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 discussion comparing Bakelite and hard rubber distributor materials and issues with charring.
| Identifier | ExFiles\Box 37\1\ scan 049 | |
| Date | 17th April 1918 | |
| Contd. -4- Cy6/FMF17.4.18 point came out. Originally, in their enthusiasm for the Bakelite methods of constructions, they made the whole distributor of Bakelite including the track, and delivered an enormous number of such distributors to the trade. These gave trouble whenever a car was heavily pushed, and caused the Delco Company a loss of several hundred thousands dollars. They now use hard rubber universally. They do not approve of the carbon type of distributor but their hand is forced apparently, by the aero engine designers. On their automobile work they employ a face contact distributor, using steel contacts and a light steel button forced up against the with a light spring. The contacts are simply let into a vulcanite disc which is ground off level. I believe the steel contacts are hardened, but am not quite sure. The steel is used becaused of its better wearing qualities. Mr. Chryst, the Chief Engineer, said that the hard rubber track had got them over their difficulties with burning of the surface. The bakelite showed the fault of charring along the track of a surface spark, the charred groove subsequently forming an excellent conducting track of pure carbon. The hard rubber he said did not do this. I told him that my own personal experience was that with black hard rubber a surface spark did leave a charred track, but he said he thought this was due to the use of lamp-black in the composition to give the deep color. The own hard rubber is, I imagine, very pure and is not black, but is of a seamy gray color like whalebone. X.2894. X.1618. (2) The contact breaker is of the usual plain type, as Contd. | ||