New. S.D. Developments
Page 59
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DEVELOPMENTS by Shelvoke and Drewry, Ltd., shown at Portsmouth last week, were not confined to the redpsigned bodies and air-operated semidustless loading gear described on the preceding pages. Two new Freighter chassis made their debut; the TW for gross weights of 10-11 tons and the TY for operation at 14 tons gross.
A new S.D. chassis is something of a rarity, as the last new model, the W type, which the TW succeeds, was introduced in 1946. The heavier TY, which was seen last year in rather different prototype form as the RY, represents an increase in carrying capacity for S.D. chassis and reflects the growing size of refuse-collection vehicles.
The power unit of the 13-ft.-wheelbase TY is a departure from normal S.D. practice. It is a Leyland 0.350 oil engine running at 2,400 r.p.m. to develop 105 b.h.p. A 14-in.-diameter clutch is employed and the gearbox is a five-speed constant-mesh unit.
Bolted construction is employed for the chassis, which has 9-in.-deep side members in f-in.-thick material with 3-in.-wide flanges.
Three-piece wheels are used and these
carry 8.25-20 in. (14-ply) tyres. An innovation on the chassis is the airhydraulic braking system. This type of brake actuation will probably be employed for all S.D. models in the future, because a compressed-air supply is required to operate the current bodywork mechanism.
The smaller TW chassis is similar in general layout to the preceding RW' model, but has new front and rear axles. The front axle is a heavier type than before and has a wider track to give an improved turning circle-48 ft. 6 in. swept—for the 11-ft. 6-in.-wheelbase chassis. It is powered by the Perkins Six 305 5-litre engine which produces 86 b.h.p. at 2.400 r.p.m. and drives the 6.14-to-1 ratio 6-ton rear axle through a 14-in.-diameter clutch and five-speed gearbox.
The" frame side Members are 6* in. deep with 2i-in. flanges pressed from 4g-in.-thick material. Springs all round are 3 ft. 4 in. long and 21 in.. wide. The three-piece wheels carry 8.25-15 in. (14ply) tyres to reduce the loading line and overall height.
The air-hydraulic braking system operates on Girling wheel units which provide a total 'lining area of 336 sq. in.
A new crew 'cab, differing only in its depth and wheel-arch radii, is offered on both chassis.