G'day folks,
BB,
I have wondered for a while if it is the fact that the original motors punched up and down vertically delivering full downward impact on the rails as opposed to the sloper motors that may spread the downward impact in a sort of horizontal direction.
Yes, the direction of max amplitude of the 'shakes and rattles' from the motor would definitely have significance in this failure mode.
High-tech Vibration Analysis [aka shakes and rattles] techniques are one of the core elements in any serious industrial heavy engineering Maintenance/Machine Condition Monitoring program, these days.
