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 …

vesc

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.

The Susquehanna Boxcar: A Return to Motorama

For literally over a decade now, Motorama and the NERC Robot Conflict event associated with it has been a sort of winter robotting tradition for me, minus only a few years; in 2020, I was in the middle of moving and so didn’t go back north for a while, and there was no Motorama in 2021 for Reasons.

However, the last time I really fielded a bot was in 2018 with the outgoing 30haul; I just went in 2019 for funsies and to help out. This year, with the Reasons beginning to wind down and with everybody in the robotting community ready to get competitions going again, I decided to to take a break from vans and enter something again.

But I had one rule for myself: No spending money on the robot.

This bot, whatever it’s going to be, was just a short detour from Operation IDIocracy, and it was going to just be a shitpost entry. Cleaning all the grunge and getting the engine apart has taken longer than I was counting on, and on top of that, it’s cold so I kind of lose motivation to wrench on things. Robots can be done indoors.

I had to build this entry as much out of just the materials and parts in my midden. Screws are fine, buying motors and ESCs or ordering custom cut parts is not. So what am I going to make? Initially, I thought about an extremely dirt floor rendition of Stance Stance Revolution in a 30lber, maybe using lawn care blades as the weapons.

To this end, I have plenty of weapon motor candidates in the form of 40-60mm brushless motors from Overhaul. I actually had a “preview” sketch model of what the next SSR beetleweight was going to be:

Actual stanced wheels! I had a few bright ideas on how to drive those while I was mocking the design up. This is definitely going to happen at some point; however, now getting close to the new year, I was getting less inclined to make a 30lb SSR as it was looking like more and more effort. Effort was to be avoided.

So why not a 30lb Sadbot? After all, Sadbot is my most successful heavyweight. I had plenty of 3″ C channel and 1 x 3″ rectangular tube left over from Vantruck add-on candidates, which was perfectly half the size (height) of Sadbot’s 6 inch channel stock.

We begin with a master sketch of the outline of the bot which I used to drive Inventor’s “Frame Generator” design tool, which is more or less the equivalent of a Solidworks Weldment with its libraries of standardized profiles and extrusions.

Weight was going to be a serious concern; my first pass frame measured out at 21 pounds out of 30. So having the frame size be driven by placing components and easily adjustable was important. I was basically looking at stuffing a 12lber inside a ring of steel.

The chassis material inside the beltline was going to be good ol’ UHMW plastic, a staple of my high school, pre-machine tool building. It behaves like a very dense bowl of grits and is easily workable with woodworking and handheld tools. This was really shaping up to be some kind of accidental retro-build.

Adding to the retro vibe was picking some 18V mixed-heritage cheap drill motors out of my bucket of motors. I would occasionally over the years “sample” cheap cordless drills from Harbor Freight, Walmart, and the like, so I have probably over a dozen of these which are almost all interchangeable. The newest lithium battery models have been deviating from the classic conical gearbox shape as manufacturers try to make the drills smaller/lighter while having 2 speeds as a default option.

The drill motor is to actuate a pokey stick similar to sadbot, and I was planning on a simple chain drive to an axle above the frame.

For drive, I decided to keep digging through my motor pile and found some mild-wound 555 sized motors. They’re identical in size to the usual 550 size R/C car or truck motor (and drill motors) but are typically wound to run at higher voltages, like 24 volts. The ones I have are surplus from who knows when, and have a Kv of 450 RPM per volt (Compare this with the typical 1200 to 1500 of a 550 class drill motor). They can therefore be run with a single stage of open gears, trading speed for torque.

In this bot, space was more the issue than anything, and using a single-stage spur reduction let me push the motors into the UHMW frame rails to clean up space in the middle for the drill motor and eventual electronics

So why not brushless? Well, that would involve finding 4 matching motors and/or ESCs in this size range, which I didn’t have. And no spending money!

I began sizing up the gear drive using a 4 inch wheel as a reference, using the spacing of the 555 drive motors and the drill motors as a guide for what gear size I could use. I’m going to exercise some impure nostalgia here by just 3D printing the wheel and hub. The gear pitch is 24 DP (or about Module 1), since that’s what my 3D printer flock can consistently print and have it work out well.

Initially, I was designing this hub to use the same wheels that 30haul did, made using the same methods and having the same dimensions as the Vex hubs I was using – hence the 1″ nub sticking out of the gear. I was going to hole-saw some 1″ gum rubber sheets and retain them with standoffs in the manner of its “disposable” duallies.

However, on a trip to Harbor Freight, I serendipitously found a new avenue to explore…

My only real complaint about the gum rubber wheels for 30Haul was that the sheets don’t come in any thicker dimensions than 1″, at least not with my minimal familiarity with the rubber indutry. Ideally, I’d be able to get a single 3-4″ thick wad, or laminate a few sheets together and be able to cut out wheels for actual full-size Overhaul.

