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A 32-TON I FLYING DUTCHMAN I

11th January 1963
Page 59
Page 60
Page 59, 11th January 1963 — A 32-TON I FLYING DUTCHMAN I
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In all cases identical brakes are employed, these being S-cam units actuated through a split-circuit air-pressure system and having a total lining area of 800 sq. in. The system includes two 2,430-cu.-in. reservoirs, and the trailer (or semi-trailer) brakes work off the front-axle circuit. The handbrake is of the multi-pull type, and when it is fully applied the trailer brakes also are automatically applied at their full working pressure of 74 p.s.i., the maximum working pressure for the vehicle footbrake being 105 p,s.i. Thus the handbrake can be a powerful emergency brake.

The DAF 2600 has an exhaust brake also, this being controlled by a foot-operated button to the left of the clutch pedal. German regulations stipulate that, on goods vehicles of over 9 tons gross weight, operation of the exhaust brake must apply the trailer brakes also at no less than 7 per cent of their maximum power, and in the case of the DAF this is achieved by an electro-pneumatic link between the exhaust brake and the trailer brakes, application of the exhaust brake giving a trailer line pressure of between 10 and 13 p.s.i_ Suspension consists of semi-elliptic springs, the front springs having shackled rear ends, whilst the rear springs have slipper rear ends and work in conjunction with helper springs which bear against rubber pads to eliminate rattle. All the springs are 3-9 in. wide and 63 in. long, except for the helpers, which are the same width but 41-5 in. long. Telescopic dampers are standard at the front axle.

Z.F. worm and roller steering with integral hydraulic servo is standard. It has the rather low ratio of 22-8 to 1, giving 5-5 turns from lock to lock, but this ensures that the vehicle is still controllable in the event of either a hydraulic failure or the need for towing with a dead engine. The turning circle of the vehicle tested was quite remarkable, the average of the two locks being under 60 ft., despite the —by British standards—large tyres, and this is due to a wheel-lock angle of 40°.

Welding is employed throughout the assembly of the chassis frame, except for the foremost cross-members and the side members are 0.275-in.-thick high-tensile-steel pressings with a maximum depth of 10-25 in. and 2.96-in. flanges. The side members have flat top flanges rearwards from the back of the cab, but are joggled outwards by 5-5 in. in the vicinity of the cab to provide sufficient clearance to enable the engine to be mounted fairly low in the frame.

The standard home-market 2600s have 12.00-20 (16-ply) or E.20 "X" (11.00-20) tyres, mounted on 8.5-20 (10-stud) wheels, the test vehicle having Michelin equipment. The electrical system is 12 V, with 24 V starting, and the Bosch dynamo has an output of 450 w.

Standard equipment includes a front bumper with builtin towing/pushing eye, a rear cross-member designed for trailer towing, one 44-gal. fuel tank, exhaust brake, spare wheel with winch-type carrier, paired headlamps, flashing indicators and trailer electrical and braking connections. In standard trim the chassis is supplied with front-end metalwork only, the cab being classed as an optional extra, as are various types of gearbox p.t.-o., rear-axle dampers, additional fuel tank, cab heaters and bunks. Equipment supplied with the front-end assembly includes a speedometer with trip and total odometers, engine rev, counter, twin air-pressure gauges, fuel gauge, warning lights for oil pressure, battery charging, main beam and handbrake, stalk-type switches on the panel for the direction indicators and for flashing or dipping of the headlamps, and rockingtype switches for other electrical items.

DAF is the only European vehicle manufacturer which also makes semi-trailers and drawbar trailers, and the trailer used for my tests was a DAF LVW 1616 fourwheeler rated for operation at 16 tons gross and matched in all respects to the 2600 towing vehicle. As standard, this trailer, which has an all-welded frame assembly, has DAF axles and brakes with a total lining area of 638 sq. in. but for use in Germany German B.P.W. axles and brakes are employed, these having a lining area of 844 sq. in. to cope with the additional applications of the brakes occasioned by the linkage from the towing-vehicle exhaust brake. The trailer had a single-line inverted air-pressure system, as is commonly used in Germany and Holland, and 9.00-20 " X " twin tyres at front and rear.

Overall Length of 53 ft. 6 in.

