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).
Analysis of electrical arc and spark characteristics at various engine speeds and ignition timings.
| Identifier | ExFiles\Box 63\4\ scan0023 | |
| Date | 26th May 1918 guessed | |
| -23- of flux that has to slip back between these positions to maintain the e.m.f. necessary to maintain the primary current). Arc or further sparks are only present when the gap is shorter than its limiting value. At 600 & 2000 R.P.M. the quantity is greater at retard than at advance (pp 6,7,8,9) (This is on account of the flux change available at retard being greater than that at advance) Moreover the retarded arc is softer, bushier and more flamy, whereas the advanced arc is of harder outline and more striated. The retarded spark takes place more easily than the advanced. For certain speeds and gap lengths sparks will occur at retard when none will occur at full advance. Z.A.2 At 200 R.P.M. quantity is greater at advance than retard. (pp 10, 11) At 600 R.P.M. it is only slightly greater (pp 12,13) AT 2000 R.P.M. it is somewhat less (pp14,15) Alteration to character of arc very much as for Z.F.6, but less arc (quantity) altogether. Z.F.6/C. Same general remarks re quantity as affected by advance and retard apply here as for Z.F.6. Sketch (87) should be examined. A few short sharp sparks near point, and straggly long sparks, the longest (outside one) of which is the brightest, and of which the intensity diminishes as we pass back towards the point. This is not an arc, there is no mauve colour but all is bluish white. Sparks probably represent oscillatory discharge of condenser. At 2000 R.P.M. some real mauve arc | ||