Questions and Answers about Combat Robotics from Team Run Amok.
7712 Questions and Answersabout Combat Robotics
from Team Run AmokPrivacy Policy
Team Run Amok receives a lot of email about designing and building combat robots. In 2003 my son and team member Aaron Joerger (then 12 years old) asked for a question and answer page to document our responses.
Even small combat robots can be dangerous! Learn proper construction and safety techniques before attempting to build and operate a combat robot. Do not operate combat robots without proper safeguards.
Ask Aaron is a simple little question and answer page. People ask questions about combat robots and we do our best to answer them.
Recently I've received some messages where the bulk of the text is used to express views or opinions that would be better suited as social media posts. Although I found the topics of these messages personally interesting, I did not publish them and I will continue to reject submittals of this type. I won't have Ask Aaron turned into Reddit. Let's keep it to combat robot questions, please.
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.
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:
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...
Physically reverse the polarity of the power leads from the ESC to the right-side motor.
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.
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 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.
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:
For the reasons above, I do not consider oversized beetle drive motors in a plastic ant to be practical.
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.
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.
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.
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.
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!
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.
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...
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.
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.
How to build a robot with the exact intention to protect yourself from meteor showers? - SpoopyVex029
A: Intentions are simple -- actual protection takes work.
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".
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.
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.
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:
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.
Pick One Easy to Use
Q: What type of ESC works best with the FingerTech Silver Spark 16mm Gearmotors? [Fremont, California]
A: Mark J. FingerTech Silver Sparks do not place great demands on their speed controllers. With a 2-cell LiPo battery they draw a maximum current of 1.6 amps at stall -- 2.4 amps with a 3-cell battery. The Repeat Robotics Budget Ant DESC is a very affordable, compact, and versatile dual-channel ESC for brushed motors. It is favored by many competitors for ease of use and durability.
They Do Different Things
Q: Are there any benefits to a front hinged lifter/flipper compared to a "normal" rear hinge? [Sacramento, California]
A: Mark J. From a 2012 post in the Robot Weapons archive:
Q: Are there any advantages for front hinged flippers? It seems to me they push their opponents around more than anything else.
A: A front hinged flipper will, when combined with a ramming charge, toss an opponent in a low arc up and away. This is very useful in an arena where the opponent can be thrown out over a low barrier for a instant win. Such arenas are the prevailing design in the UK, where front hinged flippers have been quite popular.
Q: Do front hinged flippers have any advantage over back hinged flippers?
A: The two designs have different applications. Relative to the resting angle, a rear-hinge flipper will launch an opponent in a high and upward arc, and a front hinge flipper will launch the opponent in a lower arc to the front. Match the flipper design to the arena, your attack strategy, and the overall design of your robot.
I Have a FAQ For That
Q: how many joules does a 15 pound battle bot weapon need [Grove City, Pennsylvania]
A: Mark J. The very first question in the Ask Aaron Spinning Weapon FAQ is: "How much energy should my spinning weapon store?". It will be in your best interest to read the entire FAQ.
Being Irrational
Q: What's the square root of 24? [West of San Antonio ✪]
A: Mark J. I dislike giving imprecise answers here at Ask Aaron. As the square root of 24 is a non-repeating non-terminating irrational number the best precise answer I can provide is the simplified radical form: √24 = √(2×2×6) = 2√6
If you prefer imprecise: √24 = not quite five.
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?
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.
Turn Two Into Four
Q: How can I convert an antweight into a 4 wheel drive? What gears or pulleys are to be used for that? [London, England]
A: Mark J. Given your location I'll assume we're discussing 150 gram UK antweights. You haven't told me anything about the design you would like to 'convert' so my comments must be very general.
The simplest and by far most common 150g 4WD solution is to add another pair of motors to directly drive the new pair of wheels. A pair of N20 motors weigh 18 grams; a pair of N10 gearmotors weigh 16.8 grams.
I do see a few 150g gear drive solutions that use custom printed plastic gears and hubs: Team Panic video.
I don't know of off-the-shelf components for the hubs, pulleys, and stub axles needed for a generic belt-drive conversion for a 150g robot. You would need to fabricate many if not all of these components.
Gear or belt drive 4WD antweight designs are generally used only where there is no space for extra motors due to weapon layout. Note that these solutions might very well weigh more than an added pair of motors and would likely be less reliable.
Weebles Wobble
Q: Help me unpack this discussion I'm having with a friend right now. He argues that one could solve the gyro dance problem that verticals have by attaching the vert to a powered rotating module (like how a gyro walker's weapon is mounted) and rotating it opposite to the turning direction. His argument is that the net forces would cancel out and the robot would turn without lifting. I feel like this is incorrect but I can't explain why. [Sacramento, California]
A: Mark J. If I properly understand your description, your friend is mostly correct. When force is applied to change the direction in which the axis of a spinning mass is pointing, gyroscopic forces act to realign the angular momentum vector in a direction perpendicular to the applied force. If you allow the weapon freedom to follow that realignment there is no force exerted on the chassis to lift one side of the 'bot in a 'gyro dance'. Note that you don't need to power the rotation of the weapon module -- the gyro forces do that work for you.
The video below is from the 2002 "Oregon Clandestine Street Fight" -- more event videos here. Team Mauser campaigned 'Strike Terror' at Comedy Central BattleBots seasons 4 and 5.
"By the way, there's nothing but gyroscopic forces making the wheel tip. It's totally free to move. The Season 4 version had a spring to help it return to center, which I should have kept."
- Team Mauser
Flashback Post from 2021
Q: Hey, Mark! 2020 has been a rough year for all of us, so I'm hoping to bring something to my local competition this year. I'd like to bring something entertaining or unique to the table, but I keep running into the same problem: I can't decide on what to build, and I can't bring myself to completing any of the projects I've started even when I get the CADs close to complete.
