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).
Magneto ignition requirements and spark gap issues for the 40/50 HP chassis.
| Identifier | ExFiles\Box 33\3\ Scan131 | |
| Date | 10th May 1921 | |
| X1812 b. To Hs.{Lord Ernest Hives - Chair} From R.{Sir Henry Royce} c. to CJ. c. to EFC. c. to EP.{G. Eric Platford - Chief Quality Engineer} c. to PN.{Mr Northey} c. to R.R. of America Inc. (For the attention of CY). X.430 - RE 40/50 H.P. CHASSIS - MAGNETOS. X.699. X.1812. With reference to your report on magneto requirements for 40/50 H.P. chassis, I think your work on this very good indeed. There is one point, however, with which I scarcely agree, and that is, that it is necessary to have a spark with a great deal of energy. This does not seem to be the case, because a magneto gives a spark at the plugs and is so tremendously more energetic than the battery ignition, and yet for certainty of ignition there is little to choose between them. We all agree that Mr. Platford's original observations of a long gap is better for the firing of light charges with battery ignition. Now this is understood to apply also to magneto. In what way the long gap enables the spark to fire these light charges better, I do not profess to know. If this long gap of ½ mm. (.020) or more is used, then your conclusion is that when the full charges high compression pressure occur the magneto sparks at the safety gap, and so fails to ignite. I also understand from your report that this occurs on the plugs in which the central electrode is positive, and therefore may affect in some irregular way, three of the plugs only out of the six. Contd. | ||