Questions and Answers about Combat Robotics from Team Run Amok.

Q: I want to get my D2 beetle running again, but I want to use something stronger than the generic Botkits 22mm gear motors to stay competitive and I can't get the Botkits motors to last on 4S. The Just 'Cuz Dragon 22mm Dartbox Gearmotors look great, but the weird clamp drive motor mounting system the D2 uses won't work with a square Just 'Cuz gearbox.

Any alternate recs for good 22 mm brushed gearmotors? [Social Media]

A: Mark J. Let me save you some money. The motor bolt pattern on the BotKits 22mm gearbox is correct for 130-size Dartbox motors, so just remove the stock motors and bolt up any of the brushed Nerf/Dartbox motors you like. You may need to shorten the shaft just a bit and/or transfer the pinion gear from the old motor.

If you want to stick with the 4S lipo pack I'd suggest the Just 'Cuz Gecko replacement motors for the Dartbox Pro. They're dirt cheap, will run all day on 4S, and at 16 volts pull only 7 amps each at stall. The Dragon motors can pull two-and-a-half times that many amps at their 12 volt max, require extra heavy duty ESCs, and are complete overkill for a four-motor beetle.

Reply: Nice, thank you

A: Mark J. I take no offense, but I won't allow readers to ask questions that dis questions from other readers. Such comments are standard business on Reddit, but on Ask Aaron I reserve that privilege for myself.

Q: Okay... in all seriousness, I've come to make a rather unfortunate announcement. I won't be finishing the RA2 models for Robotica seasons 2 and 3. My reasons are pretty extensive and complex, but since I don't want to use this website as my own personal blog (again), let's keep a long story short and say "I don’t find Robot Arena 2 to be that fun anymore". If anyone wants to continue the series in my place, please be my guest!

A: Sorry, but I also won't allow unfortunate announcements on Ask Aaron -- particularly if the announcement is not put in the form of a question. I would have deleted your announcement but my delete key finger is worn out from removing your opening question. I'll get around to it later.

Q: Because I'm sure you and others were waiting for the next installment, I figured it wouldn’t be right for me to leave it at that. So, as a "Thank you for putting up with me" award, I've gathered some .stl files for Hexbugs I made back in 2023. We've got: --- Abbatoir's spinner --- Darkness's pickax & weapon mount --- Nuts 2's Ring --- and finally the shell of Spinning Mayhem (with options to print in separate pieces, or all together)!

A: Yea, maybe I'm just being picky today but I don't think I should allow Ask Aaron to be used as a parking lot for .stl files. I mean there are lots of sites that do nothing but host 3D print files and... oh never mind. I'll find space to cram them onto my server, but if you want these files you'd better download them fast before I find a better use for the space. Here they are in a single .zip: Iceywave's 3D Hexbug files.

Q: And as a bonus, here’s a gif I made of NHRL's mascot, Sparky!
-sincerely,Iceywave

P.S. I have a couple more exciting things I’m working on. Stay tuned…

A: Hmmm... I'm not sure how an animated gif of an robot combat event mascot fits into the Ask Aaron Mission Statement. If I start accepting cute gifs the whole page might fill up with cartoon cats, bears, and penguins. I'm gonna allow it this time, but I'm gonna make it pretty small and add a really ugly border.

A: Mark J. The maximum voltage a motor can handle depends in part on how much load is placed on it. Too much load will 'bog down' the motor during spinup, causing it to draw extra current over an extended period of time. Extra current means more heat, and heat kills motors.

The FingerTech antweight beater bar kit has a relatively small weapon spun via a 1.7:1 reduction timing pulley set. This reduction reduces the torque load on the motor, shortens spin-up time, and prevents overheating on a 4S battery. If the same motor was used with a 1:1 direct drive it would not be prudent to run it at 4S.

If you want more weapon speed I would suggest sticking with a 3S battery and selecting a higher Kv 2822 weapon motor. Greater drive motor speed can make a 'bot difficult to control and is rarely usable in an insect-size arena. See:Traction and Reflex Limitedsix posts down this page.

Q: 1lb beater bot guy here. I found out that Fingertech sells 2600 kv 2822 motors, which should do nicely for increasing the weapon speed. However, the page for the motor says that the motor draws 24A, and "over double the power output [of the 1100 kv motor] requires a larger ESC." The 40A ESC is a full 6 grams heavier than the 20A ESC, which I also may or may not have already ordered, so I decided to seek a second opinion.

