A: Good news first -- the size of your steel blade is good for a hobbyweight and the weapon as described will top out at more than 2500 joules, which is killer for a hobbyweight. That is the end of the good news, bad news follows.

• That weapon is going to take a LONG time to spin up -- more than 6 seconds to get to 3000 RPM and better than 15 seconds to full speed. That won't do in a small arena.

• The blade speed (4500+ RPM) is too great to allow the blade to effectively 'bite' into your opponent and inflict significant damage. A blade passes by every 6 milliseconds, which does not give much time to insert a piece of your opponent onto the damage radius.

• The combined length of the RS-550 motor and 4:1 P60 gearbox is going to set your blade hub at least 4" off the arena floor. Are your opponents tall enough to be hit by such a weapon?

• In spinning up from a standstill, the RS-550 motor will pull more than 40 amps for the first five seconds. That's way too much for way too long for the Sabertooth 12 ESC to handle. In the best case the ESC will cut amperage back and drastically slow the already too long spin-up time. In the worst case the ESC lets out a big puff of smoke and dies.

I don't know what you have against Victor ESCs. They require no programming, have very simple wireing, and are even easier to set-up than the Sabertooth. The Victor 884 is both cost-effective and a good match for your weapon.

Of course, you can also use a solenoid to simply switch your brushed weapon motor on/off. The 120 Series White-Rodgers Solenoid is inexpensive and has more than enough capacity for your weapon.

About now you're starting to understand why I don't recommend active weapon systems for first-time builders.

A: I don't think you're going to have much luck finding a similar gearbox. My understanding is that the shortage of certain BaneBots gearboxes is temporary. If you don't have time to wait for a P60 for the 3xx motors you can switch to the RS-545 motor and the 16:1 P60 for the 5xx motors - which is in stock. The RS-545 is heavier than the RS-380 (6.2 ounces vs. 2.8 ounces) but will provide similar performance in your hobbyweight and will not overstress your Sabertooth 12 ESC. If you can afford the extra weight, go for it.

A: What's wrong with side skirts?

You can make your robot as low as you like by choice of wheel diameter and selection of the mounting point for your gearmotors, but low can cause problems. Arena floors are rarely perfectly flat and they get more uneven as the tournament progresses. Too low and you get stuck on irregular sections of the floor. Skirts are great because they self-adjust and 'float' over irregular seams and gashes.

Would that be the best way to program this, or do you have any suggestions for possible solutions?

A: Mark J. here: as the radio specialist for Team Run Amok I'm going to intercept this question.

You haven't mentioned if this weapon is a spinner, a lifter, or something else entirely. Without knowing what the weapon is I can't offer a 'best' control option. For example: that 'Throttle Cut' push button on the DX6i is not a 'toggle', it's a momentary contact switch that is active only so long as you continue to hold it down. That could become inconvenient and tiresome for some types of weaponry. You also wouldn't want to abruptly reverse a spinner from full-speed; you'd want a gradual 'spin down' to avoid killing the motor and ESC.

The simple generic solution is to assign the weapon to the ratcheted throttle channel (or rudder channel if a spring-center is more convenient) for full proportional forward/reverse weapon control from the left stick, and use Delta-Wing (Elevon) mixing to control the robot drive system from the right stick.

If you really want to use the transmitter switches for on/off and forward/reverse control the weapon, send me more information about the weapon itself and I'll see what I can recommend.

A: See #29. Additionally:

• You haven't told me what the weapon blade is made of, so I can't calculate the weapon mass and rotational inertia for the blade.

• Is this for a hobbyweight? Assuming that the blade is made from steel, the blade weighs only 20 grams and would store only 9 joules of energy at 3000 RPM -- too little for even an effective antweight weapon!

• A blade that thin will not hold up well to high-energy impact. Go thicker -- much thicker.

Q: The weapon will be either made from chromoly, mild steel or 6061-T6, but probably mild steel because it's the most available metal here.

Yup, this is for a hobbyweight.

How thick is thick? Is 1cm thick enough?

A: See #17. We have a great deal of information about the design of spinning weapons in the archive, and we have a versatile Excel spreadsheet tool to evaluate spinner weapon design. Make use of them.

