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).
Specification and testing procedures for sparking plugs, covering electrical and engine tests.
| Identifier | ExFiles\Box 58\2\ Scan109 | |
| Date | 1st April 1934 guessed | |
| -5- (b) Test for Tightness of Gland. Three sparking plugs which have been submitted to the previous three tests shall have the central electrode gland detached and then assembled again. This shall be repeated 20 times and the sparking plugs shall then be submitted to the test for gas leakage at 600 lb. per sq.in. at 200°C. In no case shall the gas leakage exceed 20 c.c. per minute measured at atmospheric temperature and pressure. 19. Electrical. (a) External Surface Flash-over Test. Three sparking plugs shall be submitted to the following test:- The sparking plug shall be screwed into a small steel vessel supplied with compressed air at a pressure sufficiently great to prevent sparking at the points. The sparking plug and steel vessel shall then be placed in a chamber in which the air pressure is maintained at an absolute pressure of 6 lb. per sq.in. Each sparking plug shall then satisfactorily withstand for 10 seconds an applied voltage of 9,000 (peak) measured as laid down in Clause 13. (b) Internal Surface Flash-over Test. Three sparking plugs shall be submitted to the following tests :- The sparking plug shall be screwed into a small steel vessel supplied with compressed air at a pressure sufficiently great to prevent sparking at the points. Externally the sparking plug and steel vessel shall be subject to atmospheric pressure only. Each sparking plug shall then satisfactorily withstand for 10 seconds without sign of internal flashing-over between the layers of insulation an applied voltage of 12,000 (peak) measured as laid down in Clause 12. (c) Dielectric Strength Test for the Central Electrode Insulation. Three sparking plugs shall be submitted to the following tests :- Each sparking plug shall withstand for 10 seconds without puncture of the insulation between the central electrode and the gland (the insulated centre being detached for this purpose) an applied voltage of 15,000 (peak) measured as laid down in clause 13. (d) Sparking Test under Air Pressure. Three plugs shall be submitted to the following tests the gap being adjusted within the limits of 0.012" minimum and 0.015" maximum :- Each sparking plug shall be screwed into vessel supplied with compressed air and provided with an observation window. Each sparking plug shall spark regularly under an air pressure of 100 lb.per sq.in. when a voltage (peak) not greater than 12,000 volts (measured as laid down in Clause 13) is applied. 20. Engine Tests. (a) On the satisfactory completion of the tests specified in clauses 17, 18 and 19 a letter of provisional approval of the type of sparking plug will be issued by the Director of Technical Development. Before any such sparking plugs are finally approved for general use on any particular type of service engine at least 75% of a half engine set of sparking plugs shall complete satisfactorily the type-test in the engine when run in accordance with the conditions of tests for type aircraft engines, Part B of Air Publication 840, etc., with the exception of power curves and detonation tests. The erosion of the electrodes after each 10 hour periods is to be recorded. After these tests the gaps may be adjusted and the tests in accordance with clauses 19(b), (c) and (d) shall be completed satisfactorily. | ||