8.  Q. Why should you not use valve oil in these bearings?

A. Valve oil cannot be used successfully in the main bearing because of its heavy body.  Valve oil could not be carried up to shaft by the oil ring in cold weather, as the ring will not revolve.

9.  Q. What is the most vital part of the dynamo?

A. The commutator.

10.  Q. What care or attention should be given the commutator?

A. The commutator must be kept clean, free from dirt, and the mica must be kept filed a trifle below the surface of the copper bars.

11.  Q. What kind of a bearing should the brush have on the commutator?

A. Brushes should be fitted to have a bearing with the same contour as the commutator.

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?

A. The copper electrode should have about one-eighth inch surface on the contact point.

16.  Q. How far should the copper electrode project over the holder?

A. About one inch.

17.  Q. Should the electrode be raised up to one and one-half inches, what might happen?

A. If the copper electrode was run at a point so near the clutch, the intense heat of the arc might do damage to the top carbon holder and clutch.

18.  Q. What regulation should be given to the tension spring No. 93 of the lamp, and why?

A. This tension spring, No. 93, should be regulated when the current is off the lamp and should be adjusted only tight enough to pull the magnet yoke up against the top stop lug on the side of lamp column.