Letter from consulting engineers Pratt & Manley regarding the features and benefits of their composite steel brake drum.
| Identifier | ExFiles\Box 120\3\ scan0109 | |
| Date | 8th December 1934 | |
| J. {Mr Johnson W.M.} H. {Arthur M. Hanbury - Head Complaints} PRATT. GILBERT MANLEY. PRATT & MANLEY, CONSULTING ENGINEERS. 23 GUILDHALL BUILDINGS, NAVIGATION STREET, BIRMINGHAM. TELEPHONE: MIDLAND 4130. GM/WEB. December 8th. 1934. Messrs. Rolls Royce Ltd., Derby. Dear Sirs, Attention of Robotham. When at your Works yesterday the writer discussed the sub-ject of our Composite Steel Brake Drum, and we are sending herewith a leaflet showing the constructional features of this drum. An important point is that we use a rolled steel section of very high quality material (.45% carbon) in which the grain of the metal runs circumferentially and without local stress. This ring is of exactly even thickness and therefore presents very little difficulty in the matter of balance; also it will not score. We have supplied large numbers of these drums for racing purposes and they have proved extremely satisfactory. Sunbeam, M.G., Lagonda, Aston-Martin and Fraser Nash all use these drums on their racing and production models; also we supplied the drums for the Napier-Railton car. This car probably provides as arduous a test of a brake drum as can be applied. Unlike a pressed drum they retain their concentricity at all times and under high temperature. The rolled steel rim section is superior to any cast iron for the following reasons:- (1) The tensile strength is far higher. (2) The frictional coefficient with the lining is retained at extreme temperatures. (3) Does not crack and possesses higher elasticity.( the modulus of elasticity is 2 1/2 times greater than cast iron.) (4) Less weight for an equivalent strength. Any desired section can be rolled. The section shown on our leaflet provides a very efficient and simple water excluder and is now being extensively used. We have found that a single robust rib gives ample rigidity and cooling , whereas a multiplicity of ribs have a tendency to become choked up with mud. We have supplied a number of these rolled section rings for insertion in Aluminium and Electron casings and these have been used on racing cars with complete satisfaction. Yours faithfully, For Pratt & Manley, GManley ppWB. | ||
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).