Archive for June, 2016


The Overhaul 2 Design & Build Series, Part 12: The Final Beast-Smash

Jun 29, 2016 in BattleBots 2016, Bots, Overhaul 2

And finally, we are here. The last build report for Overhaul 2! Just in time for Episode 3 of the season, where you’ll hopefully get to see it take on Cobalt, billed as the Tombstone of the U.K.! I guess that makes me the Complete Control of New England, or perhaps, at least the Stewbot of the Atlantic Seaboard.

So now we’re in the last week of march, and the April 5th shipment deadline is looming. Everything is in process, but nothing is particularly done. Most of the work remaining at this point was final mechanical integration, and then electrical work can begin. Electronics is usually the make-or-break of a large electromechanical project, but I think this time there was enough pre-experimentation such that I knew what had to be done. Not to say I didn’t have trust issues with the DLUX 160A controllers, though.

It’s an unfortunate effect of having a long to-do list, but the photo documentation does start getting a bit more sparse here. I usually try to stop and take photos as much as possible – usually way more than people I know – but even I occasionally get pulled into something attention-demanding and forget to get the camera until it’s done. So I’ll try to chronicle the remainder of the build as completely as I can, with the explicit caveat that there might be some things magically appearing.

As of the last episode, the rear most #35H drive chains were being hooked up. It was time to also connect the front chains.

Often times in my robot designing, I model a crude chain path that doesn’t take into account the actual number of links needed to make the chain loop. I figure that half-links do exist, even if they’re evil, and otherwise a tensioner will take up the difference. The tensioner here was “designed” after the frame was sent for machining, but it was just a matter of drilling two holes.  It’s a MarkForged nylon print, but with the wall thickness turned up to “all of it” so there was a thick layer of nylon to support the chain. The mounting holes were slotted so it was adjustable over time. Not really a traditional sprocket-on-a-bearing like you might think of chain tensioner, but it’s more of a “chain guide” similar to those found in modern car engines which don’t fail to scare the crap out of me are just blocks of tribological plastic that the chain glides over. They do work, mind you, but that doesn’t stop them from scaring me. I tend to prefer rolling tensioners whenever possible, but it was far easier to just hit “print” here, and it gets the job done.

This tensioner serves two purposes – besides making sure the chain isn’t floppy, it makes sure the bottom-most strand is not hanging out under “robot frame level”. It would suck, for instance, to have a solid aluminum and titanium frame bot slide over the arena saws and the only thing that gets taken out is the two exposed chains! These things therefore also keep the chains above frame level for a good portion of their travel.

Here is what the finished chain path of one side looks like! After this, it was repeat for the other side, and then close everything up with the outer rails.

Also visible here is a test fit of the upper clamp arm.


One of the other “machining kibbles” was finishing out the P90X gearboxes. Here is what I was talking about when I said “chamfering” the shifter ring and the new planetary carrier. This was a lathe operation, and I actually took a spare P80 shaft, bored a 1/4″-20 threaded hole into it, and used it as a mandrel to hold the planetary carrier. The chamfer (angled edge) on the carrier mashes into the mating feature on the ring gear when the gearbox shifts -acting like a crude synchromesh of sorts.

With the bot ostensibly ready to drive, it means I could no longer delay the inevitable: Electronics. Oh boy, here we go. Can’t I just hand this one off to someone else?! Why do I have to develop my own custom motor controllers again???

A few weeks before this, Paige and Cynthia had already cut out two sets of electronics box plates from 1/4″ polycarb. All that was left to do now was to dress it out – the last update had a little bit of the preparation, but now is when we start filling it up for real.

The box now has ESC mounts fitted. The mounts are attached to the box using #4-40 hexagonal NFPC “Pemserts”, which add strength to the joint by gripping more plastic than what threading the plastic can manage.

Paige also finish-machined the bus bars, which are cut from alloy 6101 aluminum. This aluminum alloy has almost the conductivity of pure aluminum, while maintaining something resembling rigidity and machinability. Here they are shown attached with some flathead screws. There is a small split in the upper one on the right side – that’s because the bar to the left is for the 4 drive controllers, and the one on the right is for the 2 lift controllers. After last year, BattleBots mandated separately switched circuits for weapon and drive.

I decided during the design phase to avoid copper here for weight savings, even though that would have made the bars smaller  – they still had to accommodate the ESC’s own wire size and screws to lock the wire in place anyway.

One of the gifts we received from HobbyKing is a small artisanal IED box o’ lithium batteries. This took the longest to get here, for obvious reasons.

Overhaul will use 4 of these 6.2Ah, 6 cell batteries. They’ll be run in 12S2P configuration for a total of 44V and 12.4Ah.

While arraging the packs for their intial charge, I noticed something funny. They felt different. Like one pack just didn’t quite feel the same size as the other. Was I going insane or something? Is it too early in the morning for robot building?

no. they actually were diffrent sizes. In fact, 3 differet sizes! What thell!? Here they are lined up across the top of the Mark Two for your amusement.

I, uhh, just picked the four shortest ones to integrate them into the first battery being made. To be clear, all of them took in the same amount of Watt-hours +/- 3%, if I recall, being first charged. I don’t claim to get what is happening.

Here is a test population of both battery box and electronics deck before I start commiting expensive wires.

I realized I’d run out of 8 gauge flexible wire at this point, so I found a local car audio place. Besides hobby shops, audio places are one of the only other suppliers of silicone-insulated high strand cound flexible wire (Welding shops would offer heavy gauges, like 4 or 2 gauge and up). This led to one of the best conversations I’ve ever had. The lead-in was me asking about “power wire” which is NOT QUITE THE SAME as “speaker wire”, which I didn’t realize – the sales guy was telling me about their selection of large gauges like 2 gauge and 1/0 and up, and I was looking for more tame 8 and 10 gauge. It turns out the smaller gauges are generally used on the speaker side of things – go figure. It didn’t help that I also showed up near the end of the workday, so this guy was probably done with people not being sure with what they were looking for. It went something like this:


“What are you using this for anyway?”

“Have you ever heard of BattleBots?”

“No, I don’t watch cartoons.”

Damn. What a burn. To his credit, he brightened up after I showed the BattleBots website and the big clamp & fork hub, with 16 3/8″ studs sticking out of it, that I happened to have in the back of the van. A small discount was obtained for 20 feet of 8 gauge red and black wire, plus a baggie of ring terminals.


To join the battery packs, I made a “octopus cable” which ended in a larger 75A Anderson Powerpole connector, and otherwise had four XT-90 connectors for the batter packs. After one was verified, Cynthia cloned it for battery #2.

Here’s one battery, after stuffing everything in!

Next came primary wiring of the bot. This is the octopus cable for the robot side. The cables divide back up into two 8 gauge wires, one circuit for the lift and clamp, and the other circuit for the drive.

Getting my other ducks in a row, the 160A HV controllers, trimming the leads and inserting them into the busbars. The holes for wires were purposefully made oversize, since I knew some of these were getting more than one wire stuffed into them. After all, the power input has to feed from somewhere.

In the interest of preserving these more delicate DLUX 160A controllers, I decided to make a soft-start circuit. Also called a precharge circuit, it is a parallel switched circuit to the main switch, which has substantial resistance in it to “slowly” fill up the motor controller inptu capacitors. Without this, I was 1. making a spot welder, and 2. potentially causing catastrophic ringing surges every time I turned the bot on, which I have personally detonated controllers with before.  When testing Sadbot, I discovered that the 13,000uF of capacitance I put on the 3 DLUX 250A controllers was actually welding shut a Hella switch when turning the bot on!

Without much time to make this circuit more integrated, I accepted that Overhaul  might just have a small bundle of wires sticking out in an awkward spot next to the master switches. In the near future, I want to revise the 3D printed switches to incorporate a precharge feature.

The order of ops for turning on the bot was therefore: Connect the two precharge pigtails, then crank the two master switches shut. An extra layer, but worthwhile for not causing premature stress to controllers of unknown reliability.

Here’s the electronics put in as a test fit. Everything goes together great so far!

I decided to perform an intial power-on and test of the system to determine motor directions. This was done with some skinny little alligator clips between the battery and ESCs, just in case one of the DLUX 160A controllers decided to go haywire. With this test, we were able to label all of the motor leads with where they should go to.

This test was conducted using one my cheap Hobbyking 6-channel radios, because at the time, I could not make heads or tails of the 9XR Pro. Full disclosure: Up until this point, I had never owned a “nice” radio – by which I mean, computerized and programmable. I scrapped by on a 2nd-hand Futaba T4VF from 2001 until 2006, then I upgraded to a Spektrum DX6-not-i, the original one. After that, I basically went straight to the cheap HK 6-channel T6A as my staple radio. (We ordered dozens of these for the 2.007 class sessions from about 2010 onwards, so I got reeeeal comfortable with them).

