A: See the for our comments on flame weapons and the reasons that we do not discuss their construction here.

A: The photo of Grabby at the Inertia Labs website shows a single standard-size servo connected to twin pushrods that activate the claw mechanism -- pulling back to close the jaw and pushing forward to open it. Two pushrods are needed because the ends of the claw mechanism diverge as they move. There is a second 'thin wing' servo attached to an arm apparently used as a SRiMech.

Given the lever advantage, the claw will actuate quickly, but will not have much grabbing force. Certainly not a crusher.

Q: Have "Grabby', 'Lifty', and 'Cutty' competed or are they just examples on the Inertia Labs website?

A: All three robots are credited as being built by The Machine Lab. I'm not sure that they were built as combat robots, and I can find no record of any robots from 'The Machine Lab' in combat competition.

Q: You said that Grabby's design was meant for speed, not force. What design would work for force? What would it take to build an antweight crusher with the Hitec 645-MG servo implementing the design of Grabby? Would the servo supply enough power of would you have to use something else like small hydraulics?

A: Mark J. here: contrasting Grabby to a crusher was a facetious exageration. Direct servo-powered clampers can have a large range of travel and little force like Grabby, or you can change the lever pivot point to reduce the range of travel and increase the clamping force. Every time you double the clamping force, you cut the amount of jaw travel in half. By the time you got enough force to do any damage, the jaw travel would be unuseably small.

You could modify the servo for continuous rotation and design an external gearbox to mulfiply the available force. The problem then becomes that force and speed are a trade-off: more force gives less speed and vice versa. Jaws with significant force and travel would be agonizingly slow.

There is nothing magical about hydraulics; you still have the problem with the inverse relationship between force and speed. If such tiny hydraulic components existed, their only advantage would be that high force can be generated without the need for heavy gearboxes and linkages.

An additional problem with crushers is the enourmous stress placed on the chassis of the robot deploying the weapon. A force equal to the force applied to your opponent must be borne by your own chassis. I've seen several would-be crushers that succeeded in ripping themselves apart.

A: Good servo choice. The 645-MG will deliver 38 ounces of lift at the end of a 3.5" arm. That's plenty to give quick and reliable lifts.

A: 'The guy who made Toro' would be either Reason Bradley or Alexander Rose of Inertia Labs. They used and sold the IFI Robotics speed controllers. If those don't look right I'm gonna need a decent description. Alternately, you can contact Reason and Alexander thru the Inertia Labs website.

Q: The speed controller is small and is for the insect classes. It has two receiver plugs and a black screw down terminal on the side. The circuit board is green and has two mounting holes. There is a black plastic thing sticking up on the board and another cylinder shaped thing that is half silver, half black. The letters and numbers on the cylinder say: 47 VFC 3T1. It looks like the flip channel plug was removed. Merci.

A: Yea, that's the Barello Ant 100. The color/style of the screw connectors changed with availability. The Barello speed controllers are no longer in production and Inertia Labs now sells them only with their full antweight kit, but you may be able to find a few in stock somewhere.

A: The kilobot version of 'Mars Attacks' was a thwackbot spinner made to look like a shell spinner. A thwackbot can't move when attacking (unless you have some fancy melty brain electronics) so all it can do for offense is sit and spin. There have been very few successful thwackbots -- judges hate them -- but they are fun to drive.

A: I hate to say it, but I think the Scottish Robot Wars spinner looked like a corkscrew sticking out of a cork.

A: Germany didn't have it's own televised Robot Wars production like Holland did, but they did stage non-televised tournaments with the winners going to the world championships in England. Many european countries saw Robot Wars dubbed in their own language.

A: The HXT 12kg (AKA Towerpro MG995) has Futaba splines and is quite inexpensive, but I strongly recommend that you buy something else.

All the reviews I've found say they're junk. They're heavy, poorly made, unreliable, and don't come close to meeting their advertized performance figures. One review thinks they may be the "world's worst servo." I wouldn't modify one of these to throw itself away. Avoid.

A: Mark J. here: I don't have enough information about 'Mangi' to make even a rough calculation on weapon energy. I've written to Al Kindle for additional info. As a pure guess I'd say 'Helios Sport' hits a little harder, but 'Mangi' is quicker. They did have one head-to-head fight won by 'Helios Sport', but they are both beautifully made top-flight robots.

UPDATE: Al got right back to me with details on Mangi's weapon. According to my calculations, 'Mangi' with 78 Joules is harder hitting than 'Helios Sport' at 50 Joules.

A: System requirements say: Windows 98/Me/2000/XP with a 450 MHz Pentium II or higher. No Mac.

A: If you want to keep it simple, try the Hitec HS-775MG servo. It's reasonably priced, has 200 oz/in torque, full metal gears, and easy mounting tabs.

Q: Which will be better for a beetle clamp: the servo you sugested running at 7.2 volts? or a BaneBots 28mm 25:1 gearmotor at 7.2 volts? If I use the BaneBots should I support the shaft?

A: I considered the BaneBots motors before I made my recommendation. The Hitec servo will hold better at a lower amperage draw, is an easier shaped package to mount, and requires no external speed controller. If you use a clamping arm that has some side flex (Lexan, maybe?) and mount close to the output bearing, either the Hitec servo or the BaneBots gearmotor should be OK with no additional shaft support.

Note that the Hitec servo is rated only up to 6 volts. I've never used this servo, but suspect it will be OK at 7.2 volts.

A: Mark J. here: the spreadsheet I have is just a few basic kinematic formulas strung together with a couple 'best guess' fudge factors. I put it together to get some order of magnitude comparisons between electric and pneumatic hammers. It has no documentation, is useable only over a small range of values without recalibration, and it relies on some questionable physics shortcuts. I don't think it would be of any use at all as a design aid.

