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).
Typed memorandum comparing brake lever ratios and efficiency for O.B.IV (Girling) brakes.
| Identifier | ExFiles\Box 83\2\ scan0347 | |
| Date | 26th July 1938 | |
| ZOOa Typed 26/7/38. COPY FOR FILES. O.B.IV (GIRLING) BRAKES. A.{Mr Adams} The 'M' series standard Bentley has a brake lever ratio front/rear = 1.00, with 1,770 brake units. B. O.B.IV has now (with longer front plate lever) a lever ratio front/rear = 1.14 with 1,770 brake units. C. With the levers sent out to France, the figures were; ratio front/rear = 1.02 with 1,075 brake units. The arrangement in 'B' appears to give a standard front/rear brake proportion, judging by road tests. The mechanical efficiency of the front brakes is about 63% whereas the mechanical efficiency of the rear brakes is approximately 73% or 15% more, and this accounts for the extra front brake leverage required. It is impossible to calculate with certainty the leverage proportions front/rear when the front and rear mechanical efficiency varies widely, and it can only be determined by trial and error by testers, or by a brake test machine. Vibration reduces the mechanical losses. Rm{William Robotham - Chief Engineer}/AFM.{Anthony F. Martindale} | ||