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 Company Ltd. regarding the spring poundage for a 10' Bentley clutch.
| Identifier | ExFiles\Box 85\2\ scan0358 | |
| Date | 29th June 1938 | |
| c. RHO. c. LA.{L. A. Archer} c. Roy{Sir Henry Royce}/Ms. c. G/Mt. Rm{William Robotham - Chief Engineer}/NRO3/R.{Sir Henry Royce} 29th June, 1938. Messrs. Borg & Beck Company Ltd., Tachbrook Road, LEAMINGTON SPA. (For the attention of Mr. Barker) Dear Sirs, re: 10" Clutch - Bentley. In confirmation of our 'phone conversation of this morning, we regret to inform you that the Black spring recently fitted to the 10" clutch is much too strong, with the result that the pedal pressure is very excessive. You will recall that at a Conference held at Derby on October 29th at which Messrs. Armitage, Barker, Thompson, Young, Robotham and the writer were present, it was reported that some fear of slip was anticipated owing to the average poundage of the Brown spring being considerably under the nominal mean of 151 lbs, some tested being under 140 lbs. Messrs. Thompson and Young considered that the Brown spring was working too near the high limit of its poundage, and did not allow sufficient margin for tolerance or subsequent settling, and that it would be better to fit a new spring having a higher nominal poundage, and it was ultimately decided to fit a Black spring of 155/170 lbs, specially selected between 160/165 lbs, as per your letter RA/WM of Nov. 11th. It was thought that these springs would give a nominal total thrust of 1440 to 1485 lbs less some small amount due to subsequent probable settling of the springs. We find, however, after careful measurement of a number of 10" clutch units, that the actual working length of the spring varies from .110 to .125 less than the nominal 1.687, | ||