Front axle snap, design flaw?

[Fredde N]

Originally Posted by lankydoug

I looks like it's been cracked for a while but still should have never cracked. If you had the wheel off 20 hrs ago you should have been able to see the crack.

Well, i guess i have had to wheels off 5-6 times during this time, because i switch between racing and practice wheels/tires, but i haven?t notice this. I ordered a new axle yesterday and i think i will put a small innertube/pipe that goes beyond this point on the new axle.

I don?t want to crash like this again because of this. When we picked up the bike the day after, i have had 4th gear in...

[mrkartoom]

This is something you certainly don't see everyday and I'm not sure you'd ever notice it unless you were looking very closely. It does look like it had a crack previously (possible very small) and finally broke. Whether that crack was from fatigue, a flaw in design or machining, or something else I guess remains to be determined. Regardless I will certainly inspect mine as well and do some measurements when I have it off. If that section is as thin as your measurements indicate then I'd be a bit concerned as well. I'd think a piece of stock the exact thickness tacked across that area as you mention would be one good way to beef it up. I had a local welder do the same for the kickstand on my husky after a section was added in the middle to lengthen it.

[bukwheat]

Originally Posted by Fredde N

Well, i guess i have had to wheels off 5-6 times during this time, because i switch between racing and practice wheels/tires, but i haven?t notice this. I ordered a new axle yesterday and i think i will put a small innertube/pipe that goes beyond this point on the new axle.

I don?t want to crash like this again because of this. When we picked up the bike the day after, i have had 4th gear in...

4th gear! Yeow! Hope you didn't get hurt....

Even having the wheel off as many times as you have, I'm not surprised you didn't notice it, I mean, how many times do you hear of an axle failing.

[bergerhag]

Looking at Fredde's pictures and using an image editor to do a few measurements, it still looks like material thickness is in the 1 mm range. I am not going to take the risk on using this axle. The 450 is gonna be an axle donor, and I am gonna cut my axle in half. I'll get back with pictures.

[GMP]

In the quest for light weight, we sometimes bump the limit of durability, and the weight/cost/MTBF ratio has to be fine tuned. A 250F is a perfect example. This is not neccessarily from a design standpoint alone, but from mfg and material tolerances being much less forgiving. Anyway, I'm not going to worry about it unless Nambo and Ivan start having issues. 4th gear? Wasn't a hard landing over a double was it?

[Fredde N]

Originally Posted by bukwheat

4th gear! Yeow! Hope you didn't get hurt....

Even having the wheel off as many times as you have, I'm not surprised you didn't notice it, I mean, how many times do you hear of an axle failing.

I did get hurt. Dislocated left shoulder and landed with the right upper leg (muscles) on a rock, the shoulder is ok, i got it back by myself the first thing i did after crash (its not the first time it happens), but my leg still hurts in the muscles. I?m planning on riding this weekend if i only get the new axle.

Bergerhag:I saw you were going to Hammarstrand, i can send the axle with some guys from Ume?, so can you inspect it more closely when u get back home, if u want.

[bergerhag]

Thank you Fredde, but it wont be necessary. I have cut mine in two.
If it was a mounting bracket for the exhaust or some other non essential part, sure, that wont matter if it breaks. But the front axle? That should NEVER happen.

Anyway, each to his own I guess. I wont be using an axle like that

[motogroove]

Originally Posted by GMP

Wasn't a hard landing over a double was it?

A hard landing over a 120' triple should be the design standard.
Just sayin'...

-Dean
singles through those three

[Fredde N]

Originally Posted by GMP

In the quest for light weight, we sometimes bump the limit of durability, and the weight/cost/MTBF ratio has to be fine tuned. A 250F is a perfect example. This is not neccessarily from a design standpoint alone, but from mfg and material tolerances being much less forgiving. Anyway, I'm not going to worry about it unless Nambo and Ivan start having issues. 4th gear? Wasn't a hard landing over a double was it?

No hard landing. But i use 13-52 for the moment, so it?s more strong than fast.

[GMP]

Yeah, I don't see the point of pushing that cut so far, a few mm more overlap won't hurt weight. Nice radius both inside and out though. See if the broken part is just like this one. Perhaps its not by design? What was the hardness like when you cut it?

These are Euro Sachs fork bikes right? Is the Sachs axel the same as the Zoke axel? Foot "looks" identical. Time to hit the parts .PDF.

It just occured to me that the dimmension from the edge of the larger clamping dia (ID) to the smaller dia can be measured on the bike in seconds. I'll do it tonight.

Lets not start a panic, there are thousands of these in service for years with no documented failures that we have heard of.