I've gone everywhere from antweight clamps like 'King Googly' to overengineered monstrosities like 'Saturn' and most recently, an antweight version of 'Black and Blue' (render attached). Alas, after I get the CAD complete I still find myself dissatisfied, leading to a redesign from the ground up, then disliking something about that, and the whole process keeps happening. I don't know if other people have a similar problem. Is there any advice you can give on what I should do? What am I doing wrong? [Aurora, Illinois]
A: Mark J. Yes, other people have similar problems. It's called procrastination, but putting a title on it won't solve the issue. 'Psychology Today' has a list of 11 Ways to Overcome Procrastination that you might like to read thru. The one that may best fit your description is #11:
11. Drop the perfectionism.
Perfectionism is an all-or-nothing mentality: Something is either perfect, or it is a failure. People with perfectionistic tendencies tend to wait until things are perfect in order to proceed—so, if it's not perfect, you cannot be finished. Or if it is not the perfect time, you believe you can't start. This all-or-nothing mentality can hold you back from starting or completing tasks.
Instead, focus on being better than perfect. This means to still strive for excellence, creating excellence, or setting yourself up with excellent conditions, but at the same time, you focus on getting the job done. #DoneIsBetterThanPerfect
I like your antweight 'Black and Blue' render. It's practical. It's colorful. It's based on a robot that won some fights. Build it, name it 'Only Orange' and go fight some robots.
Wacky Trigger and Wheel
Q: I built a 150g fairyweight using a FlySky GT5 pistol grip transmitter and a Malenki Nano to control the n20 motors and a spinner. I got it all wired up, but when I pull the transmitter trigger the bot spins/turns and when I twist the transmitter wheel the bot goes forward/backward. Is something I can do to fix this? Seems like I need to swap channels 1 and 2 on the transmitter but not sure. [Parts Unknown]
A: Mark J. There aren't too many things you can get wrong when setting up a Malenki Nano and a simple transmitter like the FlySky GT5. The most common problem is getting the polarity wrong on one of the drive motors, which causes the exact symptoms you report. The fix is simple:
Identify the N20 motor that spins backward when the 'bot is given a 'forward' command.
Swap the the positions of the two power leads for that motor where they solder onto the Malenki.
That should do it.
For more complex mixing problems I recommend the Run Amok Mixer Fixer. Answer three questions about your robot and this interactive web page will give you a complete and accurate solution to your mixing problem.
Reply: Yep this fixed it. Thanks!
Adjust Size as Needed
Q: what wheels to use [Uttar Pradesh, Bharat]
A: Mark J.
If you give me no information about your robot, I can give you no guidance on components.
It's Just Too Much
Q: I'm using a Flysky i6x transmitter with a Malenki Nano receiver/ESC in my fairyweight, but the turning is too fast. How do I turn it down? [Social Media]
A: Mark J. The easiest and most flexible solution is to assign a 'Dual Rate' for CH1:
Hold down 'OK' to open the 'MENU' screen.
Tap the 'Down' key to highlight 'Functions Setup' and tap 'OK'.
Tap the 'Down' key to highlight 'Dual rate' and tap 'OK' to select.
Tap the 'OK' key to select 'Rate' and use the up/down keys to set the value to '50'.
Press and hold the 'CANCEL' key to save and return to the previous menu.
With this Dual Rate set you will have reduced steering response when switch SWA (top left on your FS-i6x) is 'UP'. Flipping switch SWA 'DOWN' will restore full steering response -- handy for a victory gyro dance. You may adjust the '50' rate value up or down for more or less steering response. See my FlySky Combat Programming Guide for detailed instructions.
Q: Could you set 'End Points' for Ch1 to get the same steering sensitivity adjustment?
A: The short answer in this particular case is 'Yes', but it is preferable to use a 'Dual Rate'.
Long Transmitter Wonk Answer You may want to skip to the next question.
'Dual Rate' is a 'Transmitter Level' function that adjusts the input from the control stick before it is sent thru the mixing process.
Setting a dual rate on CH1 to reduce steering sensitivity will work with either transmitter or on-board mixing.
'End Points' is a 'Receiver Level' function that effects all commands delivered from a specific receiver port. With transmitter mixing it would restrict both steering and throttle commands on one side of the 'bot and have no effect on the other side.
Setting end points on CH1 to reduce steering sensitivity will work only with an on-board mixing module on the 'bot.
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]
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":
Plugging your values into the equation I get: "Make it thinner 'cause making it thicker won't make it lighter."
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.
We welcome combat robot questions. Please search the Ask Aaron Archives first to see if we've already answered your question. Recent Q&A are posted above.
Even small combat robots can be dangerous! Learn proper construction and safety techniques before attempting to build and operate a combat robot. Do not operate combat robots without proper safeguards.
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]
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 
Q: What should be the max and minimum rpm of weapon 
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? 
Q: Are there any advantages for front hinged flippers? It seems to me they push their opponents around more than anything else.
Q: Hey, Mark! 2020 has been a rough year for all of us, so I'm hoping to bring something to my local competition this year. I'd like to bring something entertaining or unique to the table, but I keep running into the same problem: I can't decide on what to build, and I can't bring myself to completing any of the projects I've started even when I get the CADs close to complete.
For more complex mixing problems I recommend the Run Amok Mixer Fixer. Answer three questions about your robot and this interactive web page will give you a complete and accurate solution to your mixing problem.
Q: What do your combat robots think of the current COVID-19 pandemic? [Kansas City, Missouri]
We welcome combat robot questions. Please search the Ask Aaron Archives first to see if we've already answered your question. Recent Q&A are posted above.
