Wisper 905 motor cable repair

[Kabadi]

I took off my back wheel today to replace the tyre and noticed a problem with the motor cable where it enters the spindle.

On the freewheel side (where the cable goes in) I removed the rubber boot from the spindle nut and there is a sort of spring/coil thing on the outside of the cable (to protect it I assume) but it was pulled apart at the point the cable comes out of the spindle.

On closer inspection, the cable outer (under the spring thing) was also damaged. On even closer inspection, one of the eight wires was damaged. (the thin red one)

Under a magnifier, it looks like the wire is hanging on by one or two threads. Also I can see evidence of shorting. There is some very small 'balls' in the broken strands of the cable that look like they have shorted and melted.

I have no problem repairing cables but this is in the worst possible place.

Does anyone know if I remove the freewheel, will I be able to remove the long spindle to get better access to the cable for a repair?

 

[Kabadi]

Here is a photo to explain better

 

[Mussels]

Ouch, that looks bad. I haven't dismantled the motor myself but there have been posts on here about it, you may find what you need using search.

 

[flecc]

This has always been a problem with the Bafang spindle cable entry motors, any knock on the spiral protector can shear a cable and cause a short and I've no doubt that's what has happened here. The cable has 8 wires in all, 3 thick phase wires and it's one of those which has become exposed, and 5 thin sensor wires. The cable is sealed into the spindle with silicone rubber and emerges from a slot in the spindle just inside the side cover, and you can see the slot in this photo:

It's not easy to replace since it means remaking all the connections into the stator windings and Hall sensors which are embedded in the stator rim, and the sealing into the spindle makes it difficult to remove. If you were to attempt it you'd need the right sort of multi cable, but the best solution is probably a whole motor insert which could be taken from a replacement complete motor. Best have a word with Wisper to see what they can offer in the way of replacements, these motors are not a kings ransom to buy.
.

 

[Kabadi]

Thanks for the advice.

I expect the photo makes it look like these are the thick wires but they are the thin ones (which you say are for sensors)

Any idea what this thin red wire does? I guess it is bad that it is broken as it must serve a purpose.

 

[Wisper Bikes]

Cable

That looks nasty!

Give Norman a shout on Service@WisperBikes.com send him the image and I am sure he will be able to help (tell him I asked you to write to him or he may refer you back to your dealer).

How old is your bike?

Regards David

 

[Kabadi]

Ok, I'll contact him. Thanks.

I bought my bike about 6 months ago

 

[flecc]

The sensor wires connect the Hall sensors which send the rotor position information to the controller. If one becomes completely disconnected the motor "misfires" very noisily and can want to shake itself to bits. They carry very little current though, so as long as a single strand is intact there's no problem. This raises the possibility that if you could get that re-insulated and protected against further twisting/shearing damage you'd be ok.

Exactly which terminal of a sensor the red one applies to I can't say since the colour coding on these Bafang motors does vary. A sensor wire is easier than a phase wire to connect to the sensor at the internal join though, the diffculty being getting one fed through the spindle.
.

 

[Andrew harvey]

On the motors I've used the 5 sensor wires are split,
red .......positive (supply to the sensors )
black.....negative (again supply to the sensors )
blue......sensor output
yellow....sensor out put
green.....sensor output,.

If the red wire breaks completely you have had it without stripping the motor.
It is possible to pull the cables back into the housing and re-soldier all the connections, but it's a bit fiddly.
An alternative might be to pull the spring out, twist the cables so you have good access and attempt to re-soldier the red in situ, could be even more fiddly.
Other wise just epoxy the whole lot, a nice hard resin should insulate the cable and prevent further damage for the moment, but it might make it difficult to repair again later on.
If your confident you can make a nice neat job of cutting the cable, pushing it back into the motor and re-soldiering, (remember you have to dress all the wires back into the loom around the motor so they don't rub against the shell ), it is possible.
I've done this several times myself, it takes about an hour the first time, if you have all the little bits of heat shrink to hand to insulate the joints.

 

[Wisper Bikes]

Ok, I'll contact him. Thanks.

I bought my bike about 6 months ago

Thanks Kabadi

Have you managed to speak to Norman yet? The bike is obviously still under warrantee.

May I ask where you bought the bike?

Best regards David

 

[Kabadi]

Yes I have contacted Norman. He says that realistically I would need a new motor.

I bought my bike from Bristol (atmosphere bikes)

 

[Sir_Bob]

HI KAbadi

maybe you turn your handlebar to much.
do you have many corners on your root.

thc

bob

 

[Kabadi]

It took me a few seconds to understand why that would make any difference.

I guess you thought it was a front hub?

It is a rear one.

 

[Kabadi]

Well I have carefully put the cable back together and put extra heatsink around it. Also I have moved the connector around under the controller so I have more slack in the cable to the rear hub. This means the cable can now come straight out of the hub spindle without being strained on the sharp edges of the spindle.

I think it is working. It does make a noise when under strain (i.e. just starting off from stationary) but that goes away when I get some decent speed going.

One of the earlier posters suggested the motor would almost shake itself to bits if the wire was broken so I guess the wire is still holding on by the single thread still.

I did get offered a discount on a new motor by wisper (not a warranty replacement though). Does anyone think I should get the new motor or just carry on?

 

[flecc]

I think it is working. It does make a noise when under strain (i.e. just starting off from stationary) but that goes away when I get some decent speed going.

One of the earlier posters suggested the motor would almost shake itself to bits if the wire was broken so I guess the wire is still holding on by the single thread still.

A broken Hall sensor wire, depending which one, can result in violent jerkiness, a milder form of that or even failure. Since yours was almost certainly the positive feed for the sensors, it will be connecting ok since the motor couldn't run otherwise. It's normal for these Bafang motors to make quite a lot of noise when pulling away from low revs, but if it's performance is otherwise normal, I'd just carry on with it. Obviously you'll need to ensure the cable is well supported and not stressed at any future time.
.

 

[Wisper Bikes]

Motor

Hi Kabadi

How did the damage occur? Was the bike dropped?

All the best David

 

[Kabadi]

No, I've never dropped the bike. And anyway, it has a guard fitted to protect the derailleur which by consequence would have protected this electrical cable.

To be honest I have no idea. It could have been like it since the day I bought the bike for all I know, as this is the first time I have removed the plastic/rubber boot which goes over the rear wheel spindle nut and it is only when that was removed, that the damage, both to the spring/coil protector and the cable, can be seen.

Right now it appears to be working, and as per fleccs advice, I must have managed to reassemble it without breaking the last strand. I am however worried that it could break without notice at any time.

 

[Wisper Bikes]

Working

Hi Kabadi

I am delighted to read that all seems to be well again.

If you have further issues I am sure we can look at sorting this out under warrantee.

All the best David

 

[Kabadi]

Thanks David.

I would like to say how impressed I am with the response of Wisper to issues raised. I have experienced this myself and have seen it for others on the forum.

I am delighted with my 905, and although I have had a couple of problems, Wisper have always been ready and willing to help above and beyond.

I would (and have) recomend a wisper bike to anyone.

 

[the_killjoy]

i think that wisper have been very brave to keep their head(s) above the parapet and stay on the forum rather than setting up their only online Q&A.

Whilst it means we as owners get to hear about the problems we also see the response.