Originally Posted by
fietsbob
torque, pedaling, after tightened on the hub, is typically transferred to the shoulder on the hub.
I'd be interested to know how much is transferred by friction at the hub shoulder and how much is transferred by the threads, I suspect you may be correct in assuming that most of it goes through the shoulder. It's unlikely to be torque anyway in this case, though, as the lowest gear the OP has is 42/25, and there are plenty of old/cheap MTBs fitted with freewheels using much, much lower gearing than that, not to mention tandems.
Assuming it failed while riding, I'm stumped.