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).
Mechanical gain, friction, and potential issues in a new slow-speed servo for braking schemes.
| Identifier | ExFiles\Box 26\4\ Scan255 | |
| Date | 27th February 1924 guessed | |
| To HS.{Lord Ernest Hives - Chair} from DA.{Bernard Day - Chassis Design} SECRET. ~~X3409~~ X719 DA{Bernard Day - Chassis Design}2/26324. E.{Mr Elliott - Chief Engineer} A.{Mr Adams} C. RE. 'AGREED' & RRM. SCHEMES OF BRAKING. X.9940 X.3409 We wired you this morning asking for the mechanical gain from the new slow speed servo and we have your reply saying that the actual gain is 1.8 of which 1 is foot pressure. As this corresponds with the angle of thread instructed on LeC.1828 to a co-efficient of frame friction below .1 the result is rather surprising. You may however have an angle of 45° on the thread in which case the co-efficient of friction is still lower. It occurs to us that there is something more in this than the co-efficient of friction of the ferodo. There appears to be a considerable friction loss somewhere and we suggest that this may be found in the keys or dogs tying the 2 plates of the servo together. These are at a very small radius and transmitting half the torque of the servo the pressure must be very intense and the lubrication very poor. With maximum torque from the servo the resistance offered by these teeth might very well be from 130 to 200 lbs. off the end pressure. In addition to this there is some bearing friction which might represent another 100 lbs. We suggest that if you tried the gain with a gradually increasing and a gradually diminishing pedal pressure it would give an idea of the proportion of friction. At the point of changeover there should be an appreciable lag in the servo coming off. If you think there is anything in this theory contd:- | ||