Simplicity in a New Driving Bogie
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TEE new four-wheel-drive unit which Kirkstall Forge, Ltd., near Leeds, has produced for six-wheeled doubledeck buses and, which, incidentally, is being supplied to Crossley Motors, Ltd., embodies features of design, which, whilst allowing increased simplicity, ease of maintenance and lightness of weight, permit the desirable characteristic of a wide frame with low floor height.
An ipterestin.g part of the new unit is the design of the springs, this being the subject of a Kirkstall patent. An inverted semi-elliptic spring is employed at each side, the top leaves being long, so as to provide an additional auchorage for the axles' ; one anchorage is above and the other below the axle centre. This enables the driving and Licking torque reactions to be taken by the springs. The result is that torque rods or tubes are eliminated and the weight of the bogie is considerably reduced.
An accompanying illustration shows how the whole unit is simplified ; it also indicates that each spring is mounted below the top of the axle casing, permitting a wide frame.
It may be noted that the final-drive worm gems; are offset in the manner usu.al for double-deckers, and that the forward axle incorporates the Kirkstall patent third differential, this ensuring that each axle takes its own proportion of the total torque, enabling every road wheel to run at the speed best suited to its diameter.
In order further to reduce weight, the worm casings are made of Elektron. The axle casings are drop forged from the staid billet, the material used being 1-1i per cent, nickel steel. The brake drums are 6 ins. wide, the brake application layout conforming to the latest regulations.