[TR] TR4 Generator Electrical Arcing

[Randall]

> Lastly I believe the factory and Haynes manuals usually have 
> instructions on 
> cutting down the Micanite insulation between the commutators, 
> but I couldn't 
> find a reference on the internet,

Here's a copy of the TR3 workshop manual, with instructions on undercutting
the mica.
http://goo.gl/8jHM5
Basically, you take a sharp, fine tooth hacksaw blade and grind the sides
until it is the same width as the insulator; then use it to cut the slot to
about .030" (1/32") deep.  A hobby "razor saw" would probably work too.

However, I tend to doubt that is the problem.  Normally the mica only needs
to be undercut after the commutator has been turned down.  As long as it is
not actually protruding, the generator will still work fine (the .030" is
for wear allowance).

Some sparking is normal; excessive sparking usually indicates a problem with
the brushes, brush springs (insufficient tension) or something wrong within
the armature (open or shorted winding).

-- Randall