The Belated Motorama 2023 Recap: Return of the Susquehanna Boxcar

Somehow in the midst of the most unscoped, sprawling big-integration project I’ve ever found myself in, I managed to pop out yet another dumb robot! Last² year for Motorama, I spawned the Susquehanna Boxcar, which was a quick-build 30lb Sadbot using pretty much only on-hand components (I mean…. I allowed myself a trip to the hardware store and some random bolts from McMaster). So, for 2023, as I was seeking to distract myself from constantly wrenching on the ven, I decided to bring the bot back. In terms of actual timeline, this build occurred some time between The Stuffening’s conclusion and The Driveshaftening.

While the original build was conceptually sound and drove alright, the mild-wound brushed 550 motors with the spur gearing ended up being prone to burning out. Even with the RageBridge current limiting set rather low, the windings were fine enough that prolonged pushing (or binding in the drive side) would begin cooking them. By the end of the event and in the rumbles, it could barely move.

The easier way out was to just go brushless. This is a statement that, about 10-something years ago on this very website, was almost an absurdity to hear… but that’s the march of technological progress and Chinese meme manufacturing! I had a large stash of SimonK-flashed AfroESCs left over from those days, as well as a few other random SimonK/BLHeli enabled controllers. Nowadays, the new hotness is AM32 which is very promising so far for a couple of builders, but I don’t own any of that hardware yet. This build of Susquehanna Boxcar will help me draw down my existing stash of parts and equipment even further, so it’ll make sense to take the jump to something more modern later on.

The plan was pretty much the same as the first build. Just four motors with a single open spur gear stage to the wheel. The motors I picked were some NTM Propdrive 2836s from HobbyKing, probably destined originally for some kind of Roll Cake or Colsonbot. I had three of the same motors, so I decided to get an extra few from another builder. Next, to give these motors even more of a leg up on the world, I specified 6 tooth pinions, to be custom-made from cold-drawn “pinion wire” (gear on a stick) to be purchased from SDP-SI.

Yes, within the first half hour, I’d already broken my “No spending money” rule. It’s now… No Spending Money™

The smaller pinions allowed a total reduction of 10:1 to the 60 tooth drive gears. This thing will be quick, but I had no doubt it would drive well.

One of the issues (of many) that plagued Susquehanna Boxcar last time was that the four motors were independent from each other. To do this effectively in a 4WD chassis, each motor really needs a lot of torque and power overhead in case you get tilted up (which WILL happen) by an opponent or engage in a pushing match which tends to load the back set of wheels. The little mild-wound 550s….. did not have this.

In lieu of figuring out how to re-engineer a chain or belt drive onto the thing, I decided to just plop a giant bull gear in the middle. With some geometric massaging, I found that I could fit a 73 tooth gear in between the two wheel gears, offset slightly, while keeping the motor pinions from barely touching it.

Oh, yeah, the other constraint was that I wanted the motors as far inboard, towards the center of the bot, as possible. This was to make them less obvious targets as well as to let me have more volume for electronics and batteries. So, all together, this design path ended up working out quite well.

The construction method will be the exact same as version 1, using literally the same bars of UHMW. This is the generated left frame rail. Like before, I’ll be using a 3D printed template/pattern to spot the holes before drilling them, in lieu of having a milling machine with a readout or doing it High School Charles style with all-manual layout.

The drill gearbox for the Multifunction Poking Implement is mounted identically, but pushed forward a little more. There were two reasons here. One, to give me more space for electronics, as the motors are spread farther apart than before and so the contiguous space at the very back has changed in shape. And two, because I wanted to be able to run a larger sprocket on the poker hub. Having the motor directly underneath limited the sprocket selection significantly.

The poker hub this time uses a #35 sprocket instead of a #25 for greater durability. I wrote off using this #35 sprocket (from my big basket of random sprockets) last year because it was larger than the #25 I ended up going with. But now, with the motor moved, it can fit.

