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).
Reprint from 'ENGINEERING' magazine about the bonding of rubber and metal by Metalastik, Limited.
| Identifier | ExFiles\Box 133\4\ scan0303 | |
| Date | 30th September 1938 | |
| Reprinted from “ENGINEERING,” September 30, 1938. THE BONDING OF RUBBER AND METAL. MESSRS. METALASTIK, LIMITED, LEICESTER. THERE is no doubt that the use of rubber, in damping torsional oscillation, and the vibration present in practically every kind of continuously-moving machinery would have by now been more extensive had it not been so difficult to secure the elastic rubber to the rigid metal. This serious drawback, however, no longer exists, as Messrs. Metalastik, Limited, Evington Valley-road, Leicester, have perfected a method by which a rubber covering can be made virtually integral with the metal which supports it. A detailed description of the process is not available for publication. It consists in the plating of the metal parts, by electro-deposition, with a film of an alloy which, having the appearance of a light-coloured brass, is perfectly smooth, yet is of such a structure that the rubber, when treated in a vulcanising press, may be said to fuse homogeneously with it. This statement is one which at first seemed to us to require proof, but it was confirmed by a recent visit to the research laboratories of Messrs. Metalastik. The illustrations of Fig. 1 to 6 accompanying give an idea of some of the testing methods witnessed on that occasion. The first three figures show a tensile test. The test piece, as seen in Fig. 1, consists of two discs joined by a short cylinder of rubber, the whole being prepared by the process briefly outlined above. On tension being applied, the rubber extends and in doing so naturally decreases in cross-sectional area, as shown in Fig. 2. Continued increase of load eventually results in the rupture of the rubber, a condition illustrated in Fig. 3. In both Fig. 2 and Fig. 3 it must be noted that the rubber has not come away from the metal surfaces. In one case the test piece successfully withstood a pull of some 900 lb. per square inch, but we understand that considerably higher figures may be reached, the ultimate tensile load depending, no doubt, on the precise quality of the rubber used. This tensile test, though interesting, would not, however, seem to be of such practical importance as the shearing test shown in Figs. 4 to 6, as in a large number of applications, e.g., torsional vibration dampers, shear is the chief stress. The test pieces without load are shown in Fig. 4. They consist of two strips of metal with a layer of rubber between them. On the application of the load the rubber distorts in the manner indicated in Fig. 5, but it does not leave the metal, a result perhaps more strikingly illustrated in Fig. 6, in which though rupture has occurred this has taken place in the rubber itself, a layer of which is still seen firmly adherent to the bottom strip. It may be stated here that both natural and synthetic rubber are employed, the latter in those cases where the part is subjected in use to a high degree of heat, or exposed to oils and oily vapours. It would appear that the process can be applied to all types of metal, not excepting that somewhat intractable material—aluminium. As the process is a new one, the full extent of its utility has not yet been determined, but it is not difficult to foresee for it very wide and varied possibilities. Some of the actual applications up to the present may, however, be mentioned. One of these is the crankshaft torsion damper. This is fitted to the free end of the shaft of an engine in, say, a motor-car or other motor vehicle, and consists of a flanged housing in which a flywheel rim is contained, the face and rim of the flywheel being bonded to the housing by a layer of rubber. The torsional vibrations are absorbed by the rubber immediately they are set up. There is, of course, no possibility of the two parts coming adrift, while, as any relative movement is contained in the body of the rubber, no friction occurs nor can wear take place. This damper has been employed by a number of well-known motor manufacturers, e.g., Austin, Daimler, Mercedes-Benz, Chrysler, &c. Somewhat similar applications are for flexible couplings for small angular movement and heavy torque, such as occurs in marine propeller shafts; and for clutch centres, where, interposed FIG. 1. FIG. 2. FIG. 3. FIGS. 1 TO 3. STAGES OF TENSILE TEST. | ||