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 to The Lodge Sparking Plug Co. regarding the return and performance of KR5 spark plugs, detailing issues with pre-ignition.
| Identifier | ExFiles\Box 79\1\ scan0130 | |
| Date | 5th September 1918 | |
| EH2/LG6918. X601. 5th. September. 1918. The Lodge Sparking Plug Co. Ltd., R U G B Y. Dear Sirs, For the attention of Mr. Lodge. We are returning to you 12 KR5 plugs with steel electrodes. These have run for 10 hours on production engines. The fault with them, is that there are slight pre-ignitions so that the engine does not develop the same power with these plugs compared with either the KR4 or the KLG. They are better than the standard KR3 for pre-ignitions. We find it is possible to get different effects from pre-ignitions, for instance, if a plug is very hot, it will fire the charge before the piston has got very far on the compression stroke, it is this very early pre-ignition which causes over-heating. Another plug might be pre-igniting but because of its not being so hot, it will not fire until the charge is well compressed. This type of pre-ignition is very difficult to trace because the power is only reduced slightly. As regards the KR4 plugs, these are going very well. We agree, that using them continuously on the test bench the copper deteriorates and the plugs fall to bits. We think, however, these plugs would be quite alright in the | ||