A: Legos are made of acrylonitrile butadiene styrene (ABS) plastic -- reasonably tough and resilient but not equal to the strength of more commonly used plastic armor. Legos can be welded together with solvent-based glue made for polystyrene model kits, but the exposed walls are not very thick and assembled mass is not going to be nearly as strong as a single sheet of polycarbonate or UHMW polyethylene plastic.

If you're just building robots for fun, it sounds like a fine idea. If you enter a competition there'll just be a cloud of Legos where your robot used to be.

Q: Aaron, sorry to bug you with this again, but I'm on a small budget. Would the Lego armour be sufficient for an antweight? Aren't the ant weapons less damaging? Thanks!

A: I really don't see Lego armor working. Take a trip thru your local dollar store. You can find kitchen storage containers made out of polypropylene ('PP' in the recycling symbol) that are tough and flexible, and you might find a thin polyethylene cutting board that would be perfect ant armor.

I don't know about the ants where you will be competing, but high-power spinners are common ant weapons pretty much everywhere. Don't count on low-damage weaponry.

I built my first 12 pound wedge bot, yet to compete, and I am wondering about adding a weapon. With the 1-1/2 pound steel wedge my robot only weighs 10 pounds 13.5 oz. I was thinking of making another lighter wedge and putting some type of lifting mechanism using a servo or linear actuator. I know both of those are slow but it does not need to be that fast. Any advice? Thanks, Daniel.

A: Glad to hear that you found the advice here helpful, Daniel.

My advice is to enter a competition with the robot as it is. You may discover a critical use for that extra 18 ounces of weight allowance. If you're pleased with the performance of your chassis and drive train you can think seriously about modifications to give you some additional offense.

Electric lifters are effective in the sub-light classes, and judges seem to like them. You are right to say that they do not need to be fast -- they do not need to lift very high either. Even a simple servo-powered hinged wedge can be very useful and can add to the versitility of the robot, but give the robot a shake-down in combat before you start modifications.

A: What... the weapon RPM? I'd start by looking at their websites. See the for info on finding archived websites for teams that aren't on the web anymore. Many teams consider this type of data 'top secret' and do not make it available.

There is much more to a rotary weapon than just RPM. See the archive for other design criteria.

A: If it's a very small 'bot, sure. I think the Spinbrush uses the Mabuchi FF180-SH motor -- fine for an antweight. I don't know anything about the gearbox. It could be worth a try.

A: Bulletproof vests are made of Kevlar, but you don't make bullets out of Kevlar to shoot at them. Armor and impact weapons have very different material requirements:

• Robot armor must be resillient and tough in order to absorb impact without permanent deformation. Armor also needs a high strength to weight ratio to provide the greatest protection for a limited weight allowance. Titanium alloy meets these requirements well, but is quite expensive.

• Robot impact weapons must be hard and unyielding to efficiently translate force into damage. High density is not a drawback as it allows high kinetic energy storage in a compact form. Hardened tool steel alloys fit the bill here and have a much lower cost than titanium.

A: Story short: Vlad got under BioHazard's drop skirts and flipped him. BioHazard lost the ability to self-right when Carlo B. added the drop skirts in 1997.

Q: After Vlad The Impaler got under Biohazard’s skirts how does he flipped him with his forklift because I thought his forklift weren’t strength enough and too slip to flip Biohazard because those skirts?

A: Vlad's forklift was plenty strong enough to lift BioHazard, just not high enough for an unassisted turn-over. Vlad got lucky, drove in deep under the skirt, lifted, and rammed BioHazard into a wall to complete the flip.

Q: In 1999 Battlebots Las Vegas which side did Vlad got under BioHazard's drop skirts and flipped him, is it a front, left or right or a back skirts?

Did Biohazard got any flip before Vlad got under Biohazard’s skirts and flipped him or Vlad immedially got underneath and flipped him after that fight starts?

Is Vlad in a red and BioHazard in a blue square in that fight?

After Vlad The Impaler beat BioHazard, who you think who might win before that fight begins?

A: Don't make me go looking for my old tape of the event. We generally don't provide blow-by-blow commentary for fights not involving our own team. I will say that BioHazard was the strong favorite before the fight.

A: Builders have been working on flywheel powered flippers for quite some time. There is a discussion thread at the RoboWars Australia Forum. The problem with such a design is building a clutch mechanism that can withstand the brutal force instantaneously transferred from the flywheel to the flipper without tearing itself apart.

I have not seen Warrior SKF up close, but unless you can match the budget and resources available at Team Whyachi I would suggest you try a more conventional approach.

