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).
Technical memorandum on the development of brake systems, covering servo assistance, hand brakes, brake ratios, and component interchangeability.
| Identifier | ExFiles\Box 148\5\ scan0300 | |
| Date | 7th March 1938 | |
| -2- brake system in which there is no servo assistance to rear brakes, as this saves a large amount of mechanism. We can produce a servo now which is absolutely non-fading; µ = 0.31. If the front brakes are hydraulic, a double acting asymmetrical cam on the servo can directly operate the hydraulic cylinder. This is such an obvious development that it ought to be protected by a patent (if not too late already). 6.B.IV, in France, has little servo rear braking, and we think we ought to convert B.56.BN{W.O. Bentley / Mr Barrington} from a 'non-servo brake' test car into a servo to front only test car. A scheme for this servo hydraulic mechanism should be produced as soon as possible. (3) The hand brake is required by law to be mechanically operated, and on our cars it ought to be both effective and well made. The layout of rods on B.III rear is about as simple as is possible, and this type of rear linkage is our choice for future cars, because there is the minimum of duplication between hand and foot brakes, and therefore a minimum of expense. (4) A brake ratio of 1.2 front/rear is possible and desirable on cars with independent front suspension: but our present experiences on 6.B.IV in France point to the absolute necessity for more lining area on the front. A lining width of 2" is desirable on any car of our power and weight, when a two shoe brake is used. We are, of course, making a 4 shoe brake for Wraith, in view of the rapid wear on 26.C.VI in France, and the 4 shoe brake may have its uses in future designs. (5) Some measure of interchangeability between various chassis is very necessary on our cars to keep down production costs. The kind of thing that is possible is the use of a two shoe brake on some chassis and a four shoe brake on others. B.III and B.50 should have many parts interchangeable, both should have 12" dia. brake drums, to enable the standard type of rolled steel brake shoe to be used with 5/16" thick brake lining. A scheme is immediately wanted for B.III and B.50 brakes, with the following alternative features - Rear 12" dia. drums, either aluminium or iron. aluminium shoes or steel shoes. 0.625" or 0.750" travel wedge. | ||