The idea that EVERY CHANNEL IS CONFIGURABLE TO DO ANYTHING I WANT was therefore super fresh to me. Adding to that was the 9XR Pro’s nonconventional channel order as it comes. Note the highlighted “AETR” – this means Channels 1 through 4 on the receiver are Aileron, Elevator, Throttle, and Rudder respectively.
I was super confused initially when playing with the receiver because I think the stock order is “RETA” or something similar – Channel 1 is Rudder, and so on. What? Anyways, luckily, this can be changed to any of the permutations of the 4 channels, so I restored it to what I knew the best.

I set up a bunch of servos to make sure what I did was sane.

After setting up the stick modes and receiver channel order, I started messing with mixing and travel limits. This is a typical “Elevon” mix to allow single-stick driving on the right side stick. Channel 5 is assigned to the 3-position switch to talk to the shifter servo for the P90X, with the center and travel limits being 1st gear, neutral, and 2nd gear.

One thing that happened after this but I didn’t take photos of was swapping a stick from the spare 9XR Pro transmitter I requested and planting it in the left side of the working radio. Operation of OH2 like my previous clampy-grappy weapons requires two fully spring sticks, whereas you buy a normal hobby radio with one stick that has a “friction” channel which stays in place – this is the throttle channel for your plane or helicopter.

The 9XR Pro did not seem to use identical sticks between spring- and non-spring-return sides. They were mirrored parts! Often, manufacters just spin the stick 180 degrees and call it the other side, which seems to hold true for the stick body, but not the spring mounting pieces.

Lacking the time to figure out a non-hackish solution, I decided to simply swap a right stick to the position of the left stick, which is a 180 degree rotation, but all the wires came out the wrong side. That was fine – I just extended one potentiometer cable to seat in the conenctor properly.

After this radio was fully set up and readied, I went on a drive base test, which is recorded in this video.

And suddenly, ROBOT!!!

Is it done yet?! No, this was largely a test-fit of everything in place – pontoons, arms bolted in, and top clamp in place. Boy, it sure LOOKS DONE.

There was one element missing, and that was probably the most important thing on Overhaul if you asked members of the public – the ears. They aid in self-righting by forcing the bot onto a stable position on its back, from which I can power back over.

They were cut from the same 4mm AR400 plate, but as a flat part which needed bending. To do this bending, I used an oxy-acetylene torch and a giant box-and-pan brake. Heat intensely along seam until its dull red, then smash it in the brake and go for it. The faster the heat is achieved, the less the metal is tempered and loses strength. Obviously the bend was going to be weaker, but the rest of the geometry should save it.

The ears were bent separately, and I attended to other matters while Skunk welded them fully in place on the clamp arm.

I began assembling the linear actuator that pushes the clamp up and down. The assembly was very straightfoward – press in the angular-contact bearings on either half, mount the motor, slide the sprockets on to the keyed shafts (the end of the ball screw shaft being keyed according to my drawings by the seller), and there we go.

Originally, I was planning on using an offset link in the chain here, and designed the sprocket spacing to accommodate this. However, offset links are evil, so I cut the chain at the next whole-link up. This necessitated another chain guide part, which I modeled and made from plain nylon.

Assembled actuator, also showing the assembled P90X. This thing worked quite well, but the P90X needed a few minutes of gentle running to wear everything in. I’ll likely do a more detailed build on this thing, since I like it. Up until this point, however, I had not yet designed in where the shifter servo would go. It was therefore left in high gear, which its “failsafe location” if the linkage fails, as biased by the small springs visible to the upper left of the photo.

Alright, so we’re staring April 5th in the face now, and it’s time for a weigh-in. We piled everything that could possibly still be mounted onto the bot, with some extra frame bolts that had not yet been installed, and so on. Final weight here? 247.50 pounds.

This is as close as I wanted to cut it. It was a little under my final expectation of 248 pounds, in large part because of Skunk’s excellent welding that did not in fact require depositing a full 25lb spool of MIG wire into every welded assembly, like I had anticipated in my weight calculations!

After a few more hours of assembly, I’m proud to present….


The somewhat bare looking but complete Overhaul 2.0!

We decided to hold off on painting anything, because if you painted it now, I wasn’t going to touch it it again until the event, and sure as hell wasn’t going to run it into anything to save my paint job! Instead, a couple of minutes of (unfilmed) test driving was had.

My first thoughts upon the test drive:

  • oh shit this thing is fast. Exactly as I intended. It’s fast, yet stable. Still a little front heavy, but having 95 pounds of steel right up front will do that, and the 4 wheels up front (middle + fronts) made the handling much more stable than OH1 was, at least on concrete.
  • It otherwise drove like I intended, and I thought I had it down fairly well after a few sessions. To avoid premature shitting of the unknown-reliability controllers, I decided to save the rest of the driving for the test box at the event.

Speaking of the ESCs, I made sure to update all 5 of the remaining DLUX 250A controllers I had from Sadbot to the latest settings, and packed them. My electronics contingency plan was to swap four of them in as soon as I got to the event, leaving Overhaul with 4x 250A and 2x 160A – driving the lifter only. If any of the 250s let go, I would back-fill them with 160A controllers. This maximizes my reliabilty for the first matches.


The last machining operation to do was to shave down the tooth. Waterjet-cut from a slab of 4142 prehard steel, it was still reasonably soft enough to be machined with carbide cutters fairly easily. I wasn’t out to actually pierce other bots anyway, so I decided to save time and money and not have a “legit” tooth made from heat treated S7 tool steel.

Pack it up! Pack it all up!

It was now the 4th, and the whole day was basically devoted entirely to packing. One of the initial conditions of a good robot event is decided when you re packing parts. We made an inventory – spare mechanical parts, spare electrical parts, all hardware that the robot used were packed in these sorty-bins* with priority. Other spare hardware that could conceivably be used in an emergency repair was brought along, too – like half of my hardware bank came along for the trip. These were packed in different bins.

I even relabeled my toolbox with REAL, HUMAN-READABLE LABELS instead of my bullshit. That way, any of Paige, Cynthia, or Matt could immediate grab a tool without me defining what “Hoodrat Shit” contains.

Furthermore, and most importantly, all of the service tools used on the robot were put in its own sorting system in the top drawer, which was labeled. One mini-bin had the impact driver bits needed to dismantle the frame for two people working in parallel – all of the hardware was all 3/8-16 cap screws unified for a reason. Another one had the tools needed to pull the front armored pontoons, and so on.

That way, even if we were systematically fucked, the robot can come apart in an orderly fashion.

Don’t let this make you think I am some kind of experienced pit crew chief – this is just the culmination of years of mistakes made in robot competitions, and the same years of learning, finally written down at the behest of the others and implemented.

Hell, if you left me at this myself, I would have just brought my entire damn red toolbox.

*several people will hurt me if I keep calling these “SORTY BINS”, so I’ll point out that they are called ALCs – Attached-Lid Containers.

Know what else is getting sorted? Parts and hardware!

We made separate bins for primary drive & frame mechanical hardware, auxiliary hardware (electronics, actuators, etc.), and P80 parts.

There was another one for electrical system parts, such as more wire and connectors. Each of these things had a label saying exactly what they were and what they did.

When you are guaranteed only 1.0 hours to recover from a Tombstoning, every second literally counts, so digging for hardware is out of the question.


Actually not so magic – realizing that we were going to be working up until zero hour, I hired out construction of a shipping crate to a few Asylum wood nerds. This was a beautiful job – they measured all the “big things” going into the crate, and made internal shelving to accommodate!  All of the spare metal parts, for instance, will be living on that little shelf, and the robot with containerized spare parts occupy the lower floor. It had a door that doubled as a loading ramp, hinged at the bottom, and was accessibly by forklift from all 4 sides.

Wood, man.

Oh, did I say “I would have just brought my entire damn red toolbox”?

Well, I guess I did… it was part of the plan…

Oh, also Herpybike I guess. It was right there, man. I figure at the least, if my robot career doesn’t take off, I’ll go on a high speed chase in LA with it.

The robot crate was picked up on April 5th around 1PM. We breathed a momentary sigh of relief, and went home to sleep for a bit. But the story doesn’t end there.

The intervening week between shipment and us physically leaving was filled with spare parts work. This is a spare clamp arm and spare fork parts being cut out. I asked one of the MIT FSAE students to tack all of these parts together for me, such that if we HAD TO at the event, they could be fully welded up and put into service. I also converted four more DLUX 160A controllers – ones HobbyKing sent me as spares – and these were brought along with us when we departed.


So that’s it! Wow, what a journey. I honestly still am not sure how it was all pulled off – any one of several things could have gone catastrophically wrong, and I would not have had a functional robot in time. Truth be told, I didn’t get to test OH2 nearly as much as I wanted. This left me very uneasy going into the tournament, and I made one or two “bailout” solutions for problems I anticipated might occur.  What they were, and what went down at the tournament, can only be revealed after the episodes air.

