Snapped axle - causes?

We have a 30mm (3mm thick) axle that was in good shape till it snapped during racing going into a sharp hairpin. It broke off between the wheel and the bearing on the motor side in an area that was in great shape and never used for set screws etc

Could this be setup related? Maybe the kart is too tight? I know the LO206 is a torque-y motor but this seems ridiculous.

I am not sure if I should add caster to get the inside wheel to lift, or take out caster to "free" up the kart and make it easier to push through the turn. Or maybe this is just normal wear and tear?
 

Dan Brown

Member
3mm is pretty thick, I am guessing it was a stiff axle. We have never broke one, but I saw a guy snap one at Oakland Valley. Axles, like all steel, get brittle the more they flex. I would guess it just became work hardened and snapped due to flexing in the same location for a long time. If the kart is handling ok I would just replace the axle and keep running it as is.
 
Peg keyway. It broke off right at one of the holes for an unused 2 stroke keyway. All the axles come w/ 2 stroke and 4 stroke keyways. I'm not sure if I can get 30mm axles w/ 4 stroke keys only. I bought a 2.5mm axle at the track and we'll try that and see how it works.
 

flattop1

Dawg 89
Likely a stress crack . Inspect it real good it might show an area that is darker then a fresh area where the final fracture took place .
The end grain of the metal .
 
Likely a stress crack . Inspect it real good it might show an area that is darker then a fresh area where the final fracture took place .
The end grain of the metal .
It does indeed. Right around the hole for the peg it's dark on either side for about 1.5x the diameter of the hole. The rest is fresh.
 

flattop1

Dawg 89
Here's a snippet , I could not link the article . Google metal fracture for more in depth .
Screenshot_20201013-105804_Drive.jpg
 
It took me a while to get the bad axle out at home. Even if I had a spare at the track I probably could not have switched over fast enough. Do people bring complete axle assemblies to the track (bearings, cassettes, brake and sprocket carriers) already set up to make a quick change? I'm not sure I'd ever do this but it's the only way I could see getting a bent/damaged axle out and replaced quickly.
 
It took me a while to get the bad axle out at home. Even if I had a spare at the track I probably could not have switched over fast enough. Do people bring complete axle assemblies to the track (bearings, cassettes, brake and sprocket carriers) already set up to make a quick change? I'm not sure I'd ever do this but it's the only way I could see getting a bent/damaged axle out and replaced quickly.
I know some guys that bring axles with the sprocket brakes and cassetes and everything you need on an axle and it is all adjust correctly to drop in really fast
 
I know some guys that bring axles with the sprocket brakes and cassetes and everything you need on an axle and it is all adjust correctly to drop in really fast
Like Phil Remington's quick change brake assemblies at LeMans in the 60s. Especially if the axle is bent or damaged it seems simpler just to pull out the cassettes and deal with the mess back home.
 

flattop1

Dawg 89
That's true it can be a bear . Hack saw /sawzall , hammer and file speed things up .
Not as fast as the whole assembly .
 

Dan Brown

Member
We run ikarts on asphalt, the unique way the bearing hangar is designed on the ikart allows us ti pull the complete axle assembly and bolt on another one in under 10 minutes. We will switch from soft to medium axles for tuning, it's almost as fast to change axles as it is to change hubs.
 
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