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).
The performance and testing of various spark plugs in high-duty aircraft engines.
| Identifier | ExFiles\Box 58\2\ Scan271 | |
| Date | 21th December 1935 guessed | |
| -5- A.J.Rowledge, Esq. experiencing similar trouble in this type test other Wizard plugs were added and the type test was completed without trouble from the Wizards with the exception that one had to be cleaned towards the end of the test. Colonel Fell kindly showed me these plugs after the test and also one of another make which had failed, through point burning, at 90 hours whereas the Wizards were fit for indefinite further service without attention. (5) A full set of Wizard 14 m.m. plugs was used in the 50 hours type test of the "Panther X" engine and I judge that they were quite successful since Colonel Fell has expressed the wish that the five new ones I am sending to him in exchange for five from the "Panther" - which I wanted for a test in the "Pegasus X.C" - will be as good as the five he has sent me. I understand that he is testing this type of plug in other types of engines and regards it as a likely cure for the trouble she, in common with, I believe, all other engine designers, is experiencing with plugs in high duty high octane engines. (6) We have just completed tests of the 14 m.m. type in "Gipsy VI" engines on the bench and I am expecting the Air Ministry authority to continue these tests in flight. I believe these tests will be quitee satisfactory and if this proves to be the case it should open the way to standardisation of this plug for all "Gipsy" engines - and we and our associated companies have a fairly large number of them. Two or three years ago several people told me that although the Wizard method of construction had proved itself satisfactory in low duty engines it could not be expected to withstand the conditions imposed upon it by the coming high duty high octane engines. I had no evidence to the contrary because I had not an opportunity of testing the plug in such an engine and therefore I thought it worth while to be prepared, if possible, with a plug which would stand up to the conditions and produced a design which has the essential long-life features of the Wizard but may not have the same resistance to oil. This model was not proceeded with because shortly after the first samples were made we had evidence that the original type - and particularly the 14 m.m. version - promised to do all that was needed. However, I understand | ||