Palm Beach Bots appears to be reselling this motor with the claim that it is compatible with the 20A ESC, so I'm at an impasse here. Should I bite the bullet and grab the 40A, especially considering that I'm still planning to use the 14.8V battery which would probably draw more current on spinup? (since more weapon speed on a vert = good, and I drove a D2 kitbot at 4S for a couple years, so I'm reasonably confident that I can handle whatever speed two Silver Sparks can output) Or will the max current being above the ESC's rating be irrelevant since the motor will stop drawing a lot of current after spinup?

A: You're operating under a number of bad assumptions. Where to start...

A: Mark J. Yes, there is good reason to consider a lower Kv version of a given motor for an unsensored direct-drive spinner weapon. Even though a high Kv motor produces greater PEAK torque and power, a comparable low Kv motor has a smoother start-up with less "cogging" and better low-speed torque. A low Kv motor has a higher number of wire coils in the stator which provides better position feedback to the ESC, allowing the delivery of greater current at low speeds to boost initial spin response.

Limiting throttle to the weapon motor will reduce top speed, but it also reduces the current supplied to the motor which reduces both torque and power. If you can run a belt drive reduction to the weapon to take the torque load off the high Kv motor and let it spin up into its power band it can be a better choice, but for a direct drive weapon pick a Kv that keeps speed in the usable range for the weapon.

A: Mark J. The two motors are difficult to compare because their motor designations refer to differing measurements.

A 2205 Stator

The can diameter of the two motors is the same but the overall length of the SunnySky at 30mm is quite a bit greater than the Repeat Robotics motor at 22mm, and it weighs a fair bit more as well. This represents a considerably thicker stator. For brushless motors with similar voltage constants (K_v) a larger stator generally means more power, so the 1250 K_v version of the SunnySky should be a good bit more powerful than the 1100 K_v version of the Repeat Robotics motor. This also holds for the higher K_v versions of the two motors.

I will point out that the Repeat Robotics weapon motors are quite popular, and they are marketed as being designed for durability in direct-drive applications. Motor selection is not all about power.

---

I emailed Peter Garnache at Repeat Robotics to ask about performance specs for his direct-drive 2822 weapon motors -- like their internal resistance or continuous output power. He was kind enough to respond quickly:

Mark,

I don’t have either of those numbers on hand. I find that the current draw of the motors varies heavily on the weapon system that they’re spinning and the speed they spin at. In general the higher KV motors will pull more current. I'd choose a kv to get your tip speed between 150-250mph, and then do some testing with a power meter to figure out what your actual current draw is.

Thanks,
Peter Garnache.

Q: Humorous Post I'm a creatively bankrupt individual. Could you name my combat robot for me? I'm thinking of it being an antweight, but I might go up to BattleBots size, 'cause they seem pretty rad. Here’s a super detailed drawing I did of it! Hope you respond very soon. I have lot's of other NUANCED details about it (see? I'm practicing my grammar!) [West of San Antonio ✪]

A: Mark J. How about, "Vanishing Creativity". It works for all weight classes.

Q: Vanishing Creativity sounds super cool. Now I want help with those spinners. I was thinking of using the motors that drive stuff like r/c drones, and holding them on with nylon & rubber bands. My budget is negative 50 dollars(I owe my friends some money).

A: Spinner motors can be expensive, but I have a trick that will keep you on budget. Just give the weapon a good spin with your finger when you put the 'bot in the arena. It'll spin for a long time. Duct tape is good for holding stuff onto other stuff, but be sure to use the sticky side.

Then there’s the issue of speed. I want to OBLITERATE every bot! If I go antweight size, I bet 500 to 1000 miles per hour would do great. I'm gonna buy parts from Canada, but they don't use miles pers hours. How much kilometers an hour do I need?

A: Miles-per-hour (MPH) and kilometers-per-hour (KPH) are both old fashioned. The mega-cool builders specify speed in furlongs-per-fortnight (FPF). You can very easily attain huge numbers with these units: an average antweight tops out at better than 14,784 FPF!

Q: Sorrey. Parents phone broke. Laptop dont have atocorrect. Taked with sister. She said "GO HOME OR GO BIG!" So thats what Im doing. For 250 pound robot, would motors from pikup truck work? Buget now negativ 100 dollers(lost bet at skool. Need new frendz)

A: Depends. Did the truck work?

Q: Good news, phone is now fixed! The last time that truck was driven was 30 years ago. I’m assuming it works still.

I was thinking also about using a baseball bat for a backup weapon, in case the flipper breaks. Are bats allowed on BattleBots?

A: Dude, baseball bats must be illegal 'cause I never see 'bots using them, and honestly, who wouldn't wanna rock a sick weapon like that?