I went ahead and modeled the bull gear that bridges the front and rear drive wheels. It’ll spin on two FR6 type ball bearings and be unceremoniously suspected on a single shoulder bolt with a locknut. I’ll have to see if I can even make the tolerance stackup of manually drilling these holes work with it!

I generated the template that is to be used for the frame rails, and made sure to design it so it’s as hard to look at as possible. There’s no real reason for the many unrelated holes, just an aesthetic choice. If anything, it made the print process longer and made it less rigid.

The template aligns with the UHMW stock using three dowel pins. Two on the bottom side for the parallelism, and one touching the upper corner.

The Makening

The first step is to take apart the old and salvage what I can for the new! It wasn’t that much, sadly. The only things I could really reuse from this chassis is the outer steel frame itself which left the event mostly intact, and the four axle bolts.

Using the template to pilot drill the holes did work well enough, but I still needed to use the Benchmaster, Master of Benches for a counterboring operation to make pockets for the drive motors. I didn’t have a good means of ensuring that a Forstner bit (to make the flat-bottomed hole) started aligned with the pilot hole if I did this on a drill press, so I just sucked it up and spent a few hours counting dial revolutions. Still, this was more of a “close enough” operation, as the motor’s mounting axis is determined more by their countersunk mounting screws. As long as they didn’t touch the side of the pockets…

All the parts are labeled with their orientations because I will definitely mess up making the correct side otherwise!

Going back to construction methods I haven’t really utilized in a bunch of years, really dating back to my pre-machining era. These frame rails were just squared up and clamped together, with the holes laid out by hand.

In a day and age where most people default to 3D printing frames, and it’s common for newbies to think you have to have a 3D printer to get started building, I still think there is value to a frame banged together from UHMW blocks. It’s workable with almost all tools, and is a solid contiguous mass for you to zip things together wherever you want (versus 3D printed hollow infills… reminds me of drilling into drywall trying to mount something at the house)

I expect this mod to go very poorly.

That’s a 35mm class outrunner motor which shares a bolt pattern with the RS-550 sized drill motor. I was going to cram this into the drill gearbox after boring the pinion out to 5mm. Putting something like 3-4x the power of the drill motor through that gearbox is most likely going to make it very angry. My guess is the output stage pins will shear or I’ll start blowing gear teeth.

I went ahead and prepared both of the 3536 motors I had for drill gearboxes. It’s easy to keep making parts in the same sitting once you get rolling and all the tools are already out and set up.

Test fitting the bull gear here. “Shoulder bolt” decayed very quickly into “well, i’m too lazy to remove this cap screw and nut”. I found that I had the tiniest amount of axis position adjustment because the threads on the screw are a very slightly smaller diameter than the hole.

To my utter surprise, the gear mates all worked! Only a small amount of backlash was present and the bull gear didn’t really need any special treatment, like forcing off to one side of the tolerance/slop distance. Now, I used to do 32-pitch gear mates by hand on the drill press back in high school, so if I can’t even manage 24-pitch nowadays that would be quite the blunder.

Moving onto the Multifunction Poking Implement, it’s put together the same as last time: Just a square tube, appropriately drilled through, welded to the sprocket

As I touched upon before, I started with a #35 sprocket this time and turned it down (very painfully – this was a lot of sitting there cranking Tinylathe 0.5mm of feed at a time) to the thickness I needed. Then I just apply some quick blasts with Limewelder using a steel tube as a locating dowel in the center.

Now, for the drill gearbox sprockets, I had to get a bit creative. The smallest #35 sprockets I owned were these 8-toothers… but they already had a bore of 3/8″. The drill gearboxes have a 3/8″-24 threaded output shaft. There’s too little meat on the hubs to bore it out and sleeve it (I’d basically cut the sprocket bit off the hub if I tried boring it out).

The solution: Well, the welder is already out and warmed up. I just filled the hole up with Weld™. It’s like a Direct Edit button, but for real life.

Next, I chucked the sprocket up and treated it like I would any other! Drilling a center hole, then successively larger holes (the weld alloy is harder than whatever this is made of), then finally running the 3/8″-24 tap through it.

