Correct, if the engine is turning 5000 rpm then the alternator is turning 10K+. I don't recall the formula for determining centrifical and/or tangental forces but I'm guessing they increase expodentially so the stresses on the rotor/armature are a lot greater than simple math would indicate. I was mentioning this as it was noted that a soldered connection had broken and at 5000 (crank) rpm the loose connection started to short against the housing.