I could probably get away with running singles for this bot, but I’m also keeping an eye out for thick chunks of rubber foam. And I found it by accident at Harbor Freight in the form of what I call the “Harbor Freight Yoga Mat”, actually a kneeling pad. It’s part number 56572 (as of now, anyway). It’s kinda exactly what I wanted – a big slab of rigid-feeling EVA foam. The texture felt right to make into wheels, and if the traction wasn’t good enough by itself, certainly I could coat them in latex or silicone (a long time favored builder trick still in active use at BattleBots!) for more traction.

So I violated my own rule, as usual, and spent money on the robot. One Harbor Freight Yoga Mat, for science!

I started prints of the hub design on a Markforged Mark Two (hi Markforged!) as well as a new-to-me Creality Ender 3 V2 (hi Naomi Wu!) that I picked up for $40 in a “Curated Wreckage” state. The pink material is PETG, which is my preference these days for non-critical and experimental prints that nevertheless will be used in the final application, despite my denial.

Those slots in the gears were added for a wheel retention feature that I dreamed up as well, and which will be seen shortly.

One issue I ran into with making the gum rubber wheels for 30Haul was keeping the hole saws centered with respect to each other. I decided to tunnel my way through the problem this time by opening up the center bore of the 1″ hole saw to fit on the 4″ hole saw’s larger arbor thread.

These cheap hole saw sets aren’t hardened meaningfully, so I blasted the bore out to 16mm with a metric step drill I had. 5/8″ probably would have been fine also. After this, I was able to jam both of the hole saws onto the larger arbor!

It was then just a drill press job away from making wheels that were at least concentric one one side; I didn’t want to go buy 2″ deep hole saw for this, so I had to just flip the Harbor Freight Yoga Mat around and find the pilot hole.

Here is what the deal is with the six slots. I didn’t want to just adhere the surface of the foam to the printed hub face because I thought the foam was just a bit lacking in integrity and would separate under the “skin”. I decided to add some interference elements, not unlike the standoffs of 30Haul, but without the intention that I could take it apart again.

So out came these ABS trim strips I bought for something way back when. I decided to use them as quasi dowel pins or driving keys. They get cut into chunks, pressed into the hub, and then trimmed with scissos.

With six slits cut into the foam with a knife, I could press these in with adhesive covering every surface, thus ensuring that plenty of surface area grips the foam on the inside.

E6000 contact cement is my go-to for these kinds of robot shenanigans. I slathered each edge of the “blades” and the hub face with it, and left it to cure under a weight.

That’s what one wheel looks like. The next day, I was sufficiently satisfied with the roundness and rigidity, and hit the go button on 6 more wheel hubs.

Alright, experiment over. Time to flesh out the rest of the design. I needed the drill motor shaft to stick into the center of the bot, so I decided on just using some fat standoffs.

The drill motor is mounted in a slightly unusual but also traditional way, using 4 of the of ball bearing clutch holes as mounting holes (and the other 4 still serving as clutch ring locking holes). All of these holes are to be tapped #10-32. This approach is stronger than using the two very small #4-#6 holes in the nosecone area.

The poker weapon drive is as simple as it could be. I’m using the same tactic as I used on Sadbot’s latest poker: Just welding a steel tube to a sprocket. The center bore is made for a 5/8″ ID bushing, which will just be a drilled piece of Delrin plastic in a 3/4″ drilled hole. The sprocket I plucked out of my Tomb of the Unknown Power Transmission Part is a 30 tooth #25 size.

25 isn’t my go-to for lifter/hammer style weapon in a 30lber. I’d much prefer #35, but I only had very small sprockets in #35 at the time, and something something no spending money. The same applies to the 5/8″ shaft. I would prefer at least 3/4″, but had some 5/8″ 4130 chromoly tube that I figured would stand a better chance than thin-wall 3/4″ regular buttery steel.

One of the next things to settle was where to put the weapon axle. I ran through a few options for this, including having it in-line with the top surface of the frame and making a half round shaped clamp to hold the axle in place.

The “overkill V2” iteration is where I decided I also wanted the ability to tension the chain, so let’s make a fancy set of towers that have slots so I can slide it back and forth for tensioning purposes?!

The third and final iteration is the “No, that’s too much effort” revision, which was a compromise. I needed more space between the sprockets anyway, so the axle had to move up. I decided to just make a simple block mount from the same offcuts that the frame will be made from, and use shaft collars or spacers to retain it axially instead of clamping

And that….. is all the CAD that I did before starting to cut metal and plastic. After all, I had 95% of the parts in house and ready after searching around for the day.

The electronics of this thing were to be equally found-object. Namely, I “found” two brushed Ragebridges, and decided I was going to break up one of my knockoff 18V Milwaukee Fuel batteries, which contain 2500mAh 18650s. The “9Ah” knockoff contains 15 cells (5S3P) and so I was going to run 7S and make two packs out of the one battery.

Next up: Fabrication, then the Motorama trip!