The whole idea of a spinning weapon is to store a lot of kinetic energy in a heavy rotating mass and then unleash that energy on your opponent. A typical spinner devotes about 30% of the weight of the robot to the weapon system. You're going to need a WHOLE LOT more than a 20 gram blade for a hobbyweight.

A: That depends on what you're planning on doing with the RS-550 and which DeWalt motor you're talking about.

I can tell you that the RS-550 is much less expensive, and that it is not made to survive the abuse a DeWalt motor can handle. You're getting what you pay for.

Q: i'm planning to use the RS550 for my drivetrain of my hobbyweight robot. The robot's size will be: 30 cm X 15 cm X 2 cm. The body will be made from aluminium and my weapon is a horizontal bar. For the Bar's motor i'll be using EFL-25-870 Power 25 Brushless Outrunner Motor and for the Weps ESC i'll be using Phoenix 45 Brushless Speed Controller. And for the Drivetrain's ESC i'll be using a Sabertooth 12. i've just ordered the Sabertooth yesterday.

A: How do you plan on installing a 3.8 cm motor in a robot only 2 cm tall?

A pair of RS-550 motors is overkill in a hobbyweight drivetrain. Geared for reasonable speed an a typically sized arena, they would provide ten times the torque needed to break the wheels free and spin them uselessly. RS-380s might be a better choice, particularly for a 'bot with an active weapon. Keep the gearing and wheel diameter reasonable or you'll overload that Sabertooth 12 -- bogging a motor makes it use more current.

Q: i'm not planning to use the RS-550 as it is, i'm planning to use this PDX16 - 16:1 Gearmotor. Is this still overkill for a hobbyweight?

A: Even more so. The Duratrax 550 motor is more powerful than the BaneBots RS-550 -- about 50% more powerful. Stall current is 148 amps -- rather too much to control with a 12 amp ESC! A pair of these motors will provide more than one horsepower. Massive overkill.

Q: so, what motor do you recommend which is powerful(but not overkill) and not a DeWalt?

A: Control and smooth response are more important than raw power in the drivetrain of a robot with a large active weapon. You need enough torque to achieve the full pushing power available in your weightclass without bogging the motors, but tire-burning acceleration and ramming speed are neither needed or desireable.

I mentioned above that a pair of BaneBots RS-380 motors would be reasonable to move around a hobbyweight spinner. You could mate them to BaneBots P60 gearboxes. Gear ratio for the P60 will depend on the wheel diameter you plan to use and the size of the arena -- around 26:1 with 3" wheels or 20:1 with 2.25" wheels is close. Note that both of these gearboxes are in short supply at the moment.

Q: I've got a question for you about both of the RS-380 and P60 Gearbox. 1.what size of the bolt should i use to connect the RS-380 and the P60? And is the bolt included when i buy the P60 gearbox?

A: P60 gearboxes for the 5xx series motors come with a mounting kit that includes mount hardware and the required motor pinion gear. P60 gearboxes for the 3xx series motors do not mention a mounting kit. I suggest that you ask BaneBots.

A: 'Run Away' had twin 30" by 2.5" by .375" mild steel bars rotating at 1200 RPM. I should mention that the primary purpose of the weapon was to look good on TV, not to do a great deal of damage. Total energy was under 3000 joules -- about half the energy in effective heavyweight spinning weapons of the period.

By the way, does imahara's book tell me which tools are good for which weight cats?

A: Mark J. here: my recommendation is that you wait for your copy of Grant Imahara's book to arrive and give it a good read before you think any more about spending $2,000 to $4,000 on a 1200 pound machine tool. A good quality machined part requires both a good machine and an experienced machinist -- consider farming out your machining needs. A great many builders get along just fine with hand tools.

Q: Dear Aaron and Mark, what does farming out your machines mean?
Thanks, New York

A: 'Farm out' means to hire an external service provider to do the job for you. Someplace like Westar Bot Shop is accustomed to quick production of custom robot pieces made to your order. They are better equipped than a home workshop, have experienced machinists, and have materials on-hand ready to go. Draw up your plans, send them off, and get the part back in the mail.

