Archive for October, 2011


It’s random site update season

Oct 31, 2011 in Stuff

The primary purpose of my site is for me to dump the day’s progress in the form of pictureful blog-like posts. This means I usually forget about the rest of it, but I’m going to start adding things in order to bring all the projects up to date. Straight RazEr, Melonscooter, all my hub motors, and the Weird-o-copters still need project pages, and the Motor Controls page is awfully out of date too.

First up, though, by popular request now from several people – I’ve updated the “useful stuff” page with downloadable versions of all the things I keep getting asked about. Boards, various CAD files, and worst of all, Arduino code can be found there. None of it is guaranteed to work; in fact, I *know* those board files are not updated with all of their required Little Blue Wire hacks and trace jumps.

Land-Bear-Shark: I’m getting closer to blowing it up again

Oct 30, 2011 in Land-Bear-Shark, Project Build Reports

I’m starting to run out of things to work on to put off the software, which would require a substantial rewrite in order to change the signalling protocol over to R/C servo style PWM to accomodate the Hobbyking cartrollers. In the end it will be simpler, but still…. software. That’s only things that closet electronics engineers do. Otherwise, I’m taking so long on this that my load cells are probably going to arrive before I wire everything back up, but perhaps that’s just me subconsciously pulling towards trying to get that version working and skipping this steering-sense-only stopgap solusion. What I’ve also discovered to my potential dismay is that the HK cartrollers will just explode as soon as I actually get on the thing, so maybe I should start making room for the Kelly controllers again, or have another solution on hand…

Decisions, decisions. And pictures:

Speaking of closet EEs, check out these sensor holder boards by Shane. I’ve been meaning to make a clean, permanent mounting solution for my Hall sensors for a while, but just Never Got Around To It.  These are external mounts – they face inwards into the can, and the slots make for adjustable timing (also addressed in that post, and an interesting read for anyone else wondering why their motor doesn’t reverse).

Normally, I’m a fan of the internal slot-mounted sensor. For the SK motors, though, I would have had to mount them outside the motor because the slots are too narrow, so I got to test drive these mounts first.

Boards are nice, but that still doesn’t change the fact that the motor mounts I built have no provisions for attaching the boards. That’s fine, I’ll 3d print a little mounting ring thing.

Originally designed with 3 notches to fit the sensors by themselves (without a Nice Board), this mounting ring is aligned by the conical portion of the motor face, and protrudes very slightly past the end of it. This means when I tighten down the motor mounting screws, the ring is firmly secured by a taper fit. The whole thing is actually capable of rotating for sensor timing – with the sensor board’s mounting slots, it’s a bit redundant. A notch in one end lets the motor wiring through, and the two holes in the top face secure the sensor board.

Make-a-Bot is now on its last meter of ABS filament. Uh oh…

Sensor board attached and wired. I found some Nice 5-pin Cable that had a tension strand and braided shield. It’s a bit large and overkill for the task, but hey, 5 pin cable.

On the other end of the cable, I spliced in a standard R/C car motor sensor cable (ROAR standard) I picked up with a Hobbyking order.

The next step was to test the motors. Because I don’t know if the sensors are actually in the right position or not, this was a game of applying gentle throttle to see if the motor would spin smoothly. For a fixed sensor input combination, there are 6 motor wire combinations to try, 2 of which work.

Hmm, well this doesn’t bode well.

I probably shouldn’t have tried to sensor-find on the full 22 volts. The SK motors have an internal resistance of like 30 milliohms, which means at 20-something volts, infinity amps tries to flow. If the sensor to phase relation isn’t correct, then the controller tries to flow infinity amps vibrating the motor around. The result is a literal popping sound as one leg of the power board detonates.

Luckily, I have a spare HK cartroller (the one that I took apart and beat up), but the fact that these exploded without even running the vehicle proper yet probably means it’s not going to end well. The motors are simply too low-resistance for a non-current-controller driver of this size to handle well.

After this, I decided that sensor finding on 11.1v might be better.

With the sensor-phase combo “found”, I timed the motors by measuring the DC current draw while rotationally adjusting the sensor mount. The point of optimal timing in one direction is represented by minimum current draw.

As Shane found out, optimally timing the motor for one direction using sensors like this does not mean they will be good for reverse at all. Due to a combination of factors such as sensor hysteresis, motor magnet field leakage, sensing distance, etc. the timing in reverse will be very far off – as much as an entire sensor state.

