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).
Brake system options for the 'Myth' class vehicle, including Lockheed hydraulics and a proposed servo system.
| Identifier | ExFiles\Box 110\1\ scan0020 | |
| Date | 25th October 1940 | |
| To Rm.{William Robotham - Chief Engineer} from Ev.{Ivan Evernden - coachwork} c. to Rm{William Robotham - Chief Engineer}/PJH. c. to Rm{William Robotham - Chief Engineer}/MHR.{M. H. Rigby} c. to Ev{Ivan Evernden - coachwork}/DB.{Donald Bastow - Suspensions} re Brakes for Myth. The question of the brakes for Myth has been analysed by Ev.{Ivan Evernden - coachwork} and Ev{Ivan Evernden - coachwork}/DB.{Donald Bastow - Suspensions} It is accepted that we shall have Lockheed All-Hydraulic Brakes on all models of the Myth Class. We have already fixed up with Mr. Parnell of Lockheeds suitable sizes of master cylinder, wheel cylinder, and brake drums for the Myth cars with the M.40 power unit (8 & 10 H.P.) These have been based on a maximum pipe line pressure not exceeding 1000 lbs/in.sq. for 100% braking, the car weight being 30 cwts. and the pedal pressure 156 lbs. The scheme uses two leading shoes. If we were to go to a single wheel cylinder and one leading shoe, the pipe line pressure would be increased by 38%. For the larger models of the Myth Class, fitted with the BM.40 Unit (2.0 litres and 2.8 litres) it was proposed to retain the same brakes as the weight of the car would be increased only 10%. If necessary wider or larger drums could be fitted if experience shewed that lining area and heat absorption power insisted. It is now proposed as an alternative to fit a servo on these cars, with either one leading shoe, or two non-wrapping shoes. A sketch attached herewith shows diagramatically the layout for a R.R. servo system. We are not clear what it is hoped to get out of the introduction of a servo. Admittedly it would permit of a reduced pedal pressure and an increased amount of lining wear per adjustment. Since we are not allowed to increase the line pressure already mentioned, the adoption of the single P.T.O. | ||