Hub motor axle removal

NStone775

100 µW
Joined
Jul 30, 2019
Messages
7
I've got a cheap Chinese mfg'd hub motor (approx 750w) that I'm trying to salvage, which came out of a Wave brand ebike. Someone cut the axle to remove it. I plan to either attempt a repair or cut a new one on my lathe but im having difficulty removing it and I'm wondering if anyone is familiar w how these are constructed. There appears to be a keyway & there was a C-clip where the axle enters the bushing on the stamped sheet hub. I've got it on a 6" 3jaw puller & it won't budge.
Are these things commonly welded together? Or is it possible to remove the axle?

20221001_132700.jpg

20221001_132645.jpg
 
Might be a tapered or press(interference) fit

https://everipedia.org/wiki/lang_en/Interference_fit

You will have to figure out if it is tapered.

Pull the wires out of the axle pass-through, heat the spider and hub section to 300-400F, trying to keep heat off the axle(and windings) then press out.

You would be amazed what difference a couple ten thousandths makes from thermal expansion/contraction.

When I was rebuilding motorcycle transmissions with my dad, we would place the empty cast aluminum split cases in the oven(when mom was out running errands :lol: ) at 400F-ish, some of the bearings would just fall out of the case.
 
Looks to me like the axle is a press fit like on most direct drive hub motors. I would just remove the wires and then press the axle out on a hydraulic press.
 
Just to clarify there's clearly a bushing machine welded onto the hub. That bushing is fixed, but it seems the axle may be pressed into that bushing. On one side (2nd pic) the axle clearly looks removable (c clip, key, small gap where it meets the bushing) but on the other side it almost looks like one piece. So perhaps it is tapered or an interference fit.

From a mfg perspective I'd think they'd weld in a bushing, bore it out on a lathe & press in an axle. That seems the most practical route to guarantee concentricity & not mess up the flux gap... but im no process engineer, so who knows.

Regardless, thanks for the suggestions & sanity check!... looks like I'll continue down this path but move up to the 20-ton press and/or heat.

Unless it wouldn't b that hard to just weld on a stub, turn it down, and thread it. Iirc, there's alot of issues w that route with losing hardening/weldability/machinability.
 
NStone775 said:
Just to clarify there's clearly a bushing machine welded onto the hub. That bushing is fixed, but it seems the axle may be pressed into that bushing. On one side (2nd pic) the axle clearly looks removable (c clip, key, small gap where it meets the bushing) but on the other side it almost looks like one piece. So perhaps it is tapered or an interference fit.

The bolded above is highly likely; it's a typical way to do this, with the key being a primary torque-transfer mechanism. The axle would enter from the side opposite the c-clip.



Regardless, thanks for the suggestions & sanity check!... looks like I'll continue down this path but move up to the 20-ton press and/or heat.
Heat first.

Alternately, if that doesn't work and you have the means, you could freeze the whole assembly first, then apply heat rapidly to the stator support area including the welded-on bushing. That makes the axle contract and the rest expand, increasing the size difference and making it easier to remove.

Installing the new axle can be done by freezing it first, and heating the other, then doing the press-install (keeping keyway lined up for key insertion, if key isn't already insertable during install).
Unless it wouldn't b that hard to just weld on a stub, turn it down, and thread it. Iirc, there's alot of issues w that route with losing hardening/weldability/machinability.
The main issue with welding onto the existing axle (having done this to repair a few broken ones :lol: ) is keeping welding spatter/etc out of the rest of the motor, and keeping the new part aligned completely with the old one so it's straight, including as it cools down.

Sucks to have a warped axle that won't let the wheel sit straight in the frame. ;)

The last bit wouldn't be an issue if you're turning it down after the install, but if you do what I did and just put a new threaded part on....
 
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