More Power, Igor!

Apologies to the few readers here that I have yet to post pics of the fixed skate wheel solution. Laziness and being busy rebuilding the PWM controller with upgraded heatsinks and MOSFETs (100V/123A capable!) has kept me from sitting down and taking pics like I need to remember to do. I should have taken pics of *that* work, too, but I forgot. Have to do it when I go back to it and fix up some rough edges tomorrow evening, I hope.

Though it's been working ok with the radiator fan motors and skate wheels, I'm always looking to improve it. Preferably with slightly less crazy contraptions to drive it. :)

Pursuing that goal, I got a 10-year-old used Proforma 730si Treadmill today off of Freecycle, posted up as broken because it doesn't run, though it turns on, and the motor tested ok by the poster. Since all I *really* wanted was the motor (which I would never be able to buy even used, because they usually cost almost a couple hundred dollars!), that's fine by me. I had misunderstood exactly how big it was, and had biked out to the location to pick it up (stopping to pickup other Freecycle offers held for me along the way), only to discover it was far too big to fit in my trailer safely without completely disassembling it, which there simply was no way to do at the location (I had the tools, but would have had to do it in the street). So I gave in and called a friend with a large truck, and a couple days later when he was available, we picked it up and took it back to my place, where I took it apart to store the rest of it away for later salvage (or re-Freecycling), and pulled the 12lb+ motor.

FWIW, it looks like the AC-input rectifier bridge for the motor's PWM-style power supply has one branch cooked, with only 3 working diodes in it, which would explain why it's not getting enough power to run correctly--might've been an AC-line power surge that caused it. Doesn't matter for what I want to do with it, but satisfies my curiosity as to why it was not working (so I don't have to worry about the motor down the line).

It's a 120V *DC* motor, very powerful at that voltage (2.5HP continuous duty, 12Amp), but can be run at lower voltages--it just won't spin at the 7000RPM it was designed to run the treadmill with, which is fine by me. I tested it at 24VDC on my bike batteries, and I can't stop the motor shaft even with vise-grips. That ought to work out fine to drive the bike wheel, then. Probably not with skate wheels, though. :)

I do have to find a way to fix the shaft in place so I can unscrew the cast-metal (iron? soft steel? I can nick it with a file easily and it's highly magnetically responsive) flywheel from it--that may be half the weight (it's got to be at least 1/3). It used a belt drive with multiple small v-channels in parallel to drive the walking belt in the treadmill; I might be able to use that to drive my bike wheel, or at least as the first stage in the reduction from speed to torque that I might require. If so, I'll have to cut the drive sprocket for that belt off the flywheel after removing it from the motor, since it's not a separate piece, but is all cast as one part.

The matching wheel on the walking belt roller was easy to slide off, and is just cast plastic (dense, but light), with a core hole just about 1/2" larger in diameter than the bike's rearwheel hub bearing-holder section, inside the circle of spoke mount-holes, and about 1" wide. It'll just barely fit within the gap between the spoke-mount flange of the hub and the inside of the rear triangle frame, which means if I can bolt it to the hub/spokes I could drive the rear wheel by belt from the motor. Unfortunately that would require mounting the motor itself horizontally out from the left side of the bike in such a way and place as to be sticking out streetward it's entire length, about 10". That's not practical, both because it could hit or be hit by something, especially during a leaning-left-turn, and because it's difficult to support hanging out like that.

If I can find a longer belt than the very short one the treadmill uses, I could extend that out to where the motor could parallel the rearwheel axle but outside the diameter of the wheel itself, allowing it to be mounted across the centerline of the bike--for instance, under the seat, above or below the point the seat tube crosses the rear triangle frame. The lower, the better, as the center of gravity is best as low as possible with all that extra motor mass.

Now, since it's a 2.5CHP motor, technically it would be too much power to be legal for the bike. However, I'm not running it at even 1/4 of that power, so not even 1HP, which should be fine. It can take 12Amps of current, so a rough guesstimate is 12A x 24V = 288Watts. If I use 36V like my current motors do (which were designed for only 12V, and get to 153F after extended use at their axles!), then it's roughly 432Watts, continuous. Still well below the 750W legal limit (Federal, I think). And I could go up to as high as 72V and ensure it doesn't run it at 100% duty cycle, and it'd still be under that limit.

I'll know the actual power usages and drive capabilities in the next few days, as I test different schemes to drive the standing-test bike wheel, before I try to apply it to my (now working) Electricle™. In the meantime, I'll try to get pics of the various upgrades and fixes to the radiator-fan / skate wheel solution up here.