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 to a 4-cylinder 'Thumper' type engine for the 'Rippletto' model.
| Identifier | ExFiles\Box 134\5\ scan0020 | |
| Date | 25th October 1939 | |
| 1133 To Jnr.{Charles L. Jenner} from Rm.{William Robotham - Chief Engineer} c. Ev.{Ivan Evernden - coachwork} Rm.{William Robotham - Chief Engineer}8/MH.{M. Huckerby}25.10.39. 4-CYLINDER 'THUMPER' TYPE ENGINES. We believe that the design work for the 2.8 litre 5-bearing 4-cylinder engine has now been completed. The question then arises as to what modifications to this design are necessary in order to produce the engine for the 'Rippletto'. Originally, we agreed with you that this would have a 3" bore which gives it a taxable horse power of 14.4. However, it would seem more reasonable to make it 13.999 horse power and so get a reduction of £2/15/- per year in running cost; £1 the insurance and the rest taxation. It therefore appears that the design work outstanding on this unit is that necessary to reduce the bore to 2.95" and to modify the cylinder head so that the compression ratio is reasonable. We suggest 6.5 with this bore. The imperative requirement is that valve centres and valve sizes should not be altered in order to produce this cylinder head for the small bore engine, and, of course, if it could be made out of the same pattern with simply a different face thickness, this would be an advantage for jigging and tooling. We think that the first engine we should produce should actually be this small displacement engine and that we should follow it up with the 2.8 litre. We should like to give HPS{Horace Percy Smith - Experimental Factory Mgr} instructions for both engines at the same time. We have asked CTS.{C. Trot Salt - Carburation} to co-operate with you in issuing instructions for the job. Now, obviously, we do not expect to be able to issue the block and cylinder head until we get Hunt back. Rm.{William Robotham - Chief Engineer} | ||