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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.
A: Mark J. The short answer is "no". PETG is heavier for equivalent strength, more difficult to print, and no tougher than a good quality PLA+. Avoid.
Be sure to check tournament rules for the specific filament types they allow.
if i need to provide more information then please tell me! Hope this isnt a case of a bad hamburger
A: Mark J. From the Ask Aaron Brushless Motor Selection Guide:
I'm unable to find an exact websearch match for a specific "6354 190kv Belt Motor BLDC Motor for On-road and Off-road Electric Skateboard and Robot", but a pair of generic 6354 motors like the "Flipsky 6354 BLDC Offroad Electric Skateboard Brushless Outrunner" weigh in at better than 1100 grams and require 10s voltage to perform up to their specifications. As power is proportional to the square of voltage, on 6s these motors would have only [0.6 × 0.6 =] 36% of the 10s power. Too heavy and too little power.
Something more like the HobbyStar 4120 (5055) 710 Kv Brushless Outrunner would be close to the low end of the suggested mass range and would produce full power on 6s voltage. Gearing depends on arena size, but a 45:1 reduction (with those 25cm wheels -- why so big?) would give good performance in an 8 meter wide arena.
A: Mark J. I assume you're referring to the Fingertech 1-pound and 3-pound beater bar assemblies. These are not "drop-in" weapons -- the design of the weapons supports and fitments are left to the builder. There is typically only a small clearance between the beater and the weapon supports.
A: Mark J. No competent engineer would spec material thickness before knowing a great deal more about the design and the competition than you have told me.
Q: The college student from Baton Rouge here. I did not provide enough information on that featherweight with a spring-loaded weapon... My bad! Our combat robot competitions differs from regular combat robot competitions. The objective is pushing other robots off a 16 × 16 ft arena, so the primary loading on the chassis is expected to be ramming, sustained pushing, and edge/corner impacts rather than high-energy weapon strikes.
We are planning to fabricate our external armor/frame as a single bent metal sheet of 5052-H32 aluminum, formed on a sheet-metal press brake (bent side, front, and back panels). We chose 5052-H32 specifically for its formability and toughness. We are currently considering 0.080″ thickness, since it is affordable, easy to bend, and relatively light. However, several people have suggested 0.25″ thickness for durability. Given the amount of sheet metal required, 0.25″ would significantly increase both cost and weight.
Based on your experience, is 0.080″ 5052-H32 generally sufficient for this level of combat, assuming a properly designed bent chassis with flanges/gussets? Or is stepping up to something closer to 0.25″ truly necessary for durability in push-out competitions?
A: Warning: Mark is having a rough day and is known for being a bit terse under such circumstances.
Mark J. 5052-H32 is a fairly 'strong' aluminum-magnesium alloy known for being highly ductile and easy to bend. "Easy to bend" is not an atribute you should be looking for in material you will be ramming into hard objects. Armor that deforms enough to lift a wheel off the ground or obstruct its motion is far worse than no armor at all. Certainly 0.080" thick 5052 is unsuitable and 0.25" thick 5052 would - IMO - just be a heavier unsuitable solution. Quite seriously, you would be better off building a box out of good quality 1/4" plywood -- plywood doesn't bend.
Box chassis construction using aluminum top and botton panels with thick UHMW polyethylene side panels and a steel front wedge or 'wedgelettes' is well established in "sportsman class" (no spinner weapons) combat robots around your weight.
You previously answered a question about Mako inaccurately and I have been getting a lot of messages asking me about it. I don't use an off the shelf saw-motor or complete setup. I use an off-the-shelf saw *blade*. I specifically use a drone motor with a TPU hub.
I am a big fan by the way, I don't want this message to come off as negative. [Norwich, Connecticut]
Reply: Mark J. I greatly appreciate corrections and clarifications, Julian. The quote from the video I reference in my answer saying that the weapon was "a literal off-the-shelf circular saw that you could walk into Home Depot and buy" combined with the design of your blade retainer led me to an incorrect conclusion -- thanks for writing in to set things straight.
