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).
Failure of ignition coils on test and proposing more stringent testing standards.
| Identifier | ExFiles\Box 46\3\ Scan177 | |
| Date | 11th March 1920 | |
| c. to Ck.{Mr Clark} X.3445. EP{G. Eric Platford - Chief Quality Engineer}/3/F11.3.20. F.R. X.3445 RE. FAILURE OF COILS ON TEST. With reference to our conversation on the above matter, referring to two coils which we had returned as faulty, I find that no matter what car these coils are used on, there is a definite inclination for them to misfire when picking up, especially for a high compression engine, and the mixture is inclined to be on the weak side. My opinion is that these coils are not strong enough for the present engine requirements, and we have proved on various occasions that if the coil is replaced with another coil, the ignition is quite satisfactory. I find that according to the works tests, these are within their standard, and I now contend, in viewof our present improved coils, that this standard should be increased. The requirements we have to put up with are that the battery ignition should be capable of jumping across a plug spark gap of .035 under a compression of 65 lbs. per sq. inch of air and petrol mixture. Will you please therefore arrange that the test bench for unit testing these in the shops is arranged accordingly, or such as to give comparative results. I think it necessary, in order for us to have something in hand, that the coil should be capable of jumping a .040 gap under this condition. Could you please arrange therefore that a corresponding spark on their test rig is arranged so as to give comparative results. According to our personal observation, this appears to be at least 10 m/m.{Mr Moon / Mr Moore} but I think this can be confirmed by tests already made by Mr. Clark. EP.{G. Eric Platford - Chief Quality Engineer} | ||