A. Valve oil.
16. Q. Is it necessary to clean the electrode every trip?
A. No.
17. Q. Why?
A. The dynamo is provided with shunt fields which build up the current regardless of the arc light.
18. Q. What are the two causes of lamp burning green?
A. Speed too high, or wires to the lamp being reversed.
19. Q. If the carbons burned away too fast, but otherwise the lamp appeared to be burning properly, where would you look for the trouble?
A. It would indicate that tripping spring No. 209 was too tight.
20. Q. If tripping spring No. 209 was being annealed from heat and sparks were noticed at the clutch, where would you look for the trouble?