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).
The Spectre model's brake layout, comparing its efficiency to other systems and proposing modifications.
| Identifier | ExFiles\Box 92\4\ scan0026 | |
| Date | 16th November 1934 | |
| Rs{Sir Henry Royce's Secretary}/Gry.{Shadwell Grylls}11/KW.16.11.34. Brake Layout - SpectreCodename for Phantom III. We have previously reported on the fact that the efficiency of the SpectreCodename for Phantom III brake system is less than that of the Phantom II, and that we attribute this to the increase in the number of moving parts. During a recent visit to E.R.A. cars we noticed that the pedal load required to overcome the pull off spring on their cars was at most 15 lbs. for an overall ratio of about 30:1. SpectreCodename for Phantom III requires 100 lbs. at 25:1. A diagram of the layout is with the attached memo, and it will be seen that it consists of the simplest possible Girling system. They claim to have had no trouble with the brakes whatever. Rover cars, on which this brake is standard, have nothing but praise for the system, and say there is no noticeable effect due to adjustment at the shoe fulcrum. We recommend trying this scheme on the SpectreCodename for Phantom III. De, however points out that due to the independent suspension it is not possible in front to copy exactly the Girling scheme, unless the equaliser is underneath the front tray. The lowest of the 3 sketches attached shows a scheme for overcoming the difficulties of rods fouling the suspension by using hydraulic pipes from the servo to a Girling shoe actuator, the rear brakes being exactly to the Girling system. We think this scheme has the least number of moving parts and will provide good sideways compensation. Our present equalisers only move for loads varying by 25%. We do not advise that the hydraulic cylinders should actuate our usual toggle arrangement, as recent tests on the efficiency of these toggles on a Bentley show that the efficiency varies from 50% at low loads to 70% at high loads. We do not think the Girling wedge and rollers could be as low as this. | ||