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BEDFORD ND 5-TONNER

15th April 1966, Page 64
15th April 1966
Page 64
Page 65
Page 66
Page 71
Page 64, 15th April 1966 — BEDFORD ND 5-TONNER
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ALTHOUGH the Bedford KD 5-tonner is not a new model it is significant that its performance is as good, if not better, than some of the models that were, introduced at the 1964 Commercial Vehicle Show in London.

The Bedford TK range made its debut late in 1960 and was the second of the "new look" vehicles that are today commonplace. Positioning the 'engine behind and below the driving seat permitted the cab to be manufactured without it being necessary to have complicated tilting mechanisms or numerous draughtproducing flaps and hatches required in fixed cabs, with engines alongside or beneath the driver.

Although the degree of accessibility is not quite as high as that provided by the tilt cab, it is far better than that obtainable with the conventional forward-control layout. From the comfort point of view there is far less noise than in the older types, there are no fumes, and the flat floor gives a third person a comfortable ride without him having to be a contortionist. One advantage with the TK range is the ample storage space for the crew's personal gear.

Many people may think that this is not a very important point to make in a road test, but I feel that a vehicle of this nature may well be used on multi-delivery, semi-long-distance work, where both a driver and a van boy or mate will be carried and perhaps work away from base for up to a week at a time.

Two fairly large suitcases take up an awful lot of room in a cab, and during the winter period, when both men need waterproofs, gum boots and overcoats, to say nothing of the indispensable shovel, the space left in many cabs for the poor second man is often reduced to something akin to a Chinese torture chamber. Ten or 12 hours

spent sitting with your knees under your chin is tiring, to say the least, and whether or not the TK cab was designed with this point in mind, it is nevertheless a boon to such crews as those described.

Following the standard Bedford practice, the KD chassis is designed to be flexible; therefore, to ensure this it must be fitted with a suitable body. The Hawson body fitted on the test vehicle employs a pedestal-type mounting which allows for the fullest articulation of the chassis frame whilst at the same time providing adequate support, spread equally over the main members. It is constructed from conventional materials and employs steel-bound drop-sides and tailboard and has straight-through, 0-section crossbearers.

With the steel pedestal mountings fitted at each cross-member from the front of the body to a point adjacent to the rear axle, and

from there to the rear of the chassis a rectangular-section steel box-member running longitudinally and flush with the top of the chassis, there is ample anchorage to withstand braking and acceleration forces. It will be seen that there is a complete steel sub-frame beneath the floor level on which the bulk of the load stresses are concentrated.

Three engine options

There are three engine options. They are the six-cylinder, 2I4 cu. in. petrol which develops 100 b.h.p.; the four-cylinder, 220 Cu. in. diesel which develops 70 b.h.p.; and the unit fitted in the test vehicle, the six cylinder, 300 cu. in. diesel, which develops 97 b.h.p. When either the petrol engine or the 300 cu. in. diesel engine is fitted, a five-speed gearbox with overdrive can be specified in place of the standard four-speed, direct-drive unit as fitted in the test vehicle.

An area around Barton-in-the-Clay, Bedfordshire, was chosen for the tests. This is one frequently used by COMMERCIAL MOTOR and known to give very good representative results. The test started off badly with the test weights "shooting" during one of the first maximum brake-pressure stops. A considerable amount of body damage was sustained, with the headboard of the body jammed hard into the back of the cab.

A second movement of the test weights, this time backwards, came at the start of the acceleration tests. The force of the weights hitting the tailboard was so great that the shock transmitted to the differential burst the outer track of the pinion nose bearing. From that point on there was a nasty noise eminating from the differential the whole time power was applied.

It was after taking acceleration figures and one fuel-consumption figure that I decided to abandon the test at this stage and returned the vehicle to Vauxhall to be repaired.

Results recorded on this occasion showed that at an average speed of 31 m.p.h. fully laden, the vehicle returned 14.4 m.p.g., but when the differential bearing was replaced, the same test, running this time at 29.3 m.p.h., returned a figure of 21.25 m.p.g. Acceleration tests carried out with the damaged pinion-bearing returned figures for 0 to 30 m.p.h. through the gears of 24.3 sec., and 0 to 40 m.p.h., 64.45 sec. When this test was completed after repairs had been carried out, the relevant figures were 0 to 30 m.p.h., 20.25 sec., and 0 to 40 m.p.h., 39.1 see. When the bearing was stripped out it was found that only the outer track had cracked and the considerably better figures obtained after the repairs show how important it is to search for the small points that can, nevertheless, have amazing effects on both performance and fuel consumption.

Throughout the fuel tests the results obtained were, if not surprising, extremely satisfying. Each consumption run proved that the average speed aimed at could either be easily kept up or comfortably exceeded. This proved to me that the choice of gearing was right for operations requiring short-distance hops on ordinary roads. Aiming at 30 m.p.h., and not exceeding at any time 35 m.p.h., the average returned was 29.3 m.p.h. over a stretch of undulating main road passing through four country villages. Fuel consumption at this speed, as I have already said, was 21.25 m.p.g., and the handling of the machine was extremely pleasant.

