From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Translated Bosch instruction manual on the use, setting, and maintenance of spark gaps.
| Identifier | ExFiles\Box 167\2\ img085 | |
| Date | 23th November 1937 guessed | |
| RR Cat. apparatus general BT{Capt. J. S. Burt - Engineer}15 6103 Translation of Bosch Instruction No. AWR1 on SPARK GAPS. ---------------------------------------------------- The Spark Gap is used for the measurements of the performance of magneto and coil ignition. As a measuring apparatus it must consequently be carefully handled and set. With a wrongly adjusted spark gap, incorrect results will be obtained. Setting of the Spark Gap ------------------------ The particular object is to adjust the ionising point correctly. This must be in a position such that a gap of 0.05 to 0.1 mm. separates the conical surfaces of the ionising point and high tension point (See Fig.1.). To best obtain this position, use a stiff, uncrinkled paper of 0.075 mm. thickness. The spark length between the high tension point and earth point is adjusted by movement of the earth point according to instruction EF 1070. Treatment of the Spark Gap -------------------------- The situation of the spark gap during testing must be such that it is free from vibration, otherwise alteration of the setting will result. Dust on the bed plate favours the creeping of the spark from one spark point to the others, and the bed plate should, therefore, be continually kept clean by means of a dry duster. A renewal or re-sharpening of the points is found from experience only necessary if the spark gap has been employed for a long time for endurance testing. In figures 4, 5 and 6 is shown how much the points should be allowed at the most to burn away before attention. In renewal of the points, the following should be noted:- They must be made of Tungsten or Platinum; Iron, Nickel, Brass, etc. are not useable. The points can be used as long as the length of the 1.5 mm. diameter cylindrical part exceeds about 0.5 mm. The angle of the cone should be 54 - 56°. After filing or grinding of the conical portion the point should be lightly rounded off with an oil-stone. | ||