General Chompsalot 3 look's very heavy! Is it a superheavyweight?

A: No, GC3 was originally built to Robot Wars specifications -- 100 KG heavyweight.

A: I was in the Team JuggerBot workshop a few months ago and there was no sign of an upgrade to JuggerBot 3.0. Team leader Mike Morrow is working on other things.

A: No -- we designed our 'bots to fight other 'bots in our weight class, not the Housebots. We were happy to let other teams have a go at that!

A: Sure: www.ebay.com -- that's where I got mine.

A: We didn't fight 'Sir Forcealot' at RWEW2. 'Sir Forcealot' was a renamed version of our nemesis from Robotica, 'Ram Force'. The tournament trees didn't lead us into any of the same matches in England.

A: The robot combat community is a small one. Teams that compete in one series often show up at other events. We've met dozens of teams from BattleBots.

A: My mom is a big part of the team as well! She makes our travel and shipping arrangements, does most of our banners and graphics, and keeps us from doing anything stupid. That last part is really hard.

We also expanded our team for our second trip to Robot Wars to include our chief metal guy, Max Chapin and his familly. Max does the metal forming and welding on our big 'bots and contributes to design and engineering.

A: We build 'bots to win matches, not destroy other 'bots.

A: Yes - 'Rat Amok' won the daVinci Days tournament, and 'Mini Maxbot' won the first Antbotica.

A: Mark J. here: This is a good time to tell the whole story. 'Nasty Glass of Water' was built for the September 2001 NERC Hobby Expo event in Chicago. I was sharing a hotel room with Team Delta's Dan Danknick at the event. Dan built a lightweight 'bot called 'Evil Fishtank' for BattleBots and I wanted to play on that name for my hobbyweight. What's smaller than a fish tank? A glass of water. What's a little less than evil? Nasty!

NGOW was an open 'dustpan' design powered by two very large automotive windshield wiper motors running at 24 volts. Even with the overvolting it was very slow, but it could really push! In our first match a motor capacitor failed and shorted to ground. The battery pack got so hot that I blistered two fingers prying it out of the 'bot. By the time I had the pack cooled down and the capacitor fixed, we'd missed our next match and were out.

The next day we were back for the hobbyweight 'rumble'. NGOW scooped up and trapped a 'bot called 'Green Dragon' that had a good bar spinner weapon still operational. With lots of pushing power and an effective weapon, the 24 pound NGOW/GD combo 'bot cleaned house! The unimaginative event director decided that a combo-bot wasn't quite legitimate and disqualified us, but the audience really loved it!

A: Here in the Pacific NorthWest robots larger than the 60 pound 'lightweight' class are getting pretty rare -- but we have a few:

• Team LNW from Washington has been fighting heavyweight 'LNW' with good results over the last few years.

• The 2004 RFL National heavyweight champion 'SJ' belongs to Scott Kincaid. His 'Team Blackroot' is from Idaho.

• Here at Team Run Amok, we keep our heavyweight flipper 'The Gap' ready to fight, just in case.

• Team JuggerBot is just a few miles down the road. I suspect they would show up for a regional heavyweight fight.

• Gary Warren's Team Maggot fights out of Idaho with their RFL national qualified middleweight 'Botfly'.

• Robot Wars veteran Joe Murawski campaigns Team X-Bots' middleweight 'Paminator' out of Washington.

• Team Atros fights their middleweight 'Atros' out of Vancouver, Canada

A: Entry into the Robotica tournaments was by invitation only and winners weren't invited back. The producers were saving the winners from each season for a 'Challenge of the Champions' event that was to take place after a few more seasons had gone by. The ratings for seasons 2 and 3 fell off from the first season and the 'Challenge' tournament never happened. Rats!

A: Mark J. here: I've never published my journal from the second Robot Wars trip. I think you get most of the 'behind the scenes' flavor from the first journal, but I might reconsider.

There IS a Robotica Journal.

A: Mark J. here: Run Amok needed a little graphic impact to show up well on TV. My design, my decision.

A: Try emailing JuggerBot team captain Mike Morrow (mike@juggerbot.com) and asking nicely.