Update: Sorry, but Vanishing Creativity is no longer being built. Getting that baseball bat inspired me to start playing. Turns out I'm uber good! At my first day of practice, I scored 32 touchdowns and 16 layups!! Now I'll try for scholarship money. Turns out I won’t need to become a world famous robot builder after all.
- Sorry not sorry, CRAIGYBOT

Invert Makes it Worse

Q: I just finished my invertible antweight horizontal spinner. My transmitter can't do an invert correction mix, so I added a tinyMixer module to do both the single-stick mix and the invert trick. When running upright everything is fine, but when upside-down I flip the invert swich and neither the throttle or steering are right. This is worse then no invert switch. Is there something wrong with my mixer? [Hidden in an iCloud]

A: Mark J. Your mixer is fine. It turns out that there are two different mixer module set-ups that give correct response to transmitter input when the robot is right side up, but one of them does not respond correctly when the throttle channel is reversed to compensate for inverted operation.

Here is an excerpt from the help file for the Team Run Amok Combat Robot Mixer Fixer that describes the solution to your problem.

Invert Switch - Some DESCs and mixing modules have an 'Invert' function that uses a switched transmitter channel to reverse throttle response for inverted driving. If you have correct throttle and steering response but your 'Invert' switch just messes up your steering, this two-step fix should get it working:

1. Swap the positions of the two mixer or ESC plugs on your receiver -- unplug them and plug them back into each other's ports; then...
2. Physically reverse the polarity of the power leads from the ESC to the right-side motor.

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Telemetry Complication

Q: Hi, Mark. In the Radio and Electrical archive you mention the binding relationship between transmitters and receivers:

"A receiver can only be bound to one transmitter at a time, but you can have any number of receivers simultaneously bound to the same transmitter."

Does this same relationship apply to "telemetry" receivers that send a radio signal back to the transmitter? Thanks. [Sacramento, California]

A: Mark J. Telemetry receivers like the FlySky FS-iA6B make things a little complicated.

• A telemetry receiver binds to the transmitter in the same way a non-telemetry receiver does: it stores a code supplied by the binding transmitter and checks commands it receives against that code to make sure the command is valid.
• The complication arises because a telemetry receiver must store its own code on the transmitter so that its telemetry transmission is recognized as a valid source. The transmitter has only a limited amount of memory for this purpose.

The actual number of telemetry receivers a transmitter can be bound with varies with the transmitter protocol and with the specific multi-protocol adapter, if one is in use. Transmitters with which I am familiar have capacities that range from a dozen to sixty-four telemetry receivers at a time. Consult your transmitter documentation to find the applicable number.

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Traction and Reflex Limited

Q: Hello,
If I want to make a competitive plastic ant with oversize drive motors, would you recommend brushed or brushless? Palm Beach Bots recently added a couple of brushed and brushless beetle drive options that both seem light enough to put in an ant, as well as the new dual brushless drive esc that was just released. This robot would most likely be a 4wd vert or 2wd drum with a hub motor powered weapon.

Do you think this would be practical overall? It would gain a lot of pushing power and speed but I feel like I would see more people oversizing drive components if it was worth doing. I'm sure I can make everything fit, but figured I should ask before I buy any components. Thanks! [Logan, Utah]

A: Mark J. You are wise to note that oversize drive motors are not commonly encountered. If big motors gain an edge in pushing power, why isn't everyone using them? If speed is a sure path to victory, why are chunky brushless drive motors so rare?

Pushing Power - See Ask Aaron: Optimizing Drivetrains.

Pushing power is limited by traction. Once the wheels meet their traction limit additional drivetrain torque does not increase pushing power. The maximum pushing force a robot can generate is dependent on the weight bearing down on the driven wheels and the traction of the tire/arena pairing:

Maximum pushing force = Weight Supported by the Drive Wheels × Coefficient of Friction

An oversized drivetrain will "break traction" and spin the drive wheels at a small fraction of its power, but will not by itself generate additional pushing force from the tires. If you are fighting in a steel-floored arena and event rules allow it you may use chassis magnets to increase the apparent weight on the drive wheels and make use of increased motor power -- but there are significant problems with magnetic downforce, as described by multiple posts in the Ask Aaron Archives.

Greater Speed - See Tentacle Drivetrain Calculator.

There is only so much speed that can us effectively used in an insect-class arena. Like pushing force, acceleration force is also traction limited -- excess torque will break the tires free and hamper directional control of the robot. Even small ant brushless drive motors like the 24 gram Repeat Mini Mk3 deliver more speed and power than most drivers can use. Oversized drive motors will simply increase your frequency of running into the arena walls.