This means LBS will be able to reverse using the HK cartrollers, but very rudimentarily and only with extremely high current draw due to the non-optimal timing. This probably just translates into more death for the cartrollers.

Once the Band of Optimal Timing was located, the sensor mounts were fixed in place by tightening the motor mounting screws.

After wrapping the whole package up and potting the sensors to make them a little more waterproof, it was time to mount the motors.

Hey, that’s an awfully small sprocket isn’t it? I didn’t know that they made things such as 6 and 7 tooth drive sprockets until I actually looked. The SK motors have a much higher torque constant than the CIM motors of yore, so I could bypass the CIMULINK reduction and just increase the single stage chain drive ratio by using a smaller sprocket. The motors have a RPMs-per-volt rating of 200 or thereabouts, so with a 7 tooth sprocket, resulting in a 6.4:1 ratio, the speed is approximate the same as the CIMs using the pre-reduction and 4.5:1 chain drive (about 18:1)

With the 7 tooth sprocket, the chain turned out to be essentially the correct length after I added a “halflink”, or one full pitch. There’s a small amount of slop, but it’s better than before, so I decided to not use a tensioner.

I verified that the motors were in fact still working after wrestling them into the track pods. After that, it was time to throw everything else back in. The batteries are in a different orientation this time – sitting flat instead of vertically side by side, and they have polycarbonate plates holding them from being jostled. Previously they were free to bounce around inside the cavity, which I can’t imagine was very good for them.

The next step is to Put The Arduino Back In and make some R/C based driving code – and detonate the cartrollers.

LandBearShark New Hinge Installation

Oct 26, 2011 in Land-Bear-Shark, Project Build Reports

This is the post where I take those CAD renderings from before and manifest them physically. I was able to assemble the entire new hinge today and test out the ride. Conclusion? A little soft, but the sandwich mounts I purchased were also the softest type on McMaster (50A durometer). Upgrading to the hardest type (70A) should make the board much stiffer. However, it behaves as expected, and the “pot wrench” coupling also works well.

I feel a little shameful for making yet another post where there is an instantaneous transition between CAD rendering and parts. High-school-me would have figured out how to make this new hinge solely from Home Depot aluminum angle and UHMW stock from McMaster-Carr, and early-college-years-me would have made long detailed posts filled with pictures of machining and musing about machine tool design.  So you guys over at Georgia Tech should post more pictures of your own waterjet pimping such that I feel less guilty :(

For people not in bed with the hydraulic intensifier, there’s places like Big Blue Saw which you should totally check out. That’s my promise: Every time I make a new build post involving waterjetted parts, I will spam Simon all over it.

The parts above are cut from my giant eBay haul of 1/4″ aluminum plate, the same one that Straight RazEr was made from.  The potentiometer mount is 1/8″ and was cut from scrap plate.

Alright, enough guilt tripping. This is the “pot wrench” in real life. The bottom piece is two stacked 1/8″ plates that are pre-assembled with 4-40 tapped holes. Then, treating the resulting piece as solid, I threaded one of the large mounting holes 1/2″-13.

Because the top of the hinge is also the skateboard mount, all of the screws had to be countersunk. This was a problem: the massive 1/2″-13 flathead cap screw I ordered to secure the sandwich mounts needed a countersink that was 7/8″ across. Luckily, the Edge shop had a 1″ 82 degree countersink.

I later found out they make countersinks over 3″ diameter. What the hell are you countersinking that’s that large? Container ships?

Because the load cells (Keli Electric SQBY 500lb type, as it turns out) haven’t arrived yet, nor am I in the mood to diddle with them, I made these temporary mock load cells with the same outer dimensions out of aluminum bar. They will provide the bridging connection between the hinge and the rest of the frame. The holes are tapped and cleared for 1/2″-13 screws.

Here’s the front and rear hinge assemblies put together. The large shoulder screws solidly define the axis of pivot.

After the hinges were asssembled, I officially committed to the rebuild.

I tore out everything – all the electronics, and the batteries, and most non-fixed wiring. I blew out the interior (which was very much filled with dirt thrown around by the tracks) and cleaned up all the surfaces. The old hinges have also been removed.

One downside of the redesign is that I will lose my “dead rider switch” until the load cells come in and I can read them. So I’ll be keeping the throttle manually controlled for now – since I only need one channel in this case (assuming I can Do It Right) with the steering potentiometer, I might take advantage of the XBee socket on the 2.007 Standard Issue Arduino Carrier and make a simpler wireless link akin to the RazErBlades controller. That, in itself, would be pretty kickass.

