Bafang BPM front hub motor cable replacement part 2

As mentioned previously I used the existing cable – just shortening it a bit. The remaining length is ok and I didn’t need to get a cable through the axle from scratch.

I carefully drew a diagram of the colours of the wires and reconnected the new ends to the correct colour. The soldered joints were covered in heat shrink and self-almalgamating tape.

I didn’t use any glue, putty or sealant. I reused the existing wire ties and added another around the omega clip.

Recut wire soldered in

Note that the wire exits the axle inside the motor on the same side as the aperture on the end of the axle. This means that if the aperture on the end faces downwards, and any water gets into the axle, it will drain into the motor. Whereas if the aperture on the end faces upwards then water cannot get out of the axle into the motor.

Aperture on the end matches the wire exit in the middle of the axle

Thus the aperture on the end of the axle must face upwards when fitted to the bike.

I also fitted heat-shrink to the wire in an effort to protect the wire where it exits the end of the axle. With a bit of jiggling I got the heat shrink into the axle end.

Yellow reminds me to avoid catching the wire and also matches the bike!

The next step was refitting the stator to the motor casing. I hadn’t thought about this much, but it soon proved tricky as the magnets pull the stator to one side making it hard to get the bearings aligned. I also realised (a bit slow but not too late) that if they did align the magnets would pull everything together fast enough to break something – either the motor or my fingers!

So I refitted the puller and that helped a lot. It allowed me to locate the stator well enough to jiggle the bearings into alignment, then slowly allow the stator back into the motor casing.

Refitting the stator into the motor casing with the puller

Once that was done I could remove the sun gear, refit the circlip and refit the sun gear.

Circlip fitted
Refitting sun gear
Key refitted
Planetery gears fitted
Shims fitted
Fitted to bike, with extra self-amalgamating tape to stop water ingress

When I tested it I got a nice whirring sound indicating the motor was turning – great! Unfortunately the wheel didn’t rotate. Not so good. I figured out this was because, despite my care, I had mixed up a couple of wires and the motor was running backwards. I really didn’t want to have to do the whole job again.

Fortunately the cable to the motor has a section with bullet connectors. I swapped a couple over and success – the motor works! Phew. Job done.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.