Overhaul 2 was by far the most intensive and involved engineering project of any type I’d ever been involved in, for work or otherwise. You could say it’s a “magnum opus” of sorts. I ultimately take whole responsibility for how the tournament goes: I was the chief designer, engineer, purchasing office, project manager, fabricator, QA (#ZEROSIGMAS), AS WELL AS operator/driver and field ops chief*.  Basically my decisions alone will potentially dictate the direction of the next few months, if not years, of my life. This is an enourmous weight to think about for those who might be less experienced or just starting out, and is very difficult to explain or describe. Honestly, you just kind of fall into it when the time is ready and your experiences means that a lot of things are second-nature. I’m simultaneously stoked about doing well at the tournament as well as accepting of failure as a chance to do better next time. I know I made mistakes during the design, build, and testing process.

So what’s going to happen? Tune in Thursday, 6/30, 8pm/7pm Central, on your local ABC station to find out! My goal is to have the Cobalt post-fight analysis posted a day or two after the match, so people have a chance to watch on streaming services also.

*This is honestly what kicks ass about the sport. You experience a microcosm of every step of the product engineering process. Many, many young builders have gone straight into successful engineering careers with the insights and experience they gained putting their product in the field and, uhh, “using it”. Robots is cool, kids.

The Overhaul 2 Design & Build Series, Part 11: The Race is On

Jun 24, 2016 in BattleBots 2016, Bots, Overhaul 2


If you don’t know what’s going on, obviously I’m talking about the BattleBots Season 2 “premiere”, which I put in large airquotes because I don’t believe in “teaser episodes“. It’s episode two, dammit!  Help ensure there’s a #season3 by finding your legitimate source of TV shows!

I honestly think the editing was way better this time than last, which is good to see that lessons have been learned. For one, the ratio of “builder hype” to fights was much better. I think they could have changed some of the matches being shown, but it’s likely that they need to conserve builder profiles for future episodes for the bots that did well. Another improvement is audio – last seasons sounded obviously “enhanced”, let’s put it that way, but whatever new sound recording setup used this year was able to capture the robot noises very authentically, perhaps best illustrated by the drum of Minotaur. Yes, it sounds like that in real life.  Furthermore, and perhaps most importantly, the “bot stats” – a.k.a the Tale of the Tape™, has been toned way down. Even during Season 1, I was a huge advocate of them being either removed or reduced in resolution to something like 1/5 or 1/10, because when you get too fine in resolution, people tend to ask why instead of going wow. This time, I only saw them bring brought out if there was need to drive some point home. Lastly, the commentary is way improved, with the interaction between the hosts seeming less contrived in my opinion, and more dynamic. I can only hope that this level of production is able to keep up for the entire season.

But enough about me! Let’s talk about me instead. Here we are in approximately the 3rd week of March. The machined frame was due to arrive any day now, so it was all guns blazing towards finishing the other bot elements!


The finishing step towards the intermediate shaft was to waterjet-cut some pressure plates. We simply threw these big keyed washers into the same AR400 4mm plate that the upper clamp arm was being made from. The plates are keyed in order to prevent torque transmission to the pressure-applying disc spring and adjustment nut – without these means, the nut is liable to be rotated by the torque transmission, modifying the clutch pressure.

In between the steel plates and gear are layers of clutch lining. This stuff, basically brake pads bought in Fruit Roll-Up format, is able to scrub and transmit force without tearing itself up, unlike running metal into metal. McMaster sells it with various coefficient of friction ratings – I picked a moderate one such that the clutch has substantial adjustability.

The last task was to broach the EPIC LIFT GEAR for a 1/4″ keyway. Now, with a standard 3 ton arbor press, I have to basically monkey bars off the end of the lever to be able to broach an inch or so of steel with a 1/8″ broach. This gear is 2″ in face width and the key is twice the size in every dimension. So this was done on a hydraulic press. Easy, just a lot of very rapid flicking of the pump lever was needed.

Around this time, some very heavy objects arrived.

Steel! So much steel! Look at my STEEL! This is my real steel! There is no toy steel! Shut up, Megabots. I know you’re judging me.

These plates are grade AR400, a popular and commonly used alloy in the mining, construction machinery, and bulletproof trucks industry. It’s been long favored by bot builders for its high resilience properties – not only does it have higher surface hardness in as-purchased form, but remains easily weldable. The alloy – named Abrasion Resistant for a reason – was developed specifically for tacking dumptruck bodies and armor plates together.

It only recently became more popular in robotland because of the rise of a supplier willing to do precision laser cutting for cheap – Discount Steel. All of a sudden, it seemed like everyone was using it, and Overhaul needed a stiff defense against kinetic weapons, so I jumped on the bandwagon.

Interesting to see that I have 3 different colors of plate from which my parts were cut. ARx is a specification, so many different steel houses make the material with different surface finishes and treatments. The green stuff appeared to be a primer or something, so you can paint your mining shovel right after blasting it together.

Enough cut plates were ordered to make four pontoons.

Oh, once the romance of the pieces wore off, it was time for the long drag of marriage. I was reminded of why I don’t build things from steel now. Steel needs welding, welding needs surface prep, and surface prep is what turns you into the fucking Dark Side. It took several hours of dedicated angle grinding to clean the edges of the ABRASIVE. RESISTANT. THEY NAMED THIS ABRASION RESISTANT FOR A REASON steel plates.

Out of a thinner gauge of AR400 that Discount Steel did not offer (Roughly 0.140″ to 0.150″, so I called it 4mm) comes the clamp arm parts! These were waterjet-cut in house, and once again, cleaned up using angle grinders and flappie wheels.

This is a cleaned up arm part. Now, it didn’t need to be actually this clean, but the job was passed onto the very excitable Matt. Biology bros are sure thorough!

I spent a while trimming the series of tubes from last episode into the proper lengths. In the case of the large 4″ arm base tubes, no one single saw in the place could cut either all the way through or cleanly, so they were finish machined. To prep them for welding, a quick pass across the belt sander to scrub the ends clean was all it took. Yeah, it sounds all simple, but this was 3 days or so of my life being filled with tubes.

Not just those tubes – the square skeleton tubes of the arm also had to be cut. They were first roughly sawn to shape with a…. Oh, by the way, here’s how you cut a 60 degree bevel on a saw only capable technically of doing 45 degrees. These arm tubes also needed bevels on both sides, so after the abrasive saw came the cold saw, which is more precisely adjustable by angle. Hot saw, then cold saw… Repeat about 12 times for two long arm pairs and one pair of short arms…


The first cohesive chunk of the bot emerges! This is a finished top clamp arm, minus ears.

No, those aren’t my welds.

All of the welding work on this bot was hired out to Skunk, a resident welding wizard and bike chef of the Artisan’s Asylum. I made the decision after the stark realization that it was going to be very painful for me to weld everything on this bot. What I discovered in my past experience with welding is that I don’t really have the patience to do it well. I can both TIG weld and MIG weld in steel (let’s not talk about aluminum), but the finesse needed to do it correctly escapes me. My preferred welding method is “giga-MIG”, as we tend to call it in my circle – crank the MIG welder up and insert approximately 1 spool of wire into your workpiece!

Hey, it worked for Sadbot, but for Overhaul’s more nuanced welds in thinner material…

You know, if you get Skunk to weld it, it might actually work!

- Rob Masek, when he was still Artisan’s Asylum Facilities Manager

Words of wisdom from Rob!


Skunk not only welded up the clamp arm, but all four pontoons, stitching the tab-and-slot edges shut. There wasn’t any finishing with a grinder needed at all. I was not looking forward to the hours of angle grinding that were going to be needed if I began farming ferrous banana slugs on this thing. I would have cornered the market in steel slugs, that’s for sure!


Then there were the arms. Skunk termed them “the most welded objects I’ve ever welded” and this was a completely accurate description – every possible seam was welded thoroughly. Once again, zero cleanup of any sort was needed.

Heaven forbid I ever get this good at something, eh? Honestly, seeing this work was one of my slap-in-the-head moments. I am definitely a Jack-of-Most-CAD-Programs, but I don’t think I have any outstanding skill that anyone else who builds stuff all the time wouldn’t have. You think I’m invulnerable? No, I’m probably one of the most insecure designer/engineers you’ll meet.

March 24th, 2016 was a joyful day.

It’s here. Oh my Coincident-mate, it’s here. The thing. The part that actually matters. It’s THE robot.

Without the frame, there would be no robot.

Full disclosure: At the 2nd week of March mark, my contract shop was having schedule-keeping questions and asking me if the delivery could be delayed. Again, this was a production CNC shop that I had make things like DeWuts and RageBridge heatsinks and the like, and here I was tying up their machinists with two dozen nearly one-off parts that required CAM, setup, and stock trimming for each.

There was some back and forth, and I ultimately accepted a delivery date slide of a few days (from March 21th to the 24th, basically). During this harrowing time, I blitzed out an emergency “bailout frame” to be done up by Discount Steel in AR400 plate. It had all the mounting points and features, but was just brutalist steel squares.

Luckily, this is as far as that design ever got before I received the frame parts. Remember, this is how shameful it could have all been.