This is too tempting. Way too tempting.

The fake load cells mount with a single Giant-Ass Cap Screw through the spacer plates and into the 1/2″-20 threaded hole. The spacer plates are individually retained by 1/4″-20 screws – the middle plate is a clearance hole and the bottom is threaded.

The hinge assembly drops on, and is secured from the bottom by two 1/2″-13 cap screws. The longer one (with the spacing washer) anchors the sandwich mount through the soon-to-be-real load cell. The other is threaded into the aluminum plate beneath it and stops flush with the top surface. Really only the former is needed, but I figured it was better for consistency.

Profile view of the new hinges. I guess they don’t stick out that much – not from this perspective. I will still make front and rear bumper-like structures to prevent banging the load cells into something first.

Jump testing on this assembly revealed that it is a little soft. There is much more travel available and there’s not a “hard stop” all of a sudden, so it mimics the ride of a rather softly-tuned longboard. The potentiometer mount works as designed, and after alot of jumping in the center of the board, the pot itself was not damaged.

Here’s a quick video showing a wiggle test of the new hinge assembly.

With the gory part of the hinge installation complete, I moved onto preparing the new motors.

More properly, they are new old motors. These Turnigy SK 6374/200 motors are tinyKart’s current drive motors, but the abuse of a vehicle’s shocks and jolts coupled with the fact that these motors do not have the “can bearing” of newer designs means that they’re kind of beat to shit.  On one of them, the stator was completely loose and could be easily slipped off by hand. The other suffered from an axial misalignment of the can that caused it to grind on the stationary faceplate.

I cleaned out the stator bore and stator post of the first motor with some carburetor cleaner (which is like, death and AIDS dissolved in cancer), then reattached the stator with copious amounts of thin CA glue. The mechanically gimpy second motor was just shimmed until it stopped grinding on itself.

While they had high speed resonance issues at 40 volts on tinyKart, they seem to be comfortable with 20 volts, even in their slightly dinged condition.

I made these motor mounts in conjunction with the rest of the parts. They have a semi-universal mounting pattern, fitting any of Hobbyking’s 63mm and 80mm motors. It means one day I can actually switch back to Real Melons, using the existing four mounting holes in the frame

What’s next? I need to actually perform the motor swap, but this might have to wait until I can figure out how to attach sensors to it. Unlike the 80mm motors, the stator tooth gaps on this motor are too narrow to jam a Hall-effect sensor in, unless the package was tiny. Therefore, despite the more iffy weather sealing ability, I will have to use externally-mounted sensors.

But it might be quite possible that sensorless is just fine…. I should try that.



The Potentially Forthcoming Triumphant Revival of the Land-Bear-Shark

Oct 25, 2011 in Land-Bear-Shark, Project Build Reports

Oh, this damned thing.

It’s been sitting in the same general location for a month now, having been rolled out to relative success at Maker Faire and occasionally for other events such as the Last Swapfest of the Year. LBS has existed since the installation of the Beast-it-troller, a last-ditch Hail Mary design just to see it move even a little bit, as a hollow shell of its original project design goals. It isn’t melon powered, it doesn’t travel anywhere close to the original 25 mph target (though ride testing the 15mph version has sort of dispensed with that goal), can barely turn on solid surfaces, and is controlled solely through a cheap 2 channel R/C car radio. It’s pretty much a forward-only rideable robot, so it’s not even as good as surfing Überclocker, which can at least travel backwards provided that I didn’t do anything stupid with zip ties.

While it may be visually impressive to the public, I’m unsatisfied with the vehicle in its current state.

With the Brutal Arctic Winter descending rapidly once again, something must be done about this. There’s also another important motivator to get the vehicle rolling again in a state vaguely resembling its initial goals, but I’ll get to that. No matter how much I try, melon-scooter does not do snow, and there is no way I am holding a radio transmitter in my hand all 8 months of winter.

