A: [Mark J.] By Grabthar's hammer, everybody knows who the best and most effective robot is. Now please, never mention 'Moist Pony' again.

Q: What do you think of brush wheels for antweights? Too flimsy? [Syracuse, New York]

A: [Mark J.] Are we talking 'bristlebots'? Calling them 'brush wheels' is misleading -- wheels spin, bristle brushes just hop up and down.

Combat bristlebots like 'Vibrant' are novelties: poor speed, awful pushing power, no reverse. What part of that do you like? Some builders enjoy making weird 'bots just to be different. Avoid if you're trying to win.

Q: Would an HDPE unibody work for a beetle wedge if it was protected by grade 5 titanium plates? I was hoping the unibody would work as a sort of shock absorber to protect against high energy spinners. [Oak Harbor, Washington]

A: [Mark J.] Polyethylene unibodies are common and successful in insect class combat robots, but UHMW polyethylene is preferable to HD. An image search for 'UHMW beetle robot' will provide many examples. No metal cladding is needed -- save the grade 5 titanium for your wedge.

Please share any comments or critiques you have in regards to both designs! Thanks again! [Jacksonville, Illinois]

A: [Mark J.] I don't split comments across 'Ask Aaron' and other forums/venues. If you ask a question here I will comment here. If you post on the Facebook Combat Robotics group I may comment there. However, I will not comment here on an active discussion elsewhere, and I will not link to an active forum thread.

If you want my opinion, ask here. If you want a grab bag of forum comments, ask there.

Q: OK, Mark! RESET I have a question regarding a featherweight lifter.

I wanna note that I would've built a wedge as a featherweight, but EOH requires a weapon that's at least 6 pounds in order to qualify unless the design is approved with a weapon that's less than that.

I was planning on using a 182:1 gearbox and a Banebots 775 motor for the lifter. However, I've come across a big thing in regards to their designs. One of them is inspired by 'DUCK!', with a short, beefy lifter on the front while the other is based off of the UK heavyweight 'Shockwave', with a lifter that can rotate 360 degrees around itself. I'd assume that one version is better at doing something than another, I just wouldn't happen to know what that is.

• What are the pros and cons to both designs?
• What kinds of problems might be encountered with each weapon design?

A: [Mark J.] How did you decide on a 182:1 gear ratio for your lifter before you settled on a lifter design? The gear ratio determines the torque available to the lifter, and the torque required for a simple lever-arm lifter depends on the length of the arm from axle to tip. Examples:

• A featherweight lifter with a one-foot lifter arm will require one foot * 30 pounds = 30 foot-pounds of torque to offset the weight of a featherweight opponent and start to lift it. I recommend gearing for twice that level of torque to allow the lifter motor to quickly lift that amount of weight: 60 foot-pounds of torque. A 12 volt BaneBots 775 motor delivers 61 ounce-inches of stall torque at its rated voltage; 61 in-oz = 0.18 ft-lb. That makes the required gear reduction = (1 foot * 60 pounds) / 0.18 foot-pounds = 333:1.
• Shortening the lifter arm length to half-a-foot reduces the torque requirement and required gear reduction by half: 30 foot-pounds, achieveable with a 167:1 ratio gearbox.
• Shortening the lifter arm farther to a 'Feather Duck!' range quarter-foot reduces the torque requirement and required gear reduction by a factor of four: 15 foot-pounds with an 83:1 ratio gearbox. Maybe even less because such a short lifter can really only hope to lift one end of your opponent.

Q: I want to build a switch! I'm looking at Team Whyachi's pictures and drawings on their website, and I'm confused as to how how they're able to use a metal socket screw to close the circuit. Even if there was a nylon washer separating the cap from the copper "bridge" and the two contacts, wouldn't the thread/screw body still touch and you'd get shocked if using a metal allen key? And how do they know how many turns it takes for full contact without overtightening the screw? [New York, New York]

A: [Mark J.] The Whyachi switch socket screw is completely isolated from the electrical circuit by a nylon 'top hat' grommet that extends thru the contact bar hole. The screw is isolated only to prevent the Allen wrench from accidentally shorting to another exposed electrical component. Direct current at normal robot-level voltages will not give you a 'shock' on touching a terminal -- you won't even feel it.

