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3242 Questions and Answers about Combat Robotics
from Team Run Amok

Team Run Amok receives a lot of email asking about the design and operation of combat robots. In 2002 my son and team member Aaron Joerger (now 20) requested a question and answer page to document our responses. Aaron answers most of the questions, but I'll step in if it gets very technical.

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Caution: Even small combat robots can be dangerous! Learn proper construction and safety techniques before attempting to build and operate a combat robot. Do not operate combat robots without proper safeguards.

TopRecent Questions

Q1: Hello Aaron,

Do you have a recommendation for a robot toy or if 'necessary' a kit that simulates robot fighting from tv. I was interested in in the battle bots pro series but I cannot find one for sale any more. -Please Help. Thank you very much!!!

Q1: Regarding my earlier question about the toy, I really would love to get into robot combat. do you know of any robot rumbles in the New York City area? I know this is a hard question, but thank you!

A1: The BattleBots Pro series toys would be by far the best choice to offer a reasonable simulation of robot combat. Anything else is just R/C toys pushing each other around. Of course they are toys and you aren't going to get metal-rending destruction.

Our successful beetleweight lifter 'Zpatula' is a modified BattleBots Pro 'BioHazard' toy. You can still find them from time to time on EBay -- be persistent.

A2: See FAQ #12

Q: i would like to know what circuit board is being used and where do i get the boards found on the picture on the 2.007 Arduino Nano Carrier page. thanks

A: The 'Arduino Nano Carrier' board was a prototyping board developed for a class at MIT. It is not, AFAIK, commercially available. The 'Arduino Nano 3.0' board itself is available thru a link on the page you reference.

Additional questions about Arduino microcontroller should be directed to the Arduino Forum -- it is not a component commonly used in combat robots.

Q: I just thought I'd inform you that Trevor Bommersbach, a member of Team Doall, has recently passed away (obituary).

A: We never met Trevor, but we're always saddened by the loss of a competitor. Our condolences go to his friends and familly.

Q: Is there any particular reason no one's ever used an grinding disk for a weapon?

A: There have been grinders - lightweight 'Grunion' (1 win, 1 loss) fought at the BattleBots 2.0 with a grinding wheel weapon, and 'Zero' ran a milling cutter at Robotica 3. A grinding weapon has several drawbacks: ceramic grinders are fragile, there is small potential for damage, and it's extremely difficult (impossible?) to hold correct position and pressure on your opponent in a chaotic battle arena. I couldn't recommend it.

Q: I want to build a strong wedge bot bot, but I'm stumped on what would be an efficient way to use chains: Lots of small chains like the setups in the Battle Kits and Panzer, or two long chains like that on the UK Feather weight Hunter (Bad example but it's the only one I could think up)?

A: Mark J. here: 'Panzer' and the BattleKits have 'lots of small chains' because their drive systems provide both multi-stage gear reduction and power distribution to the wheels -- something that cannot be done with a single chain. They also have separate chain systems going to each wheel so that no single chain failure will incapacitate the robot. Redundancy is good practice!

Team Hunt's 'Hunter' runs a single-stage gear reduction chain to the back wheel, and a long chain from the back wheel to the front. It is difficult (impossible?) to get adequate reduction in a single-stage chain drive, and if that single chain from the motor to the rear wheel fails they're toast. No redundancy - poor practice.

Of course, you can avoid chains entirely by driving each wheel with a dedicated gearmotor, or reduce chain useage with a gearbox to achieve your torque multiplicaion before transmitting the power to the wheels.

Q: Aaron, I had an idea! Maybe it could be possible to use a actuator that is rated for 100lbs of force on a 6lb mantis crusher! I would not be surprised if it doesn't work, but I at least want to hear your input and corrections.

A: I'd need to know more about the specific actuator you're talking about in order to offer an opinion. See: The Hamburger is Bad.

