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).
Extracts from a letter detailing the manufacturing processes for hard rubber tracks and Bakelite distributors.
| Identifier | ExFiles\Box 39\3\ Scan080 | |
| Date | 7th May 1918 | |
| EXTRACTS FROM MR. OLLEY'S LETTER OF MAY 7TH. 1918. FR. to Oy. X. 3513 8................................................................. This hard rubber track, which is habitually used by them, both in automobile and aero engine work, is made by them from the raw materials in their own Works. I was shown the process of manufacture, which consists of rolling together in a rolling mill pure native cretonne rubber, with pure shellac, ordinary powdered whiting, magnesite, flowers of sulphur and infusorial earth. The resulting sheet is not very elastic, but is soft and malleable. It is cut into strips, and these are pressed between cast iron moulds and vulcanised in the moulds, the brass contacts being moulded into place. The whole process is a very neat example of manufacturing methods. 9. I was shown the moulding of the Liberty distributor. The rubber track with the brass contact moulded into place is placed in the die, and the powdered Bakelite poured over it. The upper die is brought down till it is just pressing the powdered Bakelite. Both dies are then heated with internal steam coils to make the powdered Bakelite fuse and flow. Meanwhile the rubber track is kept cold by circulating cold water in the mandrel in which it fits. This causes it to grip the mandrel and prevents the Bakelite from getting on to the track surface. After a time the upper ram is caused to descend to bring full pressure on the fused Bakelite. When the two dies have closed together,the mandrel in the upper track which had been cooled with cold water, is heated up with steam to the temperature of the rest of the die. The die is held at this uniform temperature some minutes. Then the steam is cut off and the dies are opened. The resulting distributor is practically perfect, with the exception of a very thin flash, which it is necessary to break off. This is reduced to a minimum by having the Bakelite carefully measured out in special receptacles, each containing a complete charge. All that remains now is to polish up the inside of the track. 10................................................................ The use of Bakelite instead of Micanite of Vulcanite appears to facilitate manufacture. Bakelite is combined with various binding materials; sometimes sawdust is used, and sometimes paper. I believe mineral matter is used in the Delco distributors. Combined with sheets of canvas duck, Bakelite has been built into strong-grained substances which have been used successfully for propellers................................... combined with sheets of paper, Bakelite forms thin yellow sheets, used for the same purpose as presspahn or manilla paper. It is used for washers and tubing in rods and sheets, and excepting where high tension sparks have to be faced, such as the track of the distributor nothing else but Bakelite materials appear to be considered by the Delco people. The distributor tracks, however, are all of the hard rubber compound. | ||