Okay, that’s mean. I don’t want to knock on steel unibody bots; they work fine, but going from billet to gorillawelds to me was taking a massive step back, and addtionally, forcing the expenditure of another 4-figure sum to get the order rushed and air-freighted while also having to pay for the machining was an unpalatable scenario.

Rob being Rob immediately jumped into building my robot for me. Thanks Rob!  This was actually immensely helpful, because he discovered a few “Sigmas problems” with the frame, such as holes not being tapped quite deeply enough (likely my fault since I specified the thread lengths). I probably forgot to account for tap taper when doing so. The rest of the fitup was great.

Okay, I think I’m done. I’ll just stare at this for a while. Ignore me.

You can’t build a bot at the Artisan’s Asylum without everyone wanting to pitch in and help! Soon, I had a crew, and we put together a lot of test assemblies to make sure everything worked.

Here, the drivetrain goes in for the first time.

guys it looks like the cad model omg

The bottom and top plates were cut from 4mm thick 6Al-4V (Grade 5, because fuck 6 and 4) titanium with a waterjet, and the bottom holes in particular were countersunk using a carbide countersink. The titanium curls that resulted were given out to Asylum members for artistic and FIRE! GLORIOUS WHITE TITANIUM FIRE! purposes.

This baseplate snapped into the fully assembled frame without any fuss. The magic of actually keeping track of your tolerances and anticipating tolerance stackup, ladies and gentlemen! I’ll be here all week month #season3.

Cynthia is seen installing the rubber shock mounts, or wubbies (that’s a technical term), for the final time. The AR400 plate is actually just a millimeter or so too thin to support a countersunk 3/8″ flathead cap screw. I knew the wubbies had chamfered edges on their holes, so I was hoping the two would line up and I wouldn’t have to countersink a big bag of rubber wubbies.

Well, turns out I did. That carbide countersink I bought for $60 to do all the AR400, titanium, and other difficult countersinking jobs turned out to be a great investment! If you look at the mounting holes in the wubbies, you can see they’re all countersunk deeper.

My pride and joy, the intermediate lift shaft, drops into place!

Adding lift motors and couplings now.

This is the “everything bracket” that was detailed in the Electronics buildout post. As it turned out, it was the longest piece ever done on a MarkForged machine! Because why else would you design something so ridiculously long!?  I printed one copy, then asked MarkForged to put a full set of spares on their print farm. The fiber backing here is kevlar.

Recall that I had to bail out to using the 160A DLUX controllers after finding out that the 250A model which I’d based my strategy around was no longer stocked. I redesigned the bracket in the electronics box to hold the 160A DLUX instead.

While other parts were coming together, the Mark Two was printing these parts out. Here, I’ve pulled the parts from the machine and am test fitting them to the waterjet-cut polycarbonate (Lexan) electronics casing. Paige and Cynthia took care of most of this waterjet-babysitting offsite.

The previous drivetrain test assembly was just wheels, nothing else. The final assembly meant hooking up chains! I bought a big box of #35H chain with the intent of making several swappable spare chains as we measured and cut each type. Four chains run the drivetrain per side, with three distinct lengths. There’s the center-to-front chain, the longest. Then the middle and rear chains were the same length, and finally the shortest one that bridges the two motors.

After this madness, it was time to start making the remaining details. Remember the nylon logs from the beginning? They were reduced to smaller nylon round things! I will point out that this material is quite possibly the most irritating substance I’ve ever had to machine. Short of hand-ground and sharpened high-speed steel tools, it would not really cut so much as smush annoyingly out of the way, making a large ring of deposited material in the way of your cut. However, I can’t fault it too much, as the parts were dimensionally accurate.

Other parts that were made in the same sitting included modifying the ball screws for the lift actuators, as well as the main lift shaft endcaps…

…which Shunk quickly attached to the ends of the lift shaft tube. This is 4140 steel endcaps on a 4130 steel tube with 1/8″ walls.

The big engine head studs were installed into the lift hub and the upper clamp hub checked for fit. It’s basically time for the arms to go on now…

In the next episode, the mad rush to the finish and the outlook at the event! I want to clear that early next week, such that once Overhaul’s match with Cobalt airs, I can post the fight analysis, ala Chaos Corps.

The Overhaul 2 Design & Build Series, Part 10: What Do You Mean It’s Out of Stock?

Jun 20, 2016 in BattleBots 2016, Bots, Overhaul 2

Previously, on How to Build an Overhaul…

dramatic over the shoulder camera angle here

charles stares intently at a lathe on autofeed


“this insert seems a little dull and i want some mountain dew”

Machining the parts for the lift clutch was well under way by early March, and parts were coming in almost daily. Our goal was still to have “the robot minus the frame” done by the 3rd week of March, when the CNC machined frame was to arrive. For instance, here are infinite wheels:

After confirming that one hub works, it was time to make all of them. Now, these Colson wheels are made of polypropylene with overmolded rubber. The plastic is so soft that it would rather mush around than be cut, unless it had no other choice. Broaching the wheels made all kinds of neat Colson art, like so…

The next step to assemble all the drive wheels was to chamfer the tips of the waterjet-cut sprockets. Chamfering the tips makes the sprocket more tolerant to side-to-side chain slop since the teeth become narrower, and so the chain has more wiggle room before it tries to catch between teeth and fall off. And I can think of no better application where your chain is likely to have a sudden amount of side to side slop!

There were 30-something sprockets to machine, and I needed a solution to make life simple.

Enter MarkForged

I designed a jig that the sprockets bolted into – they had the correct center bore and two keyways to drive the sprockets, and were made using several layers of Kevlar reinforcement for strength (This wasn’t a critical application that had to be Kevlar – it was honestly what I just had loaded in the machine at the time. Any of their fibers would have been as rigid, or more rigid). On the inside of this print was a hex socket that fit a 1/2″-20 nut. A 1/2″-20 bolt runs through the body, giving it even more rigidity, as well as retaining the sprocket. It was then easy to chuck the jig into a lathe, holding the sprocket away from the chuck, and quickly chamfer both sides with a cutter. Then simply swap the sprocket out and continue!

The other piece shown is a portion of the electrical deck. It holds the robot-side main battery connector onto the electrical box, and was included with this print because why not. I wanted to try out the dimensions in real life to see if any adjustments had to be made.

After broaching the 5″ and 3″ colsons, I began to become concerned about how easy the wheels were to broach.  While the 5″ Colsons had plenty of material at the hub, the smaller 3″ ones had a significant portion of the hub’s radial thickness removed when I broached them. This was concerning, because the reduced material ring beyond the keyway, coupled with the sharp keyway edges, and the fact that the front wheels would be under the most stress when lifting an opponent, meant that the wheel was likely to crack apart.

Not cool. So one of the first “dynamic redesigns” of this build is now needed – the front wheels. I decided to design a MarkForged printable hub, to which a polyurethane tire is bonded.

The 3″ Colson wheel also only covers about half the hub width, as smaller sizes don’t come in the 2″ wide size. The new front wheel would be equally wide as the rest.

The outer ridges are to increase the surface area available for the eventual glue bond.

Here are some “cheat code” features to optimize the part for a MarkForged machine. Right now (as of 6/2016), their slicing software doesn’t yet allow you to prioritize “internal” features, such as holes or bores. All fiber lay is from the outermost perimeter inwards. The reasons for this are many (including feature recognition challenges), but bottom line is, I can’t tell the slicer to fiber up the keyed bore itself.

So in a manner similar to the “hairline split holes” method of 3d printing parts with more perimeters, I added a few Slots of Persuasion to forcefully route the fiber layers into the places where I need it – the keyway area. The fibers will handle the majority of the power transmission stress, so I was less worried about the plastic necking down here.

I also could have made the wheel a “C” shape, with the ends of the C so close together as to be almost touching – and in real life, the plastic would bond together anyhow – but I wanted to avoid having a single linear weak spot in an otherwise complete structural loop. So, little guidance slits won out here.

I then added a few Holes of Persuasion to force some fiber layers towards the outside layer, and some towards the inside of the hub surface.

Here is a finished wheel! See the keyway being surrounded by fiber, as are the inner and outer surfaces for the most part. I could have put Kevlar into all the layers, but decided to be a bit more economical. Each wheel contains just barely under half a spool of Kevlar. The rest of the volume is simply densely filled.

I’ll be the first to admit that I am not a master of composites and adhesives. I used whatever glue McMaster called “urethane glue”, part number 7493A21. My criterion for selecting this adhesive was “Says Urethane on it, does not require an expensive-ass dispensing gun or carefully pushing out with a stick, and comes in the little cute bubble packet”. This is roughly the same process used to select a bearing grease for Mikuvan’s front wheel bearings (“Well, it has a picture of a car on it”) and those haven’t blown up on me…. yet.

Help me.