Which is why I have been slowly brooding for the past few weeks on ways to turn the thing radioless. I’ve thought a little more about weight shift based throttle and brake control – while I was originally opposed to the idea based on the “it will fly out from under you as soon as you lean” argument, I’ve grown more keen on experimenting with it. Between this update and this one, I actually installed Segfault‘s IMU unit onto the frame of LBS (which pitched up and down alot due to the travel of the suspension). A fairly basic “keep under you” control loop was coded up – just an output ramp that integrated the detected lean angle. What surprised me was how well that system worked for how crude the sensor resoltuion was – the total tilt angle was probably no more than 2 or 3 degrees, and the track rumble contributed significantly to sensor noise, but for low speeds in one direction it did work satisfactorily. Changing directions was a challenge, since there was so much backlash in the chain drive that it would easily start unstably bouncing between forward and reverse unless the gain (in this case ramping) was set very slow.

In a rare move, I didn’t write home about it. It was a thought experiment relegated to the back of my mind, and occasionally I would think about how else I can sense where the rider’s center of gravity is.

simply supported beams

One thing you learn in introductory physics is that a mass placed on a beam supported at its ends will proportionally share the force (its weight) it exerts on the supports. If the entire system (mass and beam and all) were to be accelerated, then the proportion shared between the supports will change, with the support in the direction away from the acceleration experiencing a force increment. The former effect is positive in nature, the latter a net negative. If you have ever surfed a subway train (internally, I mean), then you know that weight must be shifted to the forward foot when the train accelerates, and if you don’t shift forward enough, you fall over backwards, and people look at you funny.

The same effect can be exploited in reverse. Leaning forward while riding on LBS should induce vehicle acceleration. If it launches too hard, you fall off backwards. However, if it accelerated at a reasonable rate, then an equilibrium can be reached with your rearward weight shift, and you stay on. Should you begin shifting strongly backwards, the vehicle will decelerate to compensate. The reasonable rate is what makes the difference between the thing just shooting out from under you and you coming along for the ride.

If only there were a device which could sense forces – one that was strong enough to stand the weight of a person jumping up and down on it while recording the force as an electronic signal that could be processed, that didn’t rely on physically pitching the board up and down like Segfault’s IMU relied on.

Conjecture 1: I can roughly estimate the horizontal position of a rider’s center of gravity along the skateboard by suspending it between 2 load cells.

A load cell is a fancy name for a few cleverly connected strain gauges (they’re not the same thing) inside a metal housing that can controllably deform small amounts under known loads. That’s the easy part – the hard part is that they come in thousands of varieties, from the smallest used in those cute digital crack scales (because what ELSE are you going to use that for?) to the largest that go on industrial cranes.  I think I spent a week on eBay just shopping for them.

The best would have been a button-type (or compression disk) load cell, since it would be fairly trivial to mount the board to.

…but I couldn’t find those in capacities less than thousands of pounds, because you use those to weigh trucks.

The next best choice would have been a double-beam type, since the load sensing element is in the middle between two easy-to-use end supports, and I’m sure I could whip up some kind of board mount for the middle, right?

But this was even worse – based on descriptions such as “DOUBLE ENDED SHEAR BEAM TANK RAIL AXLE SCALE”, I think you use those to weigh things bigger than trucks.

Only the single ended beam type existed in reasonable human weight (plus overhead) capacities, like 250 to 500 pounds.

I declined to consider the S-type seriously because they were very tall for their rated capacity already – LBS is already really tall for a board vehicle, so I didn’t see a need to make it worse. But, the single ended beam types also seemed a little shady to me for this application. The sensing region is very thin walled – no thicker than the outer diameter of those cylindrical indents in the picture above, and a good curb jump or obstacle impingement could just destroy the region completely.

I decided that a good enough solution to this problem is to just dramatically oversize the single-beam load cell. Not to the level of truck weighing, mind you, but such that 150 pounds of person (potentially overloaded to 200 pounds with Mountain Dew factored in) can jump up and down on it. I settled on some Rice Lake RL30000 “compatible” shady eBay load cells. LBS is not exactly a precision instrument, single ended beam knockoff brands are cheap, and I am not exactly well funded to do this. So, mysterious Chinese load cells it is. I used the RL30000 mounting dimensions to generate a part I could insert into the 3d model.

becoming unhinged

One of the other gripes that I and other enterprising riders have about LBS is that the skateboard is not very well mounted. They’re supposed to be suspended by eight rubber shock mounting rings – 2 per corner – being used as compression and extension springs, but I did not properly model them and ended up making only one mountable one per corner. The result is that the board doesn’t really offer any resistance to roll inputs, and it’s difficult on the ankles to ride because I’d be constantly correcting for side to side motion with them. The far displacement of the rubber shock mounts from the point of pivot means there was also very little roll available anyway, less than the average skateboard and way less than a longboard.