That worked amazingly. So that’s pretty much all the mechanical work going into this bot. Conceptually very simple, using techniques I’ve second-natured for years now, and not much to go wrong. Perfect zero-brain-cells-left build for a time I was mostly preoccupied with planning the L.E.W.D.

I even went and purchased a new Harbor Freight Multishovel to complement the slightly beat up (but serviceable) one from last year. All I do to these is remove the handle and stuff the stump into the adapter sleeve that sits in the hub tube. The folding telescoping sleeve thing still works. Unless destroyed, I can transform it back into a Multishovel.

Top and bottom lids for the rear section are once again made from 1/8″ G-10 grade Garolite laminate, a pleasant and multipurpose material. Pleasant, except the part where it slowly consumes your HSS/carbon steel tools from abrasiveness and also leaves little fiberglass splinters everywhere. The top and bottom screws got an upgrade to 3/8″ lag bolts. No particular reason here besides unifying the tools needed to fix this thing.

Between then and now, I grew a reel of TPU filament that was only used a little. I decided to expend more of it making the electronics cave for this thing. It’s just sandwiched in place between the top and bottom plates, then retained on one side by the steel box frame and on the other by the protruding axle bolt heads.

It’s designed to fit a 4S 1.8Ah battery, compared with the 7S flat battery last time. Nothing wrong with that battery per se, but I was using the smaller AfroESCs which weren’t rated for that voltage input. Keeping the voltage lower also kept the bot’s calculated top speed from being comically high (like 30+mph, unrealistic to achieve in the box) and makes blowing everything up much less likely.

The power “switch” and power distribution was kept simple with a single gigantic squid assembly. The big solder joint in the middle brings together four 18 gauge drive motor controller wires, a single XT-60 on 14 gauge for the poker, and an auxiliary JST-RCY (literally “a JST Connector” when left unspecified, by the way… not many people know the actual product line name) for whatever else I want, like gaudy LEDs.

This was not fun to solder together, but I was in no mood to design some kind of bus bar or power distribution terminal block system.

After some more massaging and fineries, here is the Susquehanna Boxcar for 2023! I was highly pleased with how this bot drove, actually. The four SimonK-based drive ESCs were put into reversible mode with non-synchronous PWM (they can both add power, but not regenerate from each other – no fighting through the gears) but idle-throttle braking enabled. That way the bot still stopped quickly when I centered the transmitter stick and didn’t keep coasting.

The Motoramming of 2023

For the Motorama, I was in charge of making the trophies once again using asslaser69. I got creative this time and changed the design to use a lighted base, which we liked and so the organizers commissioned a boatload of them from Amazon. This was an cute little change from the rushed-together laser cut trophies of 2022 which were made because AAAAAAAAAHHHHHHH WE DIDN’T DO IT

And so, once again, we deal with the consequences of having me be in charge of something. IYKYK, IYDK,DGI.

I elected to do a “clean trip” this time. Vantruck was obviously not available for the job like it was in 2022. Plus, at this point, I was beginning to cull my random van buying and breakdown related expenses, appraising my resources in preparation for the New Robot Trap House. So, the soulless-but-least-likely-to-explode van it is.

My first (and only) real tournament match was against EVA (stream archive link), which used a pushy configuration for the match. Right around halfway through, I lost a motor on the left side, and later on the mutual pounding also (like I suspected) sheared off the planet gears inside the ol’ crusty drill gearbox that had been brushless-swapped. It was trapped upside-down :(

I was slated for two fights that day, and taking the thing apart to get at the motor and the drill gearbox took longer than I counted on. It turns out the extension cable I made to get to the ESC had pulled out of a connector joint I thought was well-taped, but I had to take the bot apart enough to get to that point to find out. The drill gearbox and motor just needed outright replacement.

You’re only guaranteed 20 minutes turnaround at most of these events, Motorama included, and that can come to haunt you really quickly if the matches ahead of you move fast due to knockouts, or if people forfeit fights. The usual 2-ish hours I was hoping to have turned into only 45 minutes or so. So with my time having come and gone, I decided to just prepare Boxcar for a series of really funny rumbles.