The Whyachi switch uses spring pressure to make contact, not screw pressure.

• Tightening the screw pulls the contact bar down against spring pressure to break contact;
• Loosening the screw allows the contact bar to rise up by spring pressure to make contact.
• 'Four turns' is a recommendation, not an absolute.

Take a look at Charles Guan's 'Overhaul 2' Build Log - Part 9 for details on the simple and compact switches he made for the purpose. Search that page for 'master power'. Keep it simple.

A: [Mark J.] I don't know '@the_guy_who_has_a_robot' and he apparently does not know what we do here. From the Ask Aaron mission statement:

Q: I am '@the_guy_who_has_a_robot' and I would like to apologize. I told the guy who had a question about the mono tooth spinner to go to you if with his question. I didn’t know how to awnser it and I told him about you. I told him to give him lots of details. Not to ask you to make it. I apologize. Please accept my apology [Omaha, Nebraska]

A: Thanks for the explanation, Omaha. Getting caught in the middle requires no apology.

David Rush [Livermore, CA]

A: [Mark J.] OK, let's get theoretical. A spinner weapon needs a combination of things to land a powerful impact:

1. good 'bite';
2. high kinetic energy; and
3. unyielding impact surfaces.

Granted, your opponent is not made of melon -- but the various materials from which they are made can and will absorb energy by deformation. If you're trying for localized damage by tearing into your opponent to grab or rip away material, a small and possibly sharpened impactor will serve that purpose. If you're trying to 'swat' your opponent and send it flying with as much energy transfer as you can manage, a large impactor area will minimize localized deformational energy dispersion and transfer more of the kinetic energy to your opponent as a whole.

A: [Mark J.] What would I suggest? I'd suggest that you attend combat robot competitions and talk with event organizers until you no longer need to ask me to sumarize in a couple of paragraphs everything you need to know to put on a safe and well-run competition.

Unwilling to do that? Head over to SPARC: Standardized Procedures for the Advancement of Robotic Combat and read every word in their 'Event Resources' section - top of page on the right. The last item in their event resouces section is the 'SPARC Arena Construction Best Practices' which provides construction considerations, cost estimates, material recommendations, and example arena photos.

Check local plastics suppliers for polycarbonate ("Lexan") sheet. If you cannot source locally, a quick web search will turn up multiple suppliers -- but shipping on large sheets can get expensive.

As an off-topic question, if using two motors has any advantage, would using two Banebots gearboxes with 64:1 ratios be a good option, or would they be too weak for a decent lifter? [Close to Champaign, Illinois]

A: [Mark J.] Don't confuse 'power' and 'torque', Champaign. Mechanical power is expressed as rotational force (torque) multiplied by its rotational speed (RPM). A reduction gearbox will increase output torque and decrease speed in equal measure -- there is no increase in 'power' regardless of the gear ratio.

Why use two gearboxes/motors rather than one gearbox with a motor twice as powerful? Electric lifter weapons require a great deal of torque, but there is a limit to how much torque a given gearbox can handle without destroying itself. BaneBots gives this warning for their P60 gearboxes in all ratios:

The suitability of any gearbox or gearbox pair requires analysis of the loads that will be placed on the gearbox shaft(s) by your specific lifter design. I can't make a general comment about specific gearboxes without knowing much more about the lifter design. Several posts in the Ask Aaron Robot Weapons archive give examples of lifter analysis -- search there for "calculate how much torque" for a start.

A: [Mark J.] I'm reluctant to discuss my travels. I don't even tell Google.

A: [Mark J.] Yes, you can turn the 4:1 P60 into a 5:1 P60. Parts cost is about $25 - shipped.