Q: I bought two copies of "kickn' bot" [book by Grant Imahara], and I have one on my knee right now. I already had it when you asked but thats ok because I had not started reading it. He never specifies which tools are good for which weight classes. Also, he says that the miniature versions of the machine tools are great, but does not specify how mini or which ones. But dont get me wrong, the book really is excellent! It goes over everything, and the project is a great addition.

My question is this: For the purpose of a combat robot, which tools should I get if I do not want the job to take forever and have accuracy? I know that you can do curves with a jig saw, but which tools would be more beneficial than that?

What I mean is that I am trying to find a reasonable plan that falls in between using a hand saw and jig saw and purchasing a cnc mill. I don't really want to outsource. Do you have any recommendations for this? Basically, I am trying to find a reasonable medium so that the job does not take forever and the tools dont take too much space.

I hope I have explained this well, as I really love what you guys are doing and I dont want to waste your time. Also, I hope I am not being to demanding, as I hope the hamburger is not bad.

Finally, I might have missed something in the book, as I just gave the section a scan, and I also read all of the first chapter. If you think I have missed something vital, feel free to point it out!

Thank you very much, New York

A: I have a problem answering your question. If you wanted to listen to music, I couldn't recommend that you go out and buy a violin because I don't know if you can play a stringed instrument. Likewise, I can't recommend that you stock a workshop full of machine tools because machine work is a skill that does not come with the machine. If you have a good machine tool and a poor machinist all you get is ruined material and possible injury.

If you had training with machine tools you wouldn't be asking these types of tool selection questions. I think I would be doing you a disservice to give you a quick and easy answer, but I can't teach you correct machine technique either. The best I can offer is to encourage you to soak up as much information as you can from Grant's book and work on your construction skills.

Your hamburger is fine. Keep reading Grant's book.

Q: You are totally right, that question not that smart. However, I have read some of the first bit, and now I have specific questions. He seems to recommend using a jig saw a lot. My questions are these:

a) How good quality will this tool produce? Basically, which bots have had a jig saw used for them?

b) A drill press is the next level above cordless (unless you are using it in the pits). A band saw is the next level above a hand saw. A jig saw is to a what? For making curved cuts as well as straight, what tool is better and do you recommend this over a jig saw. I just don't know if a jig saw is really the tool that should be used here. Is a mill the next level? He only mentions mills once, and does not include them in his index. He says there are mini versions of the massive ones for hobbyists, but that is it. Where should one use one? Do you have a recommendation for the size of mill adequate for combat robot building?

Thanks so much, I hope I am not asking to many questions! Feel free to tell me if I am!!! -New York

A: I don't believe you're approaching this correctly.

If you're comparing a jig saw to a mill it's obvious that you have no idea what a mill is or what it does. You don't need one.

Like I said earlier, I can't teach you how to be a metal fabricator.

Another thing about this set... i've got a question for you: Because the Battlepack is 12 Volts, that means that i'll be mildly overvolting both the weapon ESC and motor. Is it okay?

A: Some problems:

• The Sabertooth 12 is marginal given that the drive motors can pull 35 amps at stall. It could be OK if you have relatively small wheels, but that creates other problems (see next bullet).

• You'll need REALLY big wheels to get decent speed from these gearmotors. With 3" diameter wheels the top speed will be just over 1 MPH -- WAY too slow! You'd need 12" wheels that are too big and heavy for a hobbyweight to get an acceptable 5 MPH speed, and then peak amp draw exceeds the capacity of the ESC. Unacceptable.

• The weapon motor is much too small for a hobbyweight spinner. It's tiny (1 inch diameter, 0.9 ounce) with a peak burst 100 watt rating. OK for an ant or maybe a beetle, but not enough for a hobbyweight. You'll need something more like this. Actual motor selection will depend on the mass and size of your weapon flywheel.

• You'll need more amp capacity to control a brushless motor appropriately sized for a hobbyweight weapon.

• NiCad batteries are big and heavy for their output capacity. Most builders favor LiPoly batteries. A comparable LiPoly pack saves 70% on both weight and space. More weight allowance for the weapon and armor!

• Good choice on the radio.

