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).
Comparison of crankshaft forging weights and costs between their engine and a Jaguar 3.5-litre engine.
| Identifier | ExFiles\Box 132\1\ scan0008 | |
| Date | 22th December 1937 | |
| see Policy for Reply from RHC.{R. H. Coverley - Production Engineer} CRHC/SB.{Mr Bull/Mr Bannister}1(MC.17.138) 1116. also D By: from Rm.{William Robotham - Chief Engineer} THC. C.E.S. Rm{William Robotham - Chief Engineer}3/R.22.12.37. CRANKSHAFT FORGING WEIGHTS. We have now obtained from Jaguars the weight of their crankshaft forging for their 3½-litre engine. The forging includes integral balance weights, but these are not quite as large as our separate balance weights. The crank pin and journal dia. of this shaft in the machined condition is exactly the same as ours, but the overall length is 2" less than that of the Wraith. The weight difference due to length one might expect to be offset by the integral balance weights. In spite of this the weight of the Jaguar forging is given as 74½ lbs, and the weight of the Wraith forging is 130 lbs without test piece. In the present material this represents a difference in cost of 46/-, which explains a fair percentage of the difference in price between the Jaguar figure which surprised us so much, and our own figure. There is no doubt that from the customer's point of view the S.S. engine is much smoother than the Bentley, and, therefore, they do not get their cost reduction at the expense of efficiency. We shall have a Jaguar car immediately after Christmas, and a careful investigation will be made of the crankshaft so that we can establish the most economical and efficient method of producing 7-bearing 6-cylinder shaft forgings in the future. Judging by the results obtained by the S.S. people, our present procedure of paying machinists to remove 46/- 's worth of expensive material cannot be justified. Rm.{William Robotham - Chief Engineer} | ||