So that was another “feature” that had to be redone. Given that the board will be mounted by two large magic-filled metal bricks anyway, I essentially had to design a skateboard truck that “didn’t turn” but only offered springing and damping. Ideally the design would be left free enough such that I can include a potentiometer in the new hinge to sense the angle of roll; this angle is directly useful in steering the vehicle.

After a while of shopping on McFaster-Carr for rubber and urethane bushings, I decided to veer slightly from product specifications and use a large female-female neoprene shock mount (such as 6488K53) in bending. Sandwich mounts like that are rated in compression and shear, but not tension and bending because it would tend to rip the rubber molding away from the steel endplates. However, I was able to find an example (of that part number, actually) and investigated its durability in bending by attaching 12″ long bolts to the anchors, mounting one side in a vise, and twiddling the other side around. It appeared to give willingly to bending as far as 30 degrees – well past what I expected, and didn’t seem to show fatigue signs after about 100 cycles or my arm becoming tired, whichever came first.


We’ll see how it stands up for realies, but given that anything on this vehicle is lucky to see 100 cycles ever, I’m going with it for now.

Conjecture 2: You can use a big rubber shock mount pretty much any way you want… because it’s a big chunk of rubber.

throwing it all together

I played Component Tetris for a little while, generating cute half-Inventor, half-MSPaint graphics like the example below.

The new hinge would have to let me use the sandwich mount to support the hinging motion while letting me use the load cell as the only force path from skateboard to frame (or to rubber thingie). I also had to make sure I could somehow stuff a potentiometer in the assembly, and finally that the board not hinge unrealistically (such as from 4 inches away, like the above design). That design didn’t quite make it.

This was what I came up with after some more hours of staring and clicking. Making assemblies like this is not unlike routing a PCB where you also have to place the components in such a way that they can be reasonably connected together through, say, the shortest possible path or somet…

…did I just make an analogy from mechanical engineering to electrical engineering? Shoot me, now.

The load cell is grounded solidly to the frame, and on its far end rests the hinge with the press-ganged sandwich mount. I’m actually using the load cell “backwards” since it is more convenient to use the end with the threaded blind hole to attach the frame. Normally, I found, this blind threaded end is for a machine foot or rest, such that the weight of the machine is transmitted to the ground.

I decided to incorporate the potentiometer mount on the other side of the rubber bushing. The bottom plate that the sandwich mount is attached to has been split into two half-thickness plates. Only the top one extend back to form the potentiometer mount. This was to prevent a solid plate from interfering with the strain region of the load cell (denoted by the circle).

The potentiometer is not affixed solidly to the skateboard mount because loading potentiometers structurally is bad. In anticipation of some vertical deflection of the board when a rider is on it, I made the potentiometer interface a “nut and wrench” – the “wrench” portion is free to move towards or away from the “nut” while still transmitting rotation.  Before settling on this, I had such ridiculous ideas as putting the pot on the frame itself and coupling it to the hinge using a stiff rubber shaft, or even worse, electronically sensing the roll angle of the skateboard (again, with Segfault’s IMU).

There is actually nothing wrong with the latter idea.

The downside of all this is just that the hinge and load sensing elements stick out from the frame by alot. So, I’ll probably make some bumpers that mount to the front and rear skid plate things which extend forward and behind the load cells, such that they are not the first things to hit the ground when (not if) I fall off this thing. Bonuts points if I end up making it look like a ATV bush guard.

I’ll take the implementation of weight shift and roll sensing one at a time – I’ll probably hook up the roll sensing first, since that’s easier, and test the vehicle’s ability to sweep a more skateboard-like curve when the board is rolled appropriately. The load cells require amplifier circuitry that will need to be designed and appropriate instrumentation op-amps purchased for, so that is slightly further off.

oh, one more thing

This is that additional motivation I talked about.

Yes! As featured in the first I Take Something Apart and Take Pictures Of It, this is indeed the mysterious possible application for the HK car controllers.

I’m going to compromise with the original design goals a little and settle for running LBS on 6S A123 cells, the same voltage it’s running right now. This allows me to use the HK cartrollers (not to be confused with kartroller) in forward-with-brake mode with a return to brushless drive while keeping the top speed of about 15 miles per hour.

I got a chance to try out the “drag brake” feature of these controllers on nothing other than Straight RazEr, which was converted into a 6S test dummy for the purpose (among other more legitimate uses).