And no Susquehanna Boxcar moment would be complete without a comically sized vegetable hanging off the end of it. Behold, the Papaya of Redemption. As I promised, I headed out to the only Asian grocery within like 50 miles or something and picked up a couple of dumb… uhh, end effectors.

Here’s the stream link for that rumble! It didn’t do that much during the rumble because the Papaya of Redemption almost immediately broke the spare drill gearbox, and then became stuck against the frame.

Once that was very rudely and inconsiderately removed by Phenomenon, I guess it ripped something completely apart inside with the toss from its weapon (maybe turning a stripped gear or two into powder), and I had some vestigial function left on the Multifunctional Poking Implement. Upon which I got promptly stuck sideways on the wall.

I also agreed to a grudge fight afterwards against Big Cookie, which is a bristlebot using the purposefully unbalanced shell to wiggle around on a series of tilted wire brushes. It demonstrates translational movement like behavior under some circumstances, but hits crazy hard because it’s basically entirely weapon.

For this fight, the Danger Potato made a return, because… why not.

I assembled a composite drill motor out of the wreckage of the two I brought, so I can swing the Danger Potato. This was 100 percent not a good idea, just as I suspected. And I think I understand why I usually spend money on robot parts.

By the end, both of the robots were thoroughly painted in taro starch. Here’s the stream archive time link so the erotic taro-grinding action can be witnessed!

I said Cookie hits hard. Look at the frame on this thing. It’s turned completely into a parallelogram!

Well then… that basically retires this Susquehanna Boxcar because I’ll need to remake the frame entirely to get it back in working order. So, if I bring it back again, I might be forced to… you know, spend money on it or something. Maybe I can use one of the leftover P61 gearboxes I have from 30Haul. Sadly, the days of competitive bots being made from power tool particles is mostly done for except the local back yard stuff, like my very own near-and-dear Robot Battles at Dragon Con. There’s just better gearboxes to handle the power of brushless and lithium.

Boxcar basically lives in a pile of its own wreckage in a tote to this day, because immediately after returning from Motorama, I went into Operation IDIocracy rescue mode. I scrapped the parallelogram along with about 700 pounds of other random metal detritus before the big move. Now that the New Robot Trap House is functional, I am certainly considering bringing it back for said Dragon Con this year!

Sadbot and Overhaul Go To Comicpalooza: Scale Model Testing Your BattleBots At Full Scale

Just because all this van stuff was going on doesn’t mean I put down the robots last year. Never a dull moment around these parts! Interspersed between the Operation IDIocracy work over the summer and the Econocrane Saga was a heavyweight sportsman-style event held at the Comicpalooza event in Houston, Texas, by the local organization Houston Area Combat Robotics.

Robots in mid-July in Houston sounds like a great way to get heat stroke, but it was a chance to do some shakedowns and validation on Overhaul that we didn’t really get to do at the 2021 BattleBots season. When you’re at the event itself, you’re really just in survival mode; whatever works works, don’t question it. Getting to run the bot at a low-stress show-off event means I can kinda retrace my steps and figure out exactly what was going on.

Anybody who watched the 2021 season probably saw that Overhaul had some… fire issues. I joked it was probably the 2nd most reliable flamethrower at the competition: It would always catch on fire somewhere around 2:15 to 2:30, plus or minus. Midway through the qualifying fights, I threw in the towel and switched the drive controllers from my 12-FET Brushless Rages to …


Disgraceful. Why not just go stick my head in the jaws and hit the go-stick at this rate?

The controller I’d worked for not too long and not very hard on… was just not capable of sustaining heavyweight-tier power reliably. The reasons were many, but centered around the fact that the old SimonK firmware, while dumb-of-ass enough to whip start any motor you want it to, was consequently also dumb enough that it never had any facilities for current control or limiting built in. So while they could overpower smaller motors, using them on anything bigger than, say, a 60mm series outrunner was asking for trouble if the motor stalled or there was a lot of reversing. A current-generation VESC frontend would easily handle the 12 FETs properly and cap the motor at whatever current you set it to.

