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SEDDON IN ODUCES A 3-TON OILER

4th August 1950, Page 42
4th August 1950
Page 42
Page 43
Page 44
Page 42, 4th August 1950 — SEDDON IN ODUCES A 3-TON OILER
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By L. J. COTTON, M.1.R.T.E.

THIS week The Commercial Motor " is able to publish a description and road-test report of the new Seddon 3-ton oil-engined chassis, the smallest compression-ignition-engined vehicle made in this country on a production basis. The Seddon Mark 7, as it is termed, has been designed as a forward-control model to provide a large platform area suitable for light but bulky loads. Wholesale deliveries from warehouses to shops. or inter-warehouse duties, are typical tasks.

It has been produced as the result of a survey by the Seddon distributors, in conjunction with the manufacturer, who found there was a potential market for an oil-engined 3-tonner, provided the initial cost was competitive with that of its petrol-engined counterpart. The basic chassis price of the new Seddon is £695, plus £193 16s. 2d. purchase tax.

Perkins P.4 Engine The 3-ton chassis is a scaled-down version of the larger Seddon goods vehicles, and is powered by the Perkins P.4 compression-ignition engine, which is supported in the frame ahead of the front axle. This unit employs the Aero-flow system of combustion, and in construction is a shortened edition of the wellestablished P.6 unit. It has the same bore and stroke of 31 ins. and 5 ins, respectively, but develops 50 b.h.p. at 2,400 r.p.m., the maximum governed speed. A torque of 123 lb.-ft. is delivered at 1,000 r.p.rn. Metalastik rubber-bonded units are used to support the engine in the frame.

The 10-in.-diameter clutch and four-speed constantmesh gearbox are built integrally with the engine, and the gear lever is attached to the top of the box and cranked for comfortable manipulation. In the transmission to the rear axle, the two-piece propeller shaft has a Layrub coupling behind the gearbox, a single-row self-aligning spherically seated centre bearing, and Hardy Spicer couplings to the 'rear section.

A fully floating axle with hypoid drive is employed, the overall ratio being 5.57 to 1. The axle is attached to the chassis through overslung semi-elliptic springs of 4-ft. 4-in, centres, with leaves 2-} ins. wide. The front axle has springs of 2,1-in, width and 3-ft. 2-in. centres.

A Girling hydraulic braking system operates highcentre-lift two-leading-shoe units at all wheels, the shoes being actuated by wedge expanders. This is the first vehicle to be equipped as standard with the high-centrelift arrangement.

Braced by pressed-steel cross-members, the, frame is an all-riveted structure, which is parallel from front to c4 rear, and level along the top flange. The 10-ft. 6-in. wheelbase, with an almost equal frame overhang at the front and rear, provides a useful turning circle of 41 ft., which is advantageous in shunting in confined areas.

In the cab assembly, the radiator-tube stack is concealed by the full front, which also accommodates the recessed headlamps. At first the 3-tonners will have a composite wood and metal cab, but the possibilities of employing an all-steel pressed assembly is tinder consideration to reduce cost. Because of the depth of the divided windscreen, door windows, and quarter lights, there is a high degree of all-round visibility. The doors a re hinged at the front and a step formed on the corner of the front bumper bar at wheel-hub level facilitates access to the cab. • Because the controls and engine are located well to the front of the chassis, a large body floor space can be provided, the width and the length of the platform being 6 ft. 6 ins. and 14 ft. respectively. The test chassis was equipped with a drop-sided body, but the sides were left at the works during the trials to compensate for a slight overload.

As the 3-tonner was born and reared on the fringe of the Pennines, it has an infinite capacity for pulling up long inclines. This I found during the earlier part of the trials, when driving from Oldham to Halifax. After 12 minutes' stiff climbing on a still, hot day, the radiator-water temperature refused to rise above 170 degrees F. Ambient at the time was 78 degrees F.

The vehicle will certainly not suffer from overheating, because in subsequent running, and when making numerous stops. the water temperature remained con.sistently between 144 and 148 degrees, even when the day warmed up to 85 degrees F. It is a simple matter to blank off part of the tube stack in cooler weather, whereas if the vehicle overheated major difficulties might arise. The efficient cooling is achieved by maintaining relatively little clearance between the fan and radiator.

With an engine governed to 2,400 r.p.m.. and gear ratios well matched to the torque available, it did not take long to reach the top of Buckstones Road, and afterwards came the steady six-mile descent into Ripponden. This provided scope for testing the new braking system, which proved adequate for the occasion. There was only slight increase of pedal movement at the end of the trial, when the brake drums were well expanded, and the facings more resilient.

I then drove back to Oldham by the same route and covered 20 miles in 45 minutes without exceeding the speed limit. This proves that the Perkins P.4 engine is suitably powered for the Seddon 3-tonner.

The initial consumption test was started in Oldham, so as to include a fair measure of town operation, and was continued on the main road towards Manchester, on which I turned at a convenient point to make a complete circuit of 12 miles. Stops were planned at an average of one to the mile, and after deducting stationary time, the average speed worked out to 22.5 m.p.h. Clearly, the Seddon will be able to complete as much work in a day as a petrol-engined 3-tonner.

The course involved reasonable proportions of running on the level and on hills, including a second-gear climb on the return leg of the circuit. Traffic delays in town caused an additional seven stops, and there were 19 occasions in 12 miles on which it was necessary to accelerate from rest. Nevertheless, the fuel consumption, according to the gauge on the test tank, was well below normal, equalling 21.3 m.p.g.

In a 10-mile " continuous " run; which unfortunately included three enforced halts, the .return was 26.7 m.p.g. at an average speed of 216 m.p.h. These tests were made with the equivalent of a_full payload and a normal body complel e with sides. In the Oldham area, there are few stretches of road which are both level and straight, and the most promising course for tha short performance test had a tarred surface. This, on a day when atmospheric temperatures of over 80 degrees were being recorded, was not conducive to accuracy in braking results, or to maximum tractive effort.

Emergency applications of the pedal during the initial brake trials caused all wheels to "pick up" immediately on the sticky surface, but subsequent tests with slightly less effort on the pedal produced average stopping distances of 48 ft. from 30 m.p.h. and 20 ft. from 20 m.p.h. Much greater efficiency might be obtained under better conditions.

Acceleration Results

Starting from rest in bottom ratio, and changing gear successively at peak engine revolutions, the Seddon accelerated from rest to 20 m.p.h. in 14.6 secs. and to 30 m.p.h. in 41 secs. Direct-drive acceleration yielded results of 10-20 m.p.h. in 17 secs., and 10-30 m.p.h. in 40 Secs.

Although the Seddon may be a trifle slower off the mark than its relatively high-powered petrol-engined contempories, the difference is barely noticeable by the ' driver. Governed at 2,400 r.p.m., the Perkins engine has a versatile performance, which was well mated to the gearbox and axle ratios of the test vehicle. There is little doubt that its economy iri fuel and competitive price will be attractive to many operators.

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Locations: Manchester, Halifax, Oldham

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