The structure of your weapon hub is now a mystery. If you would care to send in a photo I would be pleased to publish it to provide a complete answer to the question from Zanesville.
A: Mark J. That's a very general question about three materials with very different properties and uses. It's a bit like asking me to compare a helicopter to a coconut and a dollar bill.
Ask the Google AI to compare high-density polyethylene to garolite and carbon fiber. I just tried that and got a quite detailed categorized comparison. After you study that you will be able to ask me appropriate specific questions about how those materials might best be used for individual components in a combat robot.
Worst case scenario it deals absolutely no damage, which is basically what conventional bar and disk spinners do to those things anyway
A: Mark J. From memory, the sawtooth disk 'Silent Spring' used 2017 had very sharp tips designed to slash into soft materials. Ripping into soft material with sharp blade tips that can "dig in" to the soft surface even at a shallow impact angle is much more effective than using blunt 'spokes' that spend most of their energy in a low bite attack simply tapping your opponent backward. A disc with multiple teeth spinning at several thousand RPM is not going to allow time between impacts for any material to "flow" in between the teeth. Maintaining 'extended engagement' will be still be difficult, as the transferred weapon energy at a low bite angle will act to spin both you and your opponent around in opposite directions.
Take a look at this archived post about attacking TPU plastic with a 'low bite' weapon.
A: Mark J. Eggbeater weapons notoriously create a lot of aerodynamic drag. Assuming that you keep the 14:21 reduction:
A: Mark J. See Frequently Asked Questions #28 for our policy on discussing flame weaponry -- and read the rest of the FAQ while you're there. The flamethrowing beetleweight 'Dutch Oven' is currently ranked 144th in the NHRL standings.
As for the question, for the next competition I intend on building a multi-bot, since if you can't beat 'em, join 'em. For one part of the multi-bot I would like to have some control based archetype, a four-bar lifter to be exact. Thing is, nobody seems to build them nowadays, direct servo lifters (SSP, Jelly Baby, etc.) seem to be all the rage. Has anything changed in terms of the rule sets or in terms of material/manufacturing/electronics availability that would be unfavorable for a four-bar lifter over a plain servo lifter, or are people just taking the easy route?
Thanks!
A: Mark J. As I recall, your local tournaments have adopted a NERC-style multibot weight bonus. That's certainly an incentive to go multi -- particulary if you're up against sophisticated competitors like your reigning champion.
Four-bar lifters definately have become rare. The current design 'meta' favors more compact single-pivot lifters, structually strong enough to carry attached forks and still withstand spinner impacts. Such lifters also take up less room than 4-bar designs, allowing a more compact chassis layout. I think thoughful design might get you a 4-bar that will overcome these issues.
A: Mark J. Thats very easy to find. Per the websites for FingerTech Robotics, RobotShop, and Palm Beach Bots:
Alternately, you can use the 'Channel Reverse' function on your transmitter to reverse the response of your steering channel (most likely Channel 1 - Aileron). You didn't mention which transmitter you have, but most have this feature. This is handy if you have an "all-in-one" receiver/DESC with no channel plugs (like a Malenki).
I spent a good deal of time creating the Team Run Amok Combat Robot Mixer Fixer -- answer three questions about your robot and it will give you a complete and accurate solution to your mixing problems. Give it a try next time.
A: Mark J. Ask Aaron does not answer questions from builders competing in India.
A: Mark J. See Frequently Asked Questions #19 for a complete, annotated diagram -- and read the rest of the FAQ while you're there.
Q: sorry, i had a photo attached
A:
Yes, you attached a photo of your weapon ESC. It is an entirely standard brushless weapon motor ESC -- exactly as shown in the FAQ #19 diagram. I chose not to reprint the image here.
Q: also this is my esc [photo attached]
A: Yes, that is a Scorpion Nano. It wires up just as shown in the FAQ #19 diagram. A few specific comments based on your photo:
Q: Firstly I understand the whole George Collins with Boxster No Show Controversy (it is just coz I think it might be him unless we know which experienced Battlebots team it is). So, which team was it?