Q: Dear Aaron, after reading your advices, i've revised my list to be this:

• Drive ESC: same as before
• Drive Motors: from the DeWalt DCD710S2 12V MAX drill X2
• Weapon Motor: EFL-25-870 Power 25 Brushless Outrunner Motor
• Weapon ESC: Phoenix 45 Brushless Speed Controller
• Battery: from the DeWalt DCD710S2 12V MAX drill (i bought the set which consists of 2 batteries and a charger)
• Weapon Batteries: PowerEdge 2200mAh 11.1V 3S Triple Cell 30C LiPoly Pack
• Radio: same as before.

A: Better!

• DeWalt is very stingy with data on their motors. This motor and gearbox differ from the 12 volt motor and gearbox previously available to robot builders. I can only tell you that this gearmotor has a two-speed transmission: 400 max RPM and 1500 max RPM with the DeWalt 3-cell Lithium Ion battery. As with other drill motors, you will need to lock the transmission in 'high' and lock out the slip clutch for robot use. Guessing from data I have for other DeWalt gearmotors, these should be fine for your purpose, but I can only guess at torque and amperage figures. Your selected ESC may or may not be adequate, depending on wheel diameter. I'd keep the wheel diameter under 3 inches. Best luck.

• I don't recommend multiple batteries in a combat robot. You need to minimize confusion in the pits between matches, and multiple batteries to individually check and charge will only add to your troubles. I estimate that the pair of DeWalt drive motors in a hobbyweight will only use about 600 mAH in a 3-minute match. The weapon motor is harder to estimate, but won't use more than another 1000 mAH. That still leaves ample reserve capacity from the 2200 mAH main LiPoly. Don't complicate -- go with a single battery.

• Performance of that specific weapon motor will depend on the mass, shape, and size of the weapon flywheel and the speed reduction in the weapon drivetrain. You haven't told me anything about that, so I can't even guess on weapon performance.

Q: So, should use the batteries from the drills(DeWalts) or should i use the LiPoly Battery?

A: Use the LiPoly. The DeWalts are lithium ion. They are more prone to damage and bursting into flame if abused -- and combat will abuse them. We have full specs for the Lipoly: it has very high charge and discharge rates, it's compact, it's newer technology, and it's safer.

Q: According to the list, what power switch would you recommend for it?

A: Check your ruleset to see if there are special requirements. You may be able to get away with just plugging/unplugging the battery. If not, I'd use a removeable link -- search the archive for 'removable link' for a diagram.

Q: It's a dilemma. Because you said that i can only use 1 battery for simplicity sake, if i use the batteries from the DeWalt, i'll overvolt the brushless motor and ESC. If i use the LiPoly packs, i'll undervolt the DeWalt Motors. Which one is more safe?

A: No dilemma. The DeWalt isn't really 12 volts -- its Li-ion battery only produces 10.8 volts under load. DeWalt motors are commonly overvolted by as much as 33% in combat robots anyhow. Use the LiPoly.

P.S. -- it's always 'safe' to undervolt a permanent magnet DC motor. It will just run a little slower.

A: You didn't tell me what size packs you're looking for. A quick web search ('A123 battery packs') turns up several sources (Electricwingman, Esprit Model...) and a selection of small packs ARE available thru Robot Marketplace. Take another look around.

A: See #1.

A: I don't think you understand what a Battery Eliminator Circuit (BEC) does.

An R/C receiver typically requires a lower voltage power supply than the main battery for the vehicle. A BEC is a voltage regulator that connects to the main system battery and provides a stable 5 volts to power the receiver via a standard receiver cable. This eliminates the need for a separate small battery to power the receiver. Search for 'how do battery eliminator circuits work' in the archive for more info.

Receivers do not have BECs -- but Electronic Speed Controllers (ESCs) often have a built-in BEC to power the receiver. This makes sense as the ESC will be attached to the main battery and already has a cable going to the receiver that can carry the power. Check the documentaion for the ESC you plan to use to see if it has a BEC.

If main battery power is available to the BEC and the BEC is connected to your receiver, the receiver will be active and can be bound.

