A: Take a look at the Wikipedia article on Robot Combat for a good summary of the subject.

Q: Are they dangerous?

A: Dangerous? They fight in arenas behind inch-thick ballistic plastic. They can throw each other 15 feet in the air and tear titanium sheet in half. Their weapons carry more energy than half a dozen AK-47 bullets. Yes, dangerous.

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 our Book Review Page for some specific recommendations.

• You can get a step-by-step construction lesson from the 'Build a Robot' page at coolrobots.com [archived].

• Take a look at the archive to get some more ideas.

A: Whatever money you can afford and then some, all of your spare time plus any extra time you can steal, several personal relationships, and a chunk of your sanity.

Q: How can I get a sponsor?

A: If you don't have a rich uncle you're not gonna get a sponsor.

Q: How did you do all these things?

A: one thing at a time, with a lot of mistakes along the way.

A: We're happy to answer specific questions about robot design, construction, and materials, but we're not going to design your robot for you.

• Answers to a wide range of design questions plus tools to help with other design considerations can be found in the Ask Aaron Archives.

• Read thru the archives, do your homework, and come back to us with specific questions that haven't already been answered in the archives.

• When you do come back with a question, please give us enough information about your design and requirements to have a chance at giving you a useful answer.

A: Study the rules, learn what you can from the internet, watch a live competition, and ask specific questions of the builders. Check out the library and bookstores for help on building robots, too. Amazon.com has many robot books.

Q: What is the best weight class for a beginner to start in?

A: Scout the event you plan to enter and find out what weight classes are popular. It doesn't do any good to build a robot for a class that doesn't have anyone else in it! Start in the lightest weight class that has a good number of competitors. The lighter your weight class, the less your beginner's mistakes will cost you.

A: For European events try the FRA Forum.

For current North American events try the Robot Fighting League Forum.

A: Robot 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.

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: Use the search function in your browser to search a specific page: hit CTRL-F to bring up a page search box.

A: Questions submitted to 'Ask Aaron' all come in from the same webmail address. We can trace them to their source if we have a reason, but if you don't identify yourself as 'the guy who asked the titanium question' we may not figure out that your question was a follow-on. Our psychic abilities are weak.

A: Send it in thru the website, include your email address, and mark it 'CONFIDENTIAL'. I'll keep it between us.

A: Check the Robot Fighting League Events Calendar and the Builders Database for events in the US and Canada. For British events, try The Fighting Robot Association. There are also robot combat tournaments in Australia, and Brazil. Just because they aren't on TV doesn't mean they don't exist -- get out and participate!

A: The Team Run Amok video library contains complete recordings of every nationally televised combat robot event. We respect and honor the rights of the copyright holder for these programs. We will not place copyrighted video on the internet without permission and we do not support the efforts of those that do.

A: We get variations on this question a lot. 'Ask Aaron' is not a fanboy site -- see our mission statement at the bottom of this page.

A: Mark J. here: no, but the rumor will not die. Here's what happened: during the 2002 Superbowl the Anhauser-Busch company aired a humorous Bud Light commercial that featured fictional combat robots. The robot combat community thought it was great. BattleBots, however, thought it infringed on their copyrights and filed a lawsuit. The court ruled in July of 2004 that the commerical was a fair-use parody of robot combat and dismissed the suit.

BattleBot's action in filing the lawsuit may have damaged their reputation and injured combat robotics in a way that contributed to the show's demise, but there is nothing to suggest that Anhauser-Busch extorted Comedy Central into cancelling the TV show.

A: 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.

Q: OK, where can I buy good parts to build a combat robot?

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: We aren't an engineering service. Even if we were, no competent engineer would spec material or thickness before knowing a great deal more about the design than you have told us. We do provide some advice and guidance on materials in our Armor Guide. Look to see what other builders with similar designs are using and learn from their experience. If it breaks, make it stronger.

A: Radio System Requirements from the RFL 2010 Rules.
Check with the event organizer for any variation in these requirements.