I dish on VESC a lot for being another wayward open-source project turned product that requires a worldwide community of people shotgunning into the dark to support, much like 3D printers were last decade. But the truth is I basically watched the VESC project grow up and its proprietor Benjamin Vedder become a self-taught motor control engineer. He worked a lot with my buddy Shane who featured abundantly on this very site in yesteryears. I have only the highest respect for his work in development of the VESC bloodline, which started as a personal hobby project much like I never meant to sell Ragebridges.

Exclusive, never-publicly-shown photo of the Even Bigger Brushless Rage I made for Overhaul in 2021. These boards never made it off the bench because I lost motivation.

The thing that always bugged me, though, is the productizing of the hobby and community. A firmware version change might introduce new features but create new bugs and break old features. Dozens of different manufacturers stray from the project definition and controlled documents to implement their own features, some of which make it back upstream into one of said firmware updates but leave others in the lurch. Software UIs which change with every other version, and so on.

And there is, of course, no fixed documentation because it’s always out of date; the best way to get help is simply to wade through dozens or hundreds of forum posts and social media threads (just try setting up a new VESC using a Youtube video from 2017!). Because I always had my somewhat working controllers, I simply never looked in the VESC direction, and only observed the hand wringing coming from others in the community trying to blaze these new trails in the world of robot fighting.

But whatever the case, it was time to acknowledge that the combined autism of dozens of Europeans and hundreds of Chinese people was far more a force for progress than I could ever be alone. Just like how I’ll probably never build another custom hub motor unless it was purely for, uhh, self-enjoyment.

I did pick up two VESC 6 architecture based Trampa ESCs, confusingly called the “VESC 6 MK V”, right before the 2021 season because I had a SNEAKING FEELING they would be needed. And those were the ESCs which got stuffed into Overhaul. Because the C80/100 motors in Overhaul did not have Hall sensors, I had to fiddle the settings to use sensorless mode.

At the time, the sensorless FOC algorithm was pretty flaky and not great with transient loads,but worked fine for its intended purpose of skateboards, bikes, and hoverboard motor. So, I kept it on sensorless BLDC / block commutation mode, with input shaping like ramp-up times activated and the current control loop gains cranked way too high (a necessity at the time; many of these issues have been resolved in the Present Year)

This made the bot driveable but not superb, and I would have to constantly ‘drive the controller’ so to speak, instead of focusing on the bot itself. If Overhaul looked pretty slippery in the Black Dragon fight and the “Chair Fight” with Big Dill, that was why. I signed up for the event because I figured more stick time is a bare minimum even if I make no other meaningful progress on making the bot drive better.

But there was Sadbot too.

Two heavyweight platforms with allegedly identical powertrains I could use to make delta comparisons, and maybe even fight them against each other! Sadbot was in dire need of a renovation anyways, so I took this as an excuse to organize the piles of stuff that had accumulated on top of it and start appraising what needed a lube n’ tune.

I had bought two VESC 4.12 clones from Hobbyking a while back when I first felt like Brushless Rage needed to be phased out. I supplemented these with a few used units I picked up from someone who was upgrading. These 4.12s are roughly as capable as 6-fet Brushless Rage; they’re going to be underpowered driving a 80mm motor each, but the nice thing is they won’t blow up doing so.

The goal here wasn’t try to run Overhaul on these 4.1x units, but that I didn’t want to spend several hundred dollars on a set of 6.0 based ones for Sadbot yet. If these survive the C80/100 drive motors, so much the better.

Sadbot itself had gathered a whole lot of dust, cobwebs, and metal chips in random spots. Its last action was really Robot Ruckus in 2019, and it’s been pushed around the garage since then. I decided a comprehensive teardown and rebuild of the electrical deck and both Overhaul 1 wheel pods was warranted. So, I just dug in and started ripping everything out…

One increment I wanted to make from Overhaul was using the sensor-integrated C80/100 motors, since much of the development effort seems to have focused on perfecting the Field Oriented Control (FOC) algorithm assuming you have Hall sensors or an encoder.

