A. Brushes should be fitted to have a bearing with the same contour as the commutator, with bearing covering no less than two of the commutator bars, nor more than three of the bars.
44. Q. How are the brushes fitted?
A. Brushes are fitted by cutting a strip of No. O sandpaper about the width of the commutator surface. (Have the dynamo idle.) Place the strip of sandpaper under the brush on the commutator with the rough side towards the brush, then pull the sandpaper from right to left; continue this process until the brush has been fitted to a true smooth bearing. Then trim about one-eighth of an inch off the front edge of the brush.
45. Q. Is it advisable to ever try to fit a brush up with a file or knife?
A. No.
46. Q. Why is it important to clean the scale off the point of the copper electrode each trip?
A. To allow the point of the carbon and the electrode to touch to form a circuit; this scale being a non-conductor of electricity and with it on, the current would not pass from the carbon to the electrode and holder.
47. Q. How should the copper electrode be trimmed at the point?
A. Copper electrode should have about ¼-inch surface at contact point.
48. Q. How far should the copper electrode project above the holder?