A: The Revolutionist was a VERY dangerous 'bot! The Gap and the Revolutionist met in the first round Robot Wars Extreme Warriors 2 in a 3-way fight with 'Trackzilla'. While the Revolutionist was spinning up, The Gap charged over and tossed Trackzilla on its top for the fastest K.O. by an American 'bot in Robot Wars history -- about 4 seconds! Just then the Revolutionist had a radio glitch and went out of control, smashing into the back of The Gap before shutting down. Both of us went on to the next round.

We didn't meet again. The Gap was designed to get under spinners with its long lifter platform, but the exposed wheels would make a tempting target for the Revolutionist. It would have been a good match -- not sure who would have won.

A: Not many large American 'bots have a dedicated SRiMech. Run Amok was originally built for the Robotica competition where there wasn't any real need for self-righting -- if you found yourself upside-down, there just wasn't time to self-right. I don't think any of the Robotica 'bots had SRiMechs, but some could run inverted.

When we went to Robot Wars for the first time, we didn't have enough time for major changes to Run Amok. We added the 'sidewheel' rotary weapon to make 'Run Away' showy and unique, and extended the top armor as far to the rear as the rules allowed to make her more resistant to flipping and more difficult for Sir Killalot to pick up (it worked!). That was a learning trip for us.

For our second trip to Robot Wars we built our own new flipper 'bot, The Gap. The Gap does self-right. We had a chance to take a second 'bot, so brought the battle-weary Run Away along as well.

As it turned out, Run Away never really needed a SRiMech. She ended up on her back a couple of times, but by the time that happened the match was already lost and self-righting wouldn't have made a difference.

A: Nobody's ever complained before! It's kind of a cluttered view that doesn't add much to the model. You can see the steel battery box hanging from the chassis, the differential/chain drive, a peak of the drive motor, and a glimpse of the speed controller cover. There is no rear armor.

Just to keep a fan happy, here's a special 'cut and paste' rear-view insert panel to complete your Run Amok model. Don't ask for a bottom view - ain't gonna happen.

A: Mark J. here: I've got CD video of Rat Amok at Da Vinci Days and in the antweight melee at BotBash. There isn't much to see; most times the trap snapping shut squirts the other 'bot across the arena like a pumpkin seed! Having only one shot is a problem in a melee fight.

The video files are too big to download. If you really want the video, send me your email and snailmail addresses and I'll see what I can do.

A: We won the televised Robotica competition with our first heavyweight -- Run Amok.

• Robotica Journal
• Run Amok FAQ
• Construction Log
• Competitor Gallery
• More Photos
• Robotica on Video

A: No need - the Team Run Amok website has all the info on our 'bots.

A: Nope. The last POP event was 3,161 miles from our workshop. That's a long way to go for an ant fight.

A: The Twin City MechWars is a great robot combat series! We've never competed at MechWars, but we were able to stop in at a builders' meeting and talk with some of the teams. If we lived closer to Minnesota we'd be regulars.

'Rat Amok' is operational, but has been retired because the servo drive is just too slow to compete with current speedy ants. I keep thinking about a new version with better motors. Maybe someday.

A: A picture and description of 'Rat Amok' is here - larger picture here.

A: We saw a UK antweight tournament at our first trip to Robot Wars in 2001. 'Mini Razor' wasn't there, but the full-size Razor was!

A: Team Run Amok never competed at BattleBots. It was too expensive, too crowded, and I'm told the food wasn't very good. After all the expense of building a 'bot and travelling to the event, half of the 'bots lost in the first round and went home. Pretty small fun.

A: Most schools (mine included) have very little money for such projects. We'll have to keep financing our own robots.

A: Sorry, but we don't use 3D modeling software for our 'bots. Try asking that question at the Delphi Forums RFL discussion.

A: Beats me. I don't.

Mark J. here: People fight robots for all sorts of reasons. Some people like to win matches -- they don't care what design that takes, and wedges are just fine in their book. Some builders just don't think that a wedge is the way robots should fight and like to show off their active weapons. They are embarassed when they lose to a simple but well-built wedge, so they hate wedges. It's all a matter of taste. Build what you like.

A: My favorite part is hanging out in the pits and talking to other builders -- but you gotta build to fight, and you gotta fight to get into the pits. I guess I like it all.

