Archive for the 'Overhaul 2' Category


Motorama 2018: How Not to Scale Model Test Your BattleBots, The Remix

Mar 18, 2018 in Bots, Events, Overhaul 2, Überclocker 4

I had originally intended to go to Motorama 2018 solely for #vantruckjustice and to serve as an event volunteer and purveyor of Ragebridges and Brushless Rages. But with the announcement of Season 3, it became clear to me that I really should take the opportunity to get some practice driving in with 30-haul a.k.a. Überclocker v4.

Not only was my list of “things I didn’t like about Overhaul” extensively long, but based on my experiences after Franklin Institute and Moto 2017, I had several mental strategies against KE weapons I wanted to try out. Better do it on the small scale where it’s less expensive, right!?

So onto modifying Clocker!

One of my recurring themes in the past few event reports where I ran Überclocker has been the idea of reducing my wedge cross section against vertical drum and disc style spinners. I’ve had a theory for a long time now that broad armored wedges/plows are actually a liability against those kinds of weapons, despite being more effective against horizontals. There’s nothing better to confirm my theory besides Blacksmith vs Minotaur – in which Blacksmith actually does quite well against Minotaur until the latter manages to land a square hit upon the front of Blacksmith.

Essentially, a vertical weapon will tend to bend up your defenses by hitting it at a single point along its bottom edge, effectively making the length of the plow/wedge useless especially if the vertical weaponed bot has a feeder leg of some sort.

One countering strategy is going fully vertical with your defenses, like a crossing vertical bar of steel or something, making sure you hit the weapon before any feeders are able to touch you. Whoops! used this reasonable effectively against totally-not-Minotaur for quite a few hits.

That doesn’t quite work for me, though, because Clocker/Overhaul both have lifting forks.


Another strategy is minimizing your cross section ot exposure to those weapons by being extra pointy, giving them less of a chance to hit something important. This is also a strategy that I began moving towards with other ‘wedge fights’ – a broad surface is, again, vulnerable to any imperfections in not only itself but also the floor. I wanted to explore this strategy with what I call the “Wedges of Limited Liability” seen above – basically turning the armor pods into little shanky forks. I designed them to follow the profile of the existing wedges, out of the same 4mm-ish AR500 material.

These are a few ounces lighter apiece than the regular ones, which is going to mean a couple of pounds at the Overhaul scale. So it was interesting to begin thinking of the configurations I could get – freeing up a few pounds on Overhaul could let me add other attachments or additional armor (e.g. if I had to face Beta again, I’d spend the extra pounds on top armor).

While I was at it, I also redesigned the normal heavy wedges in the style of Overhaul. I had thought about ways to retain the double-angle feature but significantly reduce the number of pieces needed to construct it. Overhaul’s wedges were rather complex and made of 9 individual pieces each. I came up with an idea of making the second angled facet into a ‘backstop’ of sorts, attaching directly to the outside surfaces through extended tabs that also acted as gussets.

In essence, the above is what Overhaul’s new wedges will look like, but with some geometry placement changes. Clocker’s front is a lot more tapered than Overhaul’s, meaning the ‘backstop’ begins too far back to be really useful here to protect the gear from another Glasgow Kissing. I was more interested in the construction and their potential behavior towards deflecting  hits in general, rather than specifically trying to address last year’s weakness.

One change that has been on the docket since Franklin late last year was changing Clocker’s gearing. Using the lowest RPM/v rated NTM 42mm motors was still too much – I rarely exceeded 50% stick travel while driving, and the constant burnout mode the motors ran in during each match made fine control actually rather difficult. To give the bot more control over its own inertia, I was going to go to 11:1 P60s (from 4:1) but with a bump in motor Kv from 650 to 750. While this reduces Clocker’s nominal top speed drastically to only 10mph from like 20, it was going to mean more speed in a useful range. A lot of my strategy relies on being able to carefully control my approach and orientation to opponents, after all.

The same changes will be carrying through to Overhaul, but less drastically – I’m changing only the external motor sprockets, from 15 tooth to 12 tooth, moving the system reduction from 8:1 to more like 10:1, which is what Sadbot has been running in testing and whose maneuverability characteristics I like more. It will reduce Overhaul’s nominal top speed from 19mph to 15mph.

By the way, the NTM Propdrive 42mm series have a Mabuchi RS-700 size bolt pattern and a 5mm shaft, which mates with the Banebots P60 700-series motor blocks, not the 500 size.

Since I finally blew up the clamp collar joint at Franklin, I drilled the sheared bolts out and replaced them with a pin drive. The holes in the gear were bored out, and the “pins” in the shaft collar are actually shoulder screws with their heads milled off! I literally tightened shoulder screws into these holes and then clamped against the screws on the mill and blazed the heads off.

The shorter 4238 size motors, in combination with the 2-stage gearboxes, actually end up at the same length as before! This package is fairly potent and is a brushless 30lb drivetran of choice currently. The same two beta-version Brushless Rages still run the bot, dating now all the way back to Dragon Con 2017 and carrying the bot to victory at Franklin, then several demos at MassDestructions.

Fast forward a few days and an uneventful (!) vantrucking trip later, and here we are at the event:

So I didn’t get a chance to actually weld up the new heavy wedges – they’re shown sitting in a pile next to the bot, ready to become accessories. Since the only welder on site was a 115 v MIG welder powered by a 50 foot extension cord, my plan was basically to add some little barriers to the existing wedges in the form of strips cut from the new design.

Clocker’s first match was actually a “wedge fight” against the twin over-powered wedgebots of Boom Boom. This match was conceptually easy, but a little frustrating because Clocker kept digging into the wood floor. It was in fact too pokey and I could barely maneuver forwards. So it really wasn’t that good of a test of the Wedges of Limited Liability at all.

My next match was against Botceps, a pretty classic vertical eggbeater style spinner. Built pretty much like a BattleBotsIQ/NRL archetype, it had a very potent 50mm TPPower inrunner on the weapon. This was one of those “if I make a driving mistake, I’m kind of done” matches, so I had to be on my toes. I don’t have a video link of my match here at the moment, but should I discover one, I’ll add it in.