A: To the best of my knowledge the team in question has never mentioned their association with Robotica and I am hesitant to 'out' them if they choose to keep this quiet. I am also not entirely confident of my identification of the team member. I will note that 'Boxster' had design elements shared with other robots of the team in question.
Q: And Secondly REALLY!? A ROBOT CALLED 'LIVE WIRES' WAS IN ROBOTICA QUALIFYING!? REALLY! [Erskine]
A: Page 321 of "Build Your Own Combat Robot" by Pete Miles:
A: For reasons clearly stated above, I am unwilling to publicly reveal the name of the team I believe built 'Boxster' and I will not participate in this guessing game.
A: Mark J. RBI productions didn't want the competitors to be in contact with each other, so their emails to us had the mailing list hidden. It wasn't until about a month before the filming that a partial list of the builder emails came to light. The only team I was in contact with was Team JuggerBot, who happened to be based about 40 miles to the south of my Oregon home. Our emails were largely about battery chargers for the Hawker SLA batteries both of our 'bots used -- nothing of general interest.
In terms of the interview schedule, I'm fairly certain Pete Miles' mystery robot is "Live Wires", which he shares a bunch of information and pictures about its Robotica adventure about in his book "Build Your Own Combat Robot". Hope that helps someone out there. [Alberta, Canada]
Response: I'm glad to hear you enjoyed reading the Robotica emails and I am grateful for the pointer to Pete Miles' book. I have a copy of "Build Your Own Combat Robot" in my library, but I last read it in 2006! Right there in chapter fourteen is a twelve-page write-up on building "Live Wires" and attempting to qualify at season 1 of Robotica:
Pete's team arrived at the Robotica filming in time for the last day of qualifying but ran into both electrical and mechanical problems. Although their effort ended in a cloud of grey smoke, the design was solid. A few more days for testing and their story might well have been different.
A: Mark J. That was a great event. My flight got in too late to register 'Rat Amok' for the antweight tournament, but I did get a couple of pick-up matches and I was able to sneak into the ant rumble. I did also sit in as a judge for the SozBots ant tournament.
Although I didn't shoot any video, a search of my robot combat archive turned up a CD with twenty ant combat matches from the SOZBots 1.4 tournament at BotBash! I have no idea where the videos came from but they are so nicely captioned and edited that they may have come directly from SOZBots.
I've uploaded this set of videos to my YouTube channel as a playlist titled "SozBots 1.4: Antweight Combat Robot Tournament". I also found a bracket tree for the event: SOZBots 1.4 brackets.
My favorite fight from SOZBots 1.4? One Fierce Beer Coaster vs. Tsunami -- it has a very suspenseful ending.
However my maths is failing me (See bad drawing attached for definitions of symbols). For calculating the force on the lifter arm from the servo in the setup is it as simple as x*sin(theta)? However isn't that just the force transmitted between the servo arm and the arm of the linkage? What about transmission of force between the arm linkage and the lifter arm itself? Are there further losses there?
And then to calculate whether you can lift something or not, is it (F * y) - (W * z) (Where F is the force from the lifter motor on the arm, W is the weight of the robot being lifted, y is the distance between pivot and lifting point and z is the distance between pivot and robot being lifted)?
Hope this makes sense
Thanks in advance.
A: Mark J. You've opted to open up the jumbo can-o-worms, eh? What you have is known as a 4-bar mechanism, and the calcs are especially nasty because the lever advantages keep changing as the lift progresses. In your sketch the initial advantage is poor and a good deal of torque is needed, but as theta increases the advantage improves and less torque is required. The general approach is to calculate the actual rise in the tip of the lifter for each change of say 1 degree of servo arm motion and convert that into a torque requirement for each progressive angle.
I know this because I wrote a pair of 4-bar Excel spreadsheets that perform these calculations for standard "Biohazard" style 4-bar lifters (movement up and forward) and for the servo linkage you describe (single pivot hinge motion). That is the good news.
