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 mechanics and torque of wrapping and non-wrapping brake shoes.
| Identifier | ExFiles\Box 26\4\ Scan225 | |
| Date | 12th July 1923 | |
| R.R. 403A (40 H) (SL 43 12-7-23). J.H., D.{John DeLooze - Company Secretary} -2- EXPERIMENTAL REPORT. Exptl. No. 994- REF: HS{Lord Ernest Hives - Chair}/ACL/LG17.1.24. WRAPPING SHOE. Take moments about M.{Mr Moon / Mr Moore} Pa{Mr Paterson} + Fl = Rb{R. Bowen} F = μR ∴ Pa{Mr Paterson} + μlR{Mr Ellor} = Rb{R. Bowen} or R[b - μl] = Pa{Mr Paterson} or R = Pa{Mr Paterson} / (b - μl) Torque due to this shoe = Rrμ = Pa{Mr Paterson}μRr / (b - μl) NON-WRAPPING SHOE. For the non-wrapping shoe the action will be similar but with a reversal of the μl term. ∴ TORQUE DUE TO NON-WRAPPING SHOE = Pa{Mr Paterson}μrR / (b + μl) For external contracting brakes the action will be the same. The centre of pressure can be determined in the usual method by means of the Funicular Polygon. It is found that the above equations hold good in practice and that the co-efficient of friction determined from either of the above equations satisfies the other. Some worked examples shown to us by Messrs. Ferodo show that their method of treating wrapping and non-wrapping shoes is similar to the above. They also say that in the case of the floating fulcrum brake much more wear takes place with the wrapping shoe. The increase of 'mechanical gain' obtained from increased loads is shown from the above equations to be due to an increase in the conefficient of friction. This theory is supported by Ferodo's tests w i.e. increase of μ with temperature. contd:- | ||