New 12-ton Hypoid Axle
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ANEW hypoid-drive rear axle with art integral lubrication pump, has been designed by Kirkstall Forge. Ltd., Leeds, for use in the larger single-deck buses and coaches now permissible. Although specifically intended for the 30-ft. by 8-ft. passenger chassis, the axle is equally suitable for 12-ton gross fourwheeled goods vehicles, and is available with a gear ratio within the range from 3.9-6.1 to I.
The braking system may be operated mechanically, hydraulically, by vacuum servo, or by compressed air, and the new axle can be modified to suit individual requirements.
Rigidity is of prime importance for hypoid-bevel-drive gears, and the new axle case, which is a one-piece drop forging, has been designed to be free from deflection under load, so that the gears should have particularly long life. Special attention has been paid to the arrangement of the bearings supporting the pinion and crown wheel, the former being straddle-mounted and the bearings widely spaced.
Oil circulation to the pinion bearings, *26.
crown-wheel bearings and differential gears is provided by a Kirkstall internal oil pump.
New brakes having 151-in.-diameter drums and 7-in.-wide shoes are used, the drums being of heavy section to prevent distortion and to promote cool operation. The small diameter of the drums makes a useful contribution to the reduction of heat radiation between the wheel drums and tyres.
Moulded brake facings of 1-in, thickness are employed, these being • of reduced depth at the heel and toe. Improved shoe geometry and increased strength of the shoes, because of dimensional arrangements, are among the advantages claimed for the design.
The familiar Kirkstall two-shoe construction with fixed pivots is retained. but the brake camshafts carry a much reduced torque, because of the employment of cams with a low lift ratio. These cams are of S type and the camshafts are thus provided with worm and wheel adjustment on the brake levers. Kirkstall's leaf-type brake-shoe return springs are retained.