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O NE of the most useful and successful vehicles operating in

2nd December 1949
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Page 54, 2nd December 1949 — O NE of the most useful and successful vehicles operating in
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the oilfields is the Bedford utility pick-up. I saw this model running over the desert and in the mountains of Iran, carrying a variety of loads pertaining to oil-well construction and maintenance, and I seized the opportunity of testing one under these conditions and hauled an overload for good measure.

The Bedford pick-up is based on the K-type chassis, which has the six-cylindered overhead-valve engine and a four-speed gearbox. As the engine develops a maximum of 75 b.h.p. at 3,200 r.p.m. and a torque of 168.5 lb./ft. at 1,000 r.p.m., the power-to-weight ratio is high when judged by home standards, but is normal for the more arduous duties of overseas operation.

A standard four-speed gearbox is employed, having a direct-drive top-gear ratio and two open propeller shafts carrying the drive to the spiral-bevel gear of the semi-floating rear axle. The final-drive unit has a straddle-mounted pinion and four-pin differential.

The chassis is equipped with a hydraulic braking system, the pedal being linked direct to the tandem master cylinder. The hydraulic operating units at the wheels are externally mounted to prevent overheating. Cast-iron-alloy brake drums are employed.

Special features of this model include ambulancetype springs and shock absorbers to improve the riding qualities, and a 70-mm. radiator core in place of the standard 53-mm. unit fitted to home models. The cab roof is of aluminium, extended to form a canopy over the fore part of the body space, with the cavity between the inner and outer panels filled with Isoflex insulating material. As in the cab, the seating is of Dunlopillo, with rubberized hair squab and leather upholstery. There is a sliding-frame window on each side of the rear compartment and in the partition behind the driver. The rear portion of the body has fixed steel sides with a hinged tailboard at the rear, both sides and tailboard being of double-skin steel construction. This type of body is made by Duple Motor Bodies, Ltd., Hendon. The vehicle lent for my tests was comparatively new, having covered only 2,500 miles in oilfields operation. Apart from adjustments to brakes and normal maintenance, it had received no attention from the workshops. A 15-cwt. load of cement was carried for the trials, which, together with my Persian co-driver and native mate, brought the gross running weight to 3icwt. in excess of that advocated by the manufacturer.

I started the trials by driving up the 71-mile-long gradient to Sarri Ghatch. Temperatures were taken at the foothills, where the radiator top tank reading was 169 degrees F., engine oil 192 degrees, and ambient 114 degrees. It took 16 minutes to climb the first six miles, with the engine pulling at full bore and with third gear engaged for the major part of the distance.

There was a brief lapse into a lower ratio where the incline stiffened to 1 in 9. I did not notice any serious loss of power at the higher altitudes, and although the climb was long and strenuous, there was no appreciable rise in cab temperature.

A stop was made at the highest point to check the running tem peratures. All the vehicles I had tested up to this time had boiled when climbing long gradients, but the pick-up was an exception to the rule. The bonnet sides had been left in position for the test, and the efficiency of the cooling system was shown to be adequate for tropical areas, the radiator-water temperature having risen during the climb by only 16 degrees F. to 185 degrees F. The engine-oil reading was 211 degrees. This run was made before 7 a.m. and, with a temperature of 109 degrees F., there was a light breeze blowing across the top of the mountain.

From the details given in the data panel it will be seen that the brake frictional area is to the order of 82 sq. ins, per ton, which is an exceptionally high ratio for a commercial vehicle. With this point in mind, I decided to give the braking system a thorough test on the descent from Sarri Ghatch.

I drove all the way down the mountain road with top gear engaged, and used the brakes to control the speed on bends. The brake facings were smoking within the first mile, but the pedal was still a long way from the floorboards, and even to the last 100 yards there was ample reserve of movement, I brought the Bedford to rest on the steepest section of the road to try the hand brake, and although the drums were well expanded, it just held the vehicle stationary on the 1-in-9 gradient. The hill test was the most severe that I have ever conducted, and the Bedford

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gained full marks for its performance both up and down the mountain road.

The fuel tank was replenished before starting the consumption test, which was to include acceleration and braking. 1 cut the maximum speed down to 35 m.p.h. during the consumption run, to make the trial comparable with those conducted in this country. The route chosen was a 50-mile out-and-return course from Masjid-i-Sulaimen, which is 4,500 ft. above sea .level, down to the plains almost 4,000 ft. below.

Springs and shock absorbers work overtime on this road, but travel in the cab was comfortable, and I entrusted the vehicle to the Persian driver while I sampled the crew seat. The compartment for the crew was as comfortable as the cab, and, with three sliding windows giving adequate ventilation, and the overhead canopy to shield me from the full rays of the sun, I much preferred to be a passenger.

It is a rule of the Anglo-Iranian Oil Co. that drivers should check tyre pressures when refuelling, and the tyres had been inflated to 50 lb. per sq. in. before starting the consumption trial. I again checked the pressures when 20 miles from the refuelling depot, and found that they had risen by 10-15 lb. The tyres were deflated to correct pressure, and further checks made during the day showed an ultimate rise to 56-58 lb. per sq. in. Overheating of tyres is a major problem in hot countries. A stretch of road reasonably free from potholes was located for braking trials, and, as the results showed, the efficiency of the system had not been impaired by prolonged use when descending the mountain. When the brakes were fully applied, the vehicle came rapidly to rest without pulling to either side, a stopping distance of 33 ft. being obtained from 30 m.p.h. This was the minimum distance 'observed over a number of tests, many of which were marred by poor adhesion between the tyres and the road.

The course was retraced after

completing the 25-mile outward run, and within a few miles, after turning, the road started to rise. With such a high-powered vehicle, the gradient did not justify great use of the indirect ratios, but many of the blind corners had to be negotiated with care. and short periods had to be spent in third gear. I placed high value on the light steering of the test machine, little effort being required to negotiate the many curves in the foothills.

By the time we had returned to MIS. the clay was approaching its maximum temperature, and the windscreen had to be closed because of the intense heat. 1 made the mistake of resting my arm on the outer skin of the door, and hastily withdrew it from the hot metal.

I drove to the petrol station for refuelling, and measured 14i litres into the tank to replenish it to the original level. The total distance covered on the trial was 81 kilorns., and the consumption rate was 15.6 m.p.g. It should be noted that this trial included the short performance test, and that the quality of fuel was unknown and may have been of lower octane value than that used in Great Britain.

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