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 front wheel brakes for the 'India' model, discussing servo efficiency.
| Identifier | ExFiles\Box 57\1\ Scan144 | |
| Date | 27th May 1925 | |
| R.R. 493A (50H) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. Expl. No: Y5770 REF. Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}3/LG27.5.25. To DAJ from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} SECRET. Y5770 X5940 Y5375 'INDIA' FRONT WHEEL BRAKES. It is apparent that with the present leverages on 'India' we shall require a servo efficiency of 1 if the maximum braking to the front wheels is to be 40% of the total. It would seem to be inadvisable to make it more than this, as the static % of the total weight of the car on the front axle is less on the 20 HP. than the EAC. With a servo efficiency of 1, the available braking units on the 20 HP. are 1225. With the mean standard servo efficiency on the EAC. the available braking units are 2050, or 1.67 that of 'India'. The weight of an EAC. car is 1.37 times that of "India". Therefore with this servo efficiency 'India' will require 27½% more pedal pressure than the EAC. to produce a given retardation. This seems very undesirable as the 20 HP. is a lighter car, and in consequence the remainder of the controls are lighter than those of the EAC. A further objection to the use of a servo with an efficiency as low as 1.00 is that any slight variation of the servo efficiency will make a large variation in the proportion of front to rear braking. We suggest that we endeavour to obtain a servo efficiency of 1.5 and at the same time reduce the servo contd :- | ||