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).
Tests conducted on an improved slow-speed servo.
| Identifier | Morton\M20.2\ img021 | |
| Date | 7th April 1924 | |
| R.R. 493A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. Expl. No. 79910 [crossed out] 9910 REF: Hs{Lord Ernest Hives - Chair}/ACL/L.M.7.4.24. TESTS ON WW. SLOW SPEED SERVO - IMPROVED TYPE. This servo has thicker plates than the previous one - the area of the Ferodo is reduced - outside dia. 7" - inside dia. 5.5", and the driving dogs are set at a greater radius. The angle of the thread is 55° to the axis of rotation of the plate. The following figures are given for the output of this servo and a multiplying factor for the gain in pull obtained by the servo. It will be noticed that this factor decreases with the increase of pedal pressure. This we think is partly due to the fall in the value of co-efficient of friction with increase of temperature. When the brakes are applied on the road this value would probably be higher than given by our tests. The servo was run for one hour with an equivalent pedal pressure of 143 lbs. and speed equivalent to 30 m.p.h. The total torque output gradually fell from 2160 lbs.ft. to 1440 lbs.ft. after 45 mins. and then remained constant. The torque output went back to higher than the original value after it had been allowed to cool down:- | ||