In general I see two problems:

  1. I don't know of any actuators that are small, light, strong, and fast enough for the purpose; and
  2. The last time I counted there were three active mantisweights, and they were all in Saskatoon.
I'd suggest that you pick a more workable weapon and a more competitive weightclass.

Q: Actually, I am going to the PA Bot Blast and the 6lb class will be there. Or, is it possible to use these on a 12 as well.

A: OK, the FA-150-S-12-3 actuator weighs 2 pounds, is 7.5 inches long (closed), produces a maximum 150 pounds of force, and extends at 0.5 inch per second (at no load -- slower when loaded). You face several problems:

  1. Fitting such a large actuator into a 6-pound robot while orienting the force in a useful manner;
  2. Building a light chassis that can hold up to the force the actuator applies without bucking;
  3. Positioning the jaws someplace where 150 pounds of force will do some damage; and
  4. Holding onto an opponent while your jaws... very... slowly... close... down...
Whether 150 pounds of force will actually damage your opponent is another question. It will depend on the structure of your opponent and where you position your jaws. I'd do some testing on mock robots to see if 150 pounds of force has any real chance of damaging either 6 or 12 pound robots before I committed to a build.

There have been thousands of combat robots built, and exactly one of them was a successful crusher/piercer. Your odds of success aren't good.

A word of warning: all the mantis fights since 2006 have taken place in Canada. The PA Bot Blast may have a mantisweight class, but that doesn't mean that any will show up.

Q: Do you have team site links for wedge of doom, and viscous?

A: See FAQ #30

Q: Do you have any, I mean ANY information on the robot wars 1997 entry land shark?! He's such a creative entry with no info other than a single picture on Team nightmares site!

The Landshark - one loss and gone. A: It's been a while since I did one of these -- hope I remember how... Willis Wong's heavyweight 'The Landshark' fought a single match at U.S. Robot Wars '97 (video) and lost to Vic Lang's 'Z'. Depressed, 'The Landshark' made its way to the center of the Golden Gate Bridge and leapt off - only to land on the deck of a freighter bound for Uruguay. After hitching a ride into Montevideo, 'The Landshark' worked as a caddy at the Punta Carretas golf course for several years and saved every penny until it had enough money to open a frozen yogurt stand. It married a lovely girl named Rosalinda and had four children: a girl, two boys, and a coffee grinder. The family is doing well. See also FAQ #32.

Q: so in other words, you have no

A: I gave you the builder's name, the robot's competition record, and a link to a video. What are you complaining about?

Q: I didn't even think about the video link! thanks man! speaking of Z, can you give me some info on how his weapon worked?

A: No, sorry. It appears to be a one-shot spring loaded spike, but I cannot confirm. Although Vic Lang continued to build robots for entertainment and artistic purposes, 'Z' never fought again and Vic never entered another combat tournament.

Q: Aaron,On the Pro Series Biohazard, I'm hoping to use a brushless system and that the gears already transfering power, would give it torque. Is this possible?

A: I think the hamburger is bad. Do you want to use the brushless motor for the lifter or for the drive? Which motor(s) do you plan to use? Why do you want to use a 'brushless system'?

In general, we recommend brushless motors only for spinner weapon power. We have explained the reasons for that recommendation multiple times -- see FAQ #23.

Q: I was hoping to use some Velineon VXL 380 motor, a hobby grade motor, because it is use to stoppin because of it doesn't need to be in constant movement.(I've had experience with this in my r/c cars) I was prefering to have it as a drivetrain and have the gearsalreadyin the gearbox to gear it down for torque.

A: Mark J. here: the problem with brushless motors in combat robots is not stopping or running at reduced speed at small torque loading -- all brushless motors throttle down perfectly well. The problem comes when the motor must produce a lot of torque at low RPM, like when the robot is pushing hard against another robot. Under those circumstances the motor consumes a great amount of amperage and creates a large amount of internal heat. Hobby brushless motors do not tollerate that type of use -- they melt.