A: Mark J. here: I strongly recommend against going cheap on your electronics -- particularly on your R/C gear. It would be false economy to save a few bucks on the radio only to get washed out of a tournament when it glitches. I don't see any mention of failsafe capability for this system and it's anyone's guess if it is compatible with Spektrum receivers. Don't do it.

A: Derek Young built some of the most innovative combat robots to ever compete. Derek did not have a large budget and did a tremendous job with the resources he had available. His middleweight 'Complete Control' is a well-deserved member of the Combat Robot Hall of Fame.

Q: How does Complete Control's Weapon Work?

A: Complete Control was the original 'clampbot'. Starting with a conventional pneumatic lifter, Derek added a pneumatic arm on the lifter platform itself that clamped downward to hold the opponent in place. Once clamped, the entire platform lifted upward with the opponent in a firm grip. Awesome!

A: Mark J. here: Team Hurtz is famous for their overhead axe robots (KillerHurtz, TerrorHurtz) with which they competed in Robot Wars and BattleBots. Attempting to rapidly accelerate an overhead exe weapon causes an equal and opposite reaction which can actually flip the robot itself over.

Team Hurtz experimented with several methods of generating downforce to hold the body of the robot steady. 'Beta' attempted to use large electromagnets to hold the robot down to the steel BattleBots arena floor when the weapon was fired. Unfortunately the steel arena plates are held down only by their own weight; when Beta energized the electromagnets it pulled the arena flooring up and disrupted its own movement.

BattleBots reasonably forbade the use of the electromagnets, and without them Beta was not able to use the overhead weapon. Team Hurtz withdrew from the tournament without fighting a single match.

A: Simple: run it in both directions and listen to it. It will have a higher pitch to the sound it gives off when running in the better-timed direction. Break in the motor before you try to figure out any timing advantage -- it may change after the brushes are fully seated. Sanyo 50:1 gearmotors are supposedly 'neutral' timed, so there isn't going to be much difference.

A: Mark J. here: three possibilities:

1. the pack isn't being fully charged;
2. the pack is old, damaged, or has a dead cell;
3. the robot really is drawing that much juice.

Q: The racing battery pack is a Duratrax DTXC2146 7.2V 42000mAh HiMH Battery. It is about 6 months old,and I have a Duratrax IntelliPeak Pulse Charger. My robot isn't really a robot, its an old Tamiya King Tiger tank with clutch mechanism. I'm not sure what motor it has, but the motor is about 2 inches long and 1 1/4 inches wide. I am peak charging the battery at about 2 amps. THANKS!

A: It's unlikely that your motor could be sucking down enough amps to drain a 4200 mAh pack in 20 minutes. Make sure there is no binding in the drive mechanism, but I suspect a battery problem.

NiMH packs can be damaged by recharging while still 'hot' from a recent rapid discharge. 'Old' refers to the number of charge/discharge cycles the pack has been thru, not just it's physical age. The Duratrax charger does not display the amp-hours put into the pack during the charge, so it is of no direct diagnostic help. Still, a 2-amp charge rate should take better than two hours to fully charge your drained pack -- is that about how long it's taking?

Try charging the pack at 1 amp and letting it drop into automatic trickle charge mode overnight. If that doesn't give better results I think it's time to buy a new pack.

A: The Robot Rampage event had middeweight, lightweight, featherweight, and antweight divisions. The two featherweight qualifying rounds were not shown and I haven't been able to track down the competitors. The televised featherweight final featured 'Aargh', 'Bernard', 'Cutlet', 'Gladiator', 'Katnip', and 'Micromute'.

A: You can find full combat records for North and South American robots at BotRank.com. Look up the robot and click on its score. Complete tournament match results are at the BotRank events listing.

• Heavyweight 'Hexadecimator' made it to the semifinals in the losers bracket at RoboGames 2006 where it lost to 'SJ'. Hexy D has not fought since.

• 'Wedge of Doom' last fought at RoboGames 2005 as 'Smashbox', where it won the lightweight class.

• Middleweight 'Nasty Attitude' last fought at the 2005 RFL Nationals.

A: There's a reason that it didn't sell: Team Whyachi builds quality robots, but 'Y-Pout' was an experimental design that just didn't work. See a discussion of Y-Pout in the archive.

If you're looking for a 'pit pass' just to go to the next BattleBots and hang out, Y-pout should get you in the door. I'm assuming that it comes without radio gear, support equipment, and spares -- be prepaired to spend some money on those items. I'd rather build a 'bot than buy one.

