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).
Design and considerations for the Spectre engine's ignition system.
| Identifier | ExFiles\Box 163\7\ img249 | |
| Date | 15th February 1934 | |
| WST r6120 To Sg.{Arthur F. Sidgreaves - MD} and Wcr. from E.{Mr Elliott - Chief Engineer} E.3/HP.15.2.34. c. Hs.{Lord Ernest Hives - Chair} By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Wst. By/RD. SpectreCodename for Phantom III Ignition. We have just issued LeC.3811 showing a space time curve specifying the shape of the contact breaker cam for the SpectreCodename for Phantom III. This cam is designed to run the SpectreCodename for Phantom III engine up to 5000 r.p.m. and based on our present experience there should be no more distress on the make and break mechanism, in fact the conditions are rather easier than with the cam at present being used on the production Bentley. We have to realise that we are equipping the SpectreCodename for Phantom III engine with two completely independent sets of battery ignition right throughout, including two sets of sparking plugs, and this is not offered on any American chassis of similar type. It is true the Hispano-Suiza has two sets of battery ignition but the provision of four coils always in operation in conjunction with two double feed distributors causes the equipment to be somewhat elaborate. To avoid having a regiment of ignition coils always in operation we are hoping that the Rolls-Royce high speed coil can be developed up to the point where two coils only will be necessary on the SpectreCodename for Phantom III. We think that the results that have been reported up to date in Hs{Lord Ernest Hives - Chair}/Wst.2/MA. 13.2.34 are distinctly encouraging. The coils are mounted in a position where they will receive the full benefit of the cooling draught coming through the radiator. The SpectreCodename for Phantom III ignition in our view presents two problems, one being the distributor and the other the coil. We believe the former can be solved on the lines of the cam we have instructed by taking full advantage of the break period for reducing the decelerating load on the rocker that has to be supplied by the spring. We also have in view the Rolls-Royce stirrup anchorage which helps to relieve the spring of stresses which arise with the more normal form of spring mounting. | ||