Conclusion: Straight RazEr is not waterproof.

I believe the drag brake (and variable dynamic braking in general) will have a huge impact on how well LBS handles on-road. The problem with the beast-it-trollers was that they had no capability of stopping the motor from turning if it was being externally driven. With the cartrollers, rolling the board can command a differential speed that may utilize the braking feature on one side to force it to slow down somewhat. If I’m crazy enough, I can even try implementing the reverse-with-delay mode to fix one last annoying problem with LBS – if you’re nosed into something, you can’t back up.

The drive motor shown is a Turnigy SK3, intended for the exceedingly tinyKart, but I’ll end up with a set of 63mm drive motors one way or another. Even though Hobbyking is still out of stock on practically all 63mm and larger motors, there’s two left over in my stable, two original SK motors from the current tinyKart I could borrow, or I could turn to shady sources for them.

RazEr rEVolution: Concrete-wheel-be-gone

Oct 19, 2011 in Project Build Reports, RazEr rEVolution

Continued from last time, I’ve finished installing the 5″ Colson wheels onto RazEr rEVolution.

This was how RazEr was meant to be. Seriously, why didn’t I just start it off with Colsons initially? While it’s still not as smooth over the average sidewalk seam as, say, a pneumatic tire, it is a marked improvement over my surplus forklift tires.

The story continues…

The first order of business after the can was completed was to install the magnets. Foreseeing another potential stray magnet spacer herding episode like the first build of the motor, I went ahead and cheated by 3d-printing a small magnet spacer thing. This must have saved at least an hour or two of diddling with little wooden sticks.

The magnets were first located using rubberized CA glue wicked into the gaps.

Next, I mixed up my favorite concoction of West System 105 epoxy with 109 hardener and a ton of phenolic fluff filler. The filler adds volume and thickness to the epoxy and prevents it from running everywhere.

Make-a-Bot has actually been instrumental in the creation of RazEr. Not only did it 3d print the entire front fork, but now it’s serving as a convenient epoxy curing oven. I set the head and platform temperature to about 50 celsius each, and left the can on it overnight. This temperature isn’t enough to damage the magnets, but ensures that the epoxy sets thoroughly.

Seriously, what did I do before this thing? It’s really in need of an update.

The next day, it was time to pop back over to the Edgerton Student Shop (where Nice Things exist) to make the internally threaded wheel locking ring. They had the only internal threading bar that I knew of…and that wasn’t broken.

This recent build should probably be entitled “Charles samples a different lathe on every part”: The machine of choice of the shop is the revered Monarch 10EE, the later type without the big round knob. It’s nice.

Maybe next time I’ll pop over to the CSAIL Machine Shop for their Hardinge HLV-H.

The internal threaded Ring of Wheel-Retaining.

I actually had to make this twice, too. For one reason or another, my motor can was turned on 22 threads per inch, not 24 like I thought. I might have just been off by one gear after looking at the selection grid from the wrong angle. Regardless, my x24 thread did not fit, so I had to cut off a chunk and start over with a x22.

And this is how it goes on.

This is actually the wrong direction – the correct direction is with the chamfer facing outwards away from the wheel. What I discovered, though, is that it will thread on just fine in this orientation, but can only make it 3 or 4 threads facing the other way before it just locks up solid. The threads are definitely not crossing, since the initial engagement is smooth and there’ no resistance for several turns. But then it suddenly becomes very high friction – not even thread lubrication helps, and I’ve definitely cleaned this thing 5 times over.

I made a thread diode. What the hell?

Oh well – another engineering pass in the form of “let’s just keep it this way” is pulled.

While reinstalling the stator, I lost control of it under the magnets’ massive pull and it ended up slamming into the far endcap, shearing 4 of 5 sensor wires. Fortunately, this happened at a point which was outside the motor, so I was able to quickly repair the broken wires.

Instead of fixing the can in a drill press vise and slowly lowering the stator into it using the quill, I just held the two. Maybe it worked for tiny motors, but it definitely does not work for a motor like this, and I could have sheared off a fingernail or broken a bone.

tl;dr don’t beast large motors by hand.

And the wheel reinstalled. Black and gray wheels coordinate with the color of the scooter better, IMO.

Pursuant to this, I stole the front wheel and fork off the temporarily defunct Straight RazEr. So here is the finished conversion, except still with its shady-e-bike-troller tumor since I have not gotten around to repairing the melontroller yet.