Mark J. here: I'm not certain that 'Y-Pout' even qualifies for competition under the current BattleBots rules. Section 9.1.2b requires an active weapon which operates 'separately from the Mobility System'. I'd get an opinion from the BattleBots technical crew before committing to purchase.

I also wouldn't count too heavily on the November BattleBots happening. Just a hunch.

A: I never met Team Vladmeisters. They kept kind of a low profile and never even put up a website. Their robots were always well thought out, flawlessly constructed, and professionally prepaired. You pretty much had to tear one of their robots in half to stop it.

A: Team Razer built these two robots for very different purposes; it's kinda like asking "which is better, a boat or an airplane?"

Razer was refined over a period of years for combat in the Robot Wars arena where robots can win by tossing an opponent over the railing, shoving them into 'The Pit', or by immobilizing them. Robot Wars was about tactics and strategy.

Warhead was built for BattleBots where there is no Pit and no possibility of throwing an opponent out of the competition area. BattleBots was about destruction.

Head-to-head I'm certain that Warhead would tear Razor apart, but that's not the whole story. In a Robot Wars tournament, I think Razor would advance farther against the mixed designs that enter such tournaments. At a BattleBots tournament my money would be on Warhead to push further into the final rounds because it has fewer weaknesses that could be exploited by the usual entries at those events.

Q: Could you tell me which is better between 'Nasty Attitude' and 'Max Wedge' in your opinion?

A: As pointed out above, it's very difficult to determine the 'better' of two robots. Nasty Attitude has a narrow lead in head-to-head matches against Max Wedge, but Max Wedge has a better overall win/loss record and has won more championships.

I was willing to discuss the heavyweights from Team Razor because they were an interesting contrast in styles, but I'm not going to go thru random pairs of robots and render opinions.

A: Nice group of guys. At Robot Wars Extreme Warriors 2 they walked thru the pit area and handed out autographed posters of 'Razer' to every U.S. team. I was off someplace and didn't get to talk with them, but I still have the poster hanging in my room.

Razer itself completely rocks! It has one very clever feature (plainly visible in many photos) that significantly adds to the success in deploying the piercing weapon, yet which I've never heard anyone mention. It is an unusual use of an uncommon combat robot component. Bonus points to anyone who can identify the component and how Team Razer makes use of it.

Q: Just a guess, are the barbed teeth Razer's distinctive feature????

A: No, the jagged teeth on Razer's weapon don't help with deploying the weapon.

Q: Is the component on Razer the wings? Team Razer used them to self-right.

A: No - the powered wings were unusual, but SRiMechs were very common at Robot Wars.

The uncommon components in question replaced very common components on Razer about the time of the Third Wars. Razer used two, and they were powered. All the other robots I've seen that had powered ones used three or four. 'Killer B' had two, but they were unpowered and mounted sideways at the other end of the robot! What are they?

Q: Is the component on Razer the omniwheels?

A: Yes! A pair of omniwheels replaced the conventional wheels at the rear of Razer. Conventional wheels remain in place at the front. It is most unusual to have two powered omniwheels in parallel at one end of a robot. Now - tell me why Team Razor did this.

Q: Team Razer did this so they could maneuver around the opponent's weapon and attack them?

A: A pair of parallel-mounted omniwheels does not give powered side-slip control (omnidirectional motion). You'd need Mecanum wheels to do that, and four of them. There is a discussion of omniwheel use in the [design] archive -- search for 'omnidirectional'.

So, if the omniwheels on the rear of Razer don't give it controlled side-slip motion, what specific advantage do they provide for a four-wheel skid-steered robot? Hint: Team Razor installed a peizo gyro at the same time as the omniwheels.

Q: Did Razer use the omniwheels so it could spin its weapon around quickly to face its openents?

A: You're on the right track; I'll give it to you. Too busy right now to post a full explanation -- give me a couple of days and I'll explain how they work.

A: A standard two-channel ESC will control two motors to perform the same function as your control system. The advantage is that a hobby ESC will allow smooth variable speed control of the motors in both forward and reverse to give greater control than the combined receiver / motor controller in your RTR boat.

You would need to determine the voltage and amperage draw of your motors to select a suitable ESC to handle the power requirements. You'd also very likely need to replace the entire radio system of your boat with a hobby-grade system in order to be compatible with the signal requirements of the ESC. By the time you've done all of that, you'd likely have been better off to have chucked the Ready-to-Run boat and bought something more capable.

A: Robot Arena is a pretty fair physics simulation, but even small differences between the simulation and the 'real world' can allow unworkable design elements to appear successful. If you're fighting in the real world, look to proven designs from real robot combat for your inspiration.

