Sterling motors
 

Does sterling motors have an aluminum crank?

Fixx
 

Hell no:drink: more like billit steel..

Never heard of any such thing. The strongest grades of aluminum are good for only maybe 60,000 psi, but more importantly, aluminum alloys have no fatigue limit, meaning that as you continue to load cycle the material, it will continue to lose strength until it just breaks at zero load. Bad choice for a highly cyclic loading part. Heat does bad things to it too.

High grade steel, like 4340, on the other hand, can be tempered up to 180,000 psi or more. Some aircraft steels have gone to like 300,000 psi. Steel, unlike aluminum, usually has an endurance limit, where after a few hundred thousand or million cycles, the strength reduction due to fatigue levels off, and you can depend on it almost forever, obviously at less than original strength, but with proper design, you are good to go for something that has to do tens of millions of cycles like an engine.

So, no, don't be expecting anyone to produce an aluminum crank anytime soon, except maybe for model airplane stuff, but I think most of those are steel too.