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 wrapping and non-wrapping action of rigid brake shoes.
| Identifier | WestWitteringFiles\L\2Jan1924-March1924\ Scan6 | |
| Date | 17th January 1924 | |
| R.R. 408A (40 H) (SL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. Expl. No. REF: Hs{Lord Ernest Hives - Chair}/ACL/LG17.1.24. WRAPPING AND NON-WRAPPING ACTION OF RIGID BRAKE SHOES. The apparent co-efficient of friction determined from our results on front brakes on the test rig are as follows :- Wrapping shoe µ = .84 Non-wrapping shoe µ = .27 This was determined from the static pressure on the shoes. Ferodo Ltd. say that this is about the ratio to be expected and that the mean of these two results will not be the true co-efficient of friction. It can be proved that the increased braking torque obtained by a wrapping shoe is entirely due to an increase in the normal reaction of the drum at the centre of pressure of the shoe, above the static value of that reaction. In the case of the non-wrapping shoe the normal reaction will be lower than the static value. Consequently the co-efficient of friction determined in the usual way, and calculation made on the static reactions, will not be true. TREATMENT OF WRAPPING AND NON-WRAPPING BRAKES. DIRECTION OF ROTN. r = rad. of drum. P = Force applied at end of shoe. A = Perpendicular distance between line of force P and Pivot M.{Mr Moon / Mr Moore} NO = Line of centre of pressure. b = Perpendicular distance between line of centre of press: and pivot. R = Normal reaction at C p l = ⊥ line between friction force and pivot. contd:- | ||