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Can you replace axle shaft?

Posted: Apr 06 2021 3:38pm
by powrtrip
Have a customer bike that spun a few times and now the axle shafts are stripped badly.

Bafang 750 watt geared rear hub...
Anyone press out or remove and replace axle shafts in these?
IMG_20210403_121935753.jpg
IMG_20210403_121935753.jpg (793.61 KiB) Viewed 184 times

Re: Can you replace axle shaft?

Posted: Apr 06 2021 8:03pm
by motomech
On that motor, it's a one piece axle and to get it out a gear puller is used, but it's very difficult and might require heat.
There are dis-assemble vids, but few go that far.
There's one on the net where a member here, spinningmagnets took an Ezee geared motor apart(he may chime in).
But it's probably moot, as I doubt a new axle is available. If you had it in your hand, I guess a machinist could weld it up and cut new threads, but at that point, it would be less expensive to buy a new motor.
If it is replaced w/ the same motor, the cores could be swapped out, saving the trouble of relacing the whl.

Re: Can you replace axle shaft?

Posted: Apr 07 2021 2:14am
by amberwolf
Since the bike's dropouts are damaged from the axle spinning out, you'd be better off to install clamping dropout torque plates on both sides, than to change the axle. Then you won't even need the axle nuts, because the dropout clamps will hold the flats and prevent any movement. ;)

Note that a clamping dropout torque plate is NOT just a torque arm. If you look thru the Torque Arm Picture Thread you'll see pictures of both types.

Also, you'll probably have to re-cable the motor anyway, replacing the phase/hall wiring cable starting from inside the motor, to ensure there are no damaged wires inside the twisted motor wire cable. Even if there is no apparent damage externally, there could be inside the cable housing, even the part inside the axle itself, and if the insulation between any pair of wires in there fails from that, it could damage the motor (halls) and / or the controller (fets, mcu, power supply, etc).

Re: Can you replace axle shaft?

Posted: Apr 12 2021 5:30pm
by powrtrip
Thanks for the reply.... I am going to build torque plates for it. I kinda figured it's a replace not repair..

Thanks again!
Darren
motomech wrote:
Apr 06 2021 8:03pm
On that motor, it's a one piece axle and to get it out a gear puller is used, but it's very difficult and might require heat.
There are dis-assemble vids, but few go that far.
There's one on the net where a member here, spinningmagnets took an Ezee geared motor apart(he may chime in).
But it's probably moot, as I doubt a new axle is available. If you had it in your hand, I guess a machinist could weld it up and cut new threads, but at that point, it would be less expensive to buy a new motor.
If it is replaced w/ the same motor, the cores could be swapped out, saving the trouble of relacing the whl.

Re: Can you replace axle shaft?

Posted: Apr 12 2021 5:33pm
by powrtrip
Ya, it's on a nice FLX bike. He wants to fix and sell.
I don't want to do a patch up job, but I have to keep money in mind too.....

I will make some nice clamping plates and replace the cable and call it a day..

Thank you mucho!!
Darren
Powrtrip Cycles Boston
amberwolf wrote:
Apr 07 2021 2:14am
Since the bike's dropouts are damaged from the axle spinning out, you'd be better off to install clamping dropout torque plates on both sides, than to change the axle. Then you won't even need the axle nuts, because the dropout clamps will hold the flats and prevent any movement. ;)

Note that a clamping dropout torque plate is NOT just a torque arm. If you look thru the Torque Arm Picture Thread you'll see pictures of both types.

Also, you'll probably have to re-cable the motor anyway, replacing the phase/hall wiring cable starting from inside the motor, to ensure there are no damaged wires inside the twisted motor wire cable. Even if there is no apparent damage externally, there could be inside the cable housing, even the part inside the axle itself, and if the insulation between any pair of wires in there fails from that, it could damage the motor (halls) and / or the controller (fets, mcu, power supply, etc).