The Restoration of Overhaul 1: With Liberty and Shuffles for All

Last episode of this “Overhaul” “Build” “Report”, I straightened the frame from its accumulated damage and began drawing up a plan to put new motors in. Now it’s time to execute! I had no particular goal or deadline with this project, mind you. It was something I made incremental progress on if I wasn’t doing anything else, and I already had basically all the parts in the garage already. One of those (few) nice things about building a 250lb Battlebot is that future robots are basically free for a long time due to your initial “investment”!

First order of business: get the spider couplings mounted on the motors. These scooter motors have an odd stepped shaft that usually holds a #25 sprocket. I had to make a similar stepped bore in the spider coupling halves in order to get them to seat correctly. The shoulder starts at 8mm and increases to 10mm, so I ordered 5/16″ bore couplings to start with (0.3125″ vs. 0.3145″, an easy knock-through).

The motors don’t have a good way of attaching anything to the motor shaft except with the roll pin which the original sprockets used, so I had to drill a matching hole in the spider coupling. This was “interesting” to say the least.

I mean, besides doing this on a mill having no digital readouts, the hubs were very mildly tapered to release them from their sintering molds. That means I had to first machine a flat into one side in order to register it with the vise at all. Next, I squared up the backside against the vise with a parallel, right up on the edge. This was going to be good enough to drill one hole.

In lieu of another roll pin, I went for a 1/8″ diameter solid dowel pin for extra strength. The shocks of each shuffler foot hitting the ground, I suspected, wasn’t going to play well with the hollow and split roll pins.

Some time around this point was when I decided to absolutely send it with available materials.

I decided instead of machining and welding an endcap onto the “motor rails”, I would take a page from the finest robot arm additive manufacturing research and just lay a massive circular weld bead inside the tube….

…upon which I cleaned the bore, drilled to size, and tapped it just like a regular ol’ metal piece.

Are the threads clean? Mostly. Do they go all the way around? Moooostly. Good enough for this job?

That’s what I’m after.

These… uhh, “weldments” met the motor mounting plates fresh off the printer as well.

The standoffs that bind the motors together? Left over 30haul and Uberlocker leadscrew stock I’ve had for years! I mean, these aren’t serious high grade steel or anything. I used these in the absence of having appropriately sized solid aluminum or steel stock.

The motor “cartridge” completed and assembled. It’s bound together with 5/16″-18 hex cap screws.

On the other end, the flanged Ampflow adapter with bearings in it is mounted as well.

Here’s the totality of the setup, both shuffle pods and the motor cartridge.

To install this was a little strange, as Overhaul 1 wasn’t actually designed to have something dropped in from the top. I wiggled the motor cartridge in first through the side, then lifted one side up at a time to slide the mounting rails in and add shaft collars.

At first, this assembly is left loose to slide side-to-side on purpose, since I’d need to get the horizontal alignment constrained by having the shuffle pods in place.

Funny enough, I kept the original drive chains we cut for for the shuffle pods – they were used on Sadbot when it had a geared 63-74 motor per side, and still fit today using the same sprocket!

And now we have fully assembled and motion-ready shuffle pods!

Mounting these things was fairly easy, as I’d already blown out the frame rails enough that they can slide sideways again. Drop in, mate the spider coupler, and attach the four bolts.

Soon enough, they were ready for an “initial break-in”.

I performed a bit of look-ahead work by repairing some of the motor wires and running them through spare loom. This will be handy once the new electronics assembly is installed on the four rubber wubbies seen in the bottom of the image.

Overhaul was missing a few of the very large shock mounts, or mega wubbies, that had secured the pontoons. I had to order some new ones, and then remembered that they had to be “chamfered” a little to clear weld beads on the inside of the pontoon cross beam.

With relatively minimal complaining, the straightened out pontoon weldment goes right on. I might cut the Pull-Tab off later.

From here on, I’ll take out and apart the lift and clamp actuators and work on an electronics solution. I’ll probably keep this thing on 6S (24V) or thereabouts – there is NO need for the shuffle mode to go breakneck speeds like we had it at BBS1.

The Restoration of Overhaul 1: Wait, Why Did We Do It That Way Again?

Last November, I made a trip back up to Boston in order to retrieve some of the heavy things I didn’t bring down when I moved. One of these heavy things I explicitly wanted to get was the hulk of Overhaul 1, which had traveled with me out of MIT, through the Artisan’s Asylum, into the Old New Shop, finally to the New New Shop.

There it is, in the cruft corner of the New New Shop. When the wheel modules went into sadbot back in 2015, the shuffle drive pods were put back in as a visual completion piece. The motors were removed for future other bots – I believe those drive motors might have made it into the Season 2 Road Rash. While they were never used in the Season 1 competition, they were the last piece of the purposeful “Glue 3 designs together” approach we used for Overhaul 1, and the focus of a lot of effort during the build.

Beyond missing a few motors, the bot was exactly in the state it left the Nightmare and Witch Doctor rumble of Season 1.

This was the same trip that I acquired the Benchmaster, Master of Benches on the way up. I somehow managed to fill the back of Coronavan up without even trying. Thus is my life, apparently.

