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Best of Both Latest

12th December 1958
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Page 54, 12th December 1958 — Best of Both Latest
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COMBINING the cab spaciousness and good engine accessibility of the best normal-control chaSsis with the forward vision and manceuvrability normally associated with a forward-control design, the• latest Bedford 3-ton and 4-ton chassis

are bound to have a strong appeal to operators of medium-capacity delivery Vehicles. Many of the operating problems associated with vehicles of this type can be overcome by this design.

One of the key design features of the new, range, which was introduced in September, is the use of 16-in.diameter wheels, for which special high-speed tyres have been developed so that there need be no road-speed restrictions. Besides the obvious advantages of such wheels, such as low cab, frame and body floor, good steer

ing locks are possible, the low centre a20 of gravity gives added stability, the chassis weight is lower than if conventional 20-in.-diameter wheels were employed, and axleshaft stresses are reduced because the small wheels allow the use of a higher rear-axle ratio.

Normal control has for long been favoured by operators of this class of vehicle because of the easy cab access and, in many cases, seating capacity for a driver and two mates. This layout gives the added advantage, moreover, of a light front-axle loading, which reduces the steering effort required and makes the vehicle easy to handle in thick traffic and confined spaces.

Range of 12 Models

The new range consists of 12 models,

fully described and illustrated in The Commercial Motor on September 12.

Chassis of 11-ton to 4-ton capacity have 16-in, wheels, but it is the 3-tonners and 4-tonners which offer the greatest appeal to distributive trades.

The 4-ton chassis, which was road tested last week, is available with a choice of petrol or oil engines, and is manufactured with a standard wheelbase of 13 ft. 5 in., suitable for a 14-ft. body. The turning circle of 51 ft. is only 3 ft. greater than that of the forward-control 4-ton Bedford chassis with the same length of body. Furthermore, the overall length of the

normal-control vehicle is Only 2 ft. 9 in. more than that of the forwardcontrol model and the taxation weight is some 81 cwt. less. , Thus the big advantages of this design have been obtained without noticeably detractingfrom the compactness and manoeuvrability to be expected from an equivalent forwardcontrol vehicle — a commendable achievement that might lead other manufacturers along the same lines.

Because such a vehicle will be principally engaged on service where the

Contrary to original expectations, the small tyres have been hown to give some 17 per cent. longer life than the 20-in. tyres normally fitted to a vehicle of this size. This is equivalent to a 30 per cent. reduction in terms of tyre costs per ton-mile, because of the greater payload now carried.

So far as the performance of the oilengined 4-tonner is . concerned, tests showed this to be entirely Satisfactory. The chassis tested had a low axle, ratio (6,2 compared with the optional 5.43to-i unit), which gives it a maximum speed of about 38 mph.—sufficient for normal urban working.

Acceleration fully laden, although not by any means flashing, is adequate for the class of service which is envisaged, whilst, despite the use of relatively small 13-in.-diameter brakes, the maximum retardation was found to be up to the standard normally associated with this weight of chassis.

Goad h'ill-climbing ability has been assured by the use of a wide-ratio gearbox, the bottom gear of which, having a ratio of 7.059 to 1, gives a more than sufficient gradient ability.

As Offered for test, the oil-engined 4-tonner had a standard Bedford 14-ft. double-drop-sided body and the kerb weight of the vehicle was 2 tons 113 cwt. Concrete blocks totalling 4 tons 2+ cwt. comprised the test load and the fully laden tests, with myself and Colin Prebble, of Vauxhall Motors, aboard, were made at a gross weight of 6 tons 171 cwt. This is 31 cwf. above the maximum recommended gross weight, but the excess load was not sufficient to warrant removing it.

Using a calibrated test tank, a aeries of laden fuel-consumption tests was made over the six-mile. undulating course between Barton and Clophill normally selected for Bedford tests. Despite the relatively low axle ratio, which was further accentuated by the small tyres, good fuel economy was shown when running non-stop and when making simulated delivery runs.

About half the test load Was then removed, bringing the gross vehicle weight down to 4 tons 171 cwt., and the three test runs were repeated, again with favourable results. A seventh run, made non-stop, was conducted with all the test weights out of the body. Comparison of the seven results shows that as the load is increased, the eceinomy on concentrated stop-start working improves at a relatively greater rate than when running nonstop. This is as it should be, the chassis being designed for such operation. An operator employing it under these conditions will find that, assuming a constantly decreasing load, the overall average fuel return will be in the region of 19-20 m.p.g., an attractive figure for this type of vehicle. "

Braking tests were made on a dry stretch of rough-surfaced road. The figures recorded might have been a little better had the near-side front wheel not locked on each occasion, the other three being on point of locking. Nevertheless, the provision of a vacuum servo enabled the results to be obtained without excessive pedal pressures, and the braking was found to be smooth and unaccompanied by loss of stability. • The pull-up hand brake to the left of the driver has,a short travel and was fully effective in an emergency, an average Tapley meter reading of 34.75 per cent, being obtained with it from 20 m.p.h.

