Friday, 12 July 2013

Replacing the motor

But first, some essential maintenance on bike.2 (the one I'm currently using).

I noticed that the bracket that supports the battery, is tearing apart. It's made of pretty heavy steel so as to support a heavy battery, but it's looking like it could fall apart completely any time, and I do not want that to happen when I'm in the middle of a field in the middle of nowhere..

Fortunately, I have a spare bracket, salvaged from the small-wheel bike that fell apart while I was riding it (more precisely, it fell apart while I was stationary, which was lucky for me; the frame just cracked). So I took the old bracket off, and installed the spare, which involved some soldering, and replacing a bolt that sheared when I tightened it too much, and I took it all out for a quick test ride and it's working fine.

So now to bike.1, which is the bike where the motor failed. Currently, bike.1 has the Chinese wheel, but when I apply full throttle from start, the battery cuts out, which is annoying. I'm still hoping to fix that, but as a backup plan, I'm wondering about repairing the old wheel.

I have an electric bike, called bike.1, with a front wheel with a motor that doesn't work (and worn bearings). I have a new motor  (which has new bearings). So I need to install the new motor in the old wheel.

I called a couple of bike shops, to see if they'd do it for me; I'm looking at £50. In the context of a tankful of petrol being £80, that's not a lot. But I started to wonder - can I do this myself?

I started off by removing the spokes. There's 36 of them. I used a spoke wrench to start the nipple loosening, my fingers to unscrew them some more, and finally a screwdriver to unscrew the nipple completely from the spoke. Some of the nipples wound up inside the wheel rim; vigorous and repeated shaking got them out.

Then I put the motor on my workbench, with the wheel rim around it, and started to install the 36 spokes. There's a pattern to follow; I didn't research the reason for this pattern, but I'm thinking that it spreads the load, and I just used the same pattern.

Getting the nipple started on the spoke was difficult for this rim, because the nipple is in a recess. So I put a strong magnet on a screwdriver, and used that to hold the nipple so that I could get the spoke started. Eventually, I had all 36 connected. And an extremely wobbly wheel, because I hadn't tightened them up yet.

Next, I tightened the spokes, just using my fingers, so there's no real tension on the spokes.Then I rotated the wheel. There's a slight wobble from side to side, and a slight up-and-down. I expected this - my next task will be to true the wheel. I've read some articles on this on the web, and I think I know how to do it. A truing stand would be ideal, but the general opinion seems to be that you can do it on an upturned bike, and that's what I'm going to use; a good truing stand is about £100, and the one you can get for £34 is very like an upside down bike.

So tomorrow will be wheel truing day.

1 comment:

  1. Well thanks for that. I always just got on my bike and rode. But then I dont do the mileage you do. I glanced over the article and thought, I could do this on the kids' bikes for fun just to see how it works.

    Can you do an article on replacing a rear giro BMX brake cable in your next edition, as that's my next task.