A: Sorry, I didn't have a tape measure in my hand the last time I was standing next to Sewer Snake. From memory, it's about 48" long, 30" wide and maybe 8" tall. If you need to know exactly, contact info for Team Plumb Crazy is on their web site.

A: It takes more than a powerful weapon to make a champion robot. I say this all the time: a successful combat robot has all of it's components and systems working together in balance.

A super-weapon on a chassis that doesn't work well to use that weapon is not going to perform well. A well designed chassis with a poorly set-up radio system will have a very rough time. A robot that's hard to repair and maintain won't get far in a tough tournament. The weapon is probably the least important system on a combat robot.

By the way, I think a 4 win 2 loss record is pretty successful. They were stopped at BattleBots 5.0 only by the barbaric 'Warhead'.

Q: Why did you say The Matador had a "next generation" flipper? What was so different about it?

A: Inertia Labs refered to it as a new generation. Here's what they had to say on their website:

A: Mark J. here: this is the hottest, most divisive topic in robot combat. Partisan groups each have their own arguments:

• The Spinner Faction believes that massive destruction adds excitement that will attract large audiences to watch robot combat events. Larger audiences, they say, will create greater interest for robot combat with the public and will result in the growth of the sport. The current RFL judging guidelines reward only damage and aggression, encouraging destructive spinners.

• The Sportsman Faction argues that hyper-destructive robots scare away builders and make arena costs so high that the sport cannot support itself. There was a much greater variety of robot design in the popular 'golden age' of combat robots and they believe that the lack of this variety has caused the audiences to lose interest. Although the RFL recognizes a 30 pound sportsman class, the judging guidelines have not been adjusted to reflect the needs of this class.

• The Wedge Hater Alliance blames the loss of interest in combat robotics on 'boring wedges' and will actively confront wedge builders at tournaments to tell them that wedges are destroying the sport.

• The Wedge Builders Cartel likes to think that their robots are entirely 'active weapons' and stubbornly go right on winning a higher percentage of their matches than do spinners.

• The Major Televised Event Producers all eventually required active weapons in an effort to add excitement. The rules for the most recent BattleBots tournament required an 'effective' active weapon, which set off a new storm of controversy with the spinner fetishists decrying the way the rule was enforced, questioning what qualifies as 'effective', and arguing about whether a weapon must be used during a match.

The time for putting two robots in a flat-floored plastic box and having them fight for three minutes has passed. Take a look at some alternative ideas I put together: Questioning Robot Combat Paradigms.

A: David Gribble, driver for Robot Wars' Team Pussycat, died in a motorcycle crash in October of 2002 shortly after the filming of the Fifth Wars. Recognized as one of the best drivers in the series, David was 17 years old.

A: Mark J. here: all Permanent Magnet Direct Current (PMDC) motors have an inverse linear torque-RPM 'curve': they produce maximum torque at stall and zero torque at free-running RPM. If you know the stall torque and free-running RPM of a motor you can calculate the available torque at any speed.

Running at 24 volts the S28-150 Magmotor produces 1970 oz-in torque at stall (zero RPM) and zero torque at 6000 RPM (free running RPM). The torque formula for this motor is:

PMDC motors have a direct linear relationship between torque and amperage. For each amp the S28-150 draws it produces 5.1 oz-in torque.

No trouble soldering PCBs, but the wire is giving me fits. At best, I get a shoddy coating of solder on the wire, and it doesn't seem to soak up the solder like I think it should. I have 18, 16, and 12 gauge wire yet to solder, and I'm afraid to even try it. Any advice? Is my equipment too wimpy for the job? [Dave B.]

A: Mark J. here: your equipment is more than up to the job, Dave. What you need is some paste flux. Dip the end of the wire into the flux to coat it. Apply a tinned iron and the solder will soak into the wire like water into a damp sponge.

The battery was only shorted for a moment (maybe one second). It did get pretty warm, but not hot. What are the chances that I damaged my battery? Do you think it would still be combat worthy? The robot is yet to be completed, so I won't be able to test the battery for awhile. [Dave B.]

A: Mark J. here: everybody gets a case of the dumbs now and again, Dave.

LiPolys do not appreciate being shorted. Examine the battery casing: it should be taught and flat. If there is any bulging or 'inflation' the battery has been damaged and is unsafe to use. If it looks OK I'd put it on a heat-resistant surface away from flammables and run it thru a couple of charge/discharge cycles. If it behaves normally, run it.

