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).
Design and material choices for brake drums, comparing wrought steel, cast iron, and other combinations.
| Identifier | ExFiles\Box 179\1\ img077 | |
| Date | 9th November 1931 | |
| FROM R.{Sir Henry Royce} ORIGINAL R1/M9.11.31. X4612 BRAKE DRUMS. The thin flexible wrought steel brake drums were considered many months ago to be unsatisfactory, so we went back to an earlier design which the Expl. Dept. had departed from to obtain flexibility with the object of preventing harsh front braking. On this 2nd. attempt we shewed a brake drum built up on a plate from a ring which was thought by us to be easily producible in wrought steel of almost any required composition - i.e. probably with manganese - that could be turned and grooved for stiffness, and would be more reliable in a general way than either the cast iron drum or a built up drum of aluminium with any form of liners. Until this has been made and found to have some defects we think it is better than trying brake drums in cast iron, (which may crack or cause a disaster,) or in aluminium and steel combination, (the characteristics of which we have no knowledge.) As far as I can see we have had no report on our stiffer pattern of brake drum or on its behaviour during any 10,000 miles test, and as I took particular time over producing this pattern I shall be pleased if the work is carried out as instructed. I think it is evident that we ought not to use cast iron until we have proved that the wrought ones we have designed have not sufficiently good wearing qualities. It will be noticed that if we do not completely close the throttle, we shall have a definite increase in petrol consumption and in the wear and tear on the brakes. I noticed this particularly on the recent 20/25 that you brought to WW. Its tendency to run on was so great that luffing up could not be accomplished without the more frequent and vigorous use of the brakes. This is however quite alright in our 45HP. with its engine governor. R.{Sir Henry Royce} | ||