Re: Broken axle

Posted by Fish'n Jim On 2018/4/11 20:42:09

Show the other side of the nut where the stub is (or broken end of shaft). If it has a flatish wavey crescent part ending in a reduced diameter fracture crater(grainy), then it's fatigue failure. Fatigue is failure due to cyclic stress, from dynamic forces, in this case, being out of balance, bending, or "wobbling" on a small scale.
I'm not real sure what is meant by and what evidence for installing the bearing "backward"? That would make it real interesting to get it back on or race in? Think about it. It equally might just be the wrong bearing or a poor quality? No photographic evidence is given there.
I'd bet(heavily) there's other problems going on there, such as bearing failure due to above or loss of seal and loss of lube issues, axle came loose, etc.. Wheel badly out of balance and driven at high speed. I think if it was loose enough to "break off" someone would have known of the problem and did not take action for a while. This did not happen in two revolutions. It could also just be end of life. Mileage is not given. If it's very high, fatigue failure is more likely -> Weibull.

Think about it:
That's a castle nut with a cotter pin, so it's only going to go on so tight to fit the pin. It would have to have the wrong/worn shim washer to be loose". A squeezed out film of grease would not cause it to be "loose". Every greased bearing runs that way. I'd relegate that hypothesis to the hearsay pile or every front wheel spindle today would be shearing off regularly.
But diagnosing from the internet is by definition hearsay - lacks direct/complete evidence and relies on opinions or analogy mostly. I'd much rather see a good/complete investigation presented and show the results, than this type of open question.
Conversely, one could equally argue it be due to over-tightened, shim washer too large, as that will stretch the threads which leads to cracking and compresses the bearings causing lube issues. Threads are by design stress concentrators.