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).
Examination of engine back-running during hand starting, focusing on magneto ignition timing.
| Identifier | WestWitteringFiles\V\December1930-February1931\ Scan146 | |
| Date | 16th January 1931 | |
| To R.{Sir Henry Royce} from EFC. c. Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. Ds. H.{Arthur M. Hanbury - Head Complaints} c. Dy.{F R Danby} Hs.{Lord Ernest Hives - Chair} c. Hs{Lord Ernest Hives - Chair}/AJL. ORIGINAL RECEIVED JAN 1930 EFC2/AD16.1.31. X.699. STARTING F.2. ENGINE BY HAND ON MAGNETO IGNITION. X.7791. X.6098. With reference to the second paragraph of Hs{Lord Ernest Hives - Chair}/AJL2/MJ14.1.31 given under cover of Hs{Lord Ernest Hives - Chair}1/MJ14.1.31 it is interesting to examine the circumstances in which the phenomenon of back running the engine therein described is more or less likely to happen. Such examination falls into two portions, in one of which we are concerned with the make and break timing of the magneto in relation to its armature functioning and in the other with the timing of the magneto distributor in relation to its make and break. Some time ago (about March 1926) we worked out the timing of a 60° range magneto to give, on principle, the best general alround result, and this from the point of view of both portions referred to above. The results of this investigation were communicated to Messrs. North. They professed to be in agreement with these results and it was understood that the internal timing of the magnetos would be arranged accordingly. We have examined the make and break timing of the magneto used in the tests in relation to its armature functioning and find the positions of the make and break to be 10° and 16° later respectively in this machine than was indicated by our results. With normal functioning in accordance with our results the backward running of the magneto at the slow speed likely to be encountered in the tests would probably not result in a spark occurring at the backward break (forward make); i.e. the functional timing of the magneto when running backwards (retarded as for forward running) would be far inferior to that when running forward at the likely forward speed. With the magneto as arranged, however, the backward running spark is actually as powerful as a forward running spark in the advanced position at the same speed, and this, we consider, accounts for the possibility of the engine being fired at all for backward running as described. | ||