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).
Servo-assisted brake performance, detailing modifications to cam angles and reduction ratios.
| Identifier | Morton\M20.3\ img004 | |
| Date | 24th May 1924 | |
| R.R. 493A (20H) (D.A. 652 20-3-24) J.H.D. EXPERIMENTAL REPORT. ORIGINAL Expl. No. 9940 REF Hs{Lord Ernest Hives - Chair}1/LG24.5.24. To R.{Sir Henry Royce} From Hs.{Lord Ernest Hives - Chair} c/ to CJ. RG.{Mr Rowledge} c/ to DA.{Bernard Day - Chassis Design} E.{Mr Elliott - Chief Engineer} c/ to BY.{R.W. Bailey - Chief Engineer} WOR.{Arthur Wormald - General Works Manager} SECRET. RE: ADOPTED SCHEME OF BRAKES. We have two cars fitted with the adopted scheme of servo and brake operation. The results so far are very satisfactory. We found that with a 45° angle face cam the pressure required to operate the brakes was very light. Less pressure was required than on the car we had at WW., the reason for this is that on the adopted servo, the mean radius of the servo plates is increased and also the mean radius of the face cams has been reduced. We have increased the angle to 55°. We consider it is a definite improvement. We would prefer, however, to take the average of several cars before we recommend the angle of cam we should use. Altering the angle of the cams gives us more direct braking to the rear, so that the proportion of braking to the front is reduced. The car which we had at WW. and also the car we let PN.{Mr Northey} try, had a servo running at 7 to 1. We had the first cars fitted with a 10 to 1 reduction so as to keep the servo running as slow as possible. We find on test however that we can appreciate the increased lag of the lower speed servo. As we have had cars running successfully with the 7 to 1 reduction, we recommend that we should use this ratio. The work the servo has to do will be decreased by reducing the contd:- | ||