To answer your questions:

1. For the reasons above, I do not consider oversized beetle drive motors in a plastic ant to be practical.
2. Unless you have significant experience driving insect-class 'bots and reflexes like an over-caffeinated cat, I would recommend a nice pair of Repeat Drive Brushed Mk2 drive motors.

Q: Hey, Oversized ant drive guy here again, good call on the traction, I hadn't considered it. However, I have thought of one more point.

Since spinning weapons get more bite the faster they charge at something, would it be practical in that way to increase drive speed? Most of my successful robots have essentially been fast glass cannons that rely on outmaneuvering and ending the fight without taking damage. In this way, would it be wise to have an oversize drive to allow for faster retreats and a hit and run style strategy? Or perhaps just the antweight size brushless drive options?

I've mostly used the repeat brushed mk2's, but do have a set of mk3 mini brushless motors on hand. The brushless seem to not perform as well, but it might be due to them being paired to some of the very first brushless drive esc's that were released.

Thanks as always for the knowledgeable perspectives!

A: Brushless motors are only as good as the controller firmware and setup. Trying to control them with ESCs not perfectly matched to their requirements will yield very poor results. I like brushed drive motors because they're stupid simple to set up.

As mentioned in the post above, acceleration force is also traction limited. All torque above the physical traction limit will simply set the wheels free-spinning without adding to acceleration. More power won't give you as much improved performance as you think, and the effect on robot control can be catastrophic. The Tentacle Drivetrain Calculator takes this traction limit into account when modeling robot performance, so let's use it to compare the performance of two ants powered by normal and oversized motors.

The robots are two-wheel drive with 2" diameter wheels and 3S LiPo batteries. The only difference is that one is powered by the familiar Repeat Drive Brushed Mk2 ant motors while the other is powered by the more-than-twice as powerful Repeat Compact Brushed motors. Both are modeled for a 6-foot sprint across the arena floor:

For the six-foot sprint, the 115% power increase results in:

• A speed increase of 5% from 5.96 MPH to 6.25 MPH.
• An elapsed time decrease of 14% from 1.08 sec to 0.95 sec.

Do you think that's worth the effort? Even if the additional power did not adversely affect robot control, I would say not.

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Was Down - Now Up

Q: And I have heard that the internet archive has been taken down and would like to say that even tough episodes of Robotica are on YouTube again (which I still might have a fear that they might or might never get copyright season again) I still think that we need Robotica available on streaming platform/services AppleTV Mech+ Rakuten, Discovery+ are my suggests what are yours within the aspects [Erskine, Scotland]

A: Mark J. The Internet Archive was 'down' for a while due to a series of on-going hacking attacks. As I write this post the Archive is back up with all archive files intact and available, including the Robotica videos. The Archive video player is having some trouble ["Sorry, the video player failed to load. Error Code: 101104"] but clicking any specific file in the "Download Options" will immediately start playback on your computer. That's good enough for me.

I consider the Internet Archive a suitable repository for the Robotica Videos. I have no influence in programming for any streaming service, and I am thankful that the videos are available at all.

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Better Ways to Spend

Q: For a beetle weight: Have 2 brushed (max current= 4.9A) drive motors and 1 brushless motor (max current = 22A) for vertical spinner running off a 3sLiPo. How do I spec the Ah rating for the battery? Assuming worst case:

- 2 motors each draw 4.9A = 9.8 + 22 = 31.8A.
- Need it to run for 3 minute match = 0.05 hr
- Ah = 1.6 required

but ideally it could run for multiple matches without being recharged.

Does this estimate seem right? Would it be bad to have to much Ah? Would it be overkill to get a 3300mAh battery? [Winchester, Virginia]

A: Mark J. Your approach to the calculations is correct, but a couple of things are not quite as they appear. You may benefit from reading Frequently Asked Questions #21, #29, and the Ask Aaron Spinner Weapon FAQ. Here is some background info:

• Your unspecified brushed drive motors likely do have a stall current around 5 amps, but in a properly designed drive train they will rarely see even half that current draw. If they did draw that much current for three minutes they would turn into useless incandescent blobs. Current consumption is proportional to the load placed on the motor, and maximum load is limited by the weight on the drive wheels and the traction coefficient. The Tentacle Torque Calculator can provide an estimate of the battery requirement for your drivetrain, but there isn't much variation from one three-pound 'bot drive train to the next. Allot about 100 mAh for the drive.
• The "max current" listed for brushless motors is the greatest sustained current they can draw for an extended time period. For short periods they can draw much higher current -- but again, their current consumption is proportional to the load placed on them. During spinup for a rotational weapon the current draw may be much greater than the "max", but once the weapon is up to speed current draw drops to a much lower sustaining level. The Runamok Spinner Spreadsheet can provide an estimate of the current requirement for a weapon system based on the rotational mass of the weapon, terminal weapon speed, and the number of times the weapon is expected to spinup from a dead stop during a match. Again, there isn't a great deal of variation for reasonable weapon sizes in the weight class. A 22 amp "max current" weapon motor is fairly tame for a beetle, but you didn't mention the size or mass of your weapon.

