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).
Describing a modified semi-servo brake operating system scheme.
| Identifier | ExFiles\Box 22\1\ Scan124 | |
| Date | 3rd March 1924 | |
| 44214 To HS.{Lord Ernest Hives - Chair} & DA{Bernard Day - Chassis Design} FROM R.{Sir Henry Royce} SECRET. R1/M3.3.24. c. to CJ. BJ. RG.{Mr Rowledge} WOR.{Arthur Wormald - General Works Manager} E.{Mr Elliott - Chief Engineer} BY.{R.W. Bailey - Chief Engineer} Mr. Claremont. E.A.C. BRAKE OPERATING SYSTEM. X.9940 X.4214 Referring again to my memo of yesterday, for convenience I designate the modified semi-servo scheme "R.R.M." scheme. It can be easier understood by saying the foot brake as now standard is only altered by making it pass through the servo operating levers, thus :- SEE ORIGINAL FOR SKETCH. otherwise it is not altered. Naturally this takes a little of the pedal stroke, but it should only be about 15% and after the servo friction surfaces are closed, no more loss takes place, but the foot has to follow the further putting on the back brakes by the servo about half that of the Hispano scheme. This is another reason for the backward braking being superior if correctly arranged. These levers can be at any angle and can move through any angle, and the servo can go either way round, though preferably all in one direction (when car going forwards). The angle of movement of these levers naturally would be less than the servo: for convenience say less than 60º (for the full pedal stroke), whereas the servo should go more than 75º. The two levers should have their pulls as near together as convenient to reduce stresses and friction - i.e. levers set over or near centre of bearing as shewn. It may be difficult to realise how this scheme is better for braking when the conditions are that of being unassisted by servo - i.e. backwards, and holding the car, but it should give an advantage of nearly 100% because we have only to take the slack up in 2 instead of 4 brakes, and as we take the slack up by the same leverage as we apply the brakes we only lose half the movement, hence we can have nearly double the leverage. The foot pedal will still only be required to follow the same distance. I have suggested this should be 1 3/4 times - i.e. if leverage to 4 brakes was 20 to 1 then this scheme the leverage to 2 brakes could be 35 to 1. contd:- | ||