A: Hard to comment since I have no idea what type of structure you plan to build, what your budget is, or what tools and skill level you have. In general, aircraft aluminum alloys like 6061 are popular for structural elements.

A: I don't think the Advanced Antweight Starter Package is good for an antweight, let alone a beetle. The radio is not current specification, the charger is really marginal, and the power supply is overkill. The actual robot components are not a kit but just a collection of pieces without a plan or instructions. The motors, hubs, speed controller, battery, and wheels are fine for an antweight but there is no chassis -- just a pile of assorted carbon fiber pieces. An experienced builder could turn this pile of pieces into a functional antweight, but unless you plan a beetle with a huge weapon that you just want to push slowly around the arena it just wouldn't work.

A: Not recommended. If you connect the batteries in series, the weaker battery will drain down before the other and current flow will try to reverse-charge it. At best this could damage the discharged battery and at worst it could burst into flame. Connecting them in parallel would be safer, but I think I'd avoid the whole thing.

A: What does this have to do with combat robots?

A: We are not involved in posting copywritten material on the internet and we have no knowledge of the actions of those who are.

A: Mark J. here: climbing a ribbon is a little different than combat robotics, but I think I can point you in the right direction.

A few basics: you're controlling speed on a single motor and I assume you will want to control it in both directions (forward/reverse), so you will be looking for a single-channel dual-direction permanent magnet DC controller. A key factor in motor controller selection is knowing how many amps of current the motor will be consuming, and for how long. For example, here are the ratings for a popular line of robot controllers:

Once you have examined the torque demands your design will place on the motor, you can match up the amperage demands to a suitable controller. It does no particular harm to go 'overkill' here -- better to have a controller with too much capacity than too little.

A: Terrible idea! 'Robotica' and 'Full-body Spinner' go together like 'Ice Cream' and 'Anchovies'. In three seasons of 'Robotica' nobody entered a full-body spinner and no sane competitor would. Even die-hard spinner builders like Brian Nave and Terry Ewert built non-spinners for 'Robotica'.

A: Mark J. here: I guess it's time to put this question in the . 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.

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.

A: I'm not sure that I understand your question. NiMH cells in series can deliver as much voltage as you like, so I'm guessing you mean the voltage where the cell is effectively drained? The chart shows a typical voltage vs. discharge state for a NiMH cell. When fully charged the cell can provide a little better than 1.3 volts under load. By the time it gets down to 1.1 volts it's pretty much drained. The discharge rate and cell temperature will impact the discharge curve.

A: Chaos 2.

A: Either will have to be geared down to perform well with most spinner designs, but it's generally easier to work with a high torque motor. This is why the high-torque 'outrunner' style brushless motors are popular for spinner power. High RPM means high gear reduction and potential problems keeping drive belts in place on small drive sprockets.

A: Not a great idea. Commonly available stepper motors are a type of brushless motor designed to rotate in precise increments to position something accurately -- like the read/write head on a disc drive. They require special driver circuits and are not designed for high power output.

When brushless motors were first being used in model airplanes, some hobbyists found ways to convert specific stepper motors for aircraft applications. Now that brushless motors designed for the purpose are widely available there is no need to go thru the trouble. I'd suggest sticking with more conventional motors.

A: Why do people write to a combat robot site with mousetrap car questions?

Most mousetrap cars are designed for distance, not speed. The best distance moustrap cars creep forward very slowly -- speed is inefficient. For distance you want large, skinny wheels like CDs or even old LP records.

If you're building for speed you have other considerations. If it's a drag race style event for lowest time over a fixed distance you'll want the entire energy of the moustrap to expend itself in about the first 3/4ths of the course and then coast the rest of the way. Size the wheels accordingly. The tires will need enough traction to avoid power-wasting wheelspin, so some type of rubber tire may be needed. Experiment!

You can find more help for mousetrap cars of all types over at the Doc Fizzix website.

A: I don't have a weight chart for drill motors with attached gearboxes, but BaneBots planetary gearmotors come in a wide range of sizes and start at under 3 ounces. Their 28mm planetary gearbox with RS-385 motor weighs in at less than 6 ounces.

A: Mark J. here: I believe I only say that only once. I consider it to be inferior to other plastics like polycarbonate or UMHW polyethylene and I have numbers to back that up. Take a look at the table below: the mechanical properties of polypropylene are far below those for polycarbonate. Both polycarbonate and UHMW polyethylene have much greater ability to absorb impact without failing, as shown in the 'Tensile Elongation' and 'Izod Impact' tests that reflect the 'toughness' of the material.

In thin sections for an insect class robot polypropylene can be put to good use. I've used it myself for my antweight 'Rat Amok' because I happened to have a polypropylene box just the right size for my purpose. If I had a polycarbonate box that same size, I would have used it instead.

A: See the , about 20 questions down. A good place to start with a weapon around that size would be the brushless Axi 4130/16 or the DeWalt 18 volt drillmotor.

