Snapped axle on Crystalyte TC100 hub motor, almost died

[madin88]

However, undertightening (so you get the axle moving back and forth slightly every regen/accel cycle) can be worse.

1) You are loosening the nut a little every time, so you have to keep tightening it daily.
2) Every time it hits its limits it wears the contact point a little more. Wear it enough and it will cam out.

You must be aware that it works like this:

If the axle nut is loose or just tightened a little bit, then for instance the axle would be able to transfer an alternating torque of 200Nm.
Now if you tight the nut as hard as usually those M14 or M16 threads needs to be tightened, then the maximum torque you can transfer over the axle WILL BE WAY LOWER as the 200Nm from before.

If there is some play in the dropouts, it will not help much if you further tight the axle nut. It will always move back and forth no matter how hard you tight it because to motor has simply to much torque.
What you should do instead is removing the play by adding thin metal sheets, or rebuild the dropouts (a clamping with two bolts would be optimal).

@ chalo

yes you are right that this axle is way to weak for the torque the motor can produce.
it probably had been abused too with that big 280A controller , but nonetheless there is a weak point where it broke because of the bore for the wire.

 

[SirLongAss]

I don't think that's true at all. I work on all kinds of rusty bikes with all kinds of high mileage, and rust has not caused them to break. This is the consequence of bad, lazy, cheapskate design and poor manufacturing, and nothing else.

Rust makes fasteners stick, sometime permanently. It's ugly, and it can abrade moving parts. But rust doesn't get inside a metal part unless that part is cracked. This part cracked because it sucked, not because it had rust on it.

I definitely agree with you that it is a poor design/bad manufacturing. My point was there are teltale sighs of metal fatigue(hairline cracks, buckling ect) and not that the rust caused the axle to snap, but rather I'd be suspicious because I can't see what's going on underneath.

 

[fechter]

Rust can be a contributing factor, especially if there is some salt present. If the stresses on the metal were reduced, it would be less of a factor.

https://en.wikipedia.org/wiki/Stress_corrosion_cracking

 

[neptronix]

I'd say you needed torque arms, but that wasn't the problem here. It was crystalyte's axles and/or rust 'n crap, and/or you were running insanely high power levels perhaps ( ? )

You know, i've seen people have issues with snapped Crystalyte axles since the HS35 hit the scene. I wonder if they are still using swiss cheese metal even on the crown versions.

I've seen much cheaper motors with better axles than this.

 

[APL]

I have to say also, hub motor axle design isn't the greatest. Clearly, they machined part of the axle away to
run wires through,..not good. Then there was no concern for champhering the transition to the axle. Another
mistake. Always provide a radius. Also, these axles are not made of chromo, but soft steel. And lastly, I have
never seen any info on torque specs. for the large Crystalyte axle nuts.

A solid chromo through axle would be a much better system.

Hub motors work well on simple bikes, although just barley. The whole system is really for the convenience
of being able to just slip a wheel in, and boom, you have an electric bike. Now the industry is happy.

But the motor is lugged, which is inefficient, all the torque is on the axle flats, and the rear wheel gets pounded
like a sledge hammer.

Anyway, I wish I could be constructive, and offer a solution, but in this bikes current form, and weight, that axle
system is not sufficient. Perhaps another motor type, as has been suggested.

 

[Jg33]

Hey are you selling the hub motor?

 

[APL]

https://endless-sphere.com/forums/viewtopic.php?t=34817

Information on replacing the axle. It can be pressed out, but you'll have to make one, or have one made
at a machine shop. FYI.