A: No, Antony. The BattleSwitch is a 'Single Pole Double Throw' (SPDT) switch that can be operated via hobby R/C gear. One BattleSwitch can turn on and off a single motor in a single direction.

To control a single motor 'forward / off / reverse' requires a switch arrangement called an H-bridge, and you would require two of them for two motors. The RCE220 RC Dual Relay Switch can be used as a single H-bridge. A pair of small H-bridges are more expensive, heavier, and less useful than an Electronic Speed Controller.

A: I'm not sure I understand the question. All of the loanerbots were used by teams whose own robots were destroyed in early combat, were lost in transit, or were unable to pass technical inspection. The loaner robots were returned to the Robot Wars technical staff at the end of the tournament.

See the archive for more information on the loanerbots.

A: A BattleBots tournament took place April 20-26, 2009 at Mare Island Naval Shipyard in Vallejo, California. It wasn't much like the old tournaments. There were three classes: a 120-pound class for college teams, another 120-pound class for high school teams, and a 220-pound class open to everyone. There weren't a lot of robots.

BattleBots says the college tournament will be shown on the hard-to-find CBS College Sports Network sometime in August, 2009.

A: I don't predict fantasy matches, and I don't evaluate fantasy robots. I will say that the weapon appears to store very little kinetic energy and applies it to the opponent only under specific circumstances. I'd build something else.

A: Mark J. here: an Electronic Speed Controller (ESC) controls motor speed by switching battery power on and off thousands of times per second. The longer the ratio of switched 'on' time to switched 'off', the faster the motor spins and the more power it produces. At 'full power' the ESC passes (almost) the full voltage and current from the battery on to the motors.

By using the Adjustable Throttle Volume (ATV) feature on a computerized R/C transmitter you can adjust the radio so that the ESC will never receive more than a 'partial power' signal and will never deliver more than partial current/voltage to the motors, but there is no automatic voltage limiting.

The above explanation of how an ESC works is VERY abbreviated. If you're interested in details on ESC function see the 4QD-TEC: Reference Archive.

A: The idea behind breaking in a brushed motor is to seat the brushes against the commutator to prevent destructive arcing when the motor is run at full voltage (or overvolted) under load. This is usually done with a variable voltage supply, but there are other options:

• Put your 'bot together, prop the wheels up off the ground, and run your throttle trim up until the motors are running at a moderate, steady speed. Run them for about five minutes, then turn the speed up a little for an additional five minutes.

• Wire two (or three or four) Sanyos in series with the 7.4 volt battery and let them run unloaded for about ten minutes.

• Hook one motor up to a single alkaline cell (AA, C, or D) and run it unloaded for about ten minutes.

Make sure the motors and gearboxes turn over smoothly before starting and monitor the motors during break-in for overheating or other signs of trouble.

A: I've got a couple of questions:

Why that motor? The 36 volt DeWalt with gearbox weighs a little over 3 pounds and produces about 1 HP at 36 volts. The old-style 18 volt DeWalt with gearbox weighs a little over 1.5 pounds, produces 1.5 HP at 24 volts, and is a well proven combat winner.

Next, what do you plan on doing with a 12 pound robot with 2 or 3 horsepower? It will be very good at spinning its wheels and crashing into the far wall of the arena before you can react -- is that sorta what you have in mind?

A quick check at the Team Tentacle Torque & Amp-Hour Calculator shows that a hobbyweight with a 36 volt DeWalt and 4" wheels will spin it's wheels at about 5% of the torque potential of the motor. Give this a rethink.

Q: About the ramming at a high uncontrollable speed, that's kinda the point. I want to slam the other with as much KE as possible. And I also plan to run the drive with a chain a sprocket system, at a 25:1 gear ratio with five inch wheels.

A: Check your math: a DeWalt 36 volt motor geared 25:1 with 5" wheels will give a top speed of about 11 MPH - hardly high uncontrollable speeed. You've picked the wrong motor, the wrong gearing, and the wrong attack strategy. I have nothing against ram bricks, but the whole idea behind them is 'controllable' speed and accuracy.

Q: Well, what DO you recommend for a hobbyweight rammer?

A: I can't recommend specific motors without knowing more about the rest of your design and details on the arena in which you will be competing. I can tell you that trying to put down a lot of power with a two-wheel chassis will make keeping it pointing in a straight line very difficult. For a typical sublight arena I'd go for a four-wheel drive chassis with 500 to 600 watts total motor output.

A: I don't really have any time off. I'm jumping into college classes in just a couple of weeks. The problem hasn't been my time, it's been the lack of events here in the Pacific Northwest. Western Allied Robotics have been doing a good job with small 'bots in the Seattle area, but I'm just not that into sublights right now. I like big 'bots!

