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).
The co-efficient of static friction of brake shoes.
| Identifier | ExFiles\Box 26\4\ Scan250 | |
| Date | 19th February 1924 | |
| R.R. 403A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} Expl. No. 9940 EXPERIMENTAL REPORT. To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to CJ. RG.{Mr Rowledge} c. to E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} c. to EY. WOR.{Arthur Wormald - General Works Manager} S E C R E T. CO-EFFICIENT OF STATIC FRICTION. We have carried out tests on the experimental brake rig to determine the difference between the static co-efficient of friction of the Ferodo as used on our front wheel brake shoes and the corresponding co-efficient when slipping. The method adopted was to use both shoes of a standard brake, apply a given load to the cam arm and note the retarding torque obtained at a fixed drum speed. The drum was then brought to rest and slowly pulled over until it just commenced to slip against the shoes. The torque required to accomplish this was again noted. We experienced very considerable variation in our results, the extent to which the shoes were wedged on making an appreciable difference to the static readings. As an average reading we found that the static co-efficient of friction is 15% higher than the co-efficient of friction at a slipping speed of 800 ft. per minute. If the slipping speed is further increased to 1600 ft. per minute, the co-efficient of friction decreases by another 4%. In all our tests the temperature of the drum was maintained at 100°C. Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||