As you can see, I did end up making at least 1 driving error – at the beginning, a few seconds in where I missed a charge and Clocker went halfway across the arena. Luckily, the weapon motor fizzled out barely a minute in, but I did lose the tip off one of the forks and the left pointy-wedge.

The punt that send Clocker up and over also squished one of the outer rail mounting screws clean out of its hole.

At one point, I managed to execute my anti-vertical spinner strategy well, plunging the pointy-wedge straight under the weapon of Botceps – which managed to machine the entire row of rake teeth off it! The match ended with a serendipitous flip which put Botceps on its face (“doing the thing” in robotland) and without weapon torque, it was stuck in that position.

My next match was against Crippling Depression, a pretty innocuous-looking bot (by design) that actually puts a massive amount of power into the undercutter disc – two NTM 50-series motors, which is more motor than Glasgow Kiss. By the way, its builder Robert Cowan has a very detailed video series on a lot of engineering subjects, including full video reports of the build of CD. Basically if I were more keen about doing video versus text, I’d be like that! So go Like and Subscribe™

Clocker didn’t make it out of this match all that well, and I ended up tapping out.

The disc of CD hits very hard, and very low – lower than most of my side rails, so it polished off a lot of the bottom screw heads. It was also positioned just at the right height for Clocker to barely ride up on it, meaning I would actually lose a head to head pushing match. With brushless drive and weapons, we’re now squarely in the era of 30lbers with absolutely no compromises – CD and Clocker have identical drive motors and identical gearing!

The super low level of impact meant a lot of extra stress was put on the wedges here, and it never actually got to ride up to the point of hitting my welded barrier strips. In fact, the first few hits managed to bend down the corners of the left side wedge enough that I had some trouble driving afterwards due to it being hung up on the arena floor on occasion. It also caused the rubber shock mounts to shear off early, leaving me with fewer defensive options as the match wore on, until both the wedges came off and my only real strategy was to try and stay on him. You can see some of the resultant impacts causing a little bit of “Cobalting” on the right side (upper of image), but the middle tie plate kept this very limited and I didn’t even notice while servicing.

Eventually, the disc ended up shearing out a few sprocket teeth and jamming the drive on one side, so I just wiggled my way around until I decided I got the idea and should probably keep it repairable for the loser’s bracket.

This was about the moment I realized that disc weapons (and by extension, shell spinners and other lower-prominence weapons) were going to be a much different story than the archetypal big bar spinner in terms of how to fend them off and deflect their energy, and I decided Overhaul needed a full-span front plow style defense no matter what. Watching Jamison fight CD later on with megatRon confirmed this belief even more. I’m pretty sure if Clocker had a full span wedge, even a connector plate between the two halves, it would have gone differently.

I was losing wubbies at an alarming rate and did not have any more spares, so I had to source them from other builders. Clocker was short spare parts in general – I never got to waterjet additional frame parts or cast new wheels either, since the decision to go compete was made in very short order. This event was actually a great study in how far the design would go on attrition alone.

That was all for Saturday – on Sunday, my first match was against BEAM, a tiny Tombstone. A rookie bot that was still BRUSH-POWERED and with an EV Warrior motor at that! Basically running a classic car in battle, but it had done tremendously well up to this point.

Poor guy was probably being gunned after by every BattleBots competitor there, who saw him as “tombstone practice”. Honestly, so did I, because it could portend the results of #season3.

For this match, I was only able to get 4 wubbies per wedge, and changed out to another used wheel which didn’t have huge chunks gouged out of it. I also cut off the bent tips of the forks so they were a bit shorter, but now much less structural than they already weren’t to begin with. It is what it is, given the lack of preparation.

So how did Overhaul do against Tombstone?

That’s, uhh, not very typical, I’d like to make that point clear. Well, it seems like the front fell off again – much more epicly this time!

With as much handicap as the bot was facing, I sort of ‘drove for broke’ in this match and was determined to see how pure attrition would play out. I think I was actually quite happy with how I was able to deflect Beam repeatedly, even getting it to do The Tombstone Dance a few times.

I felt like I had Beam reasonably until roughly the 2 minute mark when one motor was knocked off internally causing it to lose drive one side. I then just kept pivoting to try and meet it with the wedges.  Also, I again kept the arms up to try and keep them out of the way of the bar, but ultimately they still ended up in Full Dab; these arms for Clocker were built quickly to Sportsmans’ class specs, so any sideways ping is going to bend them.

Near the end, though, one of my welded barriers came off due to lack of penetration from the event welder. At the last possible second, we got in a good head to head charge, and….

Clocker’s frame rails are made from 7075 aluminum, which is really a mistake. I already had the plate when it was being designed, so went for Easy first. 7075 is more brittle than 6061, and will crack instead of bending. You can see that clearly in the arm tower that took the brunt of the last hit. This is why Overhaul’s entire frame including the arm towers are 6061, and only the liftgear and clamp & actuator aluminum housing parts are 7075.

From watching videos in slow motion, Beam was able to climb up the de-barriered wedge much like Glasgow Kiss and firmly planted the bar into the side of the head, which of course shoved everything out the other side. The lift gear was also made of 7075, and I lost a chunk of it near the end – check out how clean the shatter line is. It’s barely bent at all along the rim and still sits quite flat on a table.

The ears were also obviously very suboptimal – they were re-printed, but weren’t bridged or braced and so had the same kind of failure when the bot landed upside-down with an opponent – they simply bent the aluminum clamp sides and rotated, making Clocker adorable and droopy for most of the match.

With the base still working fine after the drive motor was reattached, I entered the Sportsman’s rumble to run around like a dumbass. The P60 motor plates only have two screws, not four, so it was asking a lot to hang the entire drive motor off them. This is actually why Overhaul’s motor assemblies have bracing plates behind the motor endcap. Dumbassery was achieved until Pitter Patter sniped the power link with its sawblade.

