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).
Recommendations on magneto and spark plug requirements for the 40/50 engine based on test results.
| Identifier | ExFiles\Box 35\3\ scan 145 | |
| Date | 5th May 1921 | |
| x4196 Extract from Hs{Lord Ernest Hives - Chair}1/LG5.5.21. X.430. MAGNETO REQUIREMENTS FOR 40/50 ENGINE. Recommendations. X.1812. X.3775. X.4181. X.4279. X.3413. X.4295. X.4196. During our tests we have proved that the Watford E.0.6 magneto (sleeve type) is an improvement over the standard E.6.type magneto as regards slow running but owing to the fact that the safety spark gap is the same as on the E.6 (.300") it is liable to give us misfiring under full throttle weak mixture conditions. In future, however, we recommend that any magnetos we get from the Watford Co. shall be the E.0.6 type and that if we can, we should exchange the E.6 type magnetos which we have in stock to the E.0.6 type. This will be an improvement but we still think, however, that we need a larger magneto. It will give us a greater margin of safety. The safety spark gap on a magneto, we consider, should be 10 mm. (.400"). Perhaps one of the chief reasons why we need a larger magneto is because of the difference in sparking plugs. We have proved on the car that the Mercury plugs are liable to cause missing fire picking up with a weak mixture with the Watford magneto. It is because the resistance at the plug points appears to be higher than on the standard Lodge plugs. If we fit a Bosch magneto the trouble practically disappears. We shall be sending a separate report as regards the tests we are making on plugs. So far our tests show that plugs which are good for not sooting up, such as Mercury and Champion, are bad for resistance - the bigger margin we have on the | ||