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).
Cost comparison and analysis of aluminium versus cast iron and sheet steel engine materials, with reference to the Wraith and 25/30 models.
| Identifier | ExFiles\Box 6\6\ 06-page056 | |
| Date | 4th February 1940 | |
| (sheet 2) Lower Half C'case. 38.47. 36.6 (P.III) 36.6. Stud Tubes. 4.77 nil. nil. Total (shillings) 145.762 300.966 62.141 It is therefore seen that for the actual material involved in the change the all aluminium Wraith is five times more costly than the cast iron monobloc, and twice as costly as the 25/30. Dealing now with the proportionate cost of the engine, the present material cost of the 25/30 is £32, and using the figures above we find that the all aluminium Wraith total material cast would be £40, and the cast iron monobloc £28. In addition to this difference in material cost there is also the factor of labour, and this we know is definitely less on No.3. than on either 1 or 2. It, therefore, appears that in designing to the all aluminium scheme we have no chance of equalling the present production costs on the 25/30, and that to accomplish any marked economy the only possible policy is to make the monobloc cast iron engine. These figures appear to make it very clear why the Americans go so whole heartedly for all cast iron, and sheet steel on engines. Technically there is very little reason except weight why cast iron should not make as good if not a better power unit than aluminium, and I, therefore, think we should re-consider our decision in respect to the future Wraith. [Handwritten Notes] P3 Labour Cyc to WCOI L 4-2-40 25/30 Ben E.{Mr Elliott - Chief Engineer} 2-11 3 11-9 | ||