A: My last event was daVinci Days last July (2005). I'm a high school freshman this year and don't have as much spare time as usual, but I plan to be back at daVinci Days again this summer and maybe another event or two.

A: The Ask Aaron site is getting a lot more traffic, but I don't think there's a link between that and combat robots heading back to TV. If there are new robot shows, they aren't going to be like what we've seen before! I promise I'll let you know if producers start calling.

A: None of the classes are pushovers anymore, but the level of destruction seems to go up with the heavier classes. I'd guess that the heavyweights are the most brutal class at the moment, but competition is tough all the way from antweights thru the super-heavys.

A: Tough question. I think the toughest 'bot I ever fought was the beetleweight Trilocity -- a high-power thwackbot. He put some rips in my armor and eventually stuck his axe into my chassis so hard he couldn't get loose. I had enough pushing power to drag him around and get enough points for the win.

A: Zpatula uses a Sozbots dual motor ESC, plus a Team Delta dual-ended R/C switch for the lifter motor. Zpatula isn't based on the small custom-series BattleBot toy chassis, it's built on the larger pro-series chassis, and it uses a modified Biohazard gearbox for the lifter.

A: Could. Won't.

A: The Gap fought two great matches at the 'Oregon Clandestine Street Fight'. You can purchase a video CD of that event at The Run Amok Store or at The Robot Marketplace. The Gap also fought at Robot Wars Extreme Warriors II, but no video of that event is for sale.

I don't know of any fairy or flea matches for sale on video.

A: We were at the Robot Wars Extreme Warriors events in England twice. In 2001 we entered 'Run Away' and made it to the finals in the Tag Team competition with our friends from Team Jawbreaker. In 2002 we returned with 'Run Away' and 'The Gap' and fought in both the main tournament and the Tag Team event. I also got to drive 'Run Away' in the Nickelodeon Robot Wars series filmed in England in 2002.

A: Mark J. here: my retired antweight Rat Amok was made from a genuine Victor rat trap - larger than a mouse trap. The trap mechanism is fully functional and is controlled by a tiny servo that holds the trap open `til the weapon is fired. Rat Amok won the 2002 Western Allied Robotics daVinci Days antweight tournament. The servo drive is too slow to be competitive against faster modern `bots, but I keep thinking about a new, faster version.

Aaron had his own antweight back then called 'Mini Maxbot' that he and I built together. Aaron and Mini Maxbot won the first Antbotica competition in 2004.

A: The funniest robot I ever saw was `Psycho Chicken'. In one match at Robot Wars, it laid an egg that `hatched' into an R/C mini-bot. Funny!

A: I've played quite a bit of 'Robot Arena: Design and Destroy', but my favorite PC robot game is 'Robot Wars - Extreme Destruction'. My dad has a virtual version of our robot 'Run Amok' for Robot Arena. You can download it here: Virtual Run Amok.

A: I like to play with 'Tail Whip' in the lightweight class. With a little practice and strategy, it can be a very effective 'bot. I agree that 'Coal Miner' is the toughest computer 'bot to beat.

For more info on Robot Arena 2, visit the Robot Arena Forum.

A: Our team has both my dad's and my antweights on buildersdb.com -- along with my beetle, dad's hobbyweight, and our two heavyweights. Search for 'Run Amok' as a team name.

We haven't run antweights at an RFL qualifier for a few years now -- but I fought my beetle 'Zpatula' at nationals in 2004. It's ranked in the top 20 historic beetles at botrank.com.

A: Technical question - Mark J. here: I've gone into detail about the design decisions for Run Amok at the Run Amok FAQ page. In short, Run Amok was built for the four challenges in the first season of Robotica: The Speedway, The Maze, The Gauntlet, and The Fight to the Finish (details on the challenges). Tank steered robots have trouble making smooth turns as needed for The Speedway, and many had difficulty climbing ramps in The Maze. Also, a car-style differential as used by Run Amok can deliver a lot of pushing power in poor traction conditions for the Gauntlet.

I knew that the maneuverability of tank steering would be an advantage in The Fight to the Finish, but I wanted my best chance to at least get that far. It all worked out for us!