So that’s Motorama 2018 for Überclocker. Going 2/2 against three heavy KE weapons with almost no spare parts was certainly more than I expected, which was more along the lines of instant vaporization. I think I confirmed about every fear I had for Overhaul, whose upgrades were almost done at this point otherwise, but now needed revisiting.

but what about the Implication?

I spent the joyride back from Motorama consolidating everything I learned while running Clocker and as well as watching other matches including the final few fights with megatRon, Beam, Cripping Depression, and others. As a fair percentage of the builders at Motorama were also building for #season3, we did some bonding at the event and over pizza dinner Saturday night to consider strategies for the “full size” bots.

In terms of the knowledge gained from testing, it’s a fairly established rule of thumb in the community (if you ask) that “designs don’t scale”. The sentiment is you can’t expect to scale up or down a design 1-for-1 in terms of material sizing and dimensions of weapons and motors and expect the same kind of behavior. It’s a consequence of a whole lot of square-cube laws: motor power scales by volume, kinetic energy stored in a spinning weapon by square of velocity but also implicitly square of weapon dimensions due to moment of inertia changes, material strength both by dimension cubed and linearly by yield strength, etc. It’s why historically speaking, a scaled up or down version of a successful design might perform horribly.

Essentially, the idea is that at the small-bot scale, the energy transferred and dissipated in a hit tends to be much less than the energy needed to permanently deform a material of a given strength and size. This is how 3D printed 1lb and 3lb bots fly around arenas and bounce off walls on a whim and keep going. It’s related to the concept of why you can drop an ant off a building and have it survive the fall, but not an elephant. As robot dimensions increase, the kinetic energies stored in weapons – whether spinners, or transferred in a powerful flipper connect, or in the form of a hammer tip – begin overtaking the ability of the material to elastically deform and dissipate energy, so you end up with a lot more things bent out of shape rather than two heavyweights suddenly reappearing at the other side of the arena.

I mentally call this idea the “robot Reynolds Number” when comparing designs of different sizes: to get the same physical behavior, a bigger robot has to be simultaneously more powerful yet built more rigidly. Consider it characterized conceptually as the ratio of average kinetic energy transferred per hit in a weight class to the material yield stress * volume used in your robot ( KE [J] / σᵧ [Pa] * volume [m³ ). The best example I can think of is probably how Big Ripto and Triggo (30lbers) can both bounce around arenas like beetleweights – but both robots are made of hardened steel when it comes to the bodies in contact, whereas plastics or even aluminum is likely to just deform in the same application; as well, they both cram about 4 to 5 kW of weapon motor power behind them, which is actually more than an order of magnitude from the typical beetleweight (3lbs).

What this means for me is that I have to be careful with interpreting the results of my matches. For instance, it’s highly unlikely that Overhaul will get sent flying end over end from a single spinner hit such as that from Botceps, but rather depending on what gets hit, I’d lose one of the wedges or have a pretty big chunk bitten out of the frame. The best-in-class KE weapons in BattleBots right now run right around 15-20 kW and around 50-100kJ. Going back to Blacksmith vs. Minotaur, you’d expect with strength-invariant scaling that Blacksmith would easily hit the box lights, but rather what happens is the frame/wedge deform and fasteners begin failing.  Also, in my match against Cobalt, my one good deflect was the end result not of being ultra-rigid, but backing the hit with the arena floor by virtue of the rubber-suspended wedges, which is obviously something I want to keep.

While the exact physics won’t carry over through scaling, concepts will. For example, I am fairly confident that

  • Weapons of low prominence, such as discs/drums/shells, are best kept away from you and interacted with lightly since they are less likely to grab entire portions of your bot at once, rather chipping away at it. This is best illustrated by how megatRon was able to keep Crippling Depression at bay with a single low front armor piece, whereas CD had more inroads to damaging Clocker’s separate armor pieces.
  • Weapons of high prominence, like the archetypical spinning bar or single-tooth style weapons, should be more readily deflected if possible, since they have more potential reach (i.e. far more “bite per tooth”) and less predictable reactions. You want them to go away from you as much as possible. I rather enjoyed a lot of the driving against Beam and making it do “the Tombstone dance”, and even the small welded barrier strip made a lot of difference until it failed.

Ultimately, I had to rethink Overhaul’s armor approach and how it interacts with the lifting forks.

  • I came away 1000% convinced it needs a Full frontalplow-like surface up front. It’ll be heavier – I will make weight for it somehow. One downside of separate wedges is only one set of rubber mounts takes all the load of an impact, and while my Cobalt flip was perfect, 99% of hits I take won’t be that perfect. A spanning plow will allow the mounts on both sides to take the load. Besides that, it will obviously decrease the amount of open corners Overhaul (and Clocker!) has. In fact, the plan was for the original Overhaul 1 to have such a thing, but we ran out of weight.
  • I had to retain the ability to lift independently of being able to deflect hits. Did you see me pin CD and Beam against the wall several times, but having to back off to try and get the forks underneath them – which in both cases had bent up beyond the point of usefulness? That’s how they escaped and the match continued. I need the ability to corral spinners against a wall but keep the arms tucked behind the plow, maybe exiting via a small cutout. Overhaul has a set of short arms which remain behind the wedge profile – imagine a cross piece in front of them connecting the two wedges.
  • Beyond just dealing with horizontal KE weapons, Overhaul needs a “Wedge of Limited Liability” of its own, which still supports the bot during a lift but otherwise takes the form of a skinny fork or tine so vertical weapons and things like flipper spatulas have less edges to find. I didn’t get to exercise the WLLs of Clocker this time against a vertical drumlet weapon like Other Disko, Mega Overload, etc. but I did like piking it under Botceps. Depending on the length of the tines, it could be effective on its own by being jammed under vertical spinners, for instance.
  • I need to learn to drive “dirtier”. What this means is foregoing my desire for continous showy and aggressive action – something I am used to in the 30lb Sportsman’s class – and instead maximizing my usage of pin times and arena-outs. Jamison is a more strategic and methodical driver me in this regard – he drives to win, whereas I tend to drive to shitpost. Compare his style when fighting CD (and other heavy weapons) versus mine. In the BB arena, survival is going to be key since we are more in the realm of throwing elephants off skyscrapers than insects. The NERC arena doesn’t really have facilities for arena-outs, but the BattleBots arena does, and I think it will be a key portion of my strategy. Bounce bots up and away, keep them corralled, and try to manipulate them behind the low walls and screw embankments.

