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 to determine the equal distribution of the 20/25 and Bentley servo motor output to the front and back brakes.
| Identifier | ExFiles\Box 105\4\ scan0134 | |
| Date | 26th March 1934 | |
| x5370 26.3.34. 20/25 AND BENTLEY SERVO TESTS. We have recently carried out some tests to determine whether the 20/25 and Bentley Servo Motor output was equally distributed to the back and front brake mechanisms by the balancer lever. The attached drawing, Hs.{Lord Ernest Hives - Chair}1349, shows diagramatically the parts of the servo concerned in this test. It was at first suspected that the front brakes were not getting their proper share of the servo output due to the combined effects of friction at the ferobestos lined bearing (A) on which the swing arm (B) is hung and the flexibility of the mechanism between the servo and the front brakes which is known to be greater than that for the back brakes. The friction mentioned above is not necessarily that due to the spring load on this bearing but it was considered that the vertical reaction at this bearing which is approximately equal to the tension in link (D) might cause considerable friction when the servo was under load and prevent the swinging arm (B) from moving back as it must do due to the greater flexibility of the front brakes. The experiments were carried out on the test bed. Spring balances were connected to the ends of the balancer lever (C) and anchored to the bed. To produce conditions similar to those in the chassis, the spring balances were arranged to be of unequal rating (732 lbs/in. and 480 lbs/in.) the lever rating balance representing the front brakes. The input to the servo was not measured. The method of the test was to apply a series of increasing loads on the servo and, for each load, to measure the outputs to the front and rear spring balances. The results are shown on the attached diagram B.V.26, curve No. 1. | ||