In your proposed useage there are additional problems. Like most hobby motors, only very limited specifications are available for the Velineon VXL. From what I can tell it is a high RPM motor (4000 RPM per volt) that delivers about 40 times(!) the torque available from the FF-050 motor that comes with the BattleBots toy. There just isn't any way to make use of that much power in a small insect class arena -- it would be uncontrollable. It also has a very good chance of destroying the gearbox, which is certainly not designed to handle that much torque.

Aaron's Pro Series BioHazard hack beetleweight 'Zpatula' finished third at the RFL national championships with the stock FF-050 motors, and additional power would not have improved his performance. Motor overkill is not the path to victory. Save your money.

Q: So, I was looking at the "1000 RPM Gearmotors" and the B16 motor sold by Robot Market Place and I noticed they both have the same stats. (930 RPM@ 12volts, 3oz, ect...) Are they the same motor or am I misreading something?

A: Although Kitbots does not give full specs, I believe that the motors themselves are very similar but that the gearboxes are different. The B16 is lighter, and note that Kitbots offers different mounting plates for the B16 and '1000 RPM' motors.

Q: Has there ever been a combat robot with treads and a drum?

A: You're probably thinking of BattleBots middleweight 'El Diablo' (pictured) or its heavyweight stablemate 'El Diablo Grande'. 'El Diablo' (6 wins, 3 losses) was a very popular competitor; one of the R/C BattleBot toys was modeled after it.

Q: Ahh yes, I can't believe I forgot about El diablo! fail on my part. I should say have there been any since his time.

A: None come to mind, but currently lists 4,222 combat robots that have competed in North and South American events, and many more have fought in Europe, Asia, and Australia. I don't claim to know the design details of all of the world's robots.

I will point out that while drum weapons are common, treads are not -- for good reason. Tank treads add weight, complexity, inefficiency, vulnerability, and expense to a robot and return little or no benefit in the typical flat and smooth combat arena. They do, however, look really cool.

Q: What was your favorite bot with treads?

A: I've always been partial to 'Ronin'. Must be the flags.

BattleBots middleweight 'El Diablo'

BattleBots veteran 'Ronin'

Q: I want to use C02 for my robot's flipper. I found what tank (A fire extinguisher) and a ram (A hydraulic cylinder) but I don't know what regulator I need. I know that I know that it needs to be a C02, but there are so many things to note like ones with solenoids, some with strange gages, its all confusing me. Could you at least help me to figure out what would be a good regulator, I can find the rest of the parts myself.

A: Mark J. here: I'll be pleased to help you select a regulator, but I need more information about your robot:

  • In what weight class will you be competing?

  • What are the dimensions (bore and stroke) and pressure rating of your actuator?

  • At what pressure do you want to run the actuator?

A couple of points:
  • Hydraulic cylinders are heavier than standard pneumatic cylinders and are generally used only if you intend to operate the pneumatic system at very high pressure -- such as unregulated CO2.

  • Are you sure you're looking for a regulator? The fact that you mention solenoids makes me suspicious that you're looking at multi-port valves and not regulators. Exactly what function do you want this device to perform?
Read thru the Team DaVinci Pneumatics page to get general information on pneumatic weapon systems and to make sure we're using the same vocabulary.

Q: I'm the flipper guy again, I just want to help out with the question:

  • The weight class is middleweight, but it's flexible enough to be a heavy if it's overweight by a fair margin.

  • The cylinder is a four inch stroke with a 1 1/2" bore, and can go well up to 2500 PSI.

  • 850 PSI.
I know that I could go on with out the regulator, but I REALLY don't want my cylinder to fail.

PS: I already read the DaVinci page many times. I wasn't going to get my head into this with out the know how on to do it.

A: Go back to the Team DaVinci page and read thru the 'What a gas!' section again. Compressed CO2 liquifies and self-regulates its pressure to about 850 PSI at room temperature. The pressure will drop as phase-change thermodynamic effects reduce the temperature of the CO2 remaining in the cylinder. You have no need for a regulator -- the pressure available to your actuator will not exceed 850 PSI.

