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).
Alteration of cam diameters and its effect on the servo braking system.
| Identifier | ExFiles\Box 73\3\ scan0187 | |
| Date | 12th August 1924 | |
| In conformity with Da{Bernard Day - Chassis Design}'s memo, the result of the instruction issued by R.{Sir Henry Royce} in a previous memo, we have added metal to the outside diameter of the face cams so as to increase the mean diameter from 1.075dia. to 1.200" dia. This means that the outside diameters of the cams have been altered from 1.325" to 1.500". We are having the dies altered at once, for which purpose Mr. D'Aeth is issuing blueprints to the Operation Department to-day; but before definitely instructing this form of cam for all cars, we would like you to confirm that you are satisfied that the proposals put forward will not affect the general excellence of the brakes on the car. It appears to me that the proposal, whilst it looks sound on the face of it, has an inherent weakness in as much as it reduces the possible servo and braking, which only finally means that the driver will exert more foot pressure to accomplish what he desires. In other words, the pressure that the man exerts by his foot is not the controlling factor but the rate at which he imagines he is stopping the car or wants to stop it. BY.{R.W. Bailey - Chief Engineer} | ||