[Healeys] Starter motor

[Oudesluys]

In the past I have rebuild quite a few starter motors and dynamo's and 
often skimmed the commutators and converted the dynamo's to take roller 
or ball bearings at the same time
If to much material is taken from the commutator it may get beyond the 
working tolerance and/or the segments may fly off. The insulation also 
supports the segments sideways and gives the commutator some stability. 
However, how far one can go I do not know. In general there is no 
problem if you have to skim the commutator when renewing the brushes. 
The first time will generally not yet expose the mica insulation unless 
there has been excessive sparking or other damage beyond normal wear. 
There will be a moment that the insulation gets exposed or that it will 
not clear the brushes sufficiently which will cause sparking and 
failure. At that point on has to remove/undercut some of the insulation 
with a hacksaw blade that is ground flat to a suitable thickness as not 
to damage the segments.
Undercut no further than about 0,5mm
Normally starter motors have a very long life and may need new brushes 
after 50.000 to 100.000 or more miles. Meaning that you will be doing 
this perhaps once in a life time.
When skimming the commutator use a very sharp cutting tool at moderate 
speed with a very fine cut and remove as little material as possible. 
Remove burrs and/or insulation material carefully with the ground flat 
hacksaw blade and smooth the surface using 600 grade wet and dry paper. 
Clean thoroughly with white spirits. Do not use thinner or alcohol as 
this may damage the shellac on the windings.

Kees Oudesluijs
NL

john spaur schreef op 22-5-2014 3:51:
> Why does the workshop manual warn you to not undercut the mica on the 
> commuter?
>
> John Spaur
> San Jose, CA
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