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Monday, September 21, 2009

550 Miles Coming Up, Motor Changeout

I passed 500 miles sometime in the last week or so I think, and am now nearly at 550. That's the total miles on the whole bike/frame/etc, even though some parts have changed at various points in there. Here's to hoping it lasts at least that amount again, since it is taking far longer to get to the trike than I had expected.

Since I now have bolts that will secure the 4-pole motor in place, and the heat-damaged 2-pole motor gives me a good reason to swap it out, I'm going to try to do it this week, since I only work two days :( and packing/sorting is driving me crazy and depressing me too much to keep at it for more than short bursts before I have to do something else for a bit, then go back to it.

First I have to make a wedge-shaped box or plate to go between the new gearbox and the motor mounting plate on the frame, because the 4-pole motor has an angled top, plus a longer motor cylinder, which combine to mean that even with the cylinder touching the BB between the pedals, and the gearbox as far forward as possible without it's output shaft conflicting with the cranks' rotation, there's still a wedge-shaped gap between the gearbox's top and that mounting plate.

I'll be working on two ideas for making the wedge. One will just be wood to test the angle and see if that is sufficient, and if it holds up to tests without crushing/splintering or working loose from vibration/compression, I will just leave it. The other, if the wood isn't sufficient but does work, will be some steel plate welded into a wedge-shaped box, with reinforcement ridges inside next to the bolts, diagonally (making the interior an octagon).

The chainline shouldn't change more than a couple of millimeters laterally if I measured it correctly, so it should stay tracking fine once I put it under tension and tighten down the motor mounts.

Since it is a faster output gearbox, it'll use a smaller output sprocket on it's shaft, a 21T. This should keep the max output speed still down around something sane for pedalling along with it (since they're still linked, as I have not yet completed that sprocket adapter disc to then hook to the pedal freewheel and try it out).

I should get around the same final speed, but it should be able to handle a LOT more mass and accelerate a lot quicker (at the cost of using more power all the time, because it is 4-pole instead of 2-pole). Theoretically, it makes hill-climbing at speed much easier, but mostly it will make hauling cargo easier (especially if I carry extra batteries on the trailer).

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