The Makening of the Susquehanna Boxcar

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.

An Equals Zero Quickie: Adjusting the Voltage and Current on Your Inexpensive Chinese E-Bike Charger

So over the last few weeks I went back to my roots a little and spawned an electric bike out of basically just the hot garbage in my robot/van/go-kart storage totes and a $20 yard sale frame. That post’s for (yet) another day, but what I also needed to do is charge it… and that is where things got funny.

I still have several standalone e-bike/scooter chargers from the 2.00gokart and Power Racing Series days, but they’re all for 10S (37V for LiCo chemistry or 33V for LiFe) lithium packs. I also have a 12 LiFe-only one that I used for Melonscooter, which is the one I will be hacking up.

This new e-bike runs 12S regular lithium cobalt, with a nominal voltage of 3.7V instead of 3.3. I just had to figure out how to crank the charging voltage up some, from the 43.2V of charging 12S LiFe cells at 3.6 volts apiece, to 49.2 volts for charging lithium cobalt at 4.15 volts per cell.

So let’s crack it open. Basically every switching power supply architecture has means to do fine tuning and calibration on the factory floor, you just had to find it. They usually can’t adjust far, which is why I started with my highest-voltage charger.

I did a quick scour of the Internets for whoever has done this before. Luckily, the usual suspects at Endless Sphere (still alive and buzzing in this day of easy social media share buttons) have done this before, and I found some useful information in this thread. I seem to have a visual match with one of the chargers posted in the thread.

These things haven’t moved much technologically for over a decade if not more, so it was easy to make the visual correlations with mine. Here’s the potentiometers on my model, which was sold by ELifeBike, still around today as PSW Power:

From the schematic posted in the thread, I deduced that the termination voltage adjust trimpot was right by the output status LEDs. They usually are some place obvious for the technician. At the time I didn’t know what the other two trimpots did, but figured they were charge current and charge termination current threshold (At some point, your charge current in CV mode falls so low you might as well call it good).

The way I was going to make these adjustments, obviously, was all live, all the time. So if you do this, just remember that even if the output sounds relatively harmless like 24 volts, switching power supplies still will pack a few hundred volts right next to that. So, avoid poking the wrong thing.

We begin the prodding by checking the charger as-is after scattering it on the bench. Hmm, 44.3 to 44.4 volts on the output, you say. That’s above the termination voltage you’d want for LiFe/A123 cells, but not enough to really hurt anything.

I began cranking the CV trimpot and (many many turns later) got the voltage up to about 49 volts. Counter-clockwise is increasing voltage, at the rate of what seems like 0.2 to 0.3 volts per full rotation. I was scared of running out of potentiometer, but it got there. These small vertical trimpots are usually 25-turn.

I generally bulk charge my EV batteries, so I don’t take them all the way to 4.20 volts. Historically I’ve popped them out once every few months and balanced the packs manually…. if at all. Beyond that, you make an assumption about how far apart you can stomach having the cells drift, and assign a little safety margin. For instance, by charging to 4.15V per cell, you are saying that the summation of all cell voltage deviations both high and low shall be no more than 50mV…which is quite a lot, by the way.

So that’s why I didn’t adjust it all the way up to 50.4V, which is 4.20V/cell for 12 cells. You only get 3 or 4 percent of charge going that high compared to 4.1-4.15V/cell and it just makes for a much more relaxing experience. I dunno why, but I expected some kind of instantaneous catastrophic failure as soon as the thing hit 50.0 volts.

Next, I wanted to mess with the charge current not for any hot-rodding reasons, though you know me, but to see where the adjustment is made. On the PCB, the two (what I think are the) current-adjustment trimpots are located right next to a dual op-amp chip, part number HA17358. One of them probably adjusts the CC stage current, and the other the cutoff current.

I just picked one and started messing with it, and hey, it’s the correct one.

Pursuant to the “You know me…” up there, I gave it a few whirls to bring the charge current up to 10 amps. The “rate of adjustment” seems to be about 0.3 amps per rotation, so I was turning this thing forever to get to 10 amps from 8.

To dial the current in, you have to actually be charging the battery. Luckily, this bike uses salvaged Overhaul and Sadbot batteries. They’re 6S and 6Ah each, and I run them in a “2S2P” arrangement to get 12S 12Ah. They’ve been sitting a while, so were discharged somewhat.

Finally, after keeping an eye on it for a nervous 30-something minutes, I decided to see if I could change the threshold current for ending the charge cycle. This is probably something that is utterly unnecessary, but curiosity!

As I watched the current drop below 1 amp, I decided to give this trimpot a few spins to see if I could induce the cutoff. This time, clockwise seems to raise the cutoff current. I spun it forever counterclockwise before I realized I should probably go back the other way, as I did not actually count any of the revolutions.

A few turns clockwise later and the green LED turned on, indicating the cycle is complete. Again, there’s probably no need to mess with this at all.

While I was inside, I decided to also go ahead and shore up the completely unprotected PCB with some conformal coating around the chips and sealing the connectors. This thing no longer lives in a climate-controlled building, so I figured it wouldn’t hurt.

Some day you’ll hear about the bike itself, I promise!