[TR] TR4 Generator Electrical Arcing

Alex & Janet Thomson aljlthomson at charter.net
Fri Mar 30 14:58:45 MDT 2012


Can't remember the whole detail, but I think that may mean the mica
insulation between the commutator segments may need to be cut down. As the
copper segments wear down, the mica insulation prevents the carbon brushes
from making good contact with the armature. Seek out an old-style
auto-electric shop for details. A shop that specializes in farm, industrial
and truck components would be best. In my experience with old farm tractors,
there will always be a little arcing. Also, make sure that the carbon
brushes still float in their holders. If dirt has bound them up, they won't
make good contact with the armature. Also, make sure that the brush holders
still swing freely on their pivots, if so equipped. Check the
bearings/bushings at each end of the unit for excessive wear. Our TR-6
starter became less enthusiastic as time went on. We replaced it with a gear
reduction unit and, after inspecting the old starter, I'll never know why it
even worked.
Alex Thomson

-----Original Message-----
From: triumphs-bounces at autox.team.net
[mailto:triumphs-bounces at autox.team.net] On Behalf Of
pbrandsema at triad.rr.com
Sent: Friday, March 30, 2012 1:16 PM
To: Triumphs at autox.team.net
Subject: [TR] TR4 Generator Electrical Arcing

Has anyone had an experience with the generator (sorry, dynamo..) on a TR4,
where electrical arcing was visible at the rear of the unit?  I wouldn't
have noticed this ordinarily, but I happened to have the bonnet up last
night to rev the engine and found that the higher the revs, the more arcing
I see inside the back of the generator.  What also helped is that I had
turned most of the lights off in the garage to keep the bugs from swarming
in.  Besides a total failure of the charging system, my biggest fear is that
if for some reason I had a fuel leak, the arc would not be a good thing.

Is this a sign of worn brushes?  I've always considered converting to an
alternator, but don't have the time (or money) right now and the car has to
be ready for a trip in 2 weeks.  Brushes are cheap and should be easy to
replace.  I just don't want to waste the time that it will take to order
them if it's something more serious.

Thanks
Paul
61 TR4

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