A: Mark J. here: we selectively use rubber or spring mounts only for special cases. Armor that is inherently springy (UHMW polyethylene, polycarbonate, titanium) does not benefit much from shock mounting, although we often do use rubber grommets when mounting polycarbonate to relieve stress at the mounting points. We believe the best candidates for shock mounting are stiff plates of relatively small size: battery covers, rear panels, wheel covers.

Panels that are shock mounted do not fully contribute to the structural rigidity and strength of the chassis. Shock mounting should be used only in designs that do not rely on integrated stressed armor panels for strength.

We did have the front wedge on 'Run Amok' spring mounted at Robotica and Robot Wars Extreme Warriors 1, but it was more trouble than it was worth. We reverted to solid mounting for RWEW2.

A: Hi, Daniel. Team LNW's hobbyweight 'Defiantly Daft' (6 wins, 7 losses) is an able competitor, but it is not known for massive power. Why copy their motors?

My dad contacted Team LNW's Greg Schwartz and asked about the motors:

Q: Thanks for the help!, I once tried to modify two 12 Volt Black and Decker motors but in the end it did not seem to work well. Maybe it was the drill motors themselves, because they were not cheap chinese drills? Maybe a pair of Harbor Freights would work better, or maybe BaneBots motors? [Daniel]

A: Plenty of hobbyweights are powered by BaneBots motors. They are simple to mount and have a large range of power and gear ratio options. Some builders really like them and some really don't. In a design like 'Defiantly Daft' with bearing support on the end of each drive shaft I think they'd be fine.

A: No secrets here - Thomas Kenny packed four 16:1 BaneBots 28mm RS-385 gearmotors into his compact beetle wedge. The motors, gearboxes, and wheels make up half the weight of the robot!

Although not all that fast at about 6 MPH, 'Cloud of Suspicion' is terrifyingly quick in a small arena.

Currently ranked 5th among active beetles at BotRank.com, 'Cloud of Suspicion' has a 8 win, 4 loss record.

A: Most computerized transmitters have a menu page to swap modes. The DX6i has one, but it's undocumented and really well hidden:

Press the selection roller and hold down while turning on the transmitter. Release the roller when 'SETUP LIST' appears. Rotate the roller to highlight 'COPY/RESET' and press the roller. Rotate the roller to highlight 'RESET' and press the roller. When prompted with 'SURE NO/YES', rotate the roller to highlight 'List'. Toggle the 'AIL D/R' switch (top right of the transmitter) from position 1 to position 0 a few times. Secret hidden menu! Select your desired mode with the roller and press to accept.

I don't have a DX6i here to try this on -- let me know how it works.

A: Loaners were used to 'fill' the side events at RWEW. The Championship was restricted to real competitors.

A: None of them left an impression on me.

A: Combat robots are judged by their ability to win matches. Robots who never won are either unlucky or lacking. Either way, I find it difficult to rank them.

At any rate, 'Bender' does not qualify. Bender's record is 2 wins, 6 losses, with first round wins at BattleBots 4.0 against 'Space Ape' and BattleBots 5.0 against 'Beta'.

A: Mark J. here: I suggest you read the Run Amok Guide to Combat Robot Gyros for details on mixing and gyro inversion. Briefly:

• Gyros are not compatible with transmitter mixing. You will need to use the on-board mixer function on your Sabertooth to run a gyro.

• If you use the Sabertooth mixer you can assign the throttle and steering to any stick and axis you like: for left stick throttle with right stick steering plug throttle into channel 3 and steering into channel 1.

• An inverted robot with a gyro will go into an uncontrolable 'death spin' unless the gyro can be shut off with a spare radio channel. The 'invert' function on the Sabertooth will not solve this problem - you must have a gyro with a remote shut down feature.

Q: Thanks Mark. Could I have two gyros and use the spare chanel to switch between the one for right side up and the one for inverted with two transistors spliced into the logic cable? As an alternative, could I use the "Remote Gain Dual Mode Heading Lock Gyro MS-044"?

A: Are you all that sure that your 'bot will need a gyro at all? I'd suggest trying it before going to a gyro.

I don't like the 'two gyros' idea. If you want to try something unusual, how about mounting the gyro on a tiny servo and rotating it back upright when you invert?

The MS-44 manual does talk briefly about 'gyro sense reversal', but this will not correct the 'death spin' problem. Helicopter gyros simply never face the same problem as a skid-steer robot - when inverted, helicopter direction controls reverse and the gyros are designed for that.