Most beetles can get by with a 600 mAh 3S battery. Going to higher voltage levels will increase current draw: at 4S an 850m mAh battery is more or less standard.

Weight is precious in a combat robot and builders generally do not waste weight or space on an oversized battery. A 600 mAh 3S battery weighs about 50 grams -- a 3300 mAh 3S bettery can weigh 300 grams. There are MUCH better ways to spend that 250 grams than on an oversized battery.

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Keep the Power Output

Q: I'm building a new featherweight robot. My previous feather drive used 4245 800 Kv Flash Hobby Outrunners mated to 19:1 gearboxes with a 6S LiPo. The motors are rated 1200 max watts, and I am happy with their performance.

For the new feather I'm building custom gearboxes with a 12:1 reduction. To keep similar output RPM I'm looking at 500 Kv 6S motors, but I'm stuck in figuring out how to select motors that will supply axle torque equal to my current feather. What should I be looking for? [74° East Longitude]

A: Mark J. Power = Torque x Speed.

• You are reducing maximum motor speed by ~35% and are also reducing the gear reduction by ~35% to retain the original axle speed. If the new motor produces the same power as the previous motor you will have the same torque at the drive axle.
• "Maximum power" ratings for hobby brushless motors refer to the greatest continuous power they can supply without thermal failure. Actual available power is greater and is best evaluated by comparing the internal résistance of the motor (Ri) and the applied voltage (input watts).
• Compared to high Kv motors of the same size, lower Kv motors generally have less true output power. Pick a 500Kv motor with an Ri and voltage similar to your current motor (30 mΩ and 6S) and and you'll be on target. You may need to go up in motor size to attain this output with a 500 Kv motor.

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An Appreciated Tribute

October is a somber time here at Team Run Amok. For several years after Aaron's passing I would shut down all of runamok.tech for part of the month. This year my spirits have been lifted by a tribute to Aaron posted on Facebook by "Robot Enthusiast and All-Around Man of Supreme Awesome" Alex Valentine. Here is an excerpt:

Day 15 of Bot-tober 24 is dedicated to the late, great Aaron Joerger. He's the lawnmower, you're the grass... straight from Robotica, it's Run Amok! As has become something I like to do as part of my drawing events, I've dedicated the midpoint of this year's run to another late, great roboteer. After Rex Garrod (2020) and Grant Imahara (2021), Day 15 of Bot-tober 2024 is dedicated to Aaron Joerger, and features his most iconic bot. Large, in charge, and through all comers he'll barge, it's the first-ever "Robotica" Champion and undisputed King of the Assault Course... RUN AMOK!

The invention of father-and-son duo Mark and Aaron Joerger, Run Amok was the very definition of "simple, yet awesome". Built around the chassis of a 1972 Murray ride-on lawnmower and powered by two 24-volt motors geared down for great acceleration and torque, it uses a specially-designed short wheelbase - with car steering and unpowered front wheels using chunky pneumatic tyres - to make use of its driver's background in asphalt remote-controlled car racing, and enable it to turn quickly in tight spaces.

The version of the robot shown here lacks active weapons, but can equip a steep chequer-plate wedge up front to get underneath and shove opponents around - note the "eye holes" cut into them; those are to stop the front wheels from catching on the wedge as they turn! - or remove it to raise the ground clearance up front to easily cross obstacles without getting high-centred, and bash its way through obstacles and enemies. Add that to a welded steel chassis and a 1.9cm thick plywood lid, and you had a machine that - while it certainly wasn't the fanciest - was as rugged and dependable as they come!