The spreadsheet I wrote for the servo-powered single-pivot lifter has the correct geometry for your purpose, but the example layout has a hinge point much farther forward than your design. You will need to adjust bar lengths and angles to morph into your longer rear-hinge design. This may well take some time. Here are the spreadsheet link assignment letters as they apply to your sketch:
Give it a shot. If the calculations balk, you can wade thru the "Equations" tab on the spreadsheet and make adjustments as needed. Download the Team Run Amok Servo Lifter Spreadsheet from our Combat Robot Design Tools page.
A: Mark J. I've never actually tried, but it shouldn't be very hard. You can only go where the rails go, so just give it a little throttle and toot the whistle once in a while.
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
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:
Im trying to choose the right brushless motors for the drivetrain of my 30kg combat robot (Its a drum spinner). Im wondering if the "6354 190kv Belt Motor BLDC Motor for On-road and Off-road Electric Skateboard and Robot" would be a good fit for my two wheel drive? our wheels diameter is 25cm (9.843 inches i believe) and the voltage input is 22.2v (Will be using a 6s Lipo batter)
Thanks
Q: Just a question about beater bar kits. How does the weapon manage keep its axial position along the shaft? Would the weapon be prone to sliding since the needle roller bearings won't resist axial movement? Why don't they use thrust bearings on the sides?
For larger robots I absolutely recommend better axial control for any style of spinner, but at the insect-scale it isn't required.
Comment: Hi. Julian here, the builder of Mako.
Q: could you help compare High-Density Polyethylene to PCB and carbon fiber? [Hot 'Lanta]
Q: I'm wondering if using a multi-tooth saw (not a commercial saw but a spoked disk with many teeth) attachment as you may recall Silent Spring did in about 2017 or 2018 for a beetle weight midcutter horizontal design would allow me to defeat those "jelly" all-TPU control bot designs. I'm not a materials scientist but my intuition is that TPU's elasticity would let it slightly "flow" between teeth and get ripped apart in a very small area. Meanwhile with a usual single tooth bar, the TPU gets time to flex away and absorb the impact force with its entire volume. Since TPU has low yield strength I doubt it would be hard enough to kick the low-bite saw off of it like an AR500 plate. Since a lot of strain results in very little stress for TPU, stress = F/A, and forces are equal and opposite, I think even though the HS is not constrained like a hammer saw it would be able to maintain extended engagement unlike if I were to attack a hard metal plate with the blade.
Q: Hi Mark! It's the guy from the "Shore of the Mediterranean" again. Quite a bit of time has passed since my last question and I managed to get second place in one of the two competitions I have attended locally. I lost to the as of yet, still reigning champion (see attached photo) mostly due to my own failings, forgetting to purchase spares and even bring some ready parts.
Q: Is the fingertech viper kit underweight? If not, how much weight does it have to sacrifice to use an addon? [Hot 'Lanta]
A: Mark J. Yes -- your ESC channels are plugged into the wrong receiver ports. If you are using channels 1 and 2, unplug the receiver connectors and plug the connector that was in channel 1 into channel 2 and vice versa.
Mark J. Our friend in Erskine, Scotland read my compilation of emails sent from the Robotica producers to the contestants prior to the competition - mentioned farther down this page. He has a theory about a mystery builder whose name appears on a schedule for video interviews for the show and a mystery robot that was seen near the storage area backstage during the competition He writes:
Ain’t sure about - removed - [Erskine, Scotland]
Q: I read the compilation of Pre-Production Emails to Robotica Season 1 Competitors from the event organizers that you put together for the 25thanniversary of the show. Great stuff, but I wonder about the emails between you and the other builders. Are you going to release them as well? [Chicago, Illinois]
Q: Hi Mark. I met you way back at the 2002 Botbash tournament in Tempe, Arizona. I was with a friend who had a robot in the antweight tournament and I remember that you were one of the event judges. I've found some videos of the bigger Botbash robots from that tournament but nothing from the ant fights. Did you happen to take video of any of the ant matches? [An iCloud Server]
Remembering Aaron Joerger, 1991 - 2013
That's obviously
A question from your homework.
Do your own research.
how to design and build a battlebot
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Q: What do your combat robots think of the current COVID-19 pandemic? [Kansas City, Missouri]