And thus, the conference of heavyweight robots is convened! The still unpainted Overhaul 3 is in the background. As I’ll expound on in its build reports coming some day soon, part of the design mantra was getting back to the roots of what I liked about Overhaul 1. I wanted Overhaul 3 to drive like Sadbot – as a result, I wanted it to drive like OH1. That meant going back to large, bouncy wheels over the old Biohazard inspired 6WD setup of Overhaul 2, and if you recall, 30Haul was made two years ago to explore the same.

My plan for Overhaul 1’s resto was to straighten the frame out so I can easily mount stuff to it again (but not repairing the battle damage!), and then putting some motors back in it. The old battery bay was to become an electronics-and-battery bay since it wouldn’t need enough energy to last a 3 minute match, just to drive around. The actuators for the lift and clamp were in fine enough shape and would just be taken apart for a quick inspection and rebuild if needed.

I began taking the thing apart and assessing what needed to be done. The right side of the frame was caved inwards from Nightmare brushing against it, for instance. This really prevented the shuffle pod on that side from being fully mounted (Its sidewall was also a little caved in, but not enough to matter apparently). Dings, dents, and nibble marks abounded on the rest of the bot.

The “pontoons” in the front warped when welding, so it was already bent anyway, but during the tournament it just ended up bending more. So I also had to figure out how to pull that straight.

I decided to force the frame apart hydraulically from the inside. Doing just enough Big Chuck’s Auto Body to have watched enough repair videos of car and truck body and frame pulls, I was out to try my sense of “understanding how the metal flows” when taking damage. Nightmare pushed the steel inwards, so pull it outwards again to compensate.

Initially, I tried with Mikuvan’s OEM tire jack. While it’s fine and enough for lifting one cheek to change a tire, against the AR400 steel plate and tube weldment, it was just… no.

And so I found myself running to Harbor Freight before closing time to get one of their big 20-ton bottle jacks. With this thing and a cleverly positioned Spool Bus Lifting Tool, I was easily able to force the frame rail back straight again by targeting the upper edge (where it got chewed first). The rest followed without much fuss.

While the tubing is crimped a little on that side now, it doesn’t matter, since all I need is the clearance. The damage is character.

I flipped the frame around to also push out the other side a little. An AR500 plate sits against the bottom of the jack and the recently corrected frame rail in order to boost its rigidity, such that I didn’t just balloon both sides of the frame outwards. I was plenty satisfied with how straightened the whole thing became, really. I didn’t expect it to work out this well!

For pulling the pontoons apart again, I had a creative method in mind. To execute this, I’d first need to weld a pull tab to the end of one of the pontoons. The idea being I’d fixture the pontoon center beam element to something relatively sturdy, and use a come-along or chain binder on…

…Yeah, what was anyone expecting? Dual vantruck metal forming.

I bolted the pontoon center member through one of the former 5th-wheel hitch mounting holes on Spool Bus, suspending it slightly off the bed by using spare Overhaul wedgelets as a spacer. This would allow the beam to deflect the other way as it was pulled. I wrapped the tow chain I keep in Vantruck around the pull tab and joined it up with itself, then attached the other end around the trailer hitch.

I then used a come-along to slowly pull on the length of chain. It looks and sounds far sketchier than it was in real life, but I made sure to use double layered eye/face protection and an few “Anti-kill-yourself” blankets over the chain and cables.

I mean, not that any of that stuff would do much against a potential flying 37 pound pointy steel thing, but it made me feel better about it!

It’s not totally straight (not that it ever was), but it’s better than before for sure. At least it’ll be straight enough to get the bolts started.

With all the frame bashing work I wanted to get done completed, I next moved on to the question of how to put motors back in it. Originally, we had just hung F30-400 Ampflow motors off the sides of the shuffle pods/wheel modules and used some tie rods to secure their back sides. This worked well enough for the time we had. I wanted to execute on an idea we bounced around but did not move on because of the extra complexity.

See, the motors I wanted to use were some XYD-13 24 volt scooter motors that I originally got as a what-if for Overhaul 3. I’m perennially of the opinion that these big ol’ scooter motors are underloved in the U.S. robot fighting scene (but rather popular overseas in the U.K. and Australia, as well as mainland Europe). Uppercut, the team of MIT ducklings from yester-season, also did very well using them for drive.

The plan was to center-mount them in the bot and use flexible couplings to connect them to the shuffle pods. Those seemingly random frame holes near the center of the bot’s wheelbase that were never populated? Well, that’s what they were originally for: Motor mounting.

This is what the arrangement will look like. The motor will drive a very short floating intermediate shaft made of spider couplings, in theory giving them a lot more isolation from the high vibration of the shuffle pods. Now I just needed a way to connect the motors together with themselves.

I decided on the fast, easy, yet effective way – use a Markforged print designed to give a little bit of rotational flex to hang the motors off the two long rails. The motors will be held together with 2 of these and standoffs as a central unit.

Here’s what the design looks like. The three holes are for the motors’s mounting flange, which will bolt through to standoffs.

And this is what it will look like in the design. The former Ampflow bolt pattern will have a small (also 3D printed Onyx) bearing block embedded in it with two flanged 1/2″ bearings to support the drive sprocket.

The design now finalized, after some adjustment of spacings here and there. The motor “pod” itself will be held in place by shaft collars, so I can make everything jiggly at first to do the side-to-side alignment before locking it in.

Fabrication of all this didn’t take too much time. So the next post installment in this “Charles really doesn’t want to start down the rabbit hole of recapping all of the Overhaul 3 content thus far” will be about getting the bot driving again!