Robots with passive weapons	Minimum 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 or Digital 900 MHz/2.4 GHz Required	YES	---

Robots with active weapons	Minimum 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 or Digital 900 MHz/2.4 GHz Required	YES	YES
30 pound & up	Coded FM or Digital 900 MHz/2.4 GHz Required	YES	YES

A: 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. Check out our Beginners Guide to Combat Robot Gyros.

A: The motors you will need depend on the style of 'bot you're planning to build and your expectations. A 'bot with a massive weapon that just needs to push itself around the arena will need a lot less drive power than a ramming brick or wedge. It comes down to matching the power-to-weight ratio of your 'bot to the type of attack strategy you're planning.

Some maniac builders pack as much as 40 watts per pound into their 'bots, but there really are limits to how much power can be used in a small arena. I've built three champion robots on the 4 watts per pound formula, so please don't tell me that it can't be done.

You'll find the Team Tentacle Torque & Amp-Hour Calculator very useful in selecting motors for your robot. It has data on all popular motors and will quickly calculate the performance of your robot with any motors, gearing, and wheel size you choose. Aim for a drivetrain design that will break the driven wheels free [the 'Amps (per motor) to spin wheels' figure from the Tentacle calculator] at about half the stall amperage of the motor.

Q: What Electronic Speed Controller (ESC) should I use?

A: Once you have settled on motors and drivetrain details, the Team Tentacle Torque & Amp-Hour Calculator will calculate the peak amperage the drive motors can consume with the robot pushing at full throttle against an immoveable object [Amps (per motor) to spin wheels]. Use that number to select an ESC with suitable capacity. Give yourself a little extra capacity (~20%) to allow for unexpected conditions.

A: If a motor supplier does not provide output power specifications for their motors, you can get an approximation of output power with the following formula:

Brushless motors do not generally provide stall amperage figures. You can calculate stall amperage with the following formula:

A: A brushed permanent magnet direct current (PMDC) motor has a rotating 'armature' of wire coils, typically wound around iron pole cores. The armature is positioned in a field generated by stationary permanent magnets. Electrical power is transferred to and correctly switched between the armature windings as they rotate by stationary brushes pressing against a set of contacts on the armature (the 'commutator'). There is a good diagram at Wikipedia: DC Motors. The brushes sliding across the commutator create friction, wear, and inefficiency.

A brushless PMDC motor has stationary wire coils and rotating permanent magnets. Since the coils are stationary, sliding brushes and commutator are not required -- however, the switching of electrical power to the correct coil windings must be handled by an 'intelligent' motor controller that senses the position of the rotating permanent magnet field.

If the rotating magnets are outside the wire coils, the motor is an 'outrunner' or 'rotating can' design. If the rotating magnets are surrounded by the wire coils, it is called an 'inrunner'.

Q: Should I use a brushed or brushless motor for my robot?

A: Hobby brushless motors are generally designed for model aircraft or R/C racecars. They pack a great deal of power into a package smaller and lighter than comparably powerful brushed motors. They are able to do this only by operating high up in their RPM range in their peak efficiency zone.

Combat Robots typically spend a good portion of their matches pushing hard with their tires spinning and the motors bogged down well into the mid to low RPM range. Under these conditions brushless motors will rapidly overheat and 'melt down' due to their low mass and the small cooling surface area provided by their diminutive size. In general, we consider brushless motors to be unsuitable for combat robot drivetrains.

There is an area, however, where brushless motors can and are used in combat robots; they are commonly used to power 'spinner' weapons. In these applications the motor spends relatively little time accelerating the weapon up to speed and most of the time under low load at high RPM simply maintaining the weapon's rotation. If the weapon motor is quickly shut down when the weapon is stalled, a brushless motor can be a good choice for a rotary weapon.

A: No. Speed controllers for brushed and brushless motors are very different in design and cannot be interchanged.

