Category: Done!

Defined as “It worked enough to satisfy me”

The Makening of the Susquehanna Boxcar

chorl

It’s the middle of January, it’s still too damn cold for me anyway and all I do is stay inside and die on the couch once I get back from the lab – but Motorama is but weeks away and I don’t have a robot yet. I had one designed, I mean… but that’s not very meaningful. So let’s begin building the thing already!

Susquehanna Boxcar was meant to be very simple and crude by the standards of things I used to build here. It turns out owning your own tools is expensive. Crazy, right? I made this realization as of late, that my projects here will probably be less showy from an engineering perspective and more functional and piecemeal. While lots of machining services are available now that weren’t a decade ago, like Xometry and SendCutSend/OSHcut, as well as my numerous Chinese machining contacts… well…. they cost money. UGH.

If there is one thing I enjoy less than designing things correctly like a real engineer it’s spending money to do it.

It doesn’t help that as of a few weeks ago from time of press, my Autodesk Inventor “student” “version” has finally reached the end of the road. Autodesk started requiring you to verify your identity with a 3rd party company, in order to determine eligibility for free pizza. That’s something I absolutely refused to do on principle, and so I let my license lie fallow.

It’s not like I can’t CAD – through the lab I have just about every computer aided whatever I can possibly use, but again, it’s more of the principle of the matter. If I NEEDED to CAD something, I can pop open Solidworks or CREO. But I think I’ll start moving onto “free as in dom” software like FreeCAD. The story is much the same with Eagle, now that it’s owned by Autodesk as well – KiCAD was something I messed with years ago when it still required a full unmaintained neckbeard and stained trilby to use, but it’s gotten far more integrated UI and UX wise. We’ll see how my need evolves on this front.

Anyhow, enough philosophy. I’m not mad at all for having milked 16 years of Autodesk Inventor student editions, just mad they found out and I don’t know the CEO well enough to bug him in his DMs.

We’ll begin by sectioning the 3″ width C-channel and marking out places to drill the frame holes. I also needed to make a U-shaped cutout in the center of one of them, for the eventual poker stick weapon.

If The Benchmaster, Master of Benches were a bit larger, I’d set it up on there. I decided to just get creative with a bandsaw and a Dremel wheel instead.

I just cut partially through the C-channel with my horizontal bandsaw and knocked the horizontal cut line out with an abrasive cutoff wheel.

Front and rear frame sections now prepared and also briefly hit with an abrasive flap wheel for future welding.

The squishy center is made of 1″ thick UHMW barstock. I’ve owned this 1.5″ Forstner-ish bit for a while, inherited from one of the tool chests I bought which was full of original content. Not sure what it actually is, but it does make flat bottomed holes.

The intention is to use it to make a socket to fit the 555 motors. I took an off-cut UHMW piece to try and test drive the process and set the depth I want using the drill press feed stops.

The result of this test drill is seen behind the mockup frame. The 555 motor will stuff into the hole left by the 1.5″ drill if I wiggle the drill a little to make it slightly sloppy.

This frame mockup was just to make sure everything is (basically…) the length it has to be. Yes, one of those tubes was cut 1/8″ too short. No, I refuse to buy another segment. I instead cut a sliver off a spare chunk (seen to the left of the image) and will weld right over it. Fight me.

This 3d-printed jig will locate the drive gear mate. Using 24 pitch gears afforded me a few thousandths of an inch of slop space, but I still wouldn’t want to use it if I didn’t have to. Using the axle as a pin mate and the edge of the UHMW bar as a tangent touch-off (using a dowel pin), I was able to locate the motor’s mounting hole and its bolt circle with a 1/8″ pilot drill. Then I took the piece over to the drill press for the 1.5″ bore.

Frame rails and the lifter tower are done!

I used the center frame rails as part of the welding setup to make some initial tacks, before removing them and going crazy.

Here’s the outer frame all welded up. Limewelder has been a beast on 240 volts and did all of this cleanly with no issues.

So I wanted to bridge the cutout in the front C-channel because that’s a weak spot just begging to be bent. I reached for a piece of 1/4″ x 1″ steel bar, but my attention was diverted by the Calligator on the table.

See, Calligator is a meme over at SendCutSend. Designed by one of the other Northeast robot folks, it was legendary for crashing the SCS quoting engine before they fixed it. As a result, hundreds if not thousands of Calligators are running around the country as a result of testing, debugging, and free meme gifts used to fill leftover space on plates. I happen to own one, and it was the perfect touch to this piece of pre-destined garbage.

I cut his legs off a little in order to keep him under the level of the cutout. This Calligator is 304 stainless steel, and so I busted out my 309 alloy wire that was previously used to make van exhausts to join it to the regular carbon steel behind it. This wire flows a lot differently, so the welds came out a bit blobbier and chunker than I wanted.

Whatever, the green pukey paint will make it go away. This is apparently called “Detroit Diesel Green”, and was the result of going to Autozone and asking their employees for the ugliest color touch-up paint they carry in the body shop aisle.

For some reason, everybody there – plus friends I sent an image of the paint shelf to – all gravitated towards this color.

It is a very proper color – very “Susquehanna Boxcar“. Definitely the color you’d rattle-bomb an old factory machine in to cover up the loss of your regional manufacturing economy.

The lifter hub was made exactly as I did for Sadbot itself – by welding a piece of tube to a sprocket. The sprocket is a #25, and I’d have preferred a #35, but something about no spending money. I only had #25 sprockets in the bucket that had small and large sizes available.