A: All at the back?? The benefit from 4-wheel drive comes in getting all the robot's weight on powered wheels. If the drive wheels aren't carrying all the weight, you aren't going to gain much benefit. If you're thinking of using more wheels to get it to track better in a straight line, a gyro is a very worthwhile alternative.

A: Hi again, Anthony. I'll be glad to help, but I need to know more about your robot and where you are in setting up the electronics. I also neen to know how you'd like to have the controls set up: do you want to have forward/back and left/right on one stick or have throttle and steering on different sticks? Would you rather have independent throttle for the two sides of the robot on two sticks (tank steer)?

You can get information on some of the set-up options in the Run Amok Transmitter Programming Guide. It was written for a Futaba radio, but you have most of the same options on your Spektrum. For a little help in wiring up the receiver and your ESC, see the wiring diagram about half-way down in the .

Write back and let me know what specific help you need. Oh, and tell me if your Spektrum is Mode 1 or Mode 2.

Q: My robot uses three channels -- 2 for drive and one for weapon. It is an antweight with a vertical saw and two hacked Hitec servos for drive. I want tank steer and my transmitter is Mode 2. My electronics are already set up. What ports do I plug these parts into? Thanks for your help!!!!!

A: OK, Anthony - tank steer is the simplest control system to set-up, but your left control stick does not spring-center like the right stick. You will need to modify the spring centering system by opening up the case and transferring the spring assembly from the left-right axis to the up/down axis. Tricky, but some help with this can be found at www.max3design.com.

• Your left drive motor plugs into channel 3 and will be controlled by the left stick on your transmitter.
• Your right drive motor plugs into channel 2 and will be controlled by the right stick on your transmitter.
• The weapon ESC plugs into channel 5 and will be controlled by the landing gear switch on the upper left corner of your transmitter.

Once the receiver is 'bound', you can check the control response. Each drive motor should spin 'forward' when it's stick is moved forward and 'backward' when the stick is pulled back. They should not move at all when the sticks are centered. You can adjust the 'no movement' point with the channel 2 (elevator) and 3 (throttle) 'trim' adjustments (see your manual). If direction response is reversed, it can be corrected by the 'servo reversing' function (see your manual). Likewise, if the weapon motor is 'on' with the switch in the 'off' position, use servo reversing on channel 5 (gear). If the weapon motor spins backward, reverse the power leads from the ESC.

That should get you rolling, Anthony. Take it off the block and drive it around. Leave the weapon disconnected outside safe containment - PLEASE!

Secondly, I have no experience machining titanium. I have worked with mild steel and aluminum, and have plenty of tools in my shop to handle those. Can you advise me on any special saw blades or drill bits I'll need to work the material? I really appreciate all the help.

A: Mark J. here: second issue first - you won't need any special tools to drill or cut thin sheets of titanium alloy. Make sure your bits and blades are very sharp, reduce the drill or saw speed by about half, maintain firm tool to material pressure, and use an appropriate cutting fluid (WD-40 should be fine for your purposes).

The strength of an armor panel depends on size, shape, and the support given to it as much as on thickness, but in general your 0.041" 6AL-4V should be quite adequate for most antweight armor applications. I would consider a double-ply for a front spinner-killer scoop or ram.

The offensive capability of antweights varies a great deal. Take a look at ants active in your area and plan accordingly. Like Team JuggerBot says, "damage is weakness leaving the robot." Make everything strong; if it breaks make it stronger.

Team Run Amok prefers UHMW polyethylene for insect class side/rear armor and polycarbonate for the top. Front impact zones are heat-treated steel -- the weight saved by titanium would be small. We usually have a section of wood somewhere out of respect for our first combat 'bot.

A: Mark J. here: a well designed combat robot is not just a set of components bolted together. The design of each system must be made with consideration to the rest of the machine. Recommending a weapon drive without knowing anything about the design for the rest of the robot would be folly.

If I'm given a weapon design I can comment on potential flaws, but I have to assume the designer has an overall plan that will incorporate the proposed weapon into a well balanced robot.

Read thru recent additions to the archive for an example of integrating a weapon into a beetleweight design.

See also the about 20 questions down.

A: Why would you want to? On impact your opponent and your 'bot will be thrown clear of each other and your blade can start to spin back up.

I can't think of any simple circuitry to accomplish an electrically detected contact shut-down.

A: Mark J. here: sorry, I've never done any aluminum brazing. I cannot comment except to say that I don't know of anyone using the technique in combat robot construction -- there may be a reason.