Once I got back to the shop, it was time to refactor Overhaul’s design a little. Stay tuned for those updates!

My Life is Ruined Again: BattleBots Season 3 and the Triumphant Return (?) of Overhaul

Feb 21, 2018 in BattleBots 2018, Overhaul 2

> mfw season 3 announcement

The rumors began shortly after July, when Science Channel announced it was going to pick up BattleBots after ABC unceremoniously shat us out in favor of a …. boy band show? Well fuck me sideways with a fracking well, look at how that turned out for you guys! The rumors intensified in November as discussions and negotiations were clearly under way, and reached a crescendo in January, each week leaving us wondering if “next week” was going to be it.

Well, now they announced it. Crap. Now I actually have to finish something!

Overhaul’s upgrades have been in in the works – albeit slowly. After season 2, I had a whole list of changes I wanted to make and “design regrets” resulting from the extremely fast build season and required turnaround time I wanted to address. Really, I (and a lot of other builders) see #season3 as a chance to do Season 2 “correctly”, addressing things that didn’t go the way we want or designs that could have been done better. And frankly, anybody trying to build from scratch for the season now is either a dumbass or more of a man than I

that apparently ain’t hard

So that’s where we are now. The story of Overhaul upgrades actually goes back to right after Season 2 ended, and starts with what is basically the last large mechanical assembly that was designed, the clamp actuator…. meaning it was the most rushed and horrifying.

Ball screws were a bad idea. I was attracted too much to the promise of 90+ percent transmission efficiency, but they ended up being too fragile and also had the nasty habit of backdriving – made most obvious in my match against Beta. During the following 3-bot rumble with Sawblaze and Road Rash, the ball screw stripped out almost completely and began acting like an Acme leadscrew anyway.

Trust me, that hurts me viscerally to look at.

There was also a confounding problem with the actuator design and the clamp arm. In general, the actuator ended up too bulky to hide effectively without making the head ungainly. Because of the positioning of the motor and the bulkiness of the ball screw, I chose to simply add a little ‘horn’ to the clamp arm (the protrusion close to the pivot point) in order to protect the actuator motor from being landed on if Overhaul got flipped over.

In order to get the clamp running again quickly in case Season 3 happened relatively soon (*ahem*) and to explore the large Acme threaded rod market, I actually designed and machined up a retrofit using 7/8″ Acme screws and nuts – the odd size was for the easiest fitment to the existing actuator bearings, since the root of the 7/8″ Acme thread form required minimal machining to fit.

Also, I found the nuts on sale on eBay for like $20. There’s an engineering justification for every spur of the moment purchasing decision.

I wanted to redesign the whole upper half with a new acme screw based actuator to solve this. Furthermore, I wanted to move from a live-screw design to a dead screw one, where the actuator contains the mating nut within large carrier bearings and simply rides up and down a stationary screw, which is the design I’ve historically used for Überclocker.

The premise went from using the higher efficiency transmission option to the more durable and simple one and just overpowering the everloving fuck out of it to get my desired closing forces. As a large portion of combat robots revolves around the latter, it was clearly the way to go.

I cloned the Overhaul 2 CAD model into a new directory so I can start messing with everything. Here we go!

This is the actuator in its current position in the bot.

I wanted to try and see if I could move to a pull-stroke closing like Überclocker has been running. In general, the answer is “not really” due to how far the actuator will stick out into the ‘grabby zone’. In Überclocker, I sacrifice a whole lot of leverage to position the actuator almost vertically so it’s much more out of the way. I wanted to not make that sacrifice for Overhaul unless I had to, or if it were super convenient. functional requirement: be lazy

I also investigated the idea of flipping the thing upside down. In this configuration, if the trunnion tube is made non-offset (inline with the leadscrew) the motor will unfortunately hang down very low into the ‘grabby zone’ and be vulnerable.

All of this position testing though was enough knowledge for me to begin hashing out the next part of the design.

For now, I just imported the model of the P90X gearbox which was never quite implemented. Into the same model, I imported a bearing I bought on McMaster-Carr which I got curious about while specifying new thrust bearings for the this thing.

These are “one piece” ball and tapered-roller thrust bearings, so-called since McMaster usually sells thrust bearings in little kits of 2 washers and a basket of round things. Don’t be fooled, though… the “one piece” part is just a stamped sheet steel shell that holds the two bearing halves vaguely together.

The one on the right is a ball bearing based one, and the left one is a tapered roller bearing which is basically tapered the ‘wrong’ way compared to a normal one. This means it can support almost no radial load but a ton (or approximately 7 tons) of thrust load!

I found the tapered roller bearing one a little janky, though. The full roller complement meant it had quite a lot of drag when rotating, and the packaging was a good 3/4″ thick. There’s also no way I can reasonably use its 14,000 pound rating …. and that’s an industrial rating, mind you, meaning it will happily do that for thousands of hours and not just 3 minutes. So I chose to move along (for now) using the ball version, which only has a …. 7,000 pound dynamic load rating, but was thinner and lighter.


The brown object in the middle is a stock round Acme 1″-4 nut that will either be machined as a gear (quick modeled as teeth here) or have a machined ring gear shoved around it with a thermally-enhanced intereference fit (LN2 the nut, bake the gear, shove them together and run away fast)

You might be wondering what the plan for radial loads is, since ostensibly I have two thrust-only bearings designed into the thing so far. The fake answer is that the leadscrew nut, being bronze, will just ride in the stationary bore of the thrust bearings, since the magnitude of thrust loads will be much higher than potential radial loads on a stationary leadscrew.