Here’s the finished lifter hub with a Delrin bushing stuffed through it. Also shown is the hollow 5/8″ 4130 tubing lift shaft. As I said before, I expect this to get bent up very quickly – it’s far too skinny for what I want to put in a 30lber. Remember, 30haul used 3/4″ steel and Uberclocker up to 1 inch solid aluminum. But no spending money.

The matching sprocket for the lift motor was one of those motor sprockets often found pinned into a scooter motor. I removed it for Overhaul 1 restoration purposes, and luckily, its bore was just the right size to slam a 3/8″-24 tap through and just Loctite onto the drill motor shaft.

A part I generated on the fly and had to retroactively CAD was the drill motor’s extension shaft. This has one end threaded to jam against the sprocket; see the wrench flats on it for tightening it them up. The other end lives in the opposing side UHMW frame rail, and down the center is a hole with an internal shoulder for the reverse-threaded locking screw. Additionally, note the clearance cut I made on the lift hub to the steel tube. This turned out to be needed for the width of the chain.

The majority of steel tubing have a weld seam on the inside, so it had to be removed before I could install 1 x 1 inch square accessories. I did this by just plunging a long-cut endmill slightly into the wall of the tubing.

And a quick test with 1×1″ tubing on my stock rack…

I hand marked and drilled the holes for the drill motor’s mounting plate and went back to some good ol’ follow the marked line to make the rectangular cutout for the nosecone area. The Benchmaster, Master of Benches is fairly easy to count wheel ticks and handle turns on, but for things where NOTHING MATTERS, it’s still easier to drive by sight.

Now we’re getting what looks like the center of a robot together. You can imagine the drill motor would be extremely flexible hanging so far out of the frame rail like that if it didn’t have an extension shaft to the other side.

Drivetrain test fit time! All of these gears went together without incident.

The pinions are 9-tooth “pinion wire” stock I had from something. I assume it was a Roll Cake purchase way back when, but that is what drove the drivetrain design. I drilled and reamed the hole using Tinylathe to “3mm minus 0.0005 inch” which is a real size of reamer they sell – 0.1176″

Hell I could probably go fight this thing as-is in the 12lber class. The Boxcar is really just a 12lber wearing an enormous steel hat.

As the thing neared mechanical completion, I started keeping track of weight to forecast what kind of weapon I can even put on it.

While some of this fab was going on, I had my New-to-Me junkyard Ender 3v2 punching out the electronics mounting facilities like the battery tray and ESC mount.

Wiring the bot was very straightforward. Nothing particularly interesting here, just 3.5mm bullet connectors. The 18650 cells are, as I mentioned, from a deconstituted Milwaukee M18 knockoff battery. They’re generic 2500mAh cells. For this application they’ll be just fine.

“What’s worth buying is worth buying 10 at once” -me, probably

(Those brick packs in the Hobbyking heat shrink are also knocked-down Milwaukee knock-off packs)

All of the relevant electronics are kept in the pink suitcase. The Ragebridges face each other the receiver is adhered between them.

I closed up the battery packs using good ol’ Mountain Dew bottles. In fact, I had to buy Mountain Dew to drink it and use the bottles. I guess that meant I spent money on the robot.

Electronics bay mounting is taken care of by these strips of 1/8″ thick G-10 Garolite, one of my go-to materials. The bolt heads seen are 3/8″ flanged head self-tapping screws from mounting Vantruck’s fittings back on after the restoration. Every big frame screw on this bot is actually a lag bolt or self-tapper.

After the commissioning of electronics, it was time to find out how much weight I had left over for the funny things. Honestly, 3.5 pounds? Not bad!

The poker was to be a crowbar that Murdervan spawned out of one of its door pockets. Yeah, that thing spawned a Half Life style crowbar and a folding knife.

The shank of this crowbar was conveniently 7/8″ or so. This meant I could just machine out a 1″ OD steel tube very slightly and smash it on there in order to fit in the lift hub.

And that’s what I did. I installed the sleeve and drilled through everything for the locking screw in the socket.

I decided to turn both ends into potential weapons. There’s nothing really useful about the hook-end one as is, but maybe we’ll think of something at the event.

And now, the “Don’t talk to me or my son ever again” shot.

Driving video here and here. It drove “Alright, I guess”. Not as sharp as a proper higher-reduction gearbox, and kind of hub-motor like. The motors are definitely underpowered (being injket carriage motors and all) and it won’t be happy with a pushing match, but it’ll do.

As a final touch, I added some “car markings” to further sell that this is a railroad reference and not a Regular Car Reviews in-joke.

The Harbor Freight Multi-shovel

On a work-related trip the week before Motorama 2022, I happened to visit the local Harbor Freight and discovered they had an interesting new implement.

I called it a “multishovel” but it seems to be an entrenching tool or E-tool, another new trendy must-have in the world of quasi-military cosplaying off-road survivalist Jeep bros. I decided it was perfect as a robot weapon.

Making this adapter was very easy. The backbone of the multishovel is a 22mm x 15mm (or so) rectangular steel tube stamping. I just carved out a rectangle into a 1×1 inch square steel tube, to accommodate the 22mm length dimension (about 7/8″) and used the existing conveniently-placed cross hole in the multishovel.

And that is the story of how Susquehanna Boxcar got its Harbor Freight Multishovel.

It was a few days before Motorama now, and I was on a quest for redemption.

The Susquehanna Boxcar: A Return to Motorama

chorl

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!