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).
Letter from Ferodo Limited discussing brake lining performance, friction, and potential mechanical issues.
| Identifier | ExFiles\Box 26\4\ Scan145 | |
| Date | 19th August 1921 | |
| -2- As a matter of fact, we have tested the linings you sent us against a highly polished mild steel drum, and found no difference in co-efficient of friction over that of a new piece after it had been run for one minute. We may add, that the permanent drums of our Test Machine are of mild steel 0.3 carbon content, 40 tons tensile, and are capable of receiving a high surface polish, but not, of course, so fine as can be got on your 0.6 carbon drums, though we should say there is little in the difference from any practical point of view. Our general experience is, that our fabrics invariably produce a hard skin and smooth polish on rear wheel drums, and that scoring rarely obtains whatever class of steel is used. As we fully accept that you have carefully considered all the facts bearing on the case, it is with some diffidence we suggest there may be something mechanical that makes for the falling off. Do you attribute anything to the position of the operating cam or foot pedal in relation to its fulcrum? Certainly, a brake always appears more powerful when closely adjusted, so as to bring the operating lever into the best position to transmit the applied pressure. Mr. Frood has just mentioned to the writer that he has no experience of any greater personal effort being required on his Rolls, if it has, he has been quite unconscious of it, and he has always been perfectly satisfied with the brakes on his car. Probably the only way by which we can definately establish our view is to mount one of your drums and note the breaking effect with linings of different area and position in relation to the fulcrum. We will endeavour to get this done, and can then ask Mr. Bailey, or any other of your technical staff to take readings of power absorbed. We are quite agreeable to co-operate with you to the fullest extent, and appreciate the remarks in your very careful and informative letter are given us quite as much to our advantage to investigate as may accrue to you from any information that we can convey. Yours faithfully, FERODO LIMITED, (sgd) F.{Mr Friese} J.{Mr Johnson W.M.} Field, Chief Engineer. | ||