The real answer is “yolo”.

Here I am playing with actuator positions again. The “pull-to-close” position in this photo mimics that of Überclocker.  I still felt that the important parts were too exposed here.

Another attempt just flips the actuator upside-down and exposes pretty much only the leadscrew. This was at least tolerable in conception – something being mashed into the leadscrew (which could also be shielded) might still leave me enough travel to get a good grab.

Okay, but what else did I learn from Season 2!? That if you leave something important exposed…. say, a master power switch or similar, and run on the assumption that the chances of something getting into there and causing damage are very low, then it will happen to you 100% of the time.

So I gave up the “pull to close” actuator position in favor of just trying to keep the leadscrew short and fat in order to maximize its column rigidity.  The bonus upside is it woud let me keep the existing center hub between the two arms if need be.

This positioning candidate was actually pretty favorable. I could see how the clamp arm geometry might be changed slightly to better accommodate it, and also permit it to use a relatively short leadscrew

Using the geometric constraints put forth by the toy component placement,  I basically wrapped an aluminum chunk around it. The cavities are for the gears and bearings.

I changed the design to an “embedded P80″ to save length. The clamp motor is being moved to brushless, meaning Overhaul will be completely powered by questionable Chinesium. This time, since the Acme screw will not backdrive, I don’t have to hold the stick to apply pressure to the clamp arm any more, making it more Clocker-like in driving. Furthermore, this also affords me the opportunity to overpower the actuator while keeping a high gear ratio for force application. Überclocker’s current actuator is a regular 36:1 geared 550-class drill motor run at over 2x nominal voltage for moar powar – the short duty cycle of a grab and lift haven’t caused motor burnout problems.

A couple of different brushless motors could fit on this gearbox – right now, the SK3-6374 motor is in for modeling purposes.

Adding more parts and thinking about how to interface to the rest of the bot. The large rod-end is a convenient way to join to the wrist pin in the lift hub.

The design is more or less finished here. Those 4 square holes in the side are actually on a 2.25″ bolt circle, so four 3/8″ screws on each side will fasten the actuator to machined trunnion plates. I may end up making 2 of them dowel pins for shear strength and leaving only 2 as threaded holes.

With the new much more compact design, I was able to get a happy result for placing the actuator within the head. This was a good state to reach – I now have a solution where the trunnion bolt holes line up with the circular arc containing the patterned circular cutouts which Overhaul is known for. As a result, I can just hijack one of those holes (appropriately repositioned) as a trunnion axis, much like it is now.

All of this work occurred in the late December to mid January timeframe. I receive the new actuator billets and custom leadscrew nut back from my Chinese contract manufacturer this week.

In the next episode of Overhaul’s Improbable Overhaul Makeover?, I travel to Motorama 2018 with Überclocker in order to practice driving and strategy – and learn some disturbing new information which might disrupt my #season3 ambitions…




Overhaul vs. beta: The Post-Match

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


A little early, no? I’m going to be at the Detroit Maker Faire this weekend with all of Friday the 29th being a travel day so it’s either now or next week. If you’re in the area, stop on by the Power Racing Series track where I’ll be acting as technical inspector, Grim (penalty disher-outer), flag bro, or really whatever needs doing. Chibi-Mikuvan isn’t in a battle-ready state, so I’m foregoing bringing it.

For this match, there’s not an extensive backstory and tale of preparing, so I’m going to just jump right into the analysis! So be warned, don’t hit the “Read More” line unless you actually do want to Read More!


Overhaul 2 vs. Cobalt: The Post-Match; Plus the Lead-up to the BattleBox

Jul 02, 2016 in BattleBots 2016, Bots, Events, Overhaul 2


Okay, you get the idea. That’s what I’m going to say about every episode of BattleBots. I was there, man.

This post will dive into the details of the Overhaul vs. Cobalt match that was aired on 6/30, so what I’ll do as a favor for those who haven’t seen it – as people who haven’t gotten to see it live will probably see it with a DVR or via streaming over the next few days – is begin by talking about the event itself. Basically, there was a few days before the first matches even began where a lot of preparation was being done, and robots being, umm, finished. That way, we have a sizeable spoiler gap before getting to the match itself, and lastly what I’ll do is discuss the lead-up to the Cobalt fight, what happened during, and the results & work after. So don’t scroll too far down if you don’t want spoilers!

Here we go! After landing in Los Angeles around 2PM on the 14th of April, it took over an hour to get a rental car at LAX… because apparently everyone was also in town for Coachella. I heard from builders who arrived later that the situation only got more desperate, with some waiting over 3 hours for their allegedly guaranteed reservations. No free upgrades for you.

Now, given that it was getting close to 4PM by the time we finally high-tailed it from the airport, it was only natural that we…

…sit in traffic. The distance from the airport to the venue was about 45 minutes during a good time, and now was not a good time. Let me make it very clear that I’ve basically forgotten how to drive a normal, modern car. If you saw me make my way over from airport, you would have sworn I got my license yesterday. Mikuvan: Elevated view, infinite visibility, super short turn radius, and middle wheels only, bitch. That often means an extra 2 to 3 feet of maneuvering space since I can overhang the curb and eat a sidewalk momentarily. Modern car: I can’t see shit, I can’t turn worth shit, I have no clue where the rest of the car is but boy can I go fast. A I R B A G S.

Having to remind myself that I have an extra 5 feet ahead of me that can’t touch anything is a very demanding task, and it keeps me paranoid. Hey, that’s defensive driving right!? Plus, the first time I missed a turn going to dinner and had to swing a U-turn, I didn’t even think twice before almost plowing the fuck perpendicularly into the opposite sidewalk….. because Mikuvan would have made that turn fine, but apparently that’s too much to ask of a 2015 Nissan Maxima. Kids these days.