The tire material is a soft urethane tube, McMaster part number 87235K74. I cut rings off the long tube I purchased, 2″ wide to accommodate the hubs. It gets stretched over the hub after the hub is throughly coated in the urethane OH GOD IT DOESN’T COME OFF AND IT’S STUCK TO EVERYTHING adhesive. I wiggle the tire on and use the dribbles to fill gaps and create edge fillets. Then I leave the wheels alone for a day or two.

The evening I put these together shall forever be remembered as Urethanocalypse 2016.

Here’s a pile of infinite finished wheels! Well, semi-infinite. We decided that a 100% set of spares was sufficient to start. In the event of post-match damage, swap the wheel for a known good one right away, then deal with the repairs after

Next up, infinite spider couplings. Notice how there’s a lot of “infinite” on this bot? Again, a manifestation of the design goal that is making all of the spare parts in one shot, with the parts themselves designed to be easily replicable. Other builders prefer building 1.0 robots first, then working on spare parts.

All of the spider couplings are broached for 1/8″ keyways to slide directly on the lift motors.

And finally, we get to….

Infinite SK3 motors.

This is where I introduce Equals Zero Robotics’ 2nd sponsor for the 2016 BattleBots season…


Yes, that HobbyKing, a familiar sight on this website for many years!  I was in talks with them as early as Sadbot running on the dlux 250 hacks. Originally, it was just for more dlux 250 units, but I decided to go deeper. The robot community has a love-hate-love-again relationship with HobbyKing’s legendary Chinesium offerings, and many smaller bots have used HK parts to great effect. But can they play bigger?

Either way, some great exposure potential for HK, so they agreed to send goodies my way. One of these shipments was a nontrivial percentage of the world’s supply of SK3-6374-192 motors.

Another shipment was more running gear for the bot:


Critical subssystems and support equipment, all sponsored by HobbyKing.

Overhaul 2 will be running the 9XR Pro radio system with the long-range 433mhz R/C gear, to get me off the 2.4Ghz band. I wanted out of 2.4Ghz entirely – everything from other robots, to WiFi, to production running wireless lighting and microphones and the like, lives in 2.4Ghz. Last year, a few people had control difficulties (including yours truly) in the box, and I was not out to repeat that.

Next up are battery chargers and charger power supplies, as well as some BEC units to run the logic power (receivers, gaudy lighting, etc.) since the ESCs do not provide 5v power. Speaking of ESCs…

What’s missing is a boatload of DLUX 250 controllers.

Let’s rewind a few weeks here. What happened was that I compiled a bill of materials to send to Hobbyking, which included 12 dlux 250 controllers. Everything on the list was packed up and shipped to me, except the DLUX 250s, because…

I’ve gotten confirmation from the manager that this product has been completely discontinued and the factories are no longer making them.

Oh, snap.

After some highly intense back-and-forth over e-mail about possible replacements, I decided to spring for swapping the 250A model for the 160A model.

This was a very stressful decision. R/C amps are usually 0.2 to 0.5 of a real amp* and I was getting concerned about the real ampacity of these controllers. While I had familiarity with them from the BurnoutChibi project, the lack of large-package FETs (in favor of a sprinkling of small surface-mount FETs) and smaller thermal mass was the clincher. I also didn’t have a handle on their reliability – the only DLUX 250A units I’ve ever killed were due to my own stupidity, such as hard shorting outputs or leaving the bus capacitors off.

It was therefore imperative I get units in hand as soon as possible, as even the stock quantity of DLUX 160s was getting low (less than 15 remaining around the world in stock, as I recall). I really need to hand it to Hobbyking here for trying to round up stock in such short order.

*this statement is not backed by any form of science but is pretty accurate

The DLUX 160A controllers came a few days after the rest of the shipment. I immediate got cracking on tearing them open to see what I had to change for in the SimonK firmware. Luckily, the answer was not much. I had to redefine a few resistor values, and also set a correct deadtime (these switched slightly faster due to the smaller FET packages), but otherwise, they were the same pinout and layout. Go figure, but just to make sure.

I then uparmored them like I would the DLUX 250A, but these only had space for one big ol’ capacitor, which is better than nothing!

A set of three DLUX 160A controllers fully modded up. I was going to whip these things in Sadbot to ensure they don’t explode.

I removed the 250A controllers from Sadbot – now a valuable and rare commodity – and tied these guys in, then proceeded to drive around like a maniac, just like I did with the 250A, and lift & self right and do other things with the pokey stick.

Here’s a test video showing a little bit of it. The open floor tests were to try and stress the controller with many reversing and turning instances, and the sliding was induced by keeping the wheels spinning (drawing wheelspin current) as much as possible.

(RIP Frozen fans and normal people)

The controllers passed this test solidly, I’d say. I was beginning to smell SK3 windings before the controllers became too hot to touch, so that’s a good thing.

However, while powering up Sadbot for another test a few days later…

A minor smoke event occurred.

One issue with R/C controllers, especially large ones, is that they scale beyond their hardware designs that were originally put together for small ones. Without proper gate drive, and with the possibility of mixed parts in the power stage, if one FET blows up, it tends to start taking the rest with it. And some times, this happens almost spuriously. This is how a controller works for someone and not for the next person. Add to that the quality control generally associated with hobby parts, and….

Okay, let’s be clear: THERE IS NO SUCH THING AS A MINOR DLUX SMOKE EVENT. The whole thing is seemingly made of thermite, or the mix of materials acts as a rapid propellant, because it was over in 5 seconds, a foot of flame, and a huge plume of smoke. I was in fact fearful of a lithium fire with the batteries next to it, and was getting ready to shove the whole thing off the loading dock. The polycarbonate battery box from Overhaul 1 protected the batteries, luckily.

This was all that remained…. As you can see, the entire PCB is actually burnt in half.

By this time, I didn’t want to try to investigate yet another controller. And unless I were willing to pop out Brushless Rage™ in three weeks and get it right the first time, this is what I was going to have to deal with, and part of what I committed myself to doing – using big R/C parts in big robots – from the very start.

So it was time to put the controllers down and keep moving. I asked Hobbyking for a large stockpile of the 160A units to be laundered my way ASAP. I decided to formulate an electrical system continuity solution which used the DLUX 250As remaining (5) as much as possible, and substituting in the 160s if absolutely needed, but ensuring that I had a full bot set of DLUX 160A controllers right away.

While I was doing these tests, the others had finished machining the motor mounting blocks for the SK3s, and keying the shafts.

Ah, finally, all my ducks in a row!

The difference between a “left” motor and “right” motor is simply which direction the wire leads come out, to keep the wiring in the bot convenient.


The next step was to assemble all the gearboxes. Four left, four right, and four lift motors were to be assembled. Again, a 100% overhead (hehehe, overhead for Overhaul) such that we could pitch in a spare set right away and mull over the broken ones in the pits later.

Notice the delicious strawberry jelly on the left. Mmm, extreme-pressure additives.

Here’s a fully assembled drive motor, with retaining bracket!

Repeat like 20 billion times

Okay, so I lied about getting away from controllers, again!

Overhaul 2 still has that 1 brushed motor onboard, the A23-150 micro-Ampflow motor to run the clamping arm. To use this motor, I needed a high voltage (12S capable) DC motor controller.

Now, I had designed a 8S-capable motor controller of some type a little while ago, and in fact, one of the original RageBridge 2 plans was to have it be 12S-capable. But I decided to scale back for expense and usability reasons – most everyone runs these at 6S (around 24v) or in extreme, unsupported-by-manufacturer (AHEM, WILL BALES) cases, 10S (36-42v).

To change Rage over to the higher voltage specification was actually an intensive job, basically rebuilding the board. The main capacitors were changed to 50V types, the MOSFETs to 60v parts, and a lot of other little things moved along with them – such as changing the gate resistors to accommodate the new drive needs, and the logic regulator to a HV-rated part.

In the end, I whipped together two HVRage™ units for the clamp motor, and tested them (see the small blue wires used as scoping points) to ensure nothing was going to get TOO fiery.

And this is the conclusion of Overhaul 2: Actual Electric Boogaloo (sorry Orion). Next up? A Series of Tubes:

Side note: Overhaul 2 swag is now up on the BattleBots store, if you haven’t seen yet. All artwork by Cynthia! Proceeds of sales do go to the builders, so you’d be sponsoring supportng Overhaul for #season3!


The Overhaul 2 Design & Build, Part 9: Where We Actually Begin Building, n’Stuff

Jun 08, 2016 in BattleBots 2016, Bots, Overhaul 2

This is it! Now that my incredible van hangover has cleared, it’s time to get back to build reports. With 2 weeks left to go until the SEASON PREMIER OF BATTLEBOTS ON JUNE 23RD 8/7c ON ABC!!!! my hope is to clear the build itself and discuss the runup to the event as the season starts. As OH2′s matches are aired, I hope to immediately turn around and prepare analyses of them within a day or two. OH2 is not part of the premier itself, but look for it in the next few episodes that cover the preliminary rounds and beyond!

