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).
Article from 'The Autocar' magazine detailing the design, application, and benefits of Torsilastic rubber suspension units.
| Identifier | ExFiles\Box 82\3\ scan0293 | |
| Date | 5th April 1935 | |
| April 5th, 1935. The Autocar 575 (Above, left) The Torsilastic suspension units as applied to the rear axle. (Left) Tangential stresses are set up in Torsilastic units, splines being avoided. (Right) Two superimposed Torsilastic units are used for the front wheels which take the drive. DIAGRAM LABELS: SEGMENT RUBBER VULCANISED to SHAFT SEGMENT TANGENTIAL PULL WITH TORSILASTlC FAULTY LOADING WITH SPLINES Here is a steel tube stoutly flanged at both ends for bolting into the channel member of the frame. It carries within it two Torsilastic units, one for each rear wheel, the wheels being carried on the stub axles cranked from the centre shafts. The capacity of the Torsilastic units used is chosen to enable two units to be housed in the length of the tube and carry individually the load on the rear wheels of the car. No guide bearings or metallic contacts are required for the centralisation of the shafts, which thus operate each within its own orbit in sympathy with the changes in load without need of lubrication and in universal command of the load direction. The vehicle is entirely isolated from the wheels, literally suspended in rubber without possibility existing for direct shock of any nature to be transmitted. Here, then, is a system of suspension providing not only for motion in a vertical plane but taking care of the lurch or side-sway conditions, for the rubber both restrains the shaft it carries against rotation and locates it athwart-wise the vehicle. Complete isolation in all directions is secured between composite parts. “Hammock Action” As far as rear suspension is concerned this isolation might be discounted in importance, but examination of the illustration in which a pair of Torsilastic units are assembled one above the other to form a parallel motion for control of the steering pivots will reveal how this endwise cushioning or, as it is called in Torsilastic phraseology, “hammock action,” is of the utmost value. The construction exhibited provides for the rise and fall of the wheel at constant angle with the road surface. The outer pivots, taking care of the directional swing of the wheel, are ball joints, the adoption of balls providing for both steering action and the rise and fall of the wheel. The Torsilastic unit became practical only when the rubber chemist discovered the way to attach rubber firmly to metal, and not before, although, apart from the true bond, the creation of heavy radial pressure between the shell and the shaft relieves the bonding of a great deal, if not all, of its responsibility. The stress in the bond, however, ignoring this frictional aid, is in practice amazingly low—highest, of course, at the shaft, since the surface is less than that of the circumscribing shell, but nevertheless low enough as compared with the every-day loadings used in rubber-to-metal engineering to be almost negligible. A Torsilastic unit varies as to capacity with the diameter of the centre shaft, the thickness of the rubber lying between the shaft and the shell, and directly as its length—this all in its simplest form. In some recent modifications the rate of the Torsilastic, that is to say, the ratio of its angular movement with respect to the load causing the shaft to rotate, is made by special design to follow a pre-determined variable rate curve, and in this respect a Torsilastic presents a unique advantage not to be matched by other suspension devices without unbearable complication. Any rate curve which the engineer may choose to require can be delivered by a suitable Torsilastic unit—a supreme virtue in vehicle suspension design, since the rate may be made extremely high (or low) for the early part of the range and extremely low (or high) as the motion proceeds. It may even vary irregularly in between. This is highly desirable in vehicle suspension, because it permits the softness necessary to the complete extinction of minor irregularities of surface to be provided in conjunction with the solidity required to absorb heavy shock at high speed. It is not too early to predict universal adoption of suspension of this character in the next few years. The abolition of all lost motion, the acquisition of universal cushioning, the elimination of lubrication, and perfect silence under all conditions make a combination of virtues impossible to stifle. Practically all the unsprung weight in a Torsilastic equipped car is, as far as the springs are concerned, carried by the vehicle; only a small percentage of the reach levers remains as unsprung mass. In this regard the Torsilastic shares honours with many other individual wheel designs now current, but at wheel location even the smallest differences become valuable contributions to better riding. Streamlining Underneath the Chassis Last, but not least, the use of Torsilastic suspension permits total enclosure of the under-side of an automobile chassis by a continuous smooth surface; and, if streamlining is going to prove worth while at all, the ability properly to fair the underside of a car is going to be of vastly greater importance than the addition of a “fishtail” or the adoption of a questionably beautiful front end for resistance-reducing purposes. Torsilastics are no longer a new thing, for, although they are not yet generally on the market, the B. F.{Mr Friese} Goodrich Company in the United States have spent large sums of money and many years leading to the perfection of the process; and, although they did not originate the idea, its development did not become possible until after their discovery of adequate methods of rubber to metal attachment. | ||