D.B. Gearbox for 22-tonners F URTHER details have been given of
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1 the David Brown DB 657 six-speed gearbox, the introduction of which was announced in The Commercial Motor dated February 19. The gearbox is suitable for vehicles of up to 22 tons gross vehicle weight, and is available with either direct-drive top gear and crawler bottom gear, or overdrive top gear and normal bottom gear,
The crawler ratio is 9.23 to 1, whilst the bottom gear of the alternative gearbox is 6.61 to 1, with a top-gear ratio of 0.717 to 1.
The new gearbox has constant-mesh gearing throughout, and the reverse shaft includes a spur gear for the power takeoff drive. The gear shafts lie on a horizontal plane, thus affording good ground clearance and minimum interference with the floor line.
The gearbox can be mounted either .separately or in unit with the engine, and the aluminium case is in halves, the upper section being removable without disturbance of the mechanism.
NEW PRIMROSE AXLE CONVERSION
ANEW type of bogie suspension which gives non-reactive braking characteristics and uses four semi-elliptic springs hydraulically inter-linked has been developed by the Primrose Third Axle Co., Ltd., Clitheroe, Lancs.
The arrangement gives good wheel adhesion when braking by eliminating axle hop, and has the further advantage of being easy to apply to different chassis.
A full description will be published in The Commercial Motor next week, and an example is to be exhibited at the Commercial Motor Show, Earls Court, London.
63 B.H.P. PERKINS FOUR
AT least one vehicle manufacturer will exhibit a new Perkins four-cylindered oil engine at the Commercial Motor Show at Earls Court. This unit, known as the Four 203 and already established in industrial form, has a capacity of 3.33 litres and develops 63 b.h.p. at 2,600 r.p.m. and 148 lb.-ft. torque at 1,350 r.p.m. It incorporates Perkins' system of semi-indirect injection and is fitted with an hydraulically governed distributor-type injection pump.