We actually didn’t end up going to the venue at all on Thursday, as they were still setting up everything, and apparently word on the street was that only international teams were permitted on site during this time. So we hit up the event hotel, another 15 minutes east, and decided to settle in for now and formulate a, umm, battle plan for the weekend. There was a trip to Home Depot to pick up spraypaint so we could finish off the bot, which was unpainted when shipped.

Fresh and early Friday morning!

The venue was a series of rounded warehouses in an industrial corner of east L.A., which calls itself the cutesy name of L.A. Hangar. No, none of those buildings are hangars, they’re round warehouses. You’re no where near the airport. I promise, because I just came from the goddamned airport.

The neighborhood was “interesting” to say the least – primarily Hispanic and touted as “that part of town” to me, but hanging around made me wonder if this was actually the case, or *side-eyes* watch out for those Mexicans, man. Okay, fine, there was that whole manhunt which had the whole venue on lockdown and a police perimeter around the neighborhood and all…  but the weekend corner taco stand beat out any of the food trucks there by kilómetros.
This isn’t a photo of the venue, by the way, but of the artists nest in the building right next to it. This building will come into play later.

Hello neighbor.

Our bot crates were lined up neatly in front of our pit tables already, so the only thing to do now is unpack everything!

Ah, we meet again. That’s right, I did build one of these… I thought the last 3 months might have been a hallucination, that or someone drugged me and stole $17,000 while telling me I built a robot and that everything is okay and I was still a grown-up.

That number is not even close to being a lie, by the way, and I was by far not the most machining-heavy bot there. Oh shit, this is real.

Step 1: Pile everything on the pit table first, think about your life decisions later. After we were done unpacking, two dudes with pallet jacks double-teamed my giant 8 x 4 foot crate into the storage area. Everyone else took just one! I took two guys! AT THE SAME TIME! Wait, what were we talking about again?

Step 2: Take the whole bot apart, and have Paige and Cynthia do the very important task of painting it while I set up the battlestation.

No, this is not “have the girls do the art” – after Overhaul 1 showed up naked to BattleBots last year, and with us having built the robot brand already around the Miku-blue, there was no way they would let me fuck it up. Because don’t you all know that adding paint also adds about 27 to 33 points to your Tail of the Tapeworm score? Overhaul 2′s getting AT LEAST 65 in the DASHING GOOD LOOKS category here, guys!

After putting together the toolbox and lining up my EE tools, I went outside to check out how they were doing.

There was a van!

Outside the Artsy Building was a blue 1985 Toyota 4×4 Van. I didn’t know who it belonged to, but it was someone who worked in that building. Van bros!

I was totally scouting Craigslist the whole week trying to see if there was a cheap van I could buy on-the-spot in SoCal and then drive back across country. Based on the Mikuvan Extraction Mission, there was ABSOLUTELY NOTHING that could have gone wrong with that plan. Nothing.

Late in the day on Friday, and the primer & paint’s dried enough for us to bring everything back in. We would let everything fully dry overnight before putting the bot back together. Not shown here are the pontoons, which were still drying at the time – they’re painted flat black.

SATURDAY!!!!! It’s the day after Friday.


A view of the pits from our station facing the entrance of the venue (beyond the wall is the Artsy Building). Mutant Robots and Don Hutson to the left, and in center stage is Blacksmith. The New and Improved bunnyforce Bite Force is in the distant center.

180 degrees from that shot, and Hypershock is under a blanket, lying in wait. Behind that row is a contingent of British bots, with Cobalt on the left and the Crunchy Candies Creepie Crawlies across the aisle.. There were more pits to the left and right of this, obviously, but I’m gonna skip that for now because Hey, a robot! Look, another robot! This is a robot too! We’re all robots! YAAAAAY!


Saturday is “pretty pictures” day. So we assembled Overhaul in full, with the painted parts.

Obligatory sponsor shot!

Hobbyking, our future overlords, provided the majority of the important parts for OH2 that were not machining. Like we’re talking motors, controllers, my radio, batteries, chargers, and support equipment for all of that. They legitimately handed me around $7K of parts. Do you know how much $7,000 of Hobbyking is? For those of you who might not have purchased things from Hobbyking, that is a lot of Hobbyking.

MarkForged dropped me off a Mark Two printer specifically for this event, which I put to work immediately – you’ll see what it’s printing soon. Beyond that, if you ever don’t feel like machining something, we’ve got your back. You’ve seen MarkForged parts in action here on Chibi-Mikuvan primarily in the steering assembly. You’ll notice that many parts were printed in a black material – this was Onyx, a carbon fiber filled nylon, which was still secretly in beta testing at the time of the tournament. Check it out! This stuff is actually ridiculous.

PRETTY PICTURE TIME! We begin with the 360 degree bot shot, which is where the hovering robot icons in the background of the hosts come from. This is shot in front of a greenscreen that is actually gray. We’ve somehow gotten to the point where computers can automagically tell between a gray piece of cloth and a gray robot. May Robot Jesus save us all.

These are edited pretty much on the spot and the result piped right to the production floor. They need to assemble all of this by the start of matches, after all.

A visit to the arena, still having final light, camera, and action rigging done.  This is in a separate roundbuilding which you actually have to move your bots a fair distance – probably around 500 to 1000 feet – beyond the Artsy Building to get to.

Once again, this is real. It didn’t feel real last time, at least not RIGHT UP UNTIL the worbly light and sound mindfuck they do right at the beginning of the match when the countdown starts. That, last season, for me, was when it finally hit me that I was actually at BattleBots and holy crap Donald Hutson is coming at me. I had a miniature internal panic at that point.

For those of you who might be coming to #season3: Prepare for the Worbly Light & Sound Mindfuck. Fear it.

After this arena visit, I ran back to the pits and….

There are two vans.

Hold… Hold on just a second here… earlier, there was just one van. A second identical 4×4 Toyota Van showed up, and along side it a lowered classic pickup truck.