Run Amok's finest moment was definitely in "Robotica" Season 1, where its mix of toughness, driving skill and sheer ability to adapt to anything in its way earned it the Championship, taking out both Juggerbot (who would eventually become the first Rosie the Riveter) and Ram Force in the last battle. It also made frequent appearances on both "Robot Wars: Extreme Warriors" and "Nickelodeon Robot Wars", where it fought under the name of Run Away; receiving new active weaponry in the form of two vertical spinning bars, also receiving a new hazard-stripe paintjob (hence the choice of background). There, it finished Runner-Up in the Season 1 Tag Team event alongside General Chompsalot (from Day 4) and made Round 2 of the Season 2 U.S. Championship, as well as making its last appearance in the "Nickelodeon Robot Wars" International Tag Team alongside Zanzara.

While it ultimately had to retire due to irreparable damage to its gearboxes in the aforementioned bout, Run Away was restored after into its original Run Amok form, and made lots of appearances in events such as the "DaVinci Days" in Oregon, often alongside its sister bot, The Gap. The Joergers also became well-known for hosting the "Ask Aaron" Q&A blog and the "Combat Robot Hall of Fame" on their website, endearing them to a whole new generation of fans!

With its relatively simple box-wedge design, Run Amok was a nice change of pace from the complex death machines that I've been drawing for you all so far. The chequer-plate wedge was pretty fun to work out properly, and I'm overall very happy with the look; and hopefully, bot-fans, you'll agree. This one's for you, Aaron!

Here's a link to the full post on Facebook. Thanks, Alex.

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Previously Answered

Q: What should be the max and minimum rpm of weapon [Tamil Nadu, Bharat]

A: Mark J. Although I very much wish to support the technical aspects of robot construction in the energetic and expanding Indian subcontinent, I am also greatly worried that I may be contributing to an extremely dangerous situation for builders and spectators. This has brought me to a painful decision:

The 'Ask Aaron' website is closed to questions from builders competing in India.

The best enclosed arenas in India would be considered inadequate for 30 pound robots in Europe or the US but are hosting events for 132 pound 'bots. Aaron certainly wouldn't approve of the reckless endangerment of life and limb, and I will not contribute to the development of robots competing in India until arenas in the region are universally able to safely contain them.

The specific question you ask has been discussed multiple times here at 'Ask Aaron'. You are free to search for those discussions should you be willing to do so.

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How Time Flies

Q: Guess what day it is... It's the one year anniversary of The Iceywave Troll-igy!

Since October 11th, 2023 I've received a few messages from people that I know who want me to send their questions to you. I'm not sure why they don't just send you the questions directly, but either way, here they are...

1. Can you tell me how to get to BattleBots Destruct-A-Thon? I’m too lazy to look it up on google maps. - Kevin's Bots & Stuff

   A: Turn right out the front door of Dave's Hot Chicken on Flamingo Road and take the skyway over to the Horseshoe. Walk past the SciFi Wedding Chapel, keep going thru Sully's Bar, and take the first right after Nathan's Famous Hot Dogs. Just before you get to the fitness center there is a door on the left marked 'Housekeeping'. Go thru that door, down the stairs, and out the fire exit at the bottom. Walk under the elevated monorail track and across the employee parking lot. The big white building in front of you is the BattleBots Destruct-A-Thon stadium. Knock three times on the blue door, tell whoever answers that you're delivering Dave's Hot Chicken for Trey, and they'll let you right in. Did I mention that's why you start at the chicken place? You'll need three orders, extra hot.

2. HHEEEELLLPPP!! I THINK IM ANONAGER?!?!? AR YOU THERAPIST?? CAN YOU HELP ME.? - Mistro Deb Hamper

   A: European or Persian? Look, lots of us eat grass and travel in herds. Not all of us identify as hemione, but if that's your choice ain't anybody here gonna tamp down on you. Consider this a safe place, and be careful charging your LiPos.

3. How to build a robot with the exact intention to protect yourself from meteor showers? - SpoopyVex029

   A: Intentions are simple -- actual protection takes work.

4. It took me 10 months to finish that full scale version of Chomp, and I ran it through the hot water cycle like you said. All the electronics have been ruined beyond repair, and worst of all, the bot didn't even shrink! I showed up to my local antweight event and got the award for 'Most Stupidest Robot Builder'. What should I do now? - The guy who asked questions #16 and #20 last year

   A: You've done better than most builders. Put your award on the mantelpiece. Take a slightly out of focus picture of the award and put it on Insta. Make a video of yourself dancing on your robot and set it up on TikToc. Update your resume to mention "Award Winning Robot Builder".

5. CLICK ON THIS LINK TO WIN A FREE CRUISE >>>>> Click Me! <<<<< YOU WON’T REGRET IT!!! - Something in my Spam Folder

   A: It's true, I have no regrets. Would do again.

