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).
Cracked insulators and gas leakage in spark plugs, referencing Bosch, K.L.G., and Corundite development.
| Identifier | ExFiles\Box 162\5\ img021 | |
| Date | 9th June 1937 | |
| -2- With regard to (b) I shewed them three plugs with cracked insulators, cracked around the nose of the central electrode. I queried whether they had adopted entirely the same technique in manufacture as the Bosch Co. The three plugs are being sent to Stuttgart by Air Mail and Messrs K.L.G's Works Manager who is at present in Germany at the Bosch Works will investigate the failures with the Bosch engines. Messrs K.L.G.'s 'Corundite' manufacturing plant which I inspected is copied from the German installation and is very impressive. The exact composition of the 'Corundite' mixture is a closely guarded secret for which they have paid a large sum of money. An advantage of the scheme is that they can obtain all the help and advice of the Bosch engineers when any trouble arises. It is quite likely therefore that the three cracked insulators we have had are entirely due to faulty manufacture and not to basic design faults. The question of excessive gas leakage (c) was dealt with and here again it appeared that they had been using a different press for rolling over the sealing gland on some of our plugs with the result that there was a possibility of variation in the sealing properties. This matter is also being discussed with the Bosch engineers. We have now completed a buying specification for our car plugs which has a clause safeguarding gas leakage and Messrs K.L.G. will be asked to certify plugs as manufactured to this specification. Messrs K.L.G. are to be congratulated on their progressive policy in securing the commercial rights of the Bosch process which so far is the only satisfactory method on a production basis of making aluminium oxide insulators. A further development they are now pursuing is the actual manufacture of the aluminium oxide at their works in a special electric arc furnace. At present their supplies are obtained direct from Germany and the Air Ministry, who are actively interested in 'Corundite' development, are anxious for the raw material to be made in England. _Aero Plugs_ Sometime ago we designed a plug with special attention paid to maximum heat flow. This plug known as type 877 was produced for us by Messrs K.L.G. and has proved the most successful plug so far on all EXE. single and main engine work. Major Carington has now continued | ||