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 the angle of servo cams and lever length for the 'SS' brake gear.
| Identifier | ExFiles\Box 16\3\ Scan038 | |
| Date | 27th January 1929 | |
| HS.{Lord Ernest Hives - Chair} from DA.{Bernard Day - Chassis Design} Y7370 DA{Bernard Day - Chassis Design}1/M27.1.29. 'SS{S. Smith}' BRAKE GEAR. X.7420 X.7370 We investigated the question of the angle of the servo cams, length of lever, etc. on the SS.{S. Smith} servo and found that to obtain the proposed reduced direct braking and at the same time increase the length of the servo cam levers would be impossible without an alteration to the cross member. Though we can alter the cross member if necessary we do not wish to do so as it involves a special bracket for supporting the differential, and furthermore it approaches the floorboards rather closer than we wish. An alternative whereby we alter all the levers has the disadvantage that it puts increased torque on the differential, and as this latter is already loaded equal to the Phantom we do not wish to load it any more. As a result of our investigations we came to the conclusion that the compromise you are at present using, namely, 30° cams with the original length of lever and a longer driven lever on the countershaft across the gearbox appears to be the best under the circumstances. The only doubtful point is the angle of the cam, and we wired you asking you for your agreement that up to the present no trouble had been experienced. We may say that with extensive alterations we could not hope to increase the angle to more than 35°, and that the difference between 30° and 35° for reverse efficiency is only of the order of 10% DA.{Bernard Day - Chassis Design} | ||