Auto-Traction.
Page 10
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MWO new bus chassis, the smaller for 1 vehicles seating from 20 to 26 persons, and the larger for 30-seater bodies, together with a 6-tou tractor-trailer having a bare trailer chassis, will comprise the exhibits staged by Minerva Motors.
The engine used in the two vehicles is known as the 30-50 h.p. type. It is four-cylindered, with the cylinders cast en bloc. It is a neat, compact unit, of clean design, with an adjustable but sealed governor, shaft-driven from the crankshaft. The main feature of the engine, however, is that it is of the sleeve-valve type, the general lay-out being identical with that used for so many years in Minerva private cars, and including the Minerva lubricatOn system by means of troughs, thelevel of which is regulated' by the speed of the crankshaft, whilst separate force feed is used for the bearings.
The radiator on both models is comprised of six quickly detachable sections of the honeycomb type. Through 'these the water is circulated by centrifugal pimp. The four-speed gearbox ::s mounted as a unit with the engine, the whole being three-point suspended; the control is central, and the drive is taken through a cardan shaft with three couplings, the two at the forward end being of the Hardy type. Final drive is by spiral bevels, and the rear wheels are equipped with brake drums having internal and external brakes. An exceptionally heavy section is utilized for the front axle, chiefly for the reasons that front-wheel brakes are supplied as standard fittings.
All the foregoing refers to both models ; now we come to the differences. The smaller has a 14-ft. 7-in. wheelbase, a frame height of 2 ft. 3i ins., and a final drive ratio of 5-1, the speed being from 35 to 38 m.p.h., whilst in th larger the wheelbase is 15 ft. 7 ins., the frame height 2 ft. 4i ins., the gear ratio 5.8-1, and the speed from 28 to 30 m.p.h.
The Auto-Traction tractor-trailer is by no means new to this country. The tractor has a 20 h.p. engine developing 39 b.h.p. at 1,500 r.p.m., a multiple disc clutch, four-speed gearbox built as a unit with the engine, a radiator in sections, and a dual-type axle with separate load-carrying and driving members, the final reduction being by internal gearing.
The chief novelty is the articulation of the tractor frame behind the driver's cab, the front and rear portions being r united by a laminated cantilever spring On each side-member.
Minerva MotorS, Ltd., Chenies Street, Loudon, W.C.1.