Express Artie Motorways
Page 63
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AN engine developing 262 b.h.p., an eight-speed gearbox and a rubbersprung driving axle are features of the forward-control tractor for a maximumload articulated oufit being built by the North Derbyshire Engineering Co., Ltd.. Darley Dale. Derbyshire. It is destined for operation on motorways at sustained speeds in the order of 55 m.p.h. The tractor is nearing completion and the outfit should be in use by January, 1961. Although the tractor is designed for the motorways, its multi-speed gearbox should prove of great benefit for maintaining speed on steep gradients when the vehicle is employed on hilly routes to the North and Scotland.
The unit was evolved to meet the requirements of an associated haulage company, .Tuft Bros. and Tomlinson. Ltd., but will eventually be offered on the open market. It was decided to develop a semi-trailer outfit in preference to a rigid vehicle so that a number of semi-trailers could be used in conjunction with a single tractor. On the DerbyihireLondon run, the semi-trailer will be exchanged for a pre-loaded unit at a depot at St. Albans for the return run.
Motive power is provided by a Cummins NTO-6 turbocharged engine which develops its peak output of 262 b.h.p. at 2,100 r.p.m. and torque of 740 lb.-ft. at 1,300 r.p.m. To simplify accommodation of the unit in the cab, the turbocharger was moved from its normal position at the off-side to the rear of the induction manifold. The turbocharger is oil-cooled and provides automatic compensation for power lost with increase in altitude up to 10.400 ft. The engine is located by four flexible mountings.
Drive is transmitted through a short propeller shaft to a mid-mounted SelfChanging Gears RV30 air-operated eightspeed epicyclic gearbox which gives continuous traction during ratio changes. Gearbox ratios are: first, 9.98 to I; second, 6.57 to 1; third, 444 to 1; fourth, 3.09 to I; fifth, 2:195 to 1; sixth, 1.446 to 1; seventh, 1.022 to 1: eighth. 0.68 to I; high reverie, 2.523 to 1; low reverse, 11.53 to I. Overall final-drive ratio of • the A.E.C. heavy-duty double-reduction back axle is 6.25 to I. The gearbox is supported by two flexible mountings on the near-side and by a single flexible mounting on the off-side.
The rear suspension is of particular interest in that it is based on Hendrickson R.S.320 load cushions and auxiliary flexible bushes, modified by the vehicle makers to accommodate a single axle in place of a bogie. The axle is mounted centrally on a welded support member between the cushions in the position of the pivot for the usual oscillating beam.
It has a total deflection of in. This limited movement is important, because it reduces unladen frame height at the rear by some 5 in. compared with a conventional leaf-spring suspension system. If a suitable type of independent front suspension system were available, its adoption would have been con sidered as a means of providing a relatively low engine position. Channel-section longitudinal chassis members of material with a depth of 10 in. are employed in conjunction with tubular cross-members of 41-in.
diameter in material. Apart from the rear cross-member, the tubes are reinforced by tapered webs, welded in position, at their outer ends. The chassis structure is assembled with bolts and Simmond's self-locking nuts.
Other chassis details include semielliptic front springs 4 ft. 6 in. long, mounted on Silentbloc rubber bushes. Westinghouse direct-mounted diaphragmtype air-pressure braking equipment is fitted, with quick-release couplings.
Driver comfort has been closely studied in the design and layout of the controls and cab. The steering wheel is telescopic and the rake of the column can be varied to suit the driver. A flexible coupling at the base of the column permits variations to be made by an adjustable upper bracket. Combined with a fully adjustable seat, this permits the driver to sit close to the wrap-round windscreen.
The cab is a Bowyer plastics structure with light-alloy frame members. Side lockers on each side of the engine accommodate the batteries of the 24-volt electrical system. and shelves for storing tools and other equipment. The semitrailer frame will be based on main longitudinal § in a-in. material with a depth of 15 in. and a flange width of 3; in. Cross-members will be light-alloy channel sections. A standard Hendrickson rubber-sprung bogie will be fitted. Platform length is to be approximately 24 ft. The outfit is designed for a payload of 20 tons in anticipation of a change in the regulations to permit 28 tons gross for articulated units.