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 sources, processing, and applications of asbestos as an electrical insulating material.
| Identifier | ExFiles\Box 24\2\ Scan108 | |
| Date | 25th January 1921 guessed | |
| - 21 - In Russia the material is obtained by surface mining and it is not necessary to use explosives as the layers containing the asbestos can be broken with an axe. The yellow colored Russian asbestos differs from the White Canadian asbestos by having greater strength in its fibres. American and Russian asbestos consist of silicate of magnesia, the bluish and seldom used African asbestos is dearer and consists of silicate of iron. In making insulating materials it is often necessary to expose to further treatment and cleanse the asbestos that is received from the mines. The material often contains wood, sand and pieces of iron collected in passing through machines; the latter may be removed by passing the fibre over magnets. Fibres completely free from sand are obtained by the use of disintegrators and centrifugal machined, the material being sorted out by currents of air. For many insulating purposes the finest carded fibres are required. A few pressed asbestos products that have been extensively used for a long time and comply with the Regulations of the Institution are mentioned below. These have been tested by the methods of test laid down by the Institution and shew high dielectric strength, freedome from hygroscopic absorption and are easily machined. They can also be supplied as moulded parts containing metal insertions if required. The Sieman-Schuckert Works manufacture a material called eshallit, the Insulator Factory of Pankow, calls its product Abroln, the Allegemeine Elektricitates Gesellschaft calls them tenazit. The most fire resisting of these materials is gurmmon, made by the Insulator Factory at Munich and agalit of the Agathe Factory and australit of Adt.Bros. Ennsheim are conspicuous for their fire resisting qualities. Another of these valuable insulating materials is Festonit of the Vacuum-Pressgut Gesellschaft, Berlin. From the above remarks it may be understood how diverse is the use of compressed asbestos products. Parts of the most varied nature are manufactured of materials belonging to this group of insulating materials, such as switch and distribution boards, sheets to fix direct current and 3-phase meters, hollow and flat boards with embedded screws, metal parts, slits and holes of the most varied nature, sockets for testing terminals and switch handles, branching points, thimbles, discs, rings etc. As these products have very remarkable mechanical strength in addition to their excellent electrical properties and are generally not too dear, it may be expected that they will play an ever increasing part in electrical manufacture. contd. | ||