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).
Properties and potential cost savings of using cast iron for camshafts and crankshafts.
| Identifier | ExFiles\Box 142\4\ scan0189 | |
| Date | 2nd August 1937 | |
| To By.{R.W. Bailey - Chief Engineer} from Rm.{William Robotham - Chief Engineer} c. to Da.{Bernard Day - Chassis Design} [Handwritten] spce 1203 also 1260 Rm.{William Robotham - Chief Engineer}6/AP.2.8.37 CAST IRON CAMSHAFTS AND CRANKSHAFTS. When I was at the N.P.L. the other day, I observed a considerable amount of work going on on the physical properties of some of the cast irons at present being used in large quantities by the Americans for Camshafts and Crankshafts. From brief conversations the results appeared to be surprisingly good. Of course during the past three years an enormous amount of money has been spent in the U.S.A. on this material. With regard to Camshafts, it is significant that with the latest Wraith design chilled cast iron tappet faces give better results than any steel we have so far tried. Tappets in steel and the camshaft in cast iron would give considerable economies in the cost of the camshaft blank and in the machining required. The outstanding features of the crankshaft iron appeared to be ;- (1) Resistance to notch brittleness. (2) Internal damping two or three times that of steel. (3) A brinell figure of round about 300. It occurs to us that the Laboratory ought to make an investigation to see if it is worthwhile, at the present moment, for us to go ahead and test Wraith camshafts in cast iron and the Works to investigate reduction in cost if successful. On crankshafts, the master period on P.III. is unlikely ever to break the shaft, but we do not find it easy to damp it out so that it does not get through to the passengers. If the internal damping of cast iron is as stated, this might help us. We are tied to whitemetal on this unit at present so that the low brinell should not cause trouble. We suggest that a good method of testing would be on the large dia. shaft that has been drawn out for the P.III, but is at present held up pending the result of the overdrive. The economies on the P.III, where owing to the small numbers the cost of taking the dies in and out of the hammer is quite an appreciable proportion of the total, should be considerable. The saving in machining should also be far from insignificant. At present the P.III. shaft forging as received from outside weighs 177 1/2 lbs. and costs £ 10. 0.0. The finished crankshaft weighs 65 lbs. or 112 1/2 lbs has to be removed by machining. continued | ||