• Replace the 4:1 planet carrier output plate with a 5:1 planet carrier output plate.
• Replace the four 15-tooth planetary gears with four 17-tooth planetary gears.
• Replace the 4:1 (15-tooth) pinion gear on your motor with an 5:1 (11-tooth) pinion in your shaft size.

Q: Apparently there is no 5:1 pinion for a 5mm shaft, Any ideas?

A: A few...

1. Scour the 'net for a gear with these specs:

   Number Teeth:	11
   Gear Specs:	0.6 Modulus, 20 Pressure Angle
   Installation:	Interference (press) fit
   Bore:	5 mm

2. Make friends with a good machinist willing to bore out a 3.2mm pinion to 5mm.
3. Drive over to your local R/C hobby shop and dig thru their gear bins.
4. Switch to a VEXpro gearbox.

A: [Mark J.] The only '3-volt' gearmotors I know of are made by Tamiya, and they are not nearly strong enough for the current level of robot combat. The motors are weak, the plastic gearboxes shatter, and the skinny little axles bend. Worse, I don't know of any electronic speed controllers that will work from a 3 volt power supply -- most won't operate below 6.5 volts. You'd be well advised to dump those motors and go with something more commonly used in combat robots.

If you insist on running Tamiya gearmotors, or if you've got a motor I don't know about, you can use a 4-cell LiPo battery (14.8 volts) and program your radio transmitter to limit the drive motor controller output to a maximum 25% of full throttle -- effectively limiting motor voltage. Twenty years ago we ran Tamiya motors at more than 7 volts without trouble; if you're afraid of burning up drive motors you're in the wrong sport.

You'll need an R/C transmitter that has 'Adjustable Travel Volume' (ATV), sometimes called 'Travel Adjustment'; check your radio manual. Most combat-capable radios have this feature. Set the travel volume on the drive train throttle and turning channels to 25%, and leave the weapon channel at 100% so your brushless weapon motor will get the full 14.8 volts. This technique is a little hard on the drive motor controllers, but those Tamiya motors draw so little power that it won't be an issue.

I'd much rather see you get proper drive motors and a weapon motor that can all run on at the same voltage -- they're certainly available.

Q: Hi Mark, Had a conceptual question about impactors on horizontal spinners. Traditionally, the inserts come to a triangle point with the hypotenuse facing bot. Is there any sense in making a vertical ramp impactor to get under opponents instead of a straight line to hit anywhere in the height of the weapon?

Many Thanks. [Pittsburgh, Pennsylvania]

A: [Mark J.] I'm confused by your question. I'm not sure why you'd want to use a horizontal spinner to try to 'get under' your opponent when the weapon is designed to tear them apart. If you want to get under them, build a wedge.

The impactors and inserts I typically see on horizontal spinner weapons are typically flat, hardened, vertical surfaces designed to transfer destructive impact energy against an opponent's hard surfaces. Some spinners have special blades with sharp leading edges to swap-in against softer-armored opponents, but hitting a hardened surface with a sharp blade blunts it immediately. See the comparison of 'Tombstone' bar weapons at right.

For a reader question (now in our Ants, Beetles, and Fairies archive) I asked builder Jamison Go why he sometimes replaces the single-tooth disk (STD) with a saw-edged impactor in his beetleweight horizontal spinner 'Silent Spring'. His answer:

Everyone is hype about single tooth blades for "bite" but why? What does bite actually do for you? It is heavier engagement on a piece of material which is arguably more energy dissipated just because it has nowhere to go. What if the opponent has no such grabbable surfaces? Say for example, a robot made of rubber or foam? The traditional STD would be ineffective unless sharpened every match and even then its likely only good to the first few hits because it is THE singular wear point. The saw-blade is for whittling opponents who have only compliant armor or soft things at the hitting surface. Instead of going for one big impact which would normally be absorbed, I flake material away at a high rate. What happens is I end up grabbing the same amount, but only after several milliseconds of tearing deep into them. [My opponent was going to] use his over undercutter attachment which meant the only hitable surfaces were his wheels, hence the decision for that type of blade.