Note: the Spektrum AR6255 receiver has a relatively broad input voltage tolerance: 3.5 to 9.6 volts. If your main battery is within this range you can power this receiver directly from the main battery without a BEC via a standard receiver cable.

A: See the Wikipedia entries for omni wheel and Mecanum wheel, plus multiple posts in the archive under 'omnibot'. Omni wheels are not good at high speeds and do not provide great traction. Their strength is entirely in the amazing maneuverability they can provide. Try a video search.

I was think I would like to use two high amp Mosfets. Is this possible? If so, what would the wiring look like? Simular like battery isolator, but totally disconnect the primary battery.

A: If the two battery sources are identical, just wire them in parallel to double the capacity. No need to complicate things with MosFETs and switching. Keep it simple.

A: Mark J. here: most of the switches on your DX6i aren't 'channels'. Your radio is a six channel transmitter designed primarilly for aircraft, so some of the functions don't do anything at all useful for a combat robot.

• The first four channels (THRO) (AILE) (ELEV) and (RUDO) are proportionally controlled by left/right and up/down for the two control sticks.

• Channel 5 (GEAR) is by default controlled by the 'Gear' switch and can provide two position instruction to a device plugged into the [GER] port of the receiver with the flip of that switch. Useful for activating a flipper, gyro, or weapon ESC.

• Channel 6 (FLAP) is by default controlled by the 'Flap' switch -- but it effects multiple receiver output ports. Activation of this channel mixes in a set amount of response to both the [AILE] and [AUX] receiver outputs, plus optional response from the [ELEV] output. This makes perfect sense for an airplane, and no sense at all for a robot.

  If you really need to use the [AUX] output and control it with the Flap switch, you can either move the robot steering off the [AILE] output channel or set a 'programmable mix' to offset the effect of the (FLAP) input on the [AILE] output. Both are fairly advanced tweeks -- leave it alone unless you really need that sixth channel.

Tip: aileron dual rates are VERY useful in combat robot control. See if you can figure out why and how.

A: Sorry, we don't work with BASIC Stamp programming. There are a couple autonomous robot builders on the Western Allied Robotics forum that may be able to help -- try a post there.

A: Futaba is a major R/C manufacturer that builds quality equipment. However, the 4YF FHSS is a really basic 'entry level' radio with very limited features. Most importantly the 4YF FHSS system does not failsafe, which makes it generally unacceptable for combat robot use.

We have posts covering our recommendations for combat robot R/C gear in the archive. I suggest you start there rather than asking our opinion on every inexpensive radio you find.

A: That designation refers to the number of Lithium Polymer cells recommended in the battery. One LiPo cell provides 3.7 volts, so a 2-3S LiPo recommendation calls for 7.4 to 11.1 volts. I don't recommend overvolting hobby brushless motors.

A: Well, New York, you've put in a good share in the recent past. More generally, our questions and readers come from around the globe -- see the map at the bottom of this page. I don't generally track question sources unless I'm curious. A quick look at our recent questions shows a lot of activity from Indonesia and west coast USA, but that varies wildly.

Q: I just want to know whether there are techniques that spinners use to fight against wedges....like lowering the height of the weapon tooth etc.. A: 'Spinner killer' scoops and wedges do present a problem for spinners. The usual attack technique is to avoid a direct front attack and veer a bit to one side to 'catch' the edge of the wedge. Spinners love to attack sharp edges on their opponent. Q: Dear Aaron, if spinners love hard edges (which I am sure they do) why does Breaker Box, a very successful bot and and [maybe...] the best 'killer of spinners', have sharp 90 degree angles all around it? [New York] A: Most robots have a lot of edges because it's much simpler to build a strong boxy robot than any other shape. Jim Smentowski does his best to keep the boxy body of 'Breaker Box' hidden behind the big, smoothly curved titanium scoop in combat. Combat robot design is always a compromise, and Jim has struck a good balance this this 'bot.

A: 'Son of Whyachi' outweighed 'BioHazard' by 100 pounds. Its weapon was eight feet across and powered by two enormous 15+ horsepower motors! It was a legal heavyweight only because it was technically a shufflebot 'walker' and was given additional weight allowance. They changed the rules before the next event to take the weight allowance away from shufflebots -- that wasn't what they had in mind for a 'walker'.

