Return of the Snow Bike: It actually works now

It snowed rather a lot last Saturday, so I was finally motivated to get the snow bike up and running again.  Last episode, the rollers inside the treads kept jamming with snow.  I actually fixed this problem shortly after (almost a year ago now), but never quite got the electrical system to be solid.  The motor/controller was still plagued with position sensor errors, so the vehicle never lasted more than a couple minutes without breaking down.  For now, I've replaced the big 40V, 150A Kelly motor controller with a much more modest 50A sensorless e-bike controller borrowed from Dane.

Here it is wired-up and ready to go:

A closer look at the e-bike controller.  This is a 50V one Dane cracked open and modified the UVLO setpoint on:

Most of the streets were well-plowed by the time this thing got working, but fortunately someone had opened the gates to the courtyard of the Novartis building across the street from MITERS, and there was 6-8 inches of snow everywhere:

We also brought out the Atomic Thing and got to mess around on both vehicles for quite a while, until we got cold/were kicked out.

It's a bit underpowered right now - you end up holding the throttle all the way open the entire time, but still a good time.

Snow Bike Part 2: How Does Snow Work?

Snow Bike was more or less finished Saturday night, just in time for playing in several inches of snow before it all got plowed and salted.

Here's the motor mount, made from a couple more aluminum plates.

I cut a ski mount from a section of 3" square tubing, and pressed some brass bushings in.  The axle is a standard bike axle.  I have some long gas springs I might eventually add to the ski to return it to a neutral position, but haven't gotten around to that yet.

With seat and electronics.  The battery and motor controller are held by a bent polycarbonate shell which drapes over the frame.  I also added footpegs at the back.

I wired up all the electronics, only to find out that the hall sensors I had previously repaired the wires for were actually completely dead.  So I cracked the motor open again, and stuffed some new hall sensors in slots that weren't already filled with sensors and epoxy.

Bringing out in the snow immediately uncovered a problem.  The motor shaft was cut very short, and had two flats ground in it, so there was very little interference between my clamping motor sprocket and the shaft.  Any real torque, and the sprocket would slip off.  I thought about making a new shaft for the motor, but in the interest of time I first tried saving the situation with a giant set screw.  I drilled and tapped the sprocket-retaining shaft collar for a huge 1/4-20 set screw, and drilled a matching dimple in the end of the motor shaft, so there's both clamping action and positive interference holding the sprocket on.  Worst case, the shaft gets wrecked and I have to make a new one, but this was a last-ditch effort, so I don't mind that.

Second (and more fatal) problem was the shape of the track rollers.  The tracks would quickly get filled with snow, which was compacted by the rollers and clogged the teeth.  This stopped the track from engaging properly, and caused it to bind.  I think the answer is to just remove most of the width of the teeth, so that there's space between the teeth and the matching part of the track.  A bigger gap should make it much more difficult for snow to collect and jam things up.

Next time there's a good snow forecast, I'll fix the track roller problems and get this running again.

Emergency Snow Bike, Part 1

After the absurd amount of snow Massachusetts got last winter, I decided to prepare myself for the next winter by grabbing a pair of small snow blower treads on Ebay.  On Monday of this week, there were rumors of a foot of snow this coming weekend, so I decided to punt everything else for a few days, put the treads to use, and build an emergency snow vehicle.  Although the snow forecasts are no longer so exciting, at some point this winter it'll snow enough for some fun snow riding.

Here's the preview:

That's the frame from Herpybike, modified to accept a threadless mountain bike fork.  I removed the original 1" threaded fork, banged out the headset cups, and re-bored the head tube to accept the cups for a 1 1/8" headset.

For the tracks, I made a pair of track rollers from some scrap plastic.  The plastic centers are clamped by the original scooter wheel hubs, which conveniently already have axles and bearings.

The plastic bits were machined on the CNC mill, which was covered in lovely red and white confetti afterwards:

Here's the mostly-assembled track pod.  Two aluminum plates space the track rollers and allow the tread to be tensioned.  Don't worry, the wingnuts are temporary.

The fork is going to get a ski, and I'm temporarily borrowing the power system from Nick's old 2.007 vehicle, derpscooter.  I'm fixing the hall sensor wires, which managed to get caught in the rotor and shredded.

More to come soon.