__Fitting the motor__
This was by far the trickiest bit of the build process. I got the motor already built into a wheel, and the build quality was OK, nothing special. The spokes were very loose compared to what you'd get from a proper bike shop. Being quite light, I'm not too hard on spokes (i.e. have never broken one in many years of cycling) so I figured it would be fine. I will probably tighten up the spokes in the future when I get the right tool.
I took the cassette off the donor bike rear wheel and fitted it to the motor wheel. My first mistake was that I had the kind of cassette lockring removal tool that has the pin in the middle, which was fine for getting it off the donor wheel (which had a hollow quick release axle) but obviously didn't fit on the motor wheel with its solid axle. A bit of "modification" of the tool with a hacksaw fixed it, but if you're buying one for this purpose get the one that looks like this:
https://www.amazon.co.uk/Silverline-240618-Cassette-Lockring-Removal/dp/B00J3AA4NQ/ref=sr_1_3?ie=UTF8&qid=1506455589&sr=8-3&keywords=cassette+lockring+removal+tool
I then took the disc rotor off the donor wheel and put it on the motor wheel. When I fitted the wheel into the dropouts, the casing of the motor hub was hitting the brake caliper. So I had to take the old 160mm rotor off, fit a new 180mm rotor, and fit a 180mm adapter to the frame to move the caliper further away from the hub. If you're planning a build like this, I suggest you plan to fit a 180mm rotor if the bike doesn't already have one. There are various other ways round the problem like filing down the caliper or fitting a low profile caliper, but changing the rotor size was easy and fixed the problem completely.
Once I had the wheel sitting in the dropouts I noticed that they were a bit shallow and the axle was not sitting fully in them, so I filed the dropouts a bit with a round file.
I noticed that the torque nuts supplied with the motor were nowhere near engaging with the dropouts - the dropouts were just too shallow. Filing them deep enough to allow the torque nuts to engage would have involved removing a load of material and leaving the dropout area of the frame very thin, so I just decided not to use the torque nuts and build a torque arm instead.
I tried a few different torque arms until I found one that fit in a good position. I then measured the distance from the fixing hole in the torque arm to the closest brake caliper mouting hole, then drilled a 6mm hole in the right place in the second bit of the torque arm. Hopefully this photo of the non-drive side makes it clearer:
I ended up having to use a longer M6 bolt to secure the second bit of the torque arm to the caliper mount. The bolt goes through the torque arm, then through a few washers to make it the correct distance from the frame, then through the caliper mounting hole on the frame and into the threads on the caliper adapter. As you can see in the photo, my torque arm isn't the neatest - there is a stray hole from a previous fitting attempt, and I should probably remove the unneeded bit at the end.
In the picture you can also see the stays for a mudguard, which I fitted at the same time I put the wheel on. The mounting hole for the mudguard stay is directly behind the torque arm, but I just sandwhiched the stay between the frame and the torque arm and the friction was enough to hold it in place nicely.
Here's a photo of the non-drive side from above:
Starting at the hub, it goes:
- washer
- dropout
- spacer
- torque arm
- axle nut
- black plastic cover
For completeness sake, here's the drive side:
nothing very interesting going on here. From the hub it goes:
- washer
- dropout
- axle nut
I fitted the motor so that the cable emerges from the axle pointing down, which I think should make water less likely to run into the end of the motor.
Tip: during the process of fitting the wheel I probably put it in and out of the dropouts dozens of times, so I removed the rear derailleur during fitting so that it was easier to just drop it in.