A: [Mark J.] Thanks for the 'Run Amok' shout-out, Massachusetts.

There have been several multi-spinner combat robots, but the spinners are usually located on opposite ends of the 'bot. A current example of that design is BattleBot 'Rotator', armed with large independent horizontal disks on front and back. The flaw in this design is that only one of the two disks can impact your opponent at a time, limiting the damage the system can inflict.

An alternative twin-spinner system design is employed by 2018 BattleBots competitor 'Double Dutch'. Their design features counter-rotating bar spinners placed above and below the robot body. The two bars are powered by a single electric motor. Although both weapon bars can attack an opponent at the same time, it's likely that one bar with strike before the other and throw the opponent clear before the second bar can impact. Almost certainly the two potential weapon impacts will strike different locations on the opponent, which will also limit their effectiveness.

A different double-spinner approach is seen in antweight 'Not So Free Hugs' which has twin saw blades on articulated arms. The idea here is not impact damage but the ability to trap and saw into soft wheels or plastic side armor. Here the ability to access different locations on the opponent is a benefit as it gives a greater chance to find something vulnerable to saw damage.

You'll note that all of these designs are horizontal spinners, and that none of them are terribly successful. The potential benefits of multiple vertical drums or disks are even more difficult to imagine. Why bother with three small independent disks and three small motors when you can have one larger drum and a large motor three times as powerful? A hit anywhere on the drum would transfer full impact energy to the opponent, whereas a less-than-perfectly-aligned hit from a triple disk might only transfer impact energy from one of the disks. Sorry, but I'm seeing added weapon complexity and weight with no real advantage. Simple robots win.

A: [Mark J.] There are two broad types of brushless motor design:

• Outrunners have a stationary core (stator) and a magnet-lined 'can' (rotor) that spins around the outside.
• Inrunners have a stationary outer 'can' like a brushed motor with a spinning magnet rotor inside.

By the time you get up to heavyweight 'bots, the outrunner motor styles have disappeared and everyone uses inrunners if they're using brushless.

A: [Mark J.] Yes, with a little added hardware. Your Quantum radio, like most pistol-grip R/C systems does not have the 'mixing' capability to to control a robot. Your steering 'wheel' (radio channel 1) controls your steering servo servo to point your front wheels, and your throttle 'trigger' (radio channel 2) controls the motor speed controller for forward/reverse motion. To control a 'tank-steer' robot the control channels must be 'mixed' to each control the motor(s) on each side of the robot, but in different ways:

• The 'trigger' must instruct both motor controllers to respond together to move the robot forward/reverse; and
• The 'wheel' must instruct the motor controllers to respond in opposite directions to turn the robot.

A: [Mark J.] Machine screws / bolts are designed and rated to resist a 'pull' force that is tested by a machine that applies a gradually increasing force. That type of strength is important in many applications, but it is not the type of load fasteners will face when holding combat robot armor. Forces encountered in combat are typically sudden 'shock' loads that may have a high 'shear loading' factor. Ideally, mounting should be designed to prevent shear load on bolts, but combat impact vectors are unpredictable -- you need to design for all possible loads.

The desired material and temper of the bolts depends a great deal on the armor mounting style, but there are some general considerations. Grade 8 bolts are strong, but their added hardness results in a lack of 'toughness' needed to survive shock loads. Stainless steel fasteners have much greater toughness, but are not nearly as strong overall. Titanium falls in between, but the added expense and bother far outweigh any advantage. What you most commonly see in use are standard grade 5 steel bolts: greater strength than stainless and greater toughness than grade 8. The loss of strength can be made up by adding a few extra bolts. If your bolt heads are exposed to possible spinner attack, you'll want to countersink the heads to prevent the spinner from grabbing exposed 'spinner bait' and tossing your 'bot and/or shearing the bolt heads.

Need more info on machine screws? Curious Inventor: All about screws.

You might also be interested in searching the Ask Aaron Materials and Components archive for 'shock mount'.

