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).
Modifications and testing procedures for Spectre tappets.
| Identifier | ExFiles\Box 96\2\ scan0029 | |
| Date | 27th February 1935 | |
| SECRET +354 Ll. Smith To Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} from E.{Mr Elliott - Chief Engineer} E.1/HP.27.2.35. c. Wor.{Arthur Wormald - General Works Manager} By.{R.W. Bailey - Chief Engineer} RHC.{R. H. Coverley - Production Engineer} Hs{Lord Ernest Hives - Chair}/Swdl.{Len H. Swindell} SpectreCodename for Phantom III Tappets. We have received the model tappet fitted with roller but as the smaller diameter cam cannot be ground we are making slight modifications to the roller tappet scheme before it is detailed to use the present diameter cams. We think it would be worth while making a set of these tappets and putting them on an existing engine, fitted with an existing camshaft. Although the values for the accelerations would be wrong the difference would not be great, and we could quickly get an experimental run without waiting for a new cam form. In the meantime we should be looking into the cam form as modified by the smaller radius of the follower and checking up on the grinding wheel diameter. At the same time we do not propose to abandon the large radius plain follower in spite of the unsatisfactory results uptodate on the SpectreCodename for Phantom III since Peregrine and J.3. engines used this type of tappet successfully in chilled cast iron. We are accordingly issuing some SpectreCodename for Phantom III tappets in this material, which demands some slight modification at the top where the push rod is carried, and we are also proposing to try some with stellited ends. We are endeavouring to find a satisfactory scheme which will hold off the tappet from the back of the cam with a clearance of 2 thou/in. to avoid the concentrated rubbing in the centre of the tappet face. This may or may not prove to be practicable but the device would take the form of an assembly adjustment. E.{Mr Elliott - Chief Engineer} | ||