Q: I've built a spinner weapon similar to 'Son of Whyachi'. It weighs 7 lbs. The total bot weight is 22 lbs. What is the ideal motor rating for my weapon? The maximum voltage I can use is 24 volts.

A: More power is better for a spinner motor, so 'ideal' is as much power as you can reasonably get. The Axi motor I referenced above would be a good choice. Geared down about 3:1 and running at 24 volts it would give excellent performance. Use the Team Run Amok Spinning Weapon Excel Spreadsheet to check performance of your specific weapon with various motors.

A: Lithium batteries are picky about storage conditions, but Nickel Metal Hydride cells aren't. Store them at room temperature and give them a charge once a year. They'll loose charge during storage, but a couple of charge/discharge cycles and they'll pop right back to full capacity.

A: With only 150 grams of weight allowance, you don't have many choices. I've seen a few fairyweights made from the standard Micro R/C cars, like Mouseasaurus, but they are pretty weak. Pivot steering and gearing for speed over torque makes for a poor fairyweight.

I haven't had a chance to play with one, but the Air Hogs Zero Gravity Micro looks like it could make an interesting combat robot. It has differential steering and a suction fan to stick it down to the arena surface. The problem is the infrared R/C controller: they don't work very well in sunlight or thru Lexan arena walls. Some event organizers may not allow their use. Check with the event you'll be entering: if they'll let it run I'd give it a try.

A: The Speed 400 motor has different mounting hole spacing than the Whayachi gearbox, and the gear reduction is not correct for the Speed 400. The BaneBots 28mm gearmotors are 1.1" wide and high by 2.8 inches long.

A: Two pop to mind:

• Tornado vs. Razer in the Sixth Wars final: Tornado won by use of a special 'anti-crusher' framework added to their robot to keep Razer's piercing crusher away from vital parts. The device was pre-cleared with the technical crew, but many fans were outraged.

• Biohazard vs. Son of Whyachi in the BattleBots 3.0 heavyweight final: SoW used a rule-shaving 'shufflebot' propusion system to gain the additional 'walker' weight allowance for their monster spinner. The fight was tremendously destructive with both robots taking major damage. The judges' decision went to SoW, but a lot of fans saw it differently.

A: I remember being 8 years old and playing with Legos and a box on my bedroom floor. Why anyone would want to watch videos of someone doing this puzzles me.

At Motorama I'm going to run it as an undercutter. What other similar components could I use for mounting the weapon to the shaft? I could use the Shaftloc again since an undercutter won't be taking the same kind of vertical hits, but I'd rather use something more proven and reliable. Thanks.

A: Mark J. here: you don't have a lot of options for securing a hub to a live shaft that small. Hobbyweight mid-cutter Fiasco uses a custom hub that clamps the blade in place and is held to the shaft with four set screws. I'm not a fan of set screws! Given the options, your current solution may be the best choice; it sounds like that hit you took would have broken something else if the Shaftloc hadn't failed.

The most reliable method of securing a hub or other item to a round live shaft is to broach a keyway into the shaft and the hub and inserting a key to prevent rotation. This isn't practical for a 1/4" shaft, and neither is cross-drilling a hole thru the shaft and hub and inserting a hardened pin. I recommend using a dead shaft in insect class spinners for just this reason.

A: We liked all the fights we won -- hated all the fights we lost. The final platform match at Robotica had to be the best.

A: Once Matilda switched to the very effective flywheel weapon in the late summer of 2001, the weapon was never changed out for the old chainsaw.

The first series of 'Robot Wars Extreme Warriors' for US competitors was filmed in June/July, 2001 and Matilda was still using the chainsaw tail. This was after the UK 'Fourth Wars' and before the 'Fifth Wars' filming in August 2001 where Matilda appeared with the flywheel weapon.

The second series of 'Robot Wars Extreme Warriors' for US competitors was filmed in January, 2002. Matilda was still using the chainsaw weapon here, so the chainsaw was used in RWES series 1 and the flywheel was used in RWEW series 2.

Love the site. [BDsquint- FOBOT]

A: Mark J. here: thanks for the love, BD.

We both understand that the integrity of an arena depends on more than the thickness of the Lexan. The type of framing and fastening is critical in determining how much abuse an arena can put up with. That said, a well-constructed arena with 1/4" Lexan walls should keep you well ahead of beetleweight spinners for some time to come.

I can't give you a specific number of Joules beyond which I'd start to worry, but it's unlikely that your containment will fail abruptly and catastrophically. Lexan will deform and absorb a really enormous impact. You'll notice severe marring and obvious damage to the polycarbonate well before there is danger of a breach. As long as your framing keeps the edges of the Lexan from parting, you'll have plenty of warning when spinners get close to dangerous energy levels.

Many arenas have a 'bumper strip' of material set in just a bit from the polycarbonate walls about spinner-high. This dissipates a good amount of the energy from a spinning weapon before it can reach the outer wall. Good idea!