I pulled the gearbox off of the thrower today. I believe the root of the shear pin issue is a design flaw.
The holes in the gearbox shaft are .295", the shear pin diameter is .248". That is .047" of slop between the pin and the i.D. of the hole. I can see where it would just hammer back and forth, until the pin broke.
The reason I am quite sure its a design flaw, and not a whopped out hole, is this gearbox has (2) shafts exiting it, (1) of those has never been used, both shafts have holes in them that are the same I.D.