Acceleration times, which were obtained with a full load (as with the braking figures) were not unreasonable in view of the .relatively low powerweight ratio; When making the standing-start tests, second, third and top gears were employed between 0 and 30 m.p.h.: it was unnecessary to use bottom gear when starting from rest except on relatively steep gradients. During the direct-drive runs between 10 rn.p.h. and 30 m.p.h. the engine and transmission became decidedly rough at just below 10 m.p.h., but this roughness disappeared at about 14 m.p.h. when accelerating at full throttle.

Hill-climb and brake-fade tests were made on the 3-mile gradient known as Bison Hill. This has an average gradient of 1 in 101 and it was climbed in the total time of 4 minutes 54 seconds, bottom gear being used for 1 minute 29 seconds.

Ambient temperature during the B21

ascent was 42° F. and at the top of the hill the temperature of the water in the radiator header tank was 162° F., indicating a rise of only 15 F. The cooling system provides an ample margin for even concentrated stopstart work in hilly areas and the engine should never over-heat.

To test for brake fade, the Bedford was then coasted down the hill in neutral, using the foot brake to restrict the speed to 20 m.p.h. Towards the bottom of the hill, where the gradient is less severe, top gear was engaged and the vehicle driven against the brakes at full throttle.

Fade Results Surprising This complete test lasted 2 minutes 15 seconds, top gear being engaged for 28 seconds, and at the end of the descent a full-pressure stop was made from 20 m.p.h. This produced a Tapley meter reading of 32.5 per cent., indicating that fade had caused the brake efficiency to be -reduced by just over half.

This was somewhat surprising, particularly as moulded facings are standard equipment, but undoubtedly much of the lost efficiency was caused by excessive brake-drum expansion, the pedal travel having increased by 31 in.

This was an excessively severe test and in normal service bad brake fade should not be experienced. In any event, recovery was rapid, so that any tendency to fade when engaged on high-density delivery runs should be cancelled out between stops.

I was entirely satisfied with the general handling and comfort. Because of the deep windscreen and sharply sloped bonnet panel the range of forward vision is a vast improvement on that formerly associated with Bedford normal-control vehicles.

Controls Well Placed

The steering-column rake gives a comfortable wheel position and as the gear lever is cranked towards the driver, its knob lies close to the steering-wheel rim, with the incidental advantage that the lever is well to the right of the passenger occupying the centre of the cab. There is plenty of passenger leg room and ample width for three people.

Because of the small wheels, the step height is only 16 in., which makes for particularly easy entry to the driving seat. Similarly, because the only obstruction in• the floor is the gear lever, drivers will find it possible to reach their seats through the near-side door, which is a useful feature on delivery work. Access to the cab would be improved still further were the doors to open through a wider arc.

1322 Fittings include a neatly cowled instrument cluster immediately ahead of the steering wheel, and a separate driving seat which is adjustable fore and aft. Two-speed electrically operated windscreen wipers are provided, but for some unexplained reason these are pivoted towards the outer edges of the screen, with the result that when wiping they leave an uncleaned area in the centre. Cross-over wipers would be far more effective and would increase the advantage of a large onepiece screen.

A detail point worthy of mention is that winding windows are now fitted in the cab doors, as opposed to the push-up type installed in the previous Bedford normal-control cab.

Although there is no disguising the fact that the power unit has only four cylinders, the engine is reasonably quiet and smooth at normal road speeds. It hunts a little when idling, but it is little worse than other fourcylindered engines of about the same size.

The suspension was good under varying load conditions, and the steering was light and positive, although the absence of a pronounced castor action can mean a lot of rapid hand work on sharp corners. A 171-in.diameter three-spoke steering wheel is fitted.

Because all my testing had to be done in one day, I was unable to conduct my usual maintenance tasks. The chassis layout follows conventional Bedford practice, however, with the exception that engine accessibility is improved by the lower wing line resulting from the smaller wheels.

As the engine compartment is large enough to house a six-cylindered unit there is plenty of space around the engine and such ancillary equipment as the fuel-injection and lift pumps, the fuel and oil filters, dynamo and injectors should be easy to work upon. The engine is set well back in the bonnet-more so than might be at first expected --but this is because similar rear mountings and propeller shaft are used when the six-cylindered unit is installed. It does not detract appreciably from its accessibility.

The Bedford J3D7 4-ton oil-engined drop-sided lorry has a basic price of £995, purchase tax of £187 6s. 7d. being payable in Great Britain. The bare chassis has a basic price of £817,Whilst the chassis and cab cost £890, the purchase tax in each case being

• the same as for the cbmplete vehicld.

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