Sunday, June 20, 2010

RE: [Electric Boats] ETEK brush life findings

 

>A 36volt fan motor would be a find. You might consider a 24v fan with a power resistor to drop the extra voltage.

 

Fair suggestion.  But more work than justified.  The existing fan will stay---it's worked fine in 7years.  If anything, I'll upgrade to 48v at some point.

>Grainger makes a number of products for servicing commutator bars. By re-surfacing the copper, the brushes will be less prone to wear as arcing is reduced.

 

Sure, but wear cannot be eliminated.  And so the question becomes: What is considered normal vs excessive wear?

For all we know, 11-million revolutions and an average of 40amps typically leads to brush wear of ½" in 7yrs on an ETEK.

To my knowledge, no one else has reported statistics on this.

 

As for 'stoning' these copper commutator bars, it deserves note that his is an ETEK flat surface commutator, not the typical cylindrically shaped commutator of typical brush motors.  I am not aware of anyone having ever used such stones on ETEK flat commutators.  Also, these commutators may not be as thick as typical brush motor commutators and are certainly far more fragile.  Finally, the commutator in my case looked quite even without obvious wear.  Pics can be found here:

http://groups.yahoo.com/group/electricboats/photos/album/1522758117/pic/list?mode=tn&order=ordinal&start=1&dir=asc

 

Thanks for the suggestions.

 

-Myles

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