Q: Dear Aaron, compared to Son of Whyachi, how powerful are Last Rights, megabyte, and toro maximus? I saw the [question above] and I was just wondering how they stack up.
Thank you, New York

A: Mark J. here: I don't have enough information about weapon mass and speed on the 'bots you list to directly calculate their energy storage capacity. Comparison is further complicated because there were multiple versions of SoW with different motor configurations -- both electric and internal combustion.

In the archive you can find a post where I estimate the energy stored in Megabyte's shell at about 50,000 joules -- likely greater than the effective weapon energy for either 'Last Rites' or 'Toro Maximus'.

I have seen unofficial estimates of more than 100,000 joules for the version of 'Son of Whyachi' that won the BattleBots championship, but equally important is the ability to deliver that energy to an opponent. SoW's very large weapon diameter and relatively low spin speed allows for greater 'bite' and a more effective hit. Terrifying!

A: I don't know what aluminum alloy you'll be using, the details of your design, or the construction techniques you will employ. See #17. As a pure guess, the side panels seem thick for a hobbyweight and the top and bottom seem a thin -- particularly for a dustpan.

Q: 1 more thing, i'm new to the competition, so, i can't give you pretdictions about how the competitor's bot gonna look like. But all i know is that someone in my school robotic extracuriculum (i'm in it too, only i and that guy's gonna attend the combat robot category at my competition) is gonna look like Roadblock with a drum.

A: We've said before, a combat robot's success depends about 20% materials/components and 80% on design/construction/detail. What your opponent 'looks like' doesn't count for much.

A: I don't know why you would want to know, but about 9 minutes into this 2008 combat robot webisode of 'Systm', Dave holds up a Barello Ant 150 ESC. Barello ESCs are no longer in production -- and Dave ends up spending more like $400 on a 'pit pass' robot without a battery charger.

Q: Hi Aaron, just asking, what ESC that can control multiple channels? i'm asking that question because i'm fascinated with that ESC because Dave Calkins said that this ESC can control multiple (3) channels.

A: ESCs that control multiple channels are not unusual. The Barello Ant 150 could control two forward/reverse drive motors (2 amp continuous) plus a forward-only brushed weapon motor (8 amp continuous).

Many ESCs control two drive channels (Sabertooth, Robo Claw, some Scorpion, some Vantec...) but three channel ESCs are pretty much extinct because of the increased popularity of brushless weapon motors that require their own specialized ESC.

A: I'm looking real hard at a Sabertooth 12 and I don't see a 'relay plug' anywhere. I also don't see it mentioned in the documentation. I don't know what you're looking at.

Q: I'm sorry, it's not the relay plug, it's the "flip channel" plug from the SaberTooth that connects to the receiver. what are it's uses?

A: Aha! The 'flip channel' is used to fix the throttle response when an invertable robot gets flipped over. An inverted robot with differential steering will still steer correctly when flipped, but the throttle is reversed -- forward is reverse and vice-versa. Plug this lead into a spare receiver channel controlled by a transmitter toggle, and if your robot gets flipped over you can flip the transmitter switch to restore correct throttle direction.

A: Mark J. here: no, the electrical components of a typical combat robot are wired as a parallel circuit. Each of the components will be able to access the full voltage of the battery. The voltage needs of the components are NOT additive.

Example: a battery pack in a combat robot provides 7.4 volts. If wired as shown in #19, both drive motors, the weapon motor, both ESCs and the power light can each access the full battery voltage of 7.4 volts. The receiver is typically powered by a voltage regulator built into the drive ESC and will have its voltage limited to about 5 volts.

The voltage requirements of the components are not additive, but the amperage requirements of the components ARE additive. If the two drive motors have a maximum current draw of 4 amps each and the weapon motor has a maximum current draw of 8 amps, the battery may have to deliver 16 amps in a 'worst case' situation. The current draw of the ESCs, receiver, and power light are trivial.

A: Line followers and maze robots are a lot different than combat robots. These gearmotors are converted servos with FAR too little torque (0.9kg-cm = 12.5 oz in) for a hobbyweight. A typical hobbyweight gearmotor would have similar RPM but 20 times that much torque. The motors could work for an antweight, but no way for a hobbyweight.