I actually ran inside and hunted down the owners this time, like some van-themed serial killer. It was a married couple, and these were fucking HIS AND HERS MATCHING 4X4 TOYOTA VANS. Okay, some times people call Cynthia and I nerd-cute for having matching hair and the like, but I’ll never convince her to have matching vans.  This is… I dunno, grease-cute. Gear-cute. Faruq, King of Dubious Robot Puns, I call upon thee to help me the fuck out.

Alright, universe, you win. I’m going back to work on robots. Like a nerd.

Recall that before we shipped, I had prepared all the remaining DLUX 250A controllers I had to be installed when we got on site. This is now the time.

The plan was to run the 250s on the drivetrain only, since they were known to be reliable, and leave the DLUX 160 controllers on the lifting forks. That way, I maximize reliability for the highly pivotal first match – either you win, or you have to vie for the wildcards, which could mean it’s your one and only match.

In the background behind the extracted ESC box is one of the parts I set printing “live” on the Mark Two – it’s a “four 250A and two 160A” mount. Another one is attached to the lid already in the foreground.

An ESC swap sounds simple, but in reality, it was a lot of time-consuming rewiring. All of the 250A output wires had to be remade, as did the extensions to exit the box, since the spacings were different. This took the better part of Saturday evening and into Sunday afternoon…


Work continued into Sunday on the wiring job, which is shown here basically finished but not yet well packed. Up until this point, we haven’t even gotten a chance to drive the thing in the test arena yet, and we were all getting a bit nervous.

I moved onto closing up some unfinished business, which was the P90X. I designed and had printed earlier a servo mount that you see attached to the right side of the actuator. This holds a standard-size helicopter servo from Hobbyking.

Unfortunately, this was as far as the P90X implementation got. After some rumination, I decided not to chance this part in battle if I haven’t already tested it and found that it works reliably. The P90X work fell by the wayside as the robot build moved on, and I never really came back to it.

This will be a science experiment for another day. For now, I locked the ring gear into high (even though it spring-defaults to high, having something hold it there is better) so I prioritize grabbing speed over holding force.

Here is the aftermath of our first test drive in the box. This was when I realized that the front wheels were likely going to cause a lot of trouble, and that I have no clue how to glue things together. The “urethane adhesive” from McMaster did not adhere all that well. Lacking bail options on this part, I just swapped a front wheel (6 were made, so there were plenty of spares) for now and decided to see what happens.

I also discovered at this point that Overhaul took a bit more effort to self-right than I anticipated. It took me a few tries, first of all, to actually gather enough bravery to run the forks hard backwards such that the clamp hit the top plate. It clutched itself as designed, of course, but there’s that nervousness that comes with an untrusted and untested power system. Once I just beasted it into itself, Overhaul could self-right fine, but as known from OH1 and the new CAD model, could only do this if the clamp arm were somewhat open – above about halfway open. I had to practice going “up and to the left” on the radio stick, which from OH1 as well as Uberclocker was “Lift up forks and open clamp”. This was going to be an artform if I were in a self-righting critical match, such as Bronco or a vertical spinning weapon that caught a good bite on the frame’s underside.

With the wheel replaced and self-righting mostly conclusive, it was time to call it a night.


This was it.

We get to find out who we fight first! Monday was “practice day” by the tournament schedule – the “Alternate” entries get to run around in the box with full introductions and ceremonies, so everyone has a chance to run through their lines and get in position, and the camera crew learns how to not zoom in too hard on your robot’s acne.

Producer-bro gives everyone the “don’t impale yourself” speech before everyone moves over to the bleachers, where Aaron, one of the executive producers, primes new builders on how things went last season and how they were expecting to do things this time.

I didn’t get any pictures of this process, but as they dramatically announced each robot, the team would stand up…..then they announced the opponent, and the other team stands up. There was then several seconds of awkward searching for each other before locking eyes and usually doing something intimidating as best as robot builders could possibly, which is to say….. not very. I really, really hope a “BattleBots Outtakes” package becomes available somewhere on the black market, because this was quite priceless. Hell, I even forgot what we did once Cobalt was announced, but it was probably something cringeworthy as par for the course.

Alright. Strategy time! First, we went back to the pits and

There are three vans.

THREE! THREE VANS! IT WAS THREE!! AND COCO WAS ITS NAME! I ain’t goin to heaven no more… I already sold my soul to Trey Roski.

I quit life.

note: I did not know if the 3rd van was actually named Coco, but if you get this reference, congratulations.


We switched Overhaul to its short arms. Wait, what?!

These didn’t make an appearance during the design and build, because they were a bit of an afterthought. They are essentially the arms but cut off about 5″ shorter and at a 45 degree slope, leaving the bot a little stubby looking. They are specifically designed to rest behind the armored pontoons. This is my “spinner configuration”, especially for horizontal weapon.

My basic plan? Use the pontoons exactly as designed – fend off the blade, use Cobalt’s energy against itself, and go in for the grab once it’s disoriented or neutralized. The specific goal was to get the blade to ride up on the pontoons and then hit the second angle level, which will ideally destabilize an already rotating bot. Keep the front pointed the right way at all times, and let the rubberwubbies do their job.

Did I succeed? Spoilers lie ahead.

Overhaul vs. Cobalt



This is fun!

Everything worked quite according to plan. If you tuned in and watched the (sadly, just in highlights – damn you, ABC!) match, you saw Cobalt sail end over end repeatedly, bouncing off the pontoons. Geometry! I didn’t approach as squarely as I wanted to on a few occasions, which results in damage that will be analyzed shortly, but for the most part, this match was highly entertaining.

After 3 or 4 rocket-jumps, Cobalt began smoking significantly and losing power. The impact forces caused the weapon motor, an original ETek* motor, to begin self-destructing internally. There were several more smaller-magnitude impacts after this, and we were only 30 seconds into the match. I kept the forks down and clamp all the way open as long as it kept spinning.

*Robot nerds will point out that Cobalt used a Manta motor, which is a reconstituted freeze-dried ETek. This company bought Briggs and Stratton out of remaining ETek parts after production ended and assembled a short run of their own, advertised as wind generators, but they work okay as motors too.

