[JamesCH95]

Originally Posted by AndreaV

They may have been live, but i am sure these live axles were supported by bearings on both sides, with the shaft section probably being around 3". In a butterfly drive whatever is driving the shaft is bolted directly to the wheel or driven by the hex in close proximity to the wheel. On a live axle WCD the sprocket/belt is on the opposite side so the whole axle is susceptible to torsional loading, which is the twisting action mentioned earlier.

With a WCD you have traction wheels being cantilevered, the shaft has to deal with axial and radial loading. Sure all shafts have to deal with this in some regard, but in a WCD the wheel(which is acting like a lever) transfers it directly to one side of the shaft, instead of evenly distributing it between both. This is when these forces become a problem.

I busted out my paint skills to illustrate what this looks like on a wcd with live axles.

This is called a cantilever axle.

Simplistically, a cantilevered axle sees six times the bending stress compared to a axle (beam) fixed on both sides. I would surprised if AM churro survived as a cantilevered axle for very long because of its low XC area and relatively poor material properties compared to 7075T6.

I would also be surprised if the shaft failed in torsion instead of bending.