DC motor broken riser bar

[ronfrend]

Does anyone have any experience of vibration on a DC motor with a broken riser bar? We recently had a failure on a large DC motor where one of the riser bars from the commutators to the windings had a fatigue falure and eventually caused a catastrophic failure of the motor. We know that there was an incrase in noise prior to the actual failure but I would like to see if we could monitor this in future on-line.

Any ideas?