Unfortunately, you probably also saw the end result: Overhaul loses a drive side, then kind of sits there and flails while Cobalt contemplates existence in a more mobile, hence less county-outy fashion. Overhaul was declared knocked out around 1:30, but really I had mobility problems starting around 2:30 remaining (Note: These times are rough mental estimates, and I will not remember more until the full match gets uploaded).

EDIT: BattleBots has uploaded the full match video! My memory wasn’t that horrible after all. Around 1:31 in the video (30 seconds into the match) was the last time the left side drive was working.

Well, that part didn’t quite go according to plan… Let’s see what went down!

First of all, damn. DAYUM. Cobalt packs quite a punch – enough to straight up pierce the AR400 5mm plate weldments, in several spots.

One of the first connects actually machined off a sliver of the left-side pontoon. The big smear to the right of that is “everything working exactly as intended” – the blade hits the pontoon, glides up, and exits stage right. That hit I’m pretty sure actually sent Cobalt somersaulting over ….haul. I will need to slo-mo the fight to be sure.

Overhaul didn’t look too bad exiting the arena. Nothing was missing, or cleverly collapsed into itself, Ghost Raptor style, but the extent of the damage was discovered as soon as the pontoons came off.


Oh boy. Those are two 1.5″ section frame rails that now look like a real-life FEA simulation result. That’s a whole lot of energy, people.

Surprisingly, this side never bound up, and was working up until the end of the match. Hurray chain slop!

I surmise that the hard side-blows that Cobalt dealt pushed the pontoons sideways until the shock mounts bottomed out, at which point steel met aluminum. The linear gouge to the left is the side of the pontoon hitting the frame rail. However, the actual cause of the bending is probably the two hits (which line up with the two holes in the right pontoon) which seems to have connected AR400 straight to aluminum, with the energy of the blade behind it. I will need to review the match to see exactly which hit this was.

Cobatl definitely hit me going across the front at least once, with this nice dig out of the metal here.

So. We lost our first elimination match, but there is still a shot at the Wildcard picks. Wildcards are usually picked by a combination of factors, one of which is how ready you are when they come around to stare at your robots. Therefore, this thing is getting fixed up, and now is where my investment in two full frames’ worth of spare parts pays off.

We begin ripping the sides of the bot off – some screws had to be coerced back out, because duh.  The right side was the most damaged, but the front left tire fell off during the match, so it has to be removed. That means the left side had to come off also, and that’s when we found it.


Can you see the FUUUUUUUUUUUUUUUUUUUUUUUUUCK in this picture?

When Overhaul’s left side stopped moving, it wasn’t totally dead, but was capable of moving back and forth maybe 2 inches before stopping again. I was pretty sure one of the P80 drive gearboxes was stripped as a result. But something didn’t quite make sense when I was moving the drivetrain back and forth by hand in the pits. Those motors could spin more than a full revolution. Those gearboxes are fine…

Can you see it yet?


Oh dear. There’s a set screw caught in my drivetrain.

Yes, ladies and gentlemen. A single 1/4″-20, cup-point set screw fell into the intermediate chain and locked both drive motors up. But where did it come from? There was only 1 place nearby that I use 1/4″-20 set screws – the motor’s double sprockets. But I used custom flat-point set screws, and all of mine were still there.

That means Overhaul picked up and ate a set screw, which fell off someone else’s robot in a previous match, which landed in exactly the correct location to cause total drivetrain failure. My guess is the front wheel kicked it up and over the middle wheel, it landed in the intermediate chain and sprocket area, and a chance impact jostled it into the motors. This screw was forged into the chain and needed prying to remove. It also took out the sprocket teeth that made contact with it, as seen in the example above.

So in the pits, they have mini production teams running around filming interesting things. You could also flag one of the production staff down if you were doing something interesting, and they made an effort to divert camera and sound crew over to what you were doing. They really did go out of their way to try and capture the frantic robot work in the pits, make no mistake. I exercised this privilege and actually got a team over to film a very quick but very angry rant about how you can be utterly … screwed… by something totally out of your control and up to chance, no matter how much you prepared for it. I was pissed. In an alternate universe where BattleBots is filmed and produced my way, my angry rant against the robot gods would have taken up the entire minute long highlight.

By the way, we think we know which robot it was – and its builders are also fairly sure of it. But we’re not going to spoil it quiet yet!


Overhaul here seen at its Point of Maximum Entropy on the repair path. I eventually put back together the damaged side on its own, and if you visited any of the places I brought the bot, or the Artisan’s Asylum, this is the Science’d frame rail I displayed. Now you know what happened.

I posted a Facebook photo not long after this match with the caption “The front fell off”. It attracted a lot of speculation and attention, but was completely innocent. We in fact just slid the whole fork and clamp assembly off to open up more space to work on the frame rails.

Within about 2 hours, the frame rails had been replaced with spares. In total, it took about 4 hours of work to get everything back together, and we finished Wednesday evening. The only thing to do was to wait for the Wildcard Ceremony the next day (Thursday).

Thursday was designated as a “Repair day”, which means McMaster-Carr made bank off all of us. There seemed to be a continuous ant trail of builders going to the L.A. McMaster warehouse, and… oh, I’M SO HAPPY THERE’S A L.A. McMASTER WAREHOUSE.  Now, the plot twist here is that we had nothing left to repair after the frame pull, so we spent much of Thursday hanging out with the other builders and relaxing.

If you watched BattleBots S2E3 until the very end, you’d have seen the (much more hurried) Wildcard selection, which concluded with……………………….us. This happened in real life, too, and I think it alone contributed 50 years of aging to my cardiac health state.

Now we’re up against BETA, which is…. another British bot with a friggin ETek driving its weapon. I can NOT catch a break this event, eh? What’s going to happen? Well, I don’t know which episode it will be on yet, but for sure there will be another post-fight analysis! So stay tuned to BattleBots on Thursday nights at 8/7c, because we need those sweet, sweet ratings.

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.