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).
Investigation into brake sponginess and servo performance on the S.S. model compared to the Phantom.
| Identifier | ExFiles\Box 16\3\ Scan044 | |
| Date | 19th April 1929 guessed | |
| contd :- -2- a persisting feeling of sponginess. (3) The front brakes appeared to be doing far too much work as they started to squeak on all cars. (a) Investigation of (1) shewed it to be due to the servo. Our standard servo lining is 'Halo'. As we have previously reported the µ of Halo falls with temperature. We find that on the S.S. the servo gets warmer than on the Phantom for two reasons. (α) By reason of the unit construction, the gearbox temperature is raised by conduction from the engine. (β) The S.S. servo is over the silencer, on the Phantom it was not. Additionally, with a normal µ the servo on the S.S. requires greater end thrust than the Phantom due to its dimensions and as our tests of the servo shew its efficiency falls as the end thrust is increased the effect of a drop in the co-efficient of friction of the lining is comilative. We admit the 20 HP. servo is operating under similar conditions. Actually we find the difference between hot and cold can be detected but is not so marked as we are asking the servo to do less and have more in hand (b) Our tests on the servo shewed that its efficiency fell off with increasing output. Also our tests on the efficiency of the brake linkage shewed that its efficiency to the rear brakes fell off with increasing load, both servo and as direct braking. This accounted for observation (2). contd :- | ||