Fair enough – sensorless starting has a lot more math involved in it, needing bigger and faster microcontrollers, and often requires close-in tuning of inductance, flux linkage, etc. quantities on individual motors. This makes it much harder to get right for a general purpose plug-in controller (In the Present Time, High Frequency Injection [HFI] based pole saliency detection has made its way into VESCs with the latest hardware rev)

The spare motors I picked up for Overhaul before the 2021 season did have Hall sensors, so I went ahead and knocked them apart to switch out the custom-made shafts of the older motors.

The drive pods got cleaned up on all fronts with new chains and lube and new threadlocker in the bolt holes. There were a lot of things which were getting loose and jiggly!

I also took apart the lifter pod to take a look at it all, but it did not need any work. Here’s the reassembled drive pods! They’ll go in last since they’ll make it harder to work on the electrical bay. I’ll finish that first by remaking the wiring to accommodate the VESCs.

Oh yeah! I picked up another Harbor Freight rock chisel thing to make a spare poker. The original Long Pink Member from 2019 was straightened out some, but I figured it wouldn’t live very long if it was bent back and forth more..

Most people using VESCs just throw them in with a bunch of foam wrapped in heat shrink or tape. This approach doesn’t sit right with me (Yes, yes, I know, their robots work and mine doesn’t) and I wanted to try and give them more heat sinking. They’ll be operating close to maximum power handling levels for longer periods of time, driving those C80/100 motors. The obvious problem is that the 4.1x VESCs don’t have a good way to mount to anything because they were kind of designed with being stuffed into a wiring harness in mind.

I came up with a clamping aluminum bar mount that will grab them by the FETussy. The back of the board, with the capacitors, will be secured by a zip tie mount.

The aluminum bar gets bolted into the existing big heat sink plate with a dollop of thermal compound in between.

Here’s how that looks! #4-40 long screws capture the VESCs in between them. The FETs get silicone sheet on the top and bottom for insulation. Heat transfer out of the plastic case on these D2PAK-7 packages isn’t great, which is why Brushless Rage and other controllers have always heat sunk through via-forests in a heavy-copper PCB. But it’s better than nothing.

With the mounting solution validated, I went ahead and worked on the heavy power wiring – extending motor wires, making new battery cables, and so on.

My automotive influence is showing here with all the wire loom. The sensor cables and motor phase leads were run separately to keep the motor current from beating the little Hall sensors …. uhh, senseless.

If needed, I was ready to put them in some conductive loom and ground the ends. Luckily, this turned out not to be needed – just keeping them from running next to each other was enough.

For someone whose entire line of work for over a decade and a half is “technology”, I sure hate technology. Specifically, I’m not personally so much a fan of “just configure it in the app”. Yes, you get much more flexibility and room for features if you have an app. But give me a row of DIP switches, blinkenlichten, and trimmer potentiometers any day.

The cool kids set up their VESCs with their phones because you can get them with Bluetooth now. I, meanwhile, could only find 1 short USB cable to do this with, necessitating this comical and totally safe setup. Sadbot, propped up on one half of a moving dolly, with my computer directly in the line of “Welp it hit the ground and kept going”.

The electrical deck is now all buttoned up with everything operational. The drivetrain controllers are set up in BLDC mode using Hall sensors, but the lifter was kept BLDC sensorless because the 6374 motor running it didn’t have them, and it’s geared down so far it didn’t matter.

I didn’t set the drivetrain controllers up in FOC because for one reason or another, I couldn’t get the FOC auto-detection to take. This may be one of those mismatched firmware, hardware, and software 3-way tangles I alluded to earlier. Dumb ol’ BLDC mode worked flawlessly, however.

Up front, I added something Sadbot has never had up to this point and just got away with: A weapon lock!

Yep, it was finally time. A simple 3/4″ hole drilled in 1/4″ thick steel strips will suffice for putting a bigass square lynch pin through.

Weapon lock all welded up in-place.

While Limewelder was warm, I went ahead and welded the poker solid where the striker interfaces with the tube, just like the old one.