So, after seven episodes of working through the design – eight if you count my love affair with brushless drive – it’s time to start persuading metal into shape. At this point, it was late January, and I’d just gotten a load of RageBridge2 units in, so we were busy in “fulfill the delayed crowdfunding campaign” mode. It was between RageBridge logistics juggling that I was placing the first orders for materials and parts. As I mentioned in the last design post, a majority of the machined parts for this bot were going to get sent out to external shops which I’d done business with before.

I spent a portion of December and January shopping the design out to a few places, both domestic and in China, to gauge interest more than anything. Here I am, showing up with basically two dozen unique parts, for which I need quantity… 2…. or thereabouts. My contacts are largely production-oriented shops, since I needed, say, 250 DeWut casings or 500 RageBridge 2 heat sinks. They have otherwise much larger jobs that occupy machines for a week at a time. So it wasn’t surprising when only a few replied saying they had the capacity for it at all, much less the ability to turn around quickly.

Robot build seasons are always a blur, and a huge and complex robot even more so. In high school doing FIRST Robotics, it was easy to lose track of where on Earth the past 6 weeks went, and I was definitely in a similar situation with this build! I’m basically going off the photographs’ dates now to reconstruct the series of events which led to Overhaul 2. We begin in mid-February into early March as parts began arriving.  Yes, began. Basically everyone was cutting it this close for a variety of reasons, some of which I’ll likely talk about only after the season finishes airing.

So here we go! First, the main cast of characters involved.

  • Me, the principal designer and I suppose electrical system lead, since OH2 has the most hipster snob electrical system imaginable. I also machined stuff occasionally, I guess.
  • Cynthia, who assisted with fabrication and also creating the team aesthetic and presentation, as she is a graphics designer and illustrator.
  • Paige, chief waterjet babysitter and machinist/fabricator.
  • Matt, Paige’s boyfriend and Biology & Premed student, so we trained him on whatever needed doing at the time.

Oh, also, as the build progresses, I’ll be sprinkle CAD shots back in as things need validation or redesigning on-the-fly as disasters occur. I assure you there was a lot of that…

The stinger photo at the end of build report part 7 was of wheel hubs. This was the only “mass produced” part for OH2, since I knew I was going to need spare wheels no matter what. I sent this out to a nearby CNC shop, ARMSET who turned this around in about a week and a half.

During the intervening time period, I tried to work as ahead as I could on minor fabrication of the associated parts, such as sprockets and wheels. Additionally, I wanted to get a start on one of the weirdest parts of the bot – the welded plate armored pontoons up front.

What’s the same thickness as 5mm steel? 5mm plywood, and I think one of these substances is a little easier to put together over and over! I bought some birch model plywood from a local wood distributor, and then proceeded to barge back into my own former shop to use the laser cutter.

My rationale when putting this thing together: Wherever I can shove the hot glue gun, I can shove the MIG torch. This assembly process went as smoothly as I had hoped, and I ended up building 3 of these to test the assembly order, i.e. “Where do I spray the steel boogers first?”

Here’s a completed armor module in plywood!


I gave this pontoon a healthy coat of the closest color to Miku Blue I could locate in a Home Depot spraypaint aisle. For the record, this color is Rust-Oleum’s “Gloss Seaside”. The camera white balance isn’t happy here; it’s a lot more aqua in real life.

One of the design choices that we were making early on during the design submission period was the robot and team color palette. Overhaul during Season 1 was naked-ass steel and… red, I guess. There wasn’t much thought put into anything except making it do robot things, so we just went with a red and a gray, similar to MIT’s palette, where gray was just made of #stonecoldsteelaustenite.

This season, I was out to transition the robot to something blue. Specifically, during the early design stages that were detailed in Part 2, when the new application was being prepared, I was all set to make a Miku-themed robot. I shit you not, this is a never before seen concept image which I put together (because of course I did):


Now that I’ve scared everyone away, I can say that this concept was not used because there would have been basically no way to use a copyrighted character as a team mascot or have the character prevalent throughout the robot and team.

So the #mikubot concept was scrapped, but the color lives on.

Here is a round of sprockets (that’s a technical term for a group of sprockets!) that fit on the hubs. They’re waterjet-cut from 3/16″ 7075 aluminum plate. Basically, the idea at this point was to assemble wheels as soon as the hubs got in, and then keep assembling drive and lift motors and electronics until the frame got in

The other small parts on the left are retainer brackets for the SK3 motor rear ends.

Other interesting things also began arriving. For instance, these two piece of oil pipeline oil-filled nylon bearing stock. The large rotating arm parts will use machined nylon bushings for radial support. They’re moving at a low speed, so I opted to use plain bearings. Bronze would have been nice, but heavy. I figured at this bulk level of usage, the nylon would do just fine.

One of the first electrical system experiments I wanted to verify was the custom master power switches (a few pictures down). Recall that I designed these because fitting two Whyachi MS2s in the bot was becoming a daunting prospect when accessibility was factored in i.e I wanted to retain the side approach arming.

Shown above are some copper contacts that were cut from 1/4″ silver-plated copper bar, supplied by McMaster. It seems like this silver plating is largely decorative, because it was coming off if I was rubbing it too hard – probably for anti-corrosion purposes only. Oh well.

The internals of version 1, as simple as you can get. The body is a nylon with fiberglass print, made using a Markforged Mark Two.

I’d like to take this space to welcome Markforged as the first sponsor of the team this year. You’ve seen a lot of action on this website and on Jamison’s site with Markforged parts, and they know there’s no better application to have their parts mercilessly beat on to show the technology! Markforged is providing Mark Two prints and printing services on their print farm.


While this edition seems to work just fine (it conducts! Yay!) I wanted to refine it more and also fix the fact that the hex key could, under some angles of insertion, be the first thing to close the circuit. Obviously you don’t want this to be the case. I also wanted to add a biasing spring to lessen the likelihood that if the closing torque was insufficient, that the screw would just back off and leave everything disconnected (or worse, constantly arcing). Here is the version 2 updated basically after I finished printing Version 1. The black nylon bushing proides a long entrance guide for the hex key so it can’t touch the switched contact under normal use.

After a McMaster order, the version 2 is completed. With a dab of conductive contact grease on the spring, the action was smooth and repeatable. I was satisfied with the design at this point, so I printed more with very minor dimensional changes for fitup.

Around this time, my order of wheel bearings arrived. They’re 5/8″ bore needle roller bearings that are pressed into the hubs. Shown also is a single 5″ Colson wheel which I test-broached with 1/4″ keyways.

This work was done just in time prior to the arrival of the first big batch of parts that needed significant modification and work, which is the drive and lift gearboxes…

Oh god that’s a lot of Banebots.I ordered 10 4:1 gearboxes and 4 16:1 two-stage gearboxes, plus a basket of spare carriers, shafts, and gears.

My personal guess was that if the gearboxes were going to fail, the 4:1 drives would fail first due to rapid reversing and direct shock from the drivetrain, like running into things. The lift gearboxes would be reasonably isolated from torque impulses by the 12:1 external gearing and the clutch. I ordered enough gearboxes for drive such that I could build 10 drive motors and, in accordance to the serviceability inherent in the drivetrain design, just swap out motors and deal with piecemeal repair later.

That’s one of the things which trips up newbies some times is how expensive everything gets once you factor in the ability to repair rapidly. While the initial cost outlay might be high, what is the cost to you of losing a match when you could have been able to put the machine back together if you had parts?

Two things needed to happen to the Banebots gearboxes to turn them into drive and lift motors. The motor mounting blocks had to be machined down to 1/2″ thick, and then the hole patterns drilled. Paige and Cynthia took up this job using some of the equipment in the IDC and CNC mills in the same building.

I continued the “weird science” part of the build by working on the two-speed shiftable “P90X” gearboxes. For this, I waterjet-cut out of O-1 tool steel a replacement planetary carrier:

That’s it on the right. This carrier has (reduced size) teeth and fits perfectly into the ring gear on the left. It has hole patterns for both 4:1 and 3:1 gear stages. The idea is that the sliding ring gear either is anchored to the gearbox housing, or is meshed with this carrier and spinning with it, bypassing one stage.

Here’s a comparison of the carrier plates after I transferred the pins over. The next operation for this setup is to chamfer the edges of the carrier teeth and create a mating chamfer to the ring gear, such that they can collide and mate smoothly.

The other side of the ring gear needs to be firmly affixed to the front output block of the P80, since the ring gear is no longer held in compression between the two blocks. To do this, I basically turned the four dowel pin holes on the ring gear into holes for four shoulder screws. Notice that I’ve already cut off the ring gear here, too.

The four pins that were in the output block were removed, then their holes drilled out directly and counterbored on the other side for the shoulder screw heads.

We interrupt this build report for….

EPIC LIFT GEAR! From now on, every time I say EPIC LIFT GEAR! it will be in bolded capital letters with its own exclamation mark. Consider it a single lexeme. Anyways, the EPIC LIFT GEARS! arrived from…. Amazon. These are giant spur gears from Boston Gear, who lists its basic catalog on Amazon Prime. I’m super happy about this and encourage all industrial suppliers to do it.