A: There aren't many small gearmotors with suitable power and gearing to make a decent spinner weapon. That's part of why most spinners use a belt drive reduction. Belt drives are also better able to put up with impact stresses. Without the details of your weapon design I can't make a specific recommendation, but you might consider the Beetle B04 Gearmotor.

I get tired of answering "Where can I find..." questions with "Robot Marketplace" but it's almost always true: 15 mm weapon hub. You'll need to drill the 0.126" shaft hole out to 4 mm to use it with the B04 gearmotor.

Q: The 15mm blade hub says discontinued.

A: The Team Think Tank products have been getting scarce. It looks like most all of their stuff is sold out and they aren't making any more.

I don't have another source for 'off-the-shelf' weapon hubs. You might ask around the RFL forum to see if anyone has a spare. Team Whyachi will machine a hub to your specs -- for a price.

A: Well, they will 'work', but I have some comments.

• Not many builders use the Tamiya gearboxes anymore -- they're quite bulky and a little fragile, but they work.
• The Sabertooth 12 is overkill for the Tamiya gearmotor in an antweight. It will certainly work, but you can save considerable weight by using the Sabertooth 5.
• 8 cells (9.6 volts) is too much for that Tamiya gearmotor. I'd suggest 5 NiMH cells (6.0 volts).
• You haven't told me what type of weapon you plan, but the 150:1 Mini Metal Gear Motor is far too slow for a spinner weapon, and too weak for a lifter.
• The SpeedMax-40 ESC has features and capacity you don't need, and it is tedious to program. It's also a single-direction controller (no reverse). Consider the BaneBots 3-9 Reversible Brushed ESC. It has ample capacity for many brushed antweight weapon motors, will reverse, and will fail-safe correctly with the Spectrum AR6115 receiver.
• You might consider the Spektrum AR6115e receiver instead of the AR6115. The end pin output is a little easier to fit into a cramped antweight.

A: Victor IFI speed controllers were designed for use with a special radio system (no longer available) that provided a stronger than normal control signal from the receiver. For reliable use with non-IFI receivers, a special signal booster cable is typically needed. Like most robot supplies, signal booster cables for Victor IFI speed controllers can be purchased from the Robot Marketplace. The cable is not included with the Victor controller.

Q: One more thing....... is the Sabertooth 12 RC Dual Motor Speed Controller good for a horizontal spinner hobbyweight?

A: Proper selection of an ESC depends on more than the weight of the robot and the type of weapon. Motor type, gear reduction, wheel size, voltage, and weight on the driven wheels all go into the calculation. The Sabertooth 12 is probably a pretty close match to your needs, but if you don't do the math you're just guessing. See #21 for help.

A: That's not a bad start, but you'll need some additional armor to go with it. The Viper will not hold up against impacts from robots running up your wedge and into the vacuum-formed body of the robot.

Note that some arenas have gapped floor seams that can make life miserable for thin, sharp nosed drag wedges. Best to investigate the arena before settling on a wedge design.

We do have some comments about the Viper kit in the archive.

Q: I'm the viper kit guy again, will a dollar store tuppa ware container work as some armor, provided I let it flex?

A: If I understand your design, you're going to need something much more substantial than a sandwich box to stop a spinner running up your wedge. The Lexan body that comes with the Viper is stronger than a dollar store plastic food container. For front armor you're going to need something hard enough that a spinner blade can't 'dig in', and it has to be very well mounted to the baseplate.

I know the Viper is sold as a combat robot, but it needs a lot of help before it can stand up to serious competition.

A: You'd better ask them.

Q: How do you set up omni wheels? A: Have a look at the build report for omni-hobbyweight 'Skittlebraü'. RobotLogic makes a radio mixer for a three-wheeled omnidrive that will simplify your radio set-up. They also make a Mecanum mixer for four-wheel omnibots. Search the archive for 'omnibot' to find several posts and a diagram.

We welcome combat robot questions. Search the Ask Aaron Archives first to see if we've already answered your question. Recent Q&A are posted above.

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