With everything installed and tightened again, Sadbot came in at 220 pounds even! This is the weight of a “classic” heavyweight and what I had in mind when originally designing it in 2015 – the thought was maybe I’d head to Robogames which at the time was still running the 220 pound Heavyweight class. The ample weight allows me a lot of room to mod and add things if I wanted to run at 250 pounds.

Here’s the final hero shot of Sadbot, with weapon lock installed. And a low speed drive video!

I tried to not annihilate everything I owned, but did rip it a little harder in the driveway too. The sensored BLDC setup with the innate current-control loop drove great – I could feel the current limited acceleration, but for the most part it handled predictably. A sharp stop (like running into the curb) could trigger an overcurrent condition which needed me to back off the stick and try again. So I had to be mindful of this, but it only happened periodically. I wrote it off to “50A-ish rated controller trying to wag a motor which could easily drink 200 or more amps”.

The Road to Houston

Houston is about a 12 hour drive from Atlanta; while long, it’s certainly nothing I haven’t done many times before with my Boston to Atlanta (18 hour+) runs. For this trip, I chose the competent van because you should only live one meme at a time. This is also why I have never driven cross-country to BattleBots with a meme van: Don’t put your childhood dreams in series or you’ll cry over their shattered remains on the side of the interstate somewhere in New Texahoma. Live them in parallel with impedance matching.

Loading the robots in turned out to be very easy because I already had my equipment for hoisting heavy things around. Just chain them up and sling them in!

Overhaul was basically pulled out of the crate as-is, where-is, no warranty expressed or implied, no questions asked or answered. To be fair, it did leave the 2021 season ready to run because we were supposed to have another fight.

With all the equipment tossed in after it including handling carts, the Overhaul team tool chest, and spare parts, the reasons why I decided to maximize my automotive Asian Dad Energy for a daily consumable car are abundantly clear.

You can barely do this with a mid-size pickup truck (at least I’d need a bed cap) and the tailgate would be already up to my nostrils. One of my favorite activities is just slinging lumber and 4×8 construction panels into this thing at the Home Depot pro parking shack while dudebros hoist things into the 5’5 beds of their emotional support pickup trucks next to me.

The trip down I-10 was terminally uneventful. By the way, if you’re looking for some lizards, hit these people up! It’s been a very long time since I went to Houston – the last time I recall going was to see family friends when I was a wee caterpillar.

I chose I-10 instead of the more inland I-20 (then cutting south after the Texas border past Shreveport) because E A S Y. I got to see the swampworks of America including the Atchawichyaiwannalaya Basin Bridge among others, and traversing the lights and sights of the Houston energy corridor in southeast Texas was also entertaining.

I left Atlanta around 6AM and cruised into my hotel east of Houston around 10PM, managing to not bomb it the entire way but stop to check out some roadside knick-knack stores.

Next morning at load-in, setting Overhaul and friends up for the visiting crowd! A couple of bots were on display, such as Avalanche from Team Toad behind Overhaul there. It was also competing, so I suppose these were just demo models…

The event being one of only a tiny handful of Heavyweight-scale anything out there meant BattleBots Season 7 prospectives from all over the country also showed up. This is an early prototype version of Horizon, which was being bung together (photo captured mid-swing of the hammer) right up to the safety meeting.

Bunny of Malice set up the merch booth, which we all contributed to in order to satisfy the throngs of onlookers once the con opened.

Besides Overhaul and Sadbot, I also brought a con tchotchke in the form Your Waifu is Trash. This stupid thing has probably seen the most physical miles driven of any actual robot I’ve built, having been to almost every convention I have since 2019. I’ve worn through the brushes on at least one motor and changed wheels because they got too small and worn down from driving on concrete/asphalt.

It’s been a hit everywhere it’s gone, because giving people an avenue to depersonalize their insecurities and self-doubt has never been a flawed business model. I drove YWIT around in between fights, when we took breaks, and when the matches were done for the day.

Pit table shot! I kept Sadbot on the handtruck because it conveniently fit between the drive wheels and allowed access to it in all directions.

