[ZZII 527]

Bad news: our tempered (HRC 49.5) 42mm carrier failed in the gearbox by fast fracture. More specifically, three of the pins fractured just below the plane of the plate. This occurred at almost no load.

To confirm that it was not just the pins (and to let out frustration) we subjected the carrier itself to the "hit it hard with a hammer" test and sure enough it fractured as well (picture attached).

Conclusion: It was too brittle, by far, at this tempering. I can try it again with a higher temperature temper and longer time in the oven to get it a little softer and less brittle, but I will need to get my hands on more and I don't think I want to buy whole gearboxes. I'm now less optimistic about the tempering solution since it seemed to fracture so easily, but there may still be hope.