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 to Borg & Beck Co. Ltd. regarding a suggested 12' Long C.F. clutch for the Phantom III, discussing thrust and pedal pressure.
| Identifier | ExFiles\Box 129\4\ scan0256 | |
| Date | 11th August 1938 | |
| o 111 EXPERIMENTAL DEPARTMENT. Rm{William Robotham - Chief Engineer}/NRC.{N. R. Chandler}9/JH. 11th August, 1938. Borg & Beck Co.Ltd., Tachbrook Road, Leamington Spa. re suggested 12" Long C.F. Clutch for Phantom III. For the attention of Mr. Barker. Dear Sirs, We thank you for your letter of June 21st, to which we have delayed replying because during the last few months, we have greatly reduced the thrust on the 13 1/2" clutch, and now that this alteration has been carried out on a number of customers cars with satisfactory results, we feel satisfied that there is no risk of slip, a definite improvement is smoothness, and a desirable reduction in pedal pressure. Originally the total thrust was approx. 1900 lbs. giving a working µ of .193, but it is now reduced to 1530 lbs, which makes the µ approx. .24. If we arrange the 12" clutch to have the same µ, we estimate the thrust would be about 1830 lbs. ( assuming the inner diameter to be 7" as listed for Pierce Arrow), and with this thrust we might manage without a servo spring, although we may introduce one in order to reduce both pressure and travel. Possibly the C.F. assistance may render still lighter thrust possible, and we would be glad to have your views. It will be appreciated that the suggested application of the 12" clutch will probably mean redesigning the pedal mechanism, so that we can start with a clean sheet as regards leverage etc., and for this reason we have left this blank on the specification form attached. Cont'd.{John DeLooze - Company Secretary} | ||