Thank you for hosting my page for the past year! I hope to look back on this many years from now and say "This is where my comedy writing first began".

-sincerely, Iceywave : ) [West of San Antonio ✪]

A: Mark J. You're welcome. Remember: every comedian needs a straight man -- and the straight man gets 60% of the take.

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You Can Use What You Have

Q: I'm looking at building a featherweight robot for a competition next year. I have transferable experience in most aspects of building a combat robot but my radio control knowledge is limited.

I have recently purchased a RadioMaster Pocket ELRS transmitter to use with a drone but I don't see robot drivers using these. Can I use this transmitter for a combat robot? Many robot builders talk about OpenTX. Do I need a separate transmitter module to plug in the back of my transmitter for that? Should I buy a FS i6 like many people recommend? I'd like to stay as cheap as possible while still getting good quality equipment that I won't have to replace soon. [The Emerald Isle]

A: Mark J. Your RadioMaster transmitter will do very nicely. It runs EdgeTX firmware which is a newer development from OpenTX. There is nothing your will need for a featherweight combat robot that the RadioMaster cannot provide. The drawback is that both OpenTX and EdgeTX are very complex systems that can be difficult for new users to figure out.

Most of my guide to Programming an OpenTX Transmitter for Combat Robotics applies to EdgeTX transmitters as well. EdgeTX menus are a little different (Video) but the functions are essentially the same. Take a look at the guide and see what you think.

If you find programming an EdgeTX transmitter overwhelming, the FlySkyFS-i6 has a MUCH SIMPLER menu driven setup. My guide to Programming the FlySky FS-i6 Transmitter for Combat Robotics can have you operational in very little time.

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Kinetic Energy vs. Momentum

Q: Spinning weapons are always rated by how much kinetic energy they store (joules), but doesn't momentum also matter? If you have two spinners with the same kinetic energy storage how does momentum effect their destructive potential? [Long ago and far away]

A: Mark J. Momentum does have an effect on destructive potential, but you may be surprised by what that effect turns out to be.

Here are the equations for Kinetic Energy and Momentum:

Kinetic Energy = 1/2 × Mass × Velocity²

Momentum = Mass × Velocity

Here are three moving objects with the same Kinetic Energy but differing Momentum:

A major league fastball:

• 0.145 kg pitched at 45.5 m/s [102 MPH]
• Kinetic energy = 1/2 × 0.145 × 45.5^2 = 150 joules.
• Momentum = 0.145 × 45.5 = 6.6 kg-m/s.

A big frozen turkey tied to a skateboard:

• 14.5 kg rolling at 4.55 m/s [10.2 MPH]
• Kinetic energy = 1/2 × 14.5 × 4.55^2 = 150 joules.
• Momentum = 14.5 × 4.55 = 66.0 kg-m/s.

A Toyota Corolla sedan:

• 1450 kg rolling at 0.455 m/s [1.02 MPH].
• Kinetic energy = 1/2 × 1450 × 0.455^2 = 150 joules.
• Momentum = 1450 × 0.455 = 660 kg-m/s.

Imagine that you are sitting in a simple wooden chair on an flat and level surface. The chair can slide with only light resistance. Which of the three objects above would you least want to run into you?

• The Toyota Corolla sedan: it simply has the greatest momentum.
• The frozen turkey tied to a skateboard: its low temperature reduces the thermal kinetic energy.
• The major league fastball: its high speed will decrease the time available to transfer its kinetic energy.
• It makes no difference: they all have the same kinetic energy.

Time's up:

Being run into by the Honda Civic will accelerate you (and the chair) to about one mile-per-hour with a persistent force that will slide you (and the chair) for quite some distance. Strictly a kiddie ride.

Being struck by the runaway frozen turkey will attempt to accelerate you (and the chair) to ten miles-per-hour, but conservation of momentum will reduce the final speed of the combined turkey/skateboard/human/chair mass. Because of the higher approach speed the turkey will exert the accelerating force (kinetic energy) over a shorter period of time and, because the definition of power is work per unit time, the impact will be greater. Could leave a nasty bruise.

Getting hit by a 100+ MPH baseball is just plain ugly. The ball will attempt to transfer its entire accelerative force in a blink, resulting in a great deal of force exerted in a small impact area. We're talking potential broken bones and knocking the you/chair straight over. The full energy will be absorbed at the impact site and will not be dissipated over significant time and distance. This is a trip to the emergency room.

So, for a given level of kinetic energy greater momentum DECREASES destructive potential due to increasing the time over which the energy is transferred. However, higher speed spinning weapons have greater difficulty inserting enough of their opponent into the weapon path to reliably transfer their stored energy in an effective impact. The optimum mix of momentum and kinetic energy can be difficult to find.

