A NEW ATKINSON 6-7-TONNER
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Full Particulars of a Four-wheeled Chassis that is Obtainable with either a Gardner or a Dorman Four-cylindered Oil Engine, and Weighing, with a Flat-platform Body, Under 4 Tons
WE are able, this week, to announce an entirely new 6-7-ton goods vehicle—the product of Atkinson Lorries (1933), Ltd., of . Kendal Street, Preston. Simplicity characterizes the design, which incorporates many components made by specialists, and it is clear that in planning the mechanical details a careful eye has been kept upon problems associated with maintenance.
All the important engine auxiliaries are readily accessible, brake adjustment is easy, and the grease-gun nipples are conveniently situated, whilst the fact that a full-width cab and a completely bonneted engine installation are provided simplifies the work of the driver in attending to routine adjustment and lubrication.
• The frame is a substantial structure embodying side members, with .a maximum depth of S ins. and 34-in. flanges,
pressed out of high-tensile steel plate. These members run straight and parallel from the front of the vehicle 1328 to the forward mounting plates for the rear springs ; thereafter the undersides are tapered off to give a frame depth of 4 ins, at the rear, where they-are joined by a substantial cross-member of channel section.
Two deep pressings, one located behind the gearbox and the other at the point where the forward mounting plates for-the rear springs are situated. brace the frame amidships, whilst at the front a further channel connects the dumbirons.
Semi-elliptic springs are used for the suspension of both front and rear axles (the after pair of springs is underslung beneath the axle casing), caststeel brackets being employed to support the spring and shackle pins. These brackets are of good design, light but immensely strong, and, as they have a large area in contact with the frame, there should be no possibility of an anchorage working loose.
Purchasers are given a choice in the matter of power unit, a Dorman or a Gardner four-cylindered oil engine being installed as desired. There is a small variation in price, the Gardnerengined vehicle being slightly more expensive.
As both these units are well known to readers of The Commercial Motor there is nothing to be gained by giving a detailed description here. It will be remembered that in the Gardner unit direct injection is employed, whilst in the Dorman design swirl chambers are incorporated, with the addition of heating plugs to facilitate starting from cold.
To prevent the transmission of vibration to the chassis, rubber washers are inserted between the engine feet and the frame side members, and, as we proved to our satisfaction during a short road trial, the arrangement is eminently satisfactory. Both the torsional and 'secondary forceS are absorbed by the flexible mountings, with the result that there hardly a trace of drumming in the cab.
Built as a unit with the engine are single-plate clutch and a four-speed gearbox. All the pinions of the latter are of substantial proportions and these are mounted on large-diameter ground shafts, which run on ball races of ample
capacity. The indirect ratios in the gearbox are 1.7, 2.6 and 5.27 to 1, for 11-.. forward gears, whilst the low reverse ratio of 8.23 to 1 should be useful when the vehicle is being operated on soft or uneven ground.
From the gearbox, power is transmitted by a Hardy-Spicer tubular propeller shaft incorporating needle-roller joints, to an overhead-worm-driven rear axle, with fully floating half-shafts. When a Dorman engine forms the power unit the final reduction ratio is 6.5 to 1, giving road speeds of 35.1, 22.4, 14.6 and 7.23 m.p.h., on the four forward gears, at the governed engine speed of 2,250 n.p.m.
In Gardner-engiued chassis a slightly higher ratio than 6.5 to 1 is used, owing to the fact that the governed maxi/elm ia rather lower than that of the Dorman unit.
The brakes next claim attention. Both foot and hand-operated systems apply internal-expanding fabric-faced shoes within drums of 17 ins. diameter.
As will be seen from an accompanying illustration, the combined servo motor and master Lockheed cylinder are located on the off side of the frame, immediately behind the driver, so that a direct pull from the pedal is obtained. In this way tee brakes remain operative even in the unlikely event of a servo failure, All four brakes are applied by the pedal, whilst the lever actuates only the rear shoes, which are 6 ins. wide.
Great care has been taken by the maker in planning the steering mechanism.' A David Brown worm-andsector steeling box is used, and the disposition and leverages of the droparm, drag link, etc., give a sensitive and exceedingly light control. . Particular attention has been paid to the design of the cooling system, the construction of the radiator being especially interesiing. Instead of the usual single block, the cooling surface has been divided into four equal rectangular cells, each of which is con....pected to a common header tank by a
flanged coupling. If one block be damaged the engine will run reasonably satisfactorily on the other three, with the offending cell blanked off. Covering the whole -assembly is a shell of attractive lines with a stoneguard at the front.
For the rest, the chassis follows normal practice. Steel-disc road wheels, shod with 36-in. by 8-in. tyres (twins at the rear) are used, and Tecalemit grease nipples are standardized. The fuel tank has a capacity of 25 gallons, whilst a 12-volt 5-lamp lighting set, a mechanical tyre Pump and a.! speedometer are included in the specification.
The size of the vehicle may be judged from the fact that the wheelbase is 12 ft. 6 ins., the front track 6 ft. 31 ins, and the mean rear-wheel track 5 ft. 41 ins., whilst the overall length and width are 19 ft. 9 ins. and 7 ft. respectively. As a bare chassis the price will be fixed at about £1,000, a cab being available for an additional £50.