One other item I “invested” in before this event was a new charger for Overhaul. I wanted the ability to charge up to 12S lithium in a single bloc, as up to that point, Overhaul’s charger has been a set of 8S-limited Turnigy Reaktors. The battery enclosure had no internal wiring and just ran both battery leads out so I could plug both in. At home or if I didn’t give a shit, I just set my adjustable bench power supply to CC at 15 amps and CV at 49.2 volts (give it a bit of safety margin) and went about my day.

This iCharger X12 came to the rescue! It’s a current-generation charger that takes up to 48V in and can consequently poop up to and over 48 volts, handling over 1000 watts with an ability to regeneratively discharge into a master battery bank. The package is scary small for handling that much power, but I believe in modern semiconductors. In fact, it can overwhelm my puny 24 volt power supply instantaneously, so it’s time to upgrade!

Sadbot had an easy and fun time because of the non-spinner nature of the arena, which effectively dated back to the mid ’00s as one of the original Southeast Combat Robotics (SECR) boxes. One of my fights was with Slammo, who was also here to test out some new architectures and drive setups. This match was fun and tossy until Slammo quit working again, as for some reason it does.

Sadbot also had other fights against some more sumo/sportsman’y heavyweights from locals, and a Mild Salsa version of Mad Catter cheekily named Happy Catter.

At last, the meme happened as one of the final exhibition fights. I drove Overhaul while Bunny drove Sadbot. I literally bought a chair from Team Toad for $10 on the spot to use in this fight, where we set it up and I tried to drop Sadbot on it.

The handling difference between the two really motivated me to swap Overhaul to all new sensor-integrated C80s. Sadbot basically drove like it was brushed again, even if the VESCs still had infrequent (but still annoying) overcurrent faults just because of how outclassed they were by the motors. A swift return-stick-to-neutral was enough to overcome that. Overhaul, being still stuck in Sensorless BLDC mode with some tweaking, drove like an unloaded bus on ice in comparison. I had to anticipate when to turn and basically coast into it, or keep moving in one direction without direction changes.

Overhaul’s forks managed to tear up the drive on Sadbot pretty well, including bending both of the little chain-guiding nuggets and making Sadbot lose a drive side. In return, I accidentally drove the head actuator off the end of the screw trying to pick the chair back up, so Overhaul’s head came flopping downwards. Oops.

Unfortunately, the organizers had issues with the stream (found after the fact; they were thinnly manned and needed all the help they could get!) and as a result we don’t really have any good video from the event, especially the Heavyweight fights. They posted basically “raw” box feed videos at this link.

Sadbot appears in the following fights:

There are videos of the beetleweights and other weight classes on the promoter’s Youtube channel, though. Those were run in a separate arena and as a separate stream.

So I came away from Comicpalooza with a lot of good lessons learned and two working robots. Well how about that!? The real champion, though, we all know… is Your Waifu is Trash.

The lessons from this event went straight into Overhaul when I transitioned from Operation IDIocracy to Battlebots Season 7 prep. We changed all the drive motors – in-use and spares – to the sensored C80/100s, and I ordered spares of those.

I also got more VESC6 units from Trampa and set them all up in FOC mode with sensors, using one calibration/detection and propogating all the settings (The motors are all close enough together characteristics-wise that the small differences were not first-order impacts on control loop behavior). Other than that, the bot didn’t see that many changes and optimizations for Season 7. And, despite “Losing” a bunch again, I think Overhaul really had its best reliability and predictability season to date.

By the way, if the trip to Comicpalooza was comically loaded, the return trip was even funnier. I promised to bring Slammo back for Craig, so on top of all my gear, there was now a Slammo, its parts, its tools, and its handling equipment. He journeyed down from North Carolina a week or so later to collect it all.

I was surely running close to GVWR, and I got concerned enough to inflate the rear tires to 50 PSI for the return trip. I headed northwards out of Houston, taking the I-20 route back east because it turns out I-10 is just like the I-95 of the Gulf Coast: Always crowded, always jammed, always under construction, and everyone is out to kill you all of the time.