A: Yep, Zpatula has a lifter with a 4-bar linkage. Zpatula's drive motors are 6 volt Mabuchi 130s -- a Mabuchi 180 powers the lifter.

Q: Don't you think 130s are a bit small for a beetle? I use 300s in my ant. [Alex U., Pittsburgh, PA]

A: Mark J. here: Let me take this one, Aaron.

The maximum amount of drive power you can effectively use in a 'bot is limited by the weight on the drive wheels and the grip of the tires. Additional torque just spins your wheels. You can 'gear up' to trade torque for speed -- but how much speed can you effectively use in a 5 or 6 foot square ant/beetle arena?

Zpatula is 6-wheel drive and can easily spin it's wheels to avoid motor-destroying stall. The twin, mildly over-volted 130 motors give good controllable speed and deliver about 4 watts of power per pound of robot -- just about the same ratio as our Robotica winning heavyweight 'Run Amok'.

People often believe that Team Run Amok's 'bots are underpowered, but we have championships from half the events we've entered. Not many teams can match that record.

A: No question about it, I like heavyweights! There's just something about the noise and feel of two BIG 'bots crashing into each other that you don't get in the lighter classes.

A: Well, homework and my household duties do take a lot of time. When I'd done with them, I decide what I really should be doing -- an hour watching a TV show I don't really care about is an hour I could have been working on a robot, practicing my soccer, or preparing my Yu-Gi-Oh decks. If you really look at what you do with your spare time, you might be surprised at how much you could be doing. Remember to save some time to just kick back!

A: I count seven competition robots in all:

• Rat Amok - antweight combat - retired, but operational;
• Mini Maxbot - antweight combat & Antbotica competitor - operational;
• Mini Maxbot 2 - Antbotica competitor - operational;
• Zpatula - beetleweight combat - operational;
• Nasty Glass of Water - hobbyweight - retired and dismantled;
• Run Amok/Run Away - Heavyweight combat - retired, but operational;
• The Gap - Robot Wars heavyweight - operational.

A: Sure! I play soccer and streetball, I have a weekly Yu-Gi-Oh tournament, and I'm a counselor-in-training at the YMCA camp.

A: All of my 'bots are built for combat or head-to-head competition. No humanoid 'bots -- but I think that 'bots like Robo-One are way cool!

A: By the time we're thru with a robot it's either a champion or a pile of scrap. We don't sell our champions, and nobody would want the pile of scrap.

A: We made lots of friends at Robotica and I don't want to pick out just one 'bot as my favorite. I really liked JuggerBot, Jawbreaker, and Kritical Mass. My dad says he liked Pandora for the cool way the builder used the parts he had available.

A: Propellerhead hit one of The Gap's wheels so hard it broke the gearbox. That was a freak hit and we haven't had any trouble since then, but before The Gap competes again, there will be wheel guards! We have plenty of weight allowance left.

[Drawing of 'Run mok 2' by A.J. Hamilton]

A: Yes! Combat robots are very dangerous -- that's why they usually fight inside bulletproof plastic boxes. Most robot builders have a scar someplace that their robot gave them. You must be very careful when working with rotating weapons, exposed gears and chains, high-pressure pneumatic systems, and heavy 'bots running around at speed.

A: The last match of Robotica happened at about 3 o'clock in the morning. It was a very busy day and I was really tired. The photo was taken in the pits after our win, and I was about half asleep.

A: There are a couple of 'bots I'd like another chance to fight, but not exactly for revenge. Sir Killalot did try to throw us out of the arena for no reason, and I'd love to catch him with his back turned for a little payback. We didn't really have much of a chance to battle with General Chompsalot 'cause we were so badly damaged in an earlier fight -- I'd like to do that again.

Q: But I thought you & General Chompsalot were Tag team terror partners, you've even got his link on your web page. So why do you want to battle him?

A: Yes, the guys on Team Jawbreaker are our friends. They are really nice guys. We met them at Robotica and we were tag team partners at Robot Wars. When we met them in a battle at the next Robot Wars, Run Away had been badly damaged in an earlier match by Destructive Criticism and we just couldn't show off much. General C. even had to grab us and pull us away from the house 'bots to save us!

Fighting robots is fun. You play baseball and football with your friends, so why not battle robots with them?