Part 1 of the EPIC LIFT GEAR! is the 42 tooth, 12 pitch intermediate gear, which will be turned into the lift clutch. The other EPIC LIFT GEAR! above it is the 6 pitch output pinion. It will be face width reduced – I don’t need the ridiculous 2.25″ face width – and then broached.

I used the MITERS Clausing lathe to bore out and dish the interior of the 42 tooth gear, and also cut off its hub. This is it – the intermediate EPIC LIFT GEAR! will just have a bushing in the center such that it can spin on the clutch shaft.

Next up was the clutch shaft itself. In the latest McMaster order, I put in for a length of 1144 steel, commonly used for high-stress round things. This needed to be turned from a 1.5″ round into a 1.25″ shaft with two 0.75″ ends and a 1.25″-12 thread on one end.

I decided to practice threading again on some aluminum first, since it had been a while since I last made giant custom threads, and I was also unfamiliar with the new MITERlathe’s threading controls.

I then mounted the shaft in a mill to do the secondary keying operation. This keyway is for the 6 pitch EPIC LIFT GEAR!, since the 42 tooth intermediate gear will be sandwiched using clutch plates. However, I decided to make the keyway full-length such that I could make the clutch plates themselves keyed, to assist in torque transmission.

A little bit of Scotch-Brite and wire brushing to deburr the threads, and the clutch shaft is completed.

Here’s what the clutching setup looks like for now. I had yet to receive the order with clutch lining material and giant conical washers, and the pressure plates still need to be cut.

While this mechanical work was going on, I was working ahead a little on the electronic side of things. Little I know the build was about to take a tragic turn…



By the way, Overhaul 2 swag is now up on the BattleBots store. Builders get a cut of the sales of all swag, so here is your chance to indirectly sponsor Equals Zero Robotics!

The Unlikely Story of MomoCon; 12 O’Clocker Returns, #weeabot Intensifies, and I Haven’t Broken Down Yet

Jun 01, 2016 in Bots, Events, Twelve O'Clocker

Momocon is a pretty big anime & gaming convention that’s been running in Atlanta for about a decade now. I’ve somehow never made it to the event – either it was inconveniently timed being the end of the Georgia school year back in high school, or I was, you know, up in Boston getting my degree in Hoodrat Stuff & Bad Things.  So when the organizers of Robot Battles and the Atlanta-area builders, including some members of the Chaos Corps, were hinting that the next event might be held at Momocon, I quietly rejoiced…..and went straight back to work on Overhaul (Which I still owe everyone the next edition of the build report for…)

Whether the original announcment went unnoticed because of the build season, or it wasn’t shouted loudly enough across the community, I actually didn’t remember anything about it until, oh, about 2 weeks ago when I was reminded by some people asking if I was coming.

Ooh…. well crap. That certainly is going to mess with my plans a little. I mean, I guess I could probably go, but it’s kind of a short-notice thing and I dunno if it’s worth flying down for just one weekend and what will definitely be a small event. And I’m not sure if it’s worth the time to drive, even if it means I could bring Overhaul and display it, bec…

hold on a second. didn’t i quit a job or something so i could do stupid robot things whenever i wanted?

Hey, I’ve spent all this time promoting #weeabot, and here is a robot event at an anime con and I’m actually debating whether or not to go? Load up the van!

But before I could do that, I had to make sure of two things. One was that I had a working robot, and the other, a working van. I’m so good at life, guys.

12 O’Clocker

I stood over my pile of small robot wreckage, wondering what exactly I could bring to the competition. I was missing parts that would need to be rush-ordered for almost all of the 1lb and 3lbers, like Colsonbot and Stance Stance Revolution. Überclocker is a wreck throughout, and I also promised that it was done for real after Franklin Institute.

Then there was 12 O’Clocker. Put together for Dragon Con 2013, it didn’t do too well because its drive motors fell off. Beyond that, the bot was undamaged. I figured in the time I had remaining between when I’d need to leave, which was about 4 days spanning a weekend, I could at least remake the drive gearboxes. Those things were originally 3D printed from ABS plastic using the Dimension 1200ES machine. Now that I had access to the MarkForged Mark Twos, I could make them from nylon, which is a much stronger material in the application.

So that was it – I was just going to repair 12 O’Clocker for now. I discovered while trying to put Colsonbot back together that I was short on Vex 29 motor controllers to have it run, so there goes that.

Here it is, dug fresh from my crypt of robots. There’s really nothing wrong with it at all that I could tell, but I’m going to fully deconstruct the drivetrain and liftgear just to be on the short side. As a reminder, the drive motors broke off their mounts at Dragon Con 2014, so the drive will be my focus.

Pulling stuff apart little by little revealed things that I forgot I had Loctited, and other things which weren’t. This was chance to correctly detail the bot. For instance, the inside bolts that hold the axle stubs to the frame SHOULD be very tight and threadlocked to prevent the axle from moving. The external retainment screws should not, in case I had to change wheels. For at least 2 of the wheels, this was backwards for some reason…

Extracting the gearbox housings…. Ouch. Not only were the motors jiggling and detached, the gearcases were cracked clean through in some places. This seemed very strange to me, since I ususally know 3D printed ABS as being quite tough and flexible. Short of the oil-based grease getting into the print and damaging the polymer, I’m not sure why this happened.

You can see that the cases weren’t just cracked, but broken through in numerous places. Here are the gearboxes entirely taken apart and ready for cleaning.

I modified the gearbox part files just a little to address shortcomings in the original design, such as the diameter of the ring gear socket and its length. I do like these things, and post 12 O’Clocker I kind of want to put some more design effort into them. They were then printed using “close to solid” fill – something like 90% density and the plastic fuses together anyway, and if you go more than that it tends to be blobby.

Reassembled and relubed gearboxes using the new housings…

Beyond that, there wasn’t much else that needed work. I went ahead and cleaned and regreased the actuator, since it was very dirty from storage, and adjusted the chain tension of the lift chain also. In all, it was about 1 equivalent afternoon’s work (spread across two, to wait for the 3D print to finish) to get 12 O’clocker back in fighting shape.

cruise control for cool & operation vanfan part II

I next turned my attention to some “deferred maintenance” items on Mikuvan that were acceptable for blasting around town, but not for any type of long haul operation. After the Great Accidental Engine Rebuild Debacle of 2015, there’s been no mechanical and driveline problems at all, but some small irritating things were left over or perhaps caused indirectly by tearing everything apart.

One of these was a consistently leaking upper radiator hose which developed during last fall & wnter. It was just inconvenient enough to get to that I just accepted putting in some more coolant every few weeks. I decided to just get rid of it for the trip, since I did not want to risk losing coolant when driving in the much warmer South. Fortunately, it turned out that the hose was just seemingly improperly seated, and the cold rubber parts did not seal as well during winter.

Next, some time in February, the front heater/air conditioning blower died again. What an inconvenient time…

Now, this thing was rebuilt in the parking lot of Georgia Tech all the way back in 2013. And I quote:

Well, okay, I did have to rebuild my A/C blower motor again, in the Georgia Tech parking lot. Remember those brushes I installed? They were backwards, and they ate through the copper bus wire after a few thousand miles. A random 200W scooter motor turned out to have the exact same size brushes, and saved the day.

35,000 miles later, those little piddly scooter brushes finally bit the graphite dust themselves…

In this photo I’ve already desoldered one, but the other definitely wore all the way through and fell off. Sadness.

I actually did not have another similar scooter motor to pull brushes from, so I sacrificed a similarly sized motor with larger 6x8mm brushes…. and manually filed them down to 6×6. These brushes were much longer, but they still fit in the same holders. Hopefully, this will last more than 35,000 miles now! If the damn thing didn’t require a dashboard pull to remove, I’d have long ago replaced it with something modern and brushless…

Beyond these two items of inconvenience, there was really nothing I could work on. I know, right?! Time to make a problem for myself.

Little known trivia: Mikuvan has a cruise control system. It’s made of vacuum tubing and actuators, and has never worked. All of the vacuum lines are cracked or broken, and some just lead nowhere or are hanging around.

I wondered again how bad things could be, so I bought a spool of vacuum line and hooked everything up the way it was supposed to go. I cleaned the chevk valve and manifolds, and also took apart and relubed (to the degree I could) the throttle cable coming from the vacuum piston. I didn’t even verify if the system was holding vacuum – just shoved everything back in.

Hey, not manufacturer-approved routing, but whatever. The servo piston is seen at the bottom right – this tugs on the physical throttle pedal based on ECU commands. In new cars, everything is by electronic signalling now, so this system is absent.

During this process, I FINALLY figured out where the last missing vacuum nipple on the intake manifold was supposed to go. It was a random vacuum line connection that did not seem to go to anything, and which caused idling problems before I found it, since it was just a big air leak. In the end, this line was connected to the cruise control system. I’m guessing it uses engine manifold vacuum to purge the system. There is a small vacuum pump (which does still work) towards the top of the photo that keeps the system on the other side of the check valve purged also.

