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).
Letter discussing the performance and reliability of K.L.G. Wizard sparking plugs in aircraft engines.
| Identifier | ExFiles\Box 58\2\ Scan269 | |
| Date | 21th December 1935 | |
| Copy for - Colonel Darby. Mr.Staple. Extra copy for Rolls-Royce Ltd. 86001a C.E. NLH/LGH/24520. 21st December, 1935. (Dict. on 20th.) A.J.Rowledge, Esq., Messrs. Rolls-Royce Limited, DERBY. Dear Rowledge, K.L.G. WIZARD SPARKING PLUGS. Colonel Darby has just spoken to me and suggested that I should let you know how matters stand in connection with this plug at the present time and this I will endeavour to do as briefly as possible. We started to put the Wizard plug into our aircraft engines in May 1932 and at the present time we have about 5,000 of these plugs in use and there is no doubt but that they have saved us much trouble and a great deal of money as the result of the long periods they will go between cleanings and their very long total life. In "Jupiter" engines we clean them about every 200 hours and in "Servals" they go up to 300 hours and in all cases the average total life is about 3,000 hours - i.e. - not less than eight times the length of life of other types with which we are familiar. Other users than I.A.L. include the R.A.F. and it may interest you to learn that several thousands have been purchased for them for use in radial engines. What I have said above relates to the 18 m.m. size. A year or two ago - at Wizard Sparking Plugs works - Colonel Darby developed a 14 m.m. size and after the rights were taken over by Messrs. K.L.G. they also produced a 14 m.m. size; this was in response to my request for some of this size for test in the Napier "Rapier" and "Dagger" research units - Captain Wilkinson and Messrs. K.L.G. had asked for my suggestions for dealing with the troubles they were experiencing with ordinary types of plugs in high duty engines using 87 octane leaded fuel. The principal troubles were rapid burning out of the points, damage to the mica by deposits from the leaded fuel and short-circuiting across the mica resulting from fusing of these deposits. I knew very well that the Wizard would stand ever so much more point burning than other types and also that it ran cooler than other types but at that time I did not realise that this cool running would, in some | ||