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).
Mr. Royce's views on direct braking versus servo power, with calculations for modifying brake components.
| Identifier | WestWitteringFiles\M\2April1925-June1925\ Scan109 | |
| Date | 9th June 1925 | |
| TO HS.{Lord Ernest Hives - Chair} FROM DA.{Bernard Day - Chassis Design} Copy to RG.{Mr Rowledge} BY.{R.W. Bailey - Chief Engineer} SECRET. DA{Bernard Day - Chassis Design}1/M9.6.25. INDIA. V5940 X5370 PROPORTIONS OF BRAKING. With further reference to HS{Lord Ernest Hives - Chair}/RM{William Robotham - Chief Engineer}2/LG27525., Mr. Royce does not approve of the suggestion to reduce the direct braking and increase the power of the servo. He considers that the direct braking is very valuable. It is appreciated chiefly when shunting in difficult places, in which the full effect of the servo lag, namely, from the full amount forwards to the full amount backwards, is experienced. We estimate that with the enlarged dia. of cam shewn on N.sch.2005. with a 45° angle, a rod multiplication from the servo of approximately .8 will be obtained, which corresponds to a torque multiplication of approximately 1.25 whereas we are trying for a torque multiplication of 1. If, in addition to this, we increase the radius from the brake shoe cam from .4 to .5, and the length of the sheet metal lever on the rear brake differential slightly, it will be found that this is practically the equivalent to a torque multiplication of 1., with the present system of levers and cams, and will give us we believe what we want. We find that the sheet metal lever requires to be reduced from 2.625 as given on N.sch. 2005. to 2.150 approximately, and that this length can be used on the front brake, so that the same lever will do for both. We have looked into the question of altering the proportion of direct braking, and find that quite a considerable alteration does not make much difference to the distribution of braking for servo efficiencies within the range we are likely to get. DA.{Bernard Day - Chassis Design} | ||