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).
Proposed design changes and advisability for the Spectre engine.
| Identifier | ExFiles\Box 4\1\ 01-page014 | |
| Date | 9th May 1933 | |
| X4694 To Hs.{Lord Ernest Hives - Chair} from E.{Mr Elliott - Chief Engineer} E.2/HP.9.5.33. c.c. Sgr. Wor.{Arthur Wormald - General Works Manager} By.{R.W. Bailey - Chief Engineer} HHO. re SpectreCodename for Phantom III Engine. We think that certain departures from the original specification of the SpectreCodename for Phantom III engine will be necessary, but we should like it confirmed that everybody is in agreement on the advisability of the changes contemplated. Firstly there is the addition of self-adjusting tappet gear for the valve operating mechanism. We do not think there will be much argument about this, having regard to the fact that there are 12 cylinders to look after, and that the all aluminium construction really necessitates this modification as it does on J.3. engine. Secondly we propose to use separate side by side connecting rods in place of the articulated type originally laid down. With the articulated or blade rod type we cannot withdraw the rods through the cylinder bore, neither can we withdraw the piston pins in position to release the rods downwards owing to the interference fit employed. We, therefore, say the side by side rods are definitely necessary. As a production job they are to be recommended, but the disadvantage of their use lies in the fact that the engine is lengthened owing to staggering the cylinders. We do not anticipate much difficulty in arranging for the cylinders being staggered since the cylinder blocks will be formed in one casting with the crankcase. The valve gear will require respacing, however, to accommodate this change. Thirdly, with the very much lighter flywheel which can be employed on the 12 cylinder engine we hardly see the necessity for a double rear main bearing. At the same time the impulses affecting the vibration of the rear end, due to both inertia and gas pressure are very much toned down. It also raises the question of the form of timing gear drive to be employed, and whether after the experience we have now had with rear end timing wheel drives we still adhere to the view as to the desirability of this scheme compared with front end drive, both from a production and operational standpoint. On this last question we should like to have some further information. E.{Mr Elliott - Chief Engineer} [signature] | ||