One stop per mile at an overall average speed of 30 m.p.h.excluding the time stopped, which was 15 sec. on each occasion, during when the engine was left idling—produced a fuel consumption figure of 16 m.p.g. and at no time was it necessary to punish the machine to keep up this average. A run at around 40 m.p.h. over the same stretch of road produced an average speed of 35.1 m.p.h, and a consumption of 16.85 m.p.g.

On the high-speed test on M1 between A505 and A557, which covers a total distance of 22 miles, the behaviour of the machine can only be described as near perfect. The gearing enabled almost maximum engine revs to be held for the whole period in both directions and an average road speed on the run north of 46.4 m.p.h. was recorded. There is slightly more down gradient on the run north than when travelling south on this section of Ml. Consequently, although there was little difference in the average speed, fuel consumption was higher for the slower run at 45.1 m.p.h. On the run north, consumption proved to be 16.8 m.p.g., and on the run south 13.95 m.p.g. For continuous operations on long-distance work, optional higher axle ratios than the one used in the test vehicle-5.43 to 1—are available, these being 4.71 and 4.375 to 1. It would appear from the results obtained in the one-stop-per-mile test, however, that a higher axle ratio could considerably worsen the fuel consumption figures on delivery work.

Throughout the test I was impressed by the low level of noise that found its way into the cab. Even when climbing in a low gear it was still possible to talk to a companion quite easily without raising one's voice unduly. As with other vehicles tested recently that have been equipped with air-over-hydraulic braking systems. I found the braking on the KD to be extremely pleasant to use. Progressive application gave equally progressive retardation and the required pedal effort was enough to give adequate "feel" without being tiring.

Cold brake tests were carried out at a time when the road surface was wet and greasy; consequently, a fair amount of wheel locking was evident on the full-pressure stops. Even so, as 1 have already said, there was sufficient retardation to shoot the load and damage the bodywork, so perhaps it was a good thing that the road surface was bad on this occasion. Average retardation figures of 19.4 ft/sec2 from 20 m.p.h. and 20 ft/sec2 from 30 m.p.h. were recorded, and once again it was impressed upon me that headboards are simply not strong enough to be of any use in an emergency.

The handbrake, which on this vehicle is of the transmission type, produced excellent figures but an extremely rough stop. There was a fair amount of judder in the transmission when the brake was applied and the vehicle "bucked" a bit, which no doubt affected the reading given by the Tapley meter. In fact, the readings from this parking brake were a good deal better than a lot of those recorded by so-called emergency braking systems, with an average Tapley reading of 41 per cent from 20 m.p.h. Throughout all the brake tests the complete feeling of stability, even though the conditions were bad, was very reassuring.

Bedford was one of the first companies to realize the need for split-circuit braking systems, and this is a standard feature of all Bedford vehicles. Using a common air-pressure servo operating a dual master-cylinder, completely separate hydraulic circuits serve the front and rear axles and, in the event of a failure in either of these circuits, there is still sufficient braking power available on the remaining axle to bring the vehicle safely to rest.

Another feature of the TK range is the hydraulic non-return valve which is installed to enable the rear-wheel circuit to be primed in the applied position and held on. This has been fitted to avoid the rocking that occurs with transmission brakes whilst the vehicle is being loaded. The method of application is as follows. The brake pedal is depressed and held down, and by pulling up the non-return lever the hydraulic return in the rearwheel circuit is blanked off and the brake shoes on those wheels held on. It is necessary that this operation is repeated every 10 minutes if the brake is to be kept fully applied.

Bison Hill, near Whipsnade Zoo, was used for the hill-climb test and the vehicle proved once again that although not a super performer, it was as good as many much younger designs. Bison, which is 0.75 miles long, has a maximum gradient of I in 6.5 and an average gradient of 1 in 10. The vehicle took a total time of 3 min. 26.8 sec. to climb to the top of the hill; it recorded a minimum speed of 7 m.p.h. and required first gear to be engaged for 26.5 sec.

A header tank in the cooling system prevented coolant temperatures being taken, but judging by the gauge mounted in the cab there was no appreciable rise in the temperature. Turning round at the top of Bison, the usual brake-fade test was carried Out, with the vehicle coasting to the bottom against the brakes at 20 m.p.h. When the momentum was insufficient to keep up this speed, top gear was engaged and the vehicle was driven at 20 m.p.h. against the brakes. A full-pressure stop made at the end of the 0.75-mile descent produced a Tapley meter reading from 20 m.p.h. of 65 per cent. This compared very favourably with the 67 per cent recorded on the cold-brake tests, but the road surface on this occasion was both clean and dry. Nevertheless, there was still considerable marking of the road and I considered that there must have been little fade.

Facing back up the hill, stop-and-start tests and handbrake holding tests were carried out. Second-gear starts were not attempted as first gear was needed to climb the hill while on the roll. First-gear starts were a simple proposition and the transmission brake held the vehicle comfortably on the steepest section. The hydraulic lock was also found to hold the vehicle on this same section. Facing down the hill the picture was exactly the same, with easy reverse starts and complete holding power with the parking brake.

The standard price of the vehicle tested is £1,243, and optional extras include rear shock-absorbers, £9 10s.; 3-piece wheels, £2 5s; five-speed gearbox, £66; and two-speed rear axle, £95. The vehicle can be supplied as a chassis/cowl, a chassis/cab, drop-side truck or boxvan

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Locations: London

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