Thanks again! [Jacksonville, Illinois]

A: [Mark J.] By the numbers...

1. If you're driving front/rear wheels of different diameters, the front/rear sprockets/pulleys should be in the same proportional diameters as the wheels to avoid wasteful tire 'scrub'. In your example:
   • The front wheels are 4" diameter with 3" sprockets, making the sprockets 75% of the wheel diameter.
   • The rear wheels are 3" diameter, so their sprockets should also be 75% of their diameter: 3" * 75% = 2.25".
   If the proportions of the wheels and sprockets are correct on front and rear, entering the gear reduction for either set of sprockets and tire diameters into the Tentacle Calculator will give the correct result.
2. I'll tell you what the speed of a shufflebot is - it's too damned slow. The faster you try to go the bouncier it gets. At speed you spend as much time with the shufflepods in the air as on the ground and a lot of the drive energy goes into making the whole robot shake. Think 'robot with hexagonal wheels'.

   If you want an estimate from the Tentacle calculator of how fast it would be going if it wasn't hopping, double the offset distance for a lobe on the shufflepod cam and enter that value as the 'wheel' diameter. But seriously...

Thanks again for all your help! The bot is coming together nicely and I've registered for the Robothon in Seattle in October. [Mark from Vancouver]

A: [Mark J.] How much extra salt should you shake onto your hamburger? Some need a little, some need a lot, some have too much already.

Charles Guan is an MIT engineer who designs and manufactures ESCs in his spare time 'cause he thinks it's fun. He absolutely knows what he's doing. If you're not a electrical engineering graduate of a respected school you're likely gonna to do as much harm as good by tinkering with the components of a complex digital electronic device.

That said, the little brushless ESCs robot builders 'borrow' from the hobby R/C aircraft industry are designed for very different performance targets than we expect from them in our applications. Bumping up the voltage rating of the filter capacitors will do no harm and may provide some level of extra reliability.

Blindly increasing the capacitance is another matter. I'm pretty sure that Charles Guan had his drive system fully instrumented and was watching voltage spikes on a oscilloscope as he changed the capacitor values. Simply pouring in more capacitance is shooting in the dark.

A drive motor ESC sees a lot of high-load/low-speed action that can benefit from added capacitance, but a spinner weapon ESC operates much closer to the propeller-spinning job for which the unit was designed. I'd suggest keeping the factory capacitance value as-is unless you discover a specific reliability problem as too much capacitance can adversely effect high-speed operation. If you really want to tinker, keep the increase to no more than double the original value. I suspect that most spinner ESCs fail for reasons that more capacitance isn't going to overcome.

P.S. - I'm happy to hear that your build is going well and that you're registered for Robothon - that's a great event. Say 'hi' to the Seattle crowd for me.

Have you heard of this method, or do you know of any teams who have tried this? Would it be effective for a bar spinner? I think I'm going to give it a shot, unless I hear a good reason not to. [Mark from Vancouver - again]

A: [Mark J.] What do the things in this list have in common?

Your insight and experience is much appreciated. [Pittsburgh, Pennsylvania]

A: [Mark J.] You're asking about very popular design topics. A search of the Ask Aaron Combat Robot Design archive yields 127 hits for 'traction' and 128 hits for 'pushing'. The Ask Aaron Robot Motors and Controllers archive has dozens of posts about using brushless motors for robot drive systems -- and there are several on this page.