I also found this.

I, umm. Not sure where that came from, nor what it was doing, but it’s a big M10 flange head bolt, so it definitely was doing something important. Well, time to see if anything falls off.

Anyways, the answer was yes, everything still does work. Cruise control!

It is, however, rather boneheaded. I tried testing various potential failure modes, such as setting cruise for 55mph, cancelling, accelerating to 75mph, then hitting resume. Yes, it will attempt to dramatically engine brake from 75 to 55 by just dropping into 3rd gear.

Otherwise, on uphill inclines, it will also fall back to 3rd and make a whole lot of racket and not do much. I’m guessing it’s supposed to go harder in 3rd to bring the speed back up, but it does not seem to pull on the throttle much, and instead I thunder up a hill at 4,000 RPM, and actually also down the other side, because now it wants to go faster than the set speed and is using engine braking to maintain speed.  Definitely less useful than what you would find in a modern car, but whatever, I am told the 1980s were a wonderful time regardless.

On mild hills and flat ground, though, it works great!

The Trip Down & Momocon

There were no shenanigans.

For the first time, I can say that nothing weird happened on the way down. I’m both a little disappointed and now a little fearful of what lies in wait for the return trip.

Out of an abudance of caution, I took the 95 corridor against my own advice. Generally, I try to avoid I-95 below Connecticut and above Baltimore, but it lay closer to possible bailout points (e.g. friends with couches and shops). I tried to set out at a specific time to just barely make it past D.C. before rush hour hit, but goofed up leaving – delayed by about 45 minutes, because I was actually stuck behind a garbage truck in Cambridge slowly doing its thing down a one-way street, among other issues like construction and morning traffic in Boston – such that I managed to instead hit the afternoon commute exactly, upon which I decided to give up and grab dinner, because NO.

I overnighted in Durham, NC, at the best quality sketchy-ass motel I’ve ever seen.


Unlike most previous conventions and robot events, I hauled the 18-20 hour trip alone this time, which means that it sucked ass and also I decided to conserve energy by breaking the trip into two days. In 2011, I tried hauling the whole trip in one shot (only stopping to rest enough to continue), which meant it sucked additional ass. So really it took me over 1 day – 14 hours on Wednesday and around 5 on Thursday – but I wasn’t sad and tired when I landed in Atlanta shortly after lunchtime.

Well here I am!

I have yet to figure out how to wrestle Overhaul in and out myself. I might make some kind of sliding rail system for the cargo area here…

Anyways, let’s go check out the convention!

As I said, I haven’t ever been to Momocon previously, despite it being an Atlanta convention. It started on the campus of Georgia Tech, but recently it has amoeba’d it way into the Georgia World Congress Center, which is a huge place. What I noticed in general was that it definitely had the “big convention” atmosphere of something like Otakon or Anime Expo, but the venue is just so cavernous that the crowd density is much lower. So you’re not jammed next to hundreds of people sporting the Con Funk all the time like the former 2… or Dragon Con, which is a somewhat different beast.

The action was largely on the exhibit floor, which housed all the gaming and sporting activities. The other exhibit halls held dealers and performance stages. It seems to me like the con can easily expand another 50% in attendees without it getting crowded, which is perhaps their idea.

Besides the animus and mangoes, there is an extensive gaming section – indie games, board and card games, on-site LAN party, you name it.

i n d i e b r o s.

A few dozen arcade marchines – mostly rhythm and music games, were set up here too. Right next to where the robots were gonna go!

Dealer and artists’ hall. Nothing extraordinary to me at this point, and sadly I did not find any Miku gear sufficiently compelling ):

What was awesome, and made me seriously regret not bringing Chibi-Mikuvan… was the “Fandom Replica Vehicle” section. Wow, such a prosaic name for Jurassic Park jeeps. This wasn’t nearly on the scale of an itasha show, which made me sad – actually, there weren’t any of what would be called “itasha” at all.

Next time…

These days I’m usually out to stalk the maker-y parts of conventions, so I was excited to see this group. They make all-3d-printed props, and have the same visual and phonetic branding challenges as MarkForged.

Just kidding, guys. Also, MarkForged, please don’t drop my sponsorship over that. I love you, promise.

I’m also interested whenever someone has a mechanical prop or costume, such as these actuated wings, which were linkage driven such that when she stood upright, they were folded down, but in this attack stance they were fully out. Constructed entire using garage tools, too!

Hay guise, why drag your gaming rigs all the way out here when you can play at home?

Alright, enough con-gazing. On Saturday morning, I went in early to set up Overhaul for display!

It was set by the entrance to the pit area, and I set up a table to display all the battle damaged parts. How were they damaged?

Well you’ll just have to watch the Season Premier of BattleBots, Thursday June 23rd 8/7 Central on ABC to find out!

-me, about 1000 times during the weekend. Hey ABC, pay me to be a spokesperson already.

You know what makes the best business card and sticker holders in the world? Tiny Overhaul action figures! Print your own today!

I was actually designing these slowly before MomoCon, and sped up the effort to finish them in time. In fact, one of the last things I did before leaving was dropping by the Artisans’ Asylum to pick up 3D prints for the 2nd and 3rd one.

Saturday was the “Microbattles” ants and beetles tournament, where we had 6 in each weight class. I didn’t have an entry, so I just hung around the pit area as pit boss and general event help. The audience was quite steady throughout the event. As usual, the little bots are a bit hard to see up on the stage, so I think a lot of folks didn’t quite “get it”. I did talk to many people about BattleBots, Overhaul in particular, and some other bot talk.

I’d say about 6 in 10 people did not know BattleBots was back on air (WELL I CAN FIX THAT PROBLEM), 3 in 10 have seen parts of Season 1 but were not devout fans, and 1 in 10 knew enough about the show and the robots to ask me a lot of detail questions. I made them promise to build something for Dragon Con.

Sunday, SUNDAY, SUNDAY! It’s “relatively large” bot time! I left Overhaul & displays behind the pit banner, figuring nobody would just bail with it, so it was quick to set back up.

Here’s 12 O’Clocker before matches started. In addition to it, I was appointed to pilot Morrigan. Mike basically brought the entire tournament this time, with 4 30lbers and 2 12lbers.

A view from my corner, which I was manning when 12 O’Clocker didn’t need something tightened or recharged.

Now this audience was much livelier. I guess the bots are bigger and you can generally ‘feel’ the impacts more but we maintained this kind of crowd basically the whole day.  At one point, Morrigan was making so much noise that we were overriding the rhythm games and the whole arcade crowd wandered over to see what was happening, or if they would die shortly.

Additionally on display: Giga-Nyx…. err, Bombshell, from Chaos Corps. They only brought some weapon modules. Why?!

Well, you’ll just have to watch the Season Premier of Bat….

Oh, fuck it…

This thing I had been looking forward to. The newest kinetic bedlam from Dale, T-Boner (hhhehehehhehehe) has a scissor-action flipper driven by roughly the same mechanism  as the larger Overthruster. I have an eternal robot crush on KE-powered (flywheel) flippers, but have yet to produce a design. Better yet, it’s also all-brushless, using the same SimonK-enabled ESCs that I run on Stance Stance Revolution and a couple of other people use on other small bots.

So how did 12 O’Clocker do? Actually quite great. I went 2/2, winning against Dingleframus and Hypnus, and losing to Tetanus Shot aaaaaaaaand…. T-Boner. Of course I did. There was a lot of dancing involved, and 12 O’Clocker was a big crowd favorite. 12 O’Clocker can’t excute the “spin to win” grab-and-spin that Überclocker can, but I could relentlessly beat people on the stage over and over.

As per usual, the matches were recorded by Near Chaos, and the playlist for 12lbers is here


12 O’Clocker post-event. Someone in the 12lb rumble snagged on the left side chain and pulled it off, and shortly thereafter I actually lost the right side too. A little post-mortem showed that the drive motor on the right side destroyed its pinion press-fit. It’s a brass pinion on a steel shaft, so the steel shaft won handily.

Besides that, in one of the T-boner matches, I suddenly lost the lifting fork. Turning the bot over, I saw that the ABS mounts for the drill motor had cracked and the motor actually popped off the gearbox. While that was a quick repair for the motor itself, the ABS mount basically stripped all of its screw holes as soon as I took the screws out. To remedy this, I had to drill it all the way through and use some 2″ long bolts I packed which were part of Overhaul’s hardware package that I brought along. I’m not sure if I’ve just been spoiled completely by Markforged nylon prints, or if ABS was always this bad and I just accepted it, but I am so done with ABS as a material.

With my business at the con complete after another tour of the dealer hall, I packed everything back up. I’m actually taking some downtime to visit some possible housing & shop locations, since I am (slowly) plotting my move out of Boston. That means I’ll head back later in the week. We’ll see what van-related adventures happen this time…


Thanks Cassie Fray Cosplay!