A full-blown hammer simulator would be kind of a big deal. The motor torque continually changes with increasing speed, there is no good way to calculate the inertia of the armature from available data, and the effect of gravity on the hammer changes non-linearly all along the arc.

My best advice, as has often been repeated on the Ask Aaron webpage, is to use the construction examples provided by other builders as a starting point. In your case I'd carefully examine Helios Sport from Team Cosmos. Best luck!

A: At the first Robot Wars Extreme Warriors event in London (2001), Chris showed up with his fearsome vertical spinner 'Cyclone'. The robot was damaged beyond on-site repair in the first round of the main knock-out tournament. The production company had several 'loaner' robots on hand that were available to teams with robot problems. Chris drove one those loaners ('Tut Tut') in the Tag Team tournament.

At the second Robot Wars Extreme Warriors event (2002), Chris brought an improved version of 'Cyclone'. Although defeated by 'Probophobia' and 'Spin Doctor' in the opening round of the main knock-out tournament, Chris was able to win 'The Annihilator' tournament later in the event with 'Cyclone'. No need for a loaner that year!

A: Combat robots of any weightclass need some method of controling the direction and power of the motors. It's possible to use relays with R/C interfaces to get forward/off/reverse motor operation, but for reliability and precision driving control you need speed controllers.

A: You can go buy a 1" hole saw, but for a small job like this I'd score the outline of the hole onto the aluminum and then drill a series of small holes just inside of the scored line and use a small file to break thru from one hole to the next. A curved file can then smooth out the hole to the scored line.

A: Mark J. here: there are several posts on the design of 4-bar lifters in the archive, including a link to design software.

For an antweight the servo output can replace the entire rear (or front) bar of the mechanism to simplify construction. The diagram at right shows one possible configuration.

A: That's great! I really enjoy hearing from people who dig in and make a robot out of the pieces they have available. You'll learn a lot and have good fun while you're at it.

My dad keeps a updated mention of my age up above my picture at the top of the page. I'm 17 now and a senior at my high school. This year I'm the student manager of the football team and I'll be playing basketball. I play Yu-Gi-Oh twice a week at the local card shop.

A: Thanks for the props! It's hard to list favorites from Robotica since it took all the different 'bots and personalities to make the competitions as amazing as they were. I have listed a group of particular favorites from Season 1 in the archive -- search for 'I really liked'.

For season 2, I thought 'Ill Tempered Mutt' and 'Flexi Flier' both paid careful attention to the Robotica challenges and designed well for them. 'Wizard of Saws' gets my vote for coolest looking, and "Mechacidal Maniac" was probably the most fun to watch.

Season 3 was filled with many of our friends from Season 1 and I can't pick favorites from among them. Of the new teams, I liked the ingenuity of 'Scrap 8.2' and the design of 'Rambot' who borrowed many design features from our 'Run Amok'.

A: That wasn't a terrible noise. 'The Black Knight' was powered by an internal combustion engine -- that was the exhaust note! See the video.

A: Yes, 'The Butcher' from Inertia Labs had a massive pneumatic powered spinning weapon which was not very successful. Pound for pound, electric batteries store much more energy than compressed gas cylinders. Electric motors are also very efficient (80%) compared to compressed gas engines (15%). Pneumatics are great for quick bursts of power, but not efficient for continuous motion.

A: Read the archive for lots of info on converting R/C toys to combat robots.

A two pound robot would fight in the beetleweight class which has a maximum weight of three pounds. Full information on weight classes, radio requirements, and other design issues can be found in the current Robot Fighting League rules.

A: You shouldn't believe any of the info broadcast about the Robot Wars house robots. Shunt weighed a good bit more than 105 kg, the axe was not 'diamond edged', and there is no such thing as a cold-fusion engine. The axe was pneumatic and motive power came from a pair of Bosch GPA 750 electric motors.

A: The Spektrum DX5e is brand new and I have received no feedback from robot builders, so I cannot make a recommendation. I can tell you that it is a very basic 5-channel transmitter that lacks many useful features that make a robot much easier to set up and more comfortable to drive.

Q: What features does it lack compared to the DX6?

A: The DX5e has few features compared to the fully computerized DX6. Some examples:

• no LCD display;
• no batteries or charger;
• no multi-model memory;
• no adjustable travel volume;
• no user programmable mixes;
• no exponential response settings;
• fixed dual-rates - not selectable by channel;
• only one non-adjustable mixing mode (elevon).

Q: Could you use the DX5e with the BR6000?

A: Yes, and you should use the BR6000 receiver for the full failsafe features. The AR500 receiver does not correctly failsafe for robot applications.

Q: You can buy the DX5e on 'Mode 1' or 'Mode 2'. What does that mean?

A: There are two 'standard' ways that input channels are assigned to the two control sticks. Mode 2 is the U.S. standard with the elevator channel assigned to the vertical stick axis on the right side of the transmitter. Mode 1 is the European standard and has the elevator channel on the left stick. Computerized transmitters generally allow you to switch between modes, but the DX5e doesn't so you have to pick.

If you're going to use the included 'elevon' mixing and want 'single stick' control of throttle and steering on the right stick, pick Mode 2. Elevon mixing in Mode 1 will give you throttle on the left stick and steering on the right. More information on modes and mixing can be found in our transmitter programming guide

Q: Does the DX5e have a low battery light or something?

A: Yes, that's covered in the DX5e manual. See page six, and read the rest of it while you're there.