12. Q. How are the brushes fitted?

A. Brushes are fitted by cutting a strip of No. 0 sandpaper about the
width of the commutator surface (have the dynamo idle), place the
strips of sandpaper under the brush, then pull the sandpaper from left
to right; continue this process until the brush has been fitted to a
true smooth bearing. Then trim about one-eighth inch off of the front
edge of the brush.

13. Q. Is it advisable to ever try to fit a brush with a file or knife?

A. Most emphatically no. You could not get a bearing across the brush no
matter how hard you might try with either a file or a knife.

14. Q. Why is it important to clean the scale off of the point of the
copper electrode each trip?

A. The scale on the copper electrode after it has cooled off is a
non-conductor of current, and acts as a blind gasket between the carbon
and the copper electrode. Unless this scale is removed, the current
cannot pass between the points of carbon and electrode and you cannot,
therefore, have a light. When the dynamo fields are compound wound, it
is unnecessary to clean scale from copper electrode oftener than once a
week, at which time copper electrode should be removed from holder and
all scale cleaned off. (With compound wound dynamo fields the cab lamps
will continue to burn when head-lamp is extinguished by lifting carbon
by hand.)

15. Q. How should the copper electrode be trimmed at the point?