Here are some quick topic highlights -- search thru the archives for details:

• Brushless motors mated to assorted planetary gearboxes are VERY popular in sublight robot classes. There are plenty of examples and build logs to provide guidance, as well as many posts in the Ask Aaron archives.
• Using brushless drive motors is much more complex than using brushed drive motors. Hobby grade brushless motors and controllers are borrowed from the R/C model aircraft industry and are made to spin lightweight propellers -- not push heavy robots. Getting the motor controllers repurposed to do this work is complex and often frustrating.
• Torque is only useful to the point where the tires 'break traction' and start to slip. Torque past that point does not significantly add to pushing power. The Tentacle Drivetrain Calculator is invaluable in designing a robot drivetrain for pushing power -- if you're using brushed motors. Click its 'Help' button for details.
• The high performance AmpFlow motors are needlessly heavy for a 15-pound robot. You can get all the torque you need from much smaller/lighter motors. Want more torque? Increase the gearbox reduction ratio and/or go with smaller diameter tires to trade speed for torque.
• For maximum pushing power get as much of your robot weight as possible onto your powered wheels. A 4-wheel drive robot with all the robot weight supported by driven wheels is a great start. Two-wheeled robot? The RioBots combat tutorial has a section on calculating center of gravity placement for 2-wheel robots to get optimum traction.
• Want to win a pushing match? Get a wedge or lifter under your opponent to take weight off their drive wheels and put that weight onto your drive wheels.
• Soft 'sticky' tires have better traction than hard tires when clean, but 'sticky' tires collect a lot of grit and dirt from the arena surface which eliminates their traction advantage. Cutting a tread helps tires shed grit and oil, but if your tires are super sticky you're fighting a losing battle.
• Foam tires are soft but aren' great for traction. They can be coated with liquid latex or silicone sealant to improve their grip.
• You can GREATLY improve traction with magnetic downforce -- if the arena surface is magnetic, and if the event allows such designs. You can also boost traction with vacuum fans. Search the design archive for 'vacuum'. While you're there, search for 'sumo'.

Thanks! [Utrecht, Netherlands]

A: [Mark J.] It's very difficult to model the speed of pneumatic systems, in part because of the interaction of multiple system elements on gas flow and in part because of the compressible nature of gasses. Ultimate force is easy, but actuator motion starts as the pressure first builds past the force preventing system movement and may be complete before the force even approaches full theoretical force.

You can find a discussion of factors effecting pneumatic system speed at the Machine Design: Pneumatic Speed page, and you can poke thru the Team Run Amok: Pneumatic Tricks page for tips on improving speed.

In wildly over-simplified terms both your speed and force are related to the cross-sectional area of the actuator bore: double the area = double the force and double the time to extend.

A: [Mark J.] The Team Tentacle Torque/Amp-Hour calculator was designed for brushed motors and assumes an inverse linear relationship between motor speed and torque. Common hobby brushless motors do not have that speed/torque relationship, and the entire concept of brushless 'stall torque' doesn't really make sense. To further complicate the issue, the torque curve of a brushless motor is highly dependent on motor controller firmware and on the specific user-adjustable firmware settings. The Tentacle calculator is nearly useless for designing a brushless drive train.

See what successful bots in your weight class are using for brushless drive motors, gearboxes, ESCs, and (importantly) controller firmware/settings. In general you'll find motors with high Kv constants, high reduction ratio gearboxes, and controllers flashed with SimonK or maybe BLHeli firmware. Brushless is a whole lot more complex than brushed drive, and I'd strongly recommend that you start with a proven combination. Experiment after you have a working drive train.

Q: Great site! I'm getting a lot of good info as my son and I are building a beetleweight.

He wants to use a pistol-grip style radio, we're looking at the Spektrum DX5C with the SRS6000 receiver due to its built-in gyro. My concern is that it only lists a failsafe on the throttle channel. I see that some of the Spektrum receivers have the (sometimes undocumented) ability to switch to a mode where all of the channels will fail in the bind position if you bind it the right way, but I have not found any info on this receiver yet.

Looking through the radio archives, you have a lot of suggestions for radios/receivers with good (or at least passable) failsafe capabilities. However, when I search for them they seem to all be coming up as "discontinued" items. Do you have any suggestions for current receivers, or know of a good list somewhere? [Fredericksburg, Virginia]

A: [Mark J.] Well, now you've opened up the jumbo can-o-worms. Where to start...