A: It is common practice in combat robotics to run weapon and drive motors at higher voltages than they are rated in order to obtain greater power. How far a motor can be overvolted depends in part on how much load is placed on it. If allowed to bog down close to stall, an overvolted motor will not survive long. Better results will be obtained by setting up gearing and wheel diameter so the motor can provide enough torque to spin the wheels before it slows below about half the free RPM of the motor. The Team Tentacle Torque & Amp-Hour Calculator can help you select wheel sizes that will keep the amp load reasonable at elevated voltages.

Also, be aware that while motors from industrial equipment will usually take a large voltage increase in stride, high performance hobby motors are already being stretched about as far as they can go on voltage and will have a very short life if pressed higher.

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 and well financed builders. Overall, you might be surprised by what weapons win the most matches.

Q: I want to build a robot that combines a [weapon type 1] and [weapon type 2]. Is that a good idea?

A: If you split your weight allowance between two weapons, neither will be strong enough to be effective. It has been tried many times. Commit to a single weapon type.

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

How does [insert flamebot name here]'s flame weapon work?

A: You can search the archive for 'flame' to find our many previous posts on flame weapons. Briefly:

1. Flame weapons are ineffective in any weight class.

2. Flame weapons are built by very experienced builders who just want to show off.

3. We will not discuss flame weapon construction here because we don't want novice builders hurting themselves.

4. By the time you are experienced enough to safely build a flame weapon you won't need to ask us how to do it.

5. That flamebot that you're about to tell me is successful was built by a very experienced and well financed team and would be just as successful without the flame weapon.

A: All the tools you need to evaluate spinner weapons and motors can be found in the archives. There's a ton of information about weapon motor selection in the archive, and a metric buttload of answers to weapon design questions in the archive. In particular, the Team Run Amok Spinning Weapon Excel Spreadsheet will detail and graph the performance of specific motor/weapon pairings.

A: Pretty much everybody has or had websites. Here's my trick:

1. Go to the RobotCombat.com Links Page and click on the link to the team you want. Click 'U.K. Robots' at the top of the page to list British teams.

2. If the site no longer exists or no longer has robot info, copy the URL and go to The Wayback Machine.

3. Paste the URL into the search box and hit the 'Take Me Back' button.

4. You'll get a dated list of archived 'snapshots' for that site you can click up.

A. Complete combat records for north american robots can be found at BotRank.com. Enter the robot's name, then click on its 'history' link.

Full tournament trees for the major robot competitions can be found at the Team Run Amok tournament results webpage.

A: More than 4000 robots have fought in organized combat events in North America alone. Most of these robots have uninteresting stories -- they were built, they fought, they lost, and their builders moved on. We have very little interest in most of these obscure robots, but if you are interested and willing to dig thru old website archives and combat records, see the two questions immediately above.

We get so many variations on this question that I've started entertaining myself by playing 'Mad Libs' with the answer:

If you are interested in stories from early robot combat, drop whatever you're doing and go find a copy of 'Gearheads: the turbulent rise of robotic sports' by Brad Stone. Great reading!

A: We don't predict fantasy matches not involving our own robots. In fantasy matches involving our robots, we always win

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

A: Mark J. here: I get this same question, word for word, several times a year. Could you slackers at least re-word your class assignment before you send it in to us?

The behavior is classic approach / avoidance -- the robot will effectively 'lock up' and do nothing. The common solution adopted in sumo robots is to lock out the edge detection routines whenever the object detectors report you're heading toward your opponent.

Your Robocup robot can use a similar strategy: if the red ball is in your path, override the blue wall avoidance routine AND move toward the ball. A more sophisticated approach would utilize an elevated video camera looking down on the field to verify the relative positions of the wall and ball and determine action accordingly.

A: Beats me, but we love people who ask questions about combat robots.

A: Mark J. here: for many years Aaron and I have done our best to answer any and all questions on the broad topic of robot combat. Recently we found ourselves flooded with a large volume of trivial UK Robot Wars questions that were well outside the mission and focus of this website. 'Ask Aaron' is not a 'fanboy' site and we are not interested in investing our time in this area. We regret having to cut off all UK Robot Wars questions, but the fanboys have proven themselves persistent and sometimes quite rude.