Broken Axle

ZFD said:

There are five alterations to the original drawing. I thought I remembered one was in the region where the thread ends and the plain portion begins. Originally these had like a sharp cut going straight down to the thread diameter and later got like a gradual decline.

Click to expand...

Thanks Joe. Is there any chance we could do a follow-up on these apparent design changes so an owner can positively identify which type they have?

More info here


Ken

Guys an observation on Axles

The early commando hubs with three sprocket bolts often suffer with loose bearing fit on the drive side ( slack in hub casting )
this could be a reason for axle failure , if the double row bearing becomes a loose fit in the hub or is worn out all the axle load transfers to the main wheel spindle thread
where it meets the fixed half spindle , the half spindle is fixed by the nut clamping it in to the swing arm and its short length and support bearing limit lateral movement
so any play in the bearing or housing is applied to the spindle thread , the later cush drive type hubs do not apply the same side force as the rubbers give between the sprocket and hub
as they are no longer fixed together so any miss alignment is taken up by the cush rubbers and the load spread across the three bearings as it should be

Bear in mind if there is a few thou play in the double bearing or it has a poor fit in the hub ( which is often the case ) there is an awful lot of leverage applied by bike and rider to a small 17mm spindle

I would recommend you check your bearings and hub fit at the start of each riding season

@Kiwi 7/29

Good post. I think he has nailed it.

Slick

Back when I was fighting this issue on my race bike, another explanation occurred to me, but I didn't pursue verifying it. I noticed when adjusting the axle position to line up the front and rear wheels, the axle appeared to be at a slight angle to the swingarm pivot. Tightening the axle with it in that position put a bending force on the axle, which might help explain the breakage. It's possible I had something out of line in the frame or swingarm. When I built a new swingarm to take a larger diameter, one-piece axle and provide additional tire clearance, I also checked the frame on a jig, and tweaked the steering head slightly for trueness. So maybe the bending was a factor, and maybe not. Food for thought, though.

As another data point, I've only had the stock two-piece axles on my street Nortons, and so far haven't broken any. Still, I do intend to go to one-piece axles on the two MK III bikes I'm about to renovate. It's a cheap and easy preventative mod.

Ken

Joe,
What material are the wheel spindles made from. EN 8, EN 16 ?