Please be VERY CARFUL with high-pressure pneumatic systems! They are violent and dangerous. Handle with great care.

Q: Flipper guy once more, thank you for your help.

One last thing, is their any advice you can give with CO2 systems for optimal performance?

A: The flow performance of your valve system is critical for best performance. The flow capacity of a valve is listed as the 'Flow Coefficient' (Cv). Larger values for Cv flow more gas faster and will give better performance. Don't scrimp on the valves!

Q: Would a Fergeli mini actuator be fast enough to be rated as a flipper at a high enough voltage? -Brandon

A: Nope, no way, no how. Speed under load for the fastest Firgelli actuators is well less than one inch per second at rated voltage - a flipper should be minimally a hundred times that fast. You'd be well advised to give up on electric flippers/hammers.

Q: Would they still be useful in lifters in the 12-30lb classes?- Brandon

A: Take a look at the spec sheets on the Firgelli website. The actuators are very small, produce only a pound or two of useable force (1 Newton is approximately equal to 0.22 pound force), and typically extend only a couple of inches. Potentially useful in an insect class robot, but nothing larger.

Wendingo - Team Minus Zero at Robotica. Q: There seems to be a bit of an unspoken rule that bots must have less or equal motors to the amount of wheels a bot has, e.g, two wheels, two motors. Why is this, whats wrong with powering a wheel with two or more motors?

A: Multiple motors per wheel has certainly been done: Team Minus Zero used eight Jensen motors for their four-wheeled Robotica entry 'Wendingo' (pictured), and Banebots offers gearboxes that mount two motors to power a single shaft.

Multiple motors per wheel generally isn't done because it's mechanically simpler to use one motor for the purpose. If you need more power, use a more powerful motor. Keep it simple.

Q: how do i get an axe weapon for my beetleweight robot?

A: You build one. We give short answers here - you need a book. Suggest you browse the Team Rum Amok Book Review page.

Q: Hey do you have any good ideas for painting easter eggs? happy Easter!!

A: Krylon gives a nice, shiny result. Don't eat them.

Q: are the replacable treads sold by vex a good tank treads for sumo robot?

A: Not for serious competition. Sumo is all about traction, and while the VEX upgrade tank treads offer improved traction over the stock VEX treads they fall well short of the grip available from custom polyurethane or silicone rubber tires/treads used by serious sumo competitors.

See the previous post about sumo robots for more info on traction.

Q: I mean the treads used on the IFI wheels. Are they suitable for use as sumo robot tank treads?

A: Too 'stretchy' - treads need dimensional stability to prevent distortion under load. Tank treads, by the way, need to be well supported along their entire contact length to be effective. If you just have a floppy tread between the two end sprockets you aren't gaining any traction.

Q: Could you recommend one tank treads for a full size sumo robots?

A: I don't compete in sumo, so I'm not current on components, but I don't know of any off-the-shelf tank treads that would be competitive.

I can recommend that you find a copy of Robot Sumo: The Official Guide by Pete Miles at your local library and read it. Like I said, serious sumo competitors make their own tires/treads. Pete's book give tips on how to do that and on how to modify available components to make them more competitive.

Simple pneumatic lifter Q: How do you articulate lifter forks like the ones on Vlad The Impaler?

A: Vlad had a very simple single-pivot lifter hinged low toward the back of the chassis. I don't have a photo of Vlad's actual mechanism, but it must have looked something like the sketch at right.

Rental robot Q: What do you think of RoboGladiators?

A: Mark J. here: quite a few attempts have been made to commercialize robot combat: The Lazy Toad Robot Club and Grill, SlamBot, and Battle Ratz come to mind. None have been particularly successful. If it was still 2001 this could be 'hot', but I'm pretty sure that there isn't enough interest in 'fighting robot birthday parties' for 7 to 11 year-old boys to make any money these days. There's a lot of time, work, and overhead for the price they charge - but I'm glad they're doing it.

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