RUBBER-BUSHED COUPLINGS AND HEAVY ANGULAR LOADING CONCERNING the letter from
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Mr. T. R. Charles worth, of the Laycock Engineering Co., Ltd., published in your issue dated July 30, he does not state w hat is the maximum angular movement which the rubber-bushed type of coupling will handle without detriment to its life. This, in my opinion, is certainly much less than that of the mechanical type of universal joint.
Most rear propeller shafts with joints of the rubberbushed type are fitted without a plunger-type slip coupling to take care of axial movement, and displacement soon causes failure of the bushes.
Vehicles with soft springing are usually inclined to a certain amount of rear-spring " snaking " under hard braking or rapid acceleration, and this also is extremely destructive to such a joint if used for the axle coupling.
It is the writer's opinion that the best layout is a rubber-bushed coupling immediately behind the gearbox, with a mechanical-jointed propeller shaft from the steady bearing to the rear axle. Where there is a onepiece propeller shaft direct from the gearbox to the back axle it is suggested that a rubber-bushed joint could be used behind the gearbox and fitted with a plunger coupling, whilst there could be a mechanical joint at the rear end for attachment to the axle. This arrangement would take care of 'transmission, chatter and permit of both angular and axial movements with the types of unit best able to withstand them.
Newcastle-upon-Tyne, 1. J. L. G. BREWSTER.
(For J. Brewster and Co. (Transport Engineers), Ltd.)