Bent bafang rear axle ?

[PetriK]

Finally got the bike running and made a short trip (8km) in -15C weather. On the way back noticed that there was a problem to start the motor on the way back and keep it running. Got a really bad noise, almost like brakeing a gear - but believe that this was due to a loose motor phase wire connector. Anyway when doing a closer inspection noticed some wobbling between the hub and sprocket. Got really worried if my axle is bent ?

Anyone with more experience with rear hub motors, I would appreciate your feedback to the video below. You can see how the freewheel sprocket distance to hub motor is not stable - rather its moving all the time a couple of millimeters. I did have some problems in installig the freewheel pack, but dont understand how it could be that as the movement of the freewheel pack in relation to the hub motor is so slow.

[youtube]http://www.youtube.com/watch?v=UHiPlh2XOTQ[/youtube]
http://www.youtube.com/watch?v=UHiPlh2XOTQ

Btw - in Xie Chang programming software there is a bug, it will loose information if 120% speed is used. And the Xie-Chang controller with Bafang confirms the rule: Blue stays, Green and Yellow needs to be changed both as sensor and motor wires. As stock the Xie-Chang controller comes without sensor jumper wire configured. That took some time for me to figure out that it needs to be added to the PCB. The autopilot for speed is handy, but unfortunately only works with throttle - not with pedelec sensor, so it kind of locks the hal throttle signal to a position and keeps until brake lever is depressed or throttle is adjusted. Very handy controller with a lot of versatility.

The bike itself is otherwise nothing special, a kona with banfanfg, 36V10Ah battery and Xie-Chang programmable controller.

 

[Rassy]

PetriK, Your axle doen't turn, so that wobble is not caused by a bent axle. It is probably just a little play in your freewheel pack, and I would guess not a problem. You are probably right about the noise being a loose wire problem. I had a similar problem on a Bafang and only got it fixed by eliminating all the connectors on the phase wires. There was apparently some flaw in one or more of those little connectors that I just couldn't make a good consistent contact. Good luck sorting it out.

 

[FMB42]

Sounds like you might have problem with your freewheel sprocket and/or the freewheel threads...

 

[PetriK]

OK - thanks. I did initially misthreaded the freewheel sprocket set when installing - so sounds like I need a new motor, repairing the threading is not really possible.

Did a testride today, the intermittent "crunching" sound from the motor was indeed a loose connector as today the bike was running just fine.

 

[DAND214]

Many of the hub motors have the same problem. I know there is wobble in most of my hubs. Cheap hub motors with good or cheap freewheels all seem to have some runout at the small sprocket.
I wouldn't worry about it if the chain stays on, just ride it.
Dan

 

[FMB42]

OK - thanks. I did initially misthreaded the freewheel sprocket set when installing - so sounds like I need a new motor, repairing the threading is not really possible.

This is very easy to do...

A slight "wobble" in the freewheel is not all that uncommon (as DandD mentions).

Here's a link with some info on this issue:

http://www.bikeforums.net/archive/index.php/t-175006.html

And here's a link to a good bicycle technical reference/info guide (courtesy of the late great Sheldon Brown):

http://www.sheldonbrown.com/

SB's freewheel technical section can be found here:

http://www.sheldonbrown.com/freewheels.html

BTW, that's a great looking e build you've got there...I especially like your battery and battery mounting position! Gonna have to think about doing the same on my similar FS MTB build...