A: You want a keyed shaft, not key stock. Key stock is the sliver of metal that slides into the key of the shaft and the hub/gear/sprocket to lock them in place. The smallest keyed shaft available at Robot Marketplace is 1/2" diameter. The lack of suitable small diameter keyed shafts is why I recommend dead shafts for insect class robots.

Q: What's wrong with using the 1/2" keyed shaft????

A: Massive overkill for an insect class 'bot. It's heavy, and the 1/2" bearings to support it would also be heavy and bulky.

A: A dead shaft is fixed in place and does not rotate with the weapon. The weapon and the sprocket/pulley are fixed together and have bearings that allow them to rotate on the dead shaft as a unit. This eliminates the problems associated with trying to secure the weapon to a small diameter shaft. Seaarch the archive for more tips on dead shafts.

A: Mark J. here: the physical properties of T6 and T651 are the same -- the '51' suffix indicates only that the material has been stress-revieved by a stretching process. Go for it.

A: Two-wheeled robots tend to be difficult to keep on a straight path, but a small weight offset isn't going to be noticeable.

A: Shaft length is not included in a standard motor length measurement and is not included in the motor length given by the Robot Marketplace for the B16 motor.

The Robot Marketplace provides a great service to the robot community, but they are inconsistent in the way they report dimensions and performance figures. Mixing metric and English units or leaving key measurements out of drawings or tables is common.

A: A steel striker bar will make very pretty sparks when hitting titanium armor. I suppose you could add a titanium or magnesium insert to your steel blade to make sparks when attacking steel armor. Aluminum and plastic armor are too soft to make sparks no matter what you hit them with, and nobody would believe sparks off plastic anyhow.

Experienced judges will not be impressed by sparks, but they could help get the audience behind you.

Do you envision any problems with implementing or using this design? Do you know if anyone has used a similar idea? Do you have suggestions on materials to build the disc and teeth out of? I don't plan to go too crazy with the weapon RPM as I know my robot's weapon mount won't be indestructable. Thanks again for all the help, guys!

A: Mark J. here: I don't like the idea of putting the entire stress of impact on a hinged tooth. Even an antweight spinner will transmit a big slug of energy thru the impact tooth and I think it's best to have that solidly anchored.

Suppose only one of the teeth gets rotated - you have a serious imbalance problem that would require shutting down the weapon to reset. Worse, one of the hinges gets tweeked and the tooth is stuck either in or out.

A 4" diameter disk rotating at 3000 RPM has more than 500 g's of centrifugal acceleration acting at the edge (calculator). The 'long arm' of your tooth would need to be held in place very firmly to keep from 'rotating out' prematurely. I can't think of a simple design to hold it in place, let it swing out when triggered by an impact on the short arm, and return it to position at lower RPM.

I have seen spinners with 'free swinging' impact bars that are held outward only by centrifugal action. The idea was that the bar could deliver a good blow, then rotate out of the way to prevent the weapon from stopping. This produced a series of rapid impacts that was impressive to the judges, if not as damaging as a single big impact.

Insect class rotating weapons are typically single piece steel to take great abuse. Larger disks are often aluminum with tool-steel teeth, but I've seen large disks made of steel, titanium, end even UHMW Polyethylene.

A: First, check with the event organizer to see if traction magnets are allowed. Some events allow them, some do not.

You're correct to be worried about overloading the motors. The added traction you get from use of magnets will increase the load on the motors before the wheels start to slip. Everytime you double the traction you also double the amperage draw at maximum push, stressing the motors and the ESC.

Calculating how much extra traction you can get from a specific magnet has too many variables, but those Maxons are currently breaking traction at less than 1/10th their stall torque -- you can add a good amount of traction and still be fine. Experiment!

You might also consider using axial magnetic rings to replace your wheels. This set-up has worked very well for insect robots like 'Wallop'. Note that 'Wallop' was designed for the magnet wheels and runs a high gear reduction to avoid over-stressing the motors.

Q: How would you suggest attaching the ring magnets to the shafts of the 17:1 Maxons? It looks like Wallop used a prop adapter for his magnet wheels, but I only have about 1/2" of space for the width of my wheels.

Also, if I chose to just put a square magnet on the inside of my robot, would there be any chance of the large magnetic force messing with any of my electronics?

A: It sounds like you'd need custom hubs. Magnet wheels are best used on robots designed from scratch around them, but you might have been lucky enough to get away with it.

A stationary magnetic field is unlikely to create electronics trouble. It's more likely to stick you firmly to an arena upright support and leave you spinning your wheels in the air.