Combat robots 'borrow' most of their R/C gear from model aircraft because their control needs are the closest to those of our machines. Better than 90% of the transmitters you see at tournaments are twin-stick aircraft units. A fair number of novice builders decide that pistol-grip or gamepad-style transmitters would suit them better because they are familiar with their use in R/C cars or gaming. The great majority of those builders soon realize that combat robots have much different control requirements than cars or games and quickly switch to twin-stick. I strongly suggest that you skip over the "this doesn't work as well as I thought it would" stage and buy a twin-stick radio to start, if only for the much greater selection and the much larger support base from other builders.

Radio gear has been changing at a ridiculous rate since Chinese manufacturers jumped into the game headfirst a few years back. New transmission protocols, open-source firmware, onboard serial networks... which is why all the receivers you've found in the radio archives are outdated and no longer in production. Our robots don't really need all this new fancy stuff that's aimed mostly at the drone market, but we make up such a tiny portion of R/C gear sales that we have to go along with whatever happens in the larger industry.

The upside of the Chinese R/C takeover is a stupendous drop in prices. The downside... well there are several downsides:

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• Unreadable Documentation The quality and completeness of the manuals for Chinese R/C systems is truly awful. Here's an actual quote from one:
  The time-recorder is used calculating comparable bo stipulated time unexpectedly, or the possible time of flight under the state that the fuel fill it up with, it is very convenient. The pattern of the timer-recorder is the count-down. Pour time-recorder from set for time is it is it count to change, show surplus time at interface to begin.
  I recommend downloading the manual for any radio you consider purchasing to see if you can make any sense of it -- before you buy. I also recommend going with a system that is in use by a large number of combat robot builders, so that you have a knowledge base to tap when you realize the manual doesn't cover what you're trying to do.
• Factory Support There isn't any. That's why you need your friendly knowledge base.
• Initial Quality When you're paying $50 for a radio system with features that would have cost you $350 fifteen years ago, something's gotta give. The feel is cheap, the switches and gimbals wear out, and sometimes it doesn't work right out of the box. At these prices, you just go buy another one. Some are better than others.
• Unreadable Documentation I know I already mentioned this, but it's so bad I wanted to put it in twice.

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Alright, so what do I recommend? I personally prefer Futaba radio gear such as the '6J' for high quality and excellent manuals -- but they are not widely used in robot combat so a new user would not have the knowledge base of established users they might need. Consider one of these:

Flysky FS-i6 Probably the most common system in use in robot combat, and certainly a good choice for a first system. Comes with a very useable receiver that fully failsafes on all channels, with a wide variety of specialized receivers available should the need arise.

Taranis Q X7 A very sexy system widely used in robot combat. Better than usual quality, looks great, but it's a complex radio that will intimidate novice builders. Does not come with a receiver, but multiple full-featured receivers are available.

A quick word about 'failsafe' As fully discussed in the Robot Combat Radio Guide, there are at least three different things a receiver can do to on signal loss that qualify as a 'failsafe'. Some of these are suitable for robot combat, and some are not. Make sure you understand the differences.

One last thing I don't recommend receivers with built-in gyros. A gyro has to be specifically oriented within the robot relative to 'up' and 'forward'. This can make fitting your receiver-gyro unit into a small robot awkward. Robots also have special requirements for gyro shut-off when the robot happens to be inverted that a receiver-gyro combo is unlikely to provide. I you want a gyro, get a stand-alone unit.

Sorry for the long and rambling answer, but I did warn you that this is a big can of worms. If you'd like to hear other opinions on this subject there is an active 'Combat Robotics' group on Facebook that would love to give you a full spectrum of opinion -- and then some.

We welcome combat robot questions. Please search the Ask Aaron Archives first to see if we've already answered your question. Recent Q&A are posted above. Type your question in the box, attach file if needed, then click: 'Send' Attachment (optional): or Why is there a 'Cheerleader' button?

Thousands more robot combat questions and answers in the searchable Ask Aaron archives.

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Copyright 2009, 2018 by Mark Joerger All rights reserved.

how to design and build a battlebot

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