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).
Technical memorandum discussing hydraulic brake systems, pedal pressure, and overall ratios.
| Identifier | ExFiles\Box 179b\2\ img219 | |
| Date | 21th December 1932 | |
| x+456. x4027. R.{Sir Henry Royce} From Ha/Gry.{Shadwell Grylls} c. to SG.{Arthur F. Sidgreaves - MD} c. to Wor.{Arthur Wormald - General Works Manager} c. to A.{Mr Adams} c. to Ev.{Ivan Evernden - coachwork} c. to Du. c. to MAY. Ha/Gry.{Shadwell Grylls}1/Ma. 21.12.32. HYDRAULIC BRAKES. ----------------- No. 2/W. 7.12.32. With the present brake layout we have found successful on Peregrine we get 13300 brake units for a pedal pressure of 100 lbs., 102X units being provided by the servo. The ratio of the direct braking, pedal to cam, is 31. If we had to rely on direct braking only with no servo we should require 430 lbs. pedal pressure with the same overall ratio. Or if we reduced the pressure down to 100 lbs. on the pedal a travel of .4" (with a ratio of 133) would be required to take up the brake clearances alone. The Lockheed people recommend 46:1 as a maximum overall ratio. Our pedal effort would then be 29 lbs. We have tried on Peregrine overall ratios varying from 18:1 to 46:1. With the latter figure the pedal movement was excessive and the pedal could always be pushed to the floorboards. The ratio of 31 we use now is we consider the maximum we shall be able to use. We should not expect to reach the Lockheed figure of 46 because as well as brake clearances we have to allow for lost movement in the pilot shoe. The ratios of direct braking on F.11 and S/23 are 23.9 and 26.9 respectively. The increase is made possible by automatic adjustment will not compensate for the servo. To overcome the difficulty of the large pedal travel with light pedal pressures Lockheed's have been experimenting with a two diameter master cylinder one of large diameter being used to take up the brake clearances followed by a small diameter cylinder to give a large multiplication of effort. Although the inventors of this scheme they were against its use, being in favour of some external booster if light operation of the brakes is required. | ||