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).
Letter discussing the specifications and potential applications of the Mack rubber block coupling.
| Identifier | ExFiles\Box 74\3\ scan0008 | |
| Date | 22th October 1925 | |
| Oy8-E-102223 Mr. Claude Johnson, Rolls-Royce, Ltd., London, England. (Copy for attention of Mr. Royce) " " " Mr. Hives " " " Mr. E.Platford) Dear Sir: Re: Mack rubber block coupling We send herewith prints of the Mack rubber block coupling now used on all Mack trucks and busses to cushion the drive from engine to rear axle. This is enormously heavy as shown but the engine is a 4 cylinder 5"x6" so that the impulse variations are very great. Also the joint is between gearbox and rear axle and is designed for maximum low-gear torque. The device is an extension of the rubber shackle idea and the makers claim that while the angular variation permitted is less than with Hardy fabric joints, the following advantages are obtained -- (1) The joint can be much smaller in diameter than the corresponding fabric joint. (2) The life is much greater than the fabric joint, in fact it will outlast the metal wearing parts. (3) The cushioning effect is greater and angular deflection of the shafts does not produce the endwise knocking encountered with ordinary fabric joints. The blocks are assembled under a set-up pressure 50% greater than the load they have to carry (as with the rubber shackles) so that no scrubbing effect can take place between the unloaded block and its containing walls. We bring this to Mr. Royce's attention as a possible useful development either in aero work or in the coupling between engine and gearbox. The same joint has been recently applied to steering gears to absorb road shocks. Gy. | ||