Just looking at some motors I bought second hand and pulled the brushes to see what condition they were in.
I'm assuming the corrugated surface finish is put on from new to help the brush bed in, in which case I appear to have motors that have NOT been given the "BM" treatment
On big motors I know it's standard practice to bed in brushes to the diameter of the commutator to reduce commutator pitting and arcing. I wonder, Is fitting the brushes like this another way the manufacturers screw us over and reduce the lifetime of motors ? I cant believe they consider motors and gearboxes to be "non serviceable items" and don't supply at least the motors as spares.
I'm going to be sleeving the cush drives, I've got plenty of tube, does anyone else need some sleeves while I'm at it ?