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Feeling Overwhelmed

Q: Designing my first bot and have watched quite a few videos on it, but still feel overwhelmed, I'm aiming for a 1lb plastic since it sounds like the easiest to get into, and I want it to be a shuffler for the .5lb bonus with a spring powered hammer so it's at least a little unique.

I'm trying to figure out how to set up the electronics for fairly cheap and it sounds like a good start is a dual brushed ESC with two high ratio n20's but n20 motors say they are rated for 6v so is the 7.4v-8.4v of a 2s too much for them? I know there are better motors but I don't feel comfortable buying multiple $20 motors without a bit more understanding and I'm pretty sure a BEC can't provide enough current for running a whole bot.

I already have a Flysky controller and receiver, so I only need a power switch, esc, and motors. I thought that the most economical solution would be a Fingertech switch ($7), Repeat Electronics 'Budget Ant DESC' ($15), but then got stuck at the motors since the cheapest reliable motors I saw were $20 a pop which felt like a lot since I'd probably need three for the drive and hammer, can I just buy a few pairs of cheap n20's for $5 each and not have to worry about them failing immediately?

And for the hammer I'm going to canibalize a cheap servo that I already have, then throw some extra mosfets on it to run a snail cam that can safely charge and discharge the hammer; so I don't need an esc for the weapon motor. [Northern Arizona University]

A: Mark J. So, for your first 'bot you've decided to build a plastic ant shuffler with a pair of the cheapest N20 motors you can find on a mild voltage boost dragging around a cam-and-spring hammer weapon controlled by a cannibalized cheap servo board with extra MOSFETs. I wonder why you're feeling overwhelmed?

You've already rejected my standard advice on what a first robot should be, ignored my detailed list of reasons for that advice, and dismissed my opinion on cheap robot parts. I wonder what value you might place on my advice to the questions you now ask, particularly if I tell you something else you don't want to hear. Let's find out...

• A 2S battery is fine for N20s; I've seen them run higher. You won't have to run a BEC to drop the voltage to your drive motors.
• A pair of $5 N20s is marginal for a 16 ounce 'bot, and a shuffler system places a great deal more stress on the drive motor than do nice round wheels. A shuffler has to keep fighting gravity to raise and drop the robot as it runs -- much like like triangular wheels. If you want to use N20s at least use a pair of good ones.

Ask Aaron was founded to help builders create successful competitive robots. For some builders 'success' comes from impressing other builders rather than winning matches. To each their own.

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Can You Trust the Gerbil?

Q: Hello, I am wondering what thickness of TPU I should use for my beetleweight minibot? I started off with quarter inch, but it turned out to be to heavy. What should I do? [South of Hartford, Connecticut]

A: Mark J. See Frequently Asked Questions #17.

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Pssst! Down here... It's me, Rodger the Web Gerbil.

Mark is kinda touchy about questions that don't provide the silly little details that might give him a chance to come up with a quantified answer. This time though, I think he missed something. I have access to all of his notes and the exotic software that he doesn't share with the robot community, and I found this equation filed under "If All Else Fails":

cos² (x) + sin² (x) × (e^ix + e^-ix )² / 4 + sin² (x) × (e^2ix + e^-2ix ) / 4 + e^2ln(sin(x)) + 1/2 = What Should I Do?

Plugging your values into the equation I get: "Make it thinner 'cause making it thicker won't make it lighter."

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They Don't Get It

Q: What do your combat robots think of the current COVID-19 pandemic? [Kansas City, Missouri]

A: Mark J. My robots don't care. My robots don't spread, suffer from, or die from Covid-19 -- but you can. Don't be selfish. Follow the science. Stay safe.

Remembering Aaron Joerger, 1991 - 2013 The 'Ask Aaron' project was important to Aaron, and I continue the site in his memory. Thank you for the many kind messages of sympathy and support that have found their way to me. Aaron's obituary - Mark Joerger

Q: how can robots help us deal better with hurricanes and why? [Ontario, California]

A: [Aaron] Few people in Nebraska are threatened by hurricanes, so send a swarm of killer robots into low Atlantic and gulf coastal areas to drive the puny human inhabitants toward Nebraska. Problem solved.

Robot haiku:

That's obviously A question from your homework. Do your own research.

Aaron's Greatest Hits! More of Aaron's Poems Aaron at Nickelodeon Robot Wars Aaron's Minecraft High Dive Video Aaron's World of Warcraft Player Guide

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