The outfit which had been selected for me was temporarily in the Dusseldorf area, where it was being demonstrated from the German DAF depot. The towing unit had some 33,000 miles to its credit and, complete with 19-ft. 8-in. DAF-built drop-side body and tarpaulincovered superstructure, its kerb weight was 7 tons 2 cwt., compared with a quoted dry chassis-cab weight of 5 tons 15 cwt. Coupled to it, and making an overall length of 53 ft. 6 in., was the 22-ft. 11-in, trailer, with similar bodywork to that on the towing vehicle.

Concrete blocks totalling 8 tons 13 cwt. were in the prime mover body, whilst the trailer was carrying 11 tons 9-5 cwt. of blocks, the complete outfit grossing 31 tons 10 cwt. (32 metric tons) with no one in the cab. Being a commodious cab, the tests were carried out with five people aboard, bringing the gross train weight to 7 cwt. above the nominal figure.

A fuel-consumption test along a typical stretch of Autobahn was made first over a 39-3-mile section between Mettmann and Recklinghausen. By Autobahn standards this section is fairly level—more akin to the British Ml— but traffic was heavy and much of the road was being re-surfaced, with the result that traffic was being diverted from one carriageway to the other, such obstructions reducing the outfit from its normal cruising speed of 47 m.p.h. to speeds of 30 m.p.h. or less. Given a clear run, the speed of the DAF never dropped below 37 m.p.h. on gradients, and its maximum speed was proved to be that indicated in the sales brochures--50 m.p.h.

Despite unfavourable conditions, the course was completed at an average speed of 43-2 m.p.h., which is exceptionally good under the circumstances, and an accurate 07 top-up of the fuel tanks showed that 4.56 gal. had been used, indicating a consumption rate of 8-6 m.p.g. (32.8 litres per 100 km.).

The return to Dusseldorf was made over ordinary roads, the route taking in such busy industrial areas as Bochum, Essen and Mlitheim and including 5 miles of Autobahn, over which the speed was deliberately kept down to 32 m.p.h. This is an extremely severe route over which to test the consumption of a heavy vehicle, particularly as my test was conducted towards the evening rush-hour period with the result that congested traffic conditions combined with extensive road-works deviations to make it difficult to keep up a good average speed.

Nevertheless, the 40.5-mile route was completed at an average of 26.9 m.p.h., whilst a careful check of the fuel used showed the consumption rate to have been 7.5 m.p.g. (37.6 litres per 100 km.), an extremely good figure which gives a far higher time-load-mileage factor than the average British heavy vehicle—running some 8 tons lighter—would have given under similar conditions.

The second day of testing was started by taking the outfit to a level stretch of non-Autobahn dual carriageway for acceleration and braking tests. Such was the density of the fog, however, that I deemed it dangerous to carry out any braking tests for fear of following traffic running into the outfit. The DAF engineering section, fortunately, conducts brake tests using similar equipment to my own, so the stopping distances recorded in the data panel are those obtained by DAF with this same vehicle under more favourable weather conditions.

DAF indicates that the addition of a 16-ton trailer to the 2600 results in 2 ft. better overall retardation performance from 30 m.p.h. than when it is running solo, the greater braking capacity of the trailer more than compensating for any delay which might be present in the system. Indeed, DAF was most indignant when I suggested that the performance should be worse with a trailer than without: "Of course it is better with a trailer ", they said. "We fit more powerful brakes on the trailer to hold the outfit straight under severe braking conditions." I wish British manufacturers could think the same way. . . .

Very good acceleration figures were obtained with the outfit, both through the gears between 0 and 40 m.p.h. and in direct drive between 10 and 30 m.p.h. The times recorded would have been good for any British vehicle of over 10 tons gross weight, and I doubt if there is a British design which could achieve this acceleration performance whilst at the same time having a maximum speed of 50 m.p.h. and the sort of fuel economy obtained with the 2600 outfit—certainly not with only a six-speed gearbox and a single-speed axle. Another impressive feature of the acceleration tests was the smoothness of the engine and transmission when pulling in direct drive from 8 m.p.h.

Two hill-climb checks were made, the first being over a 4-5-mile-long stretch of main road with an average gradient of 1 in 33 and a maximum severity of 1 in 22. This ascent was made in 10 minutes 20 seconds, the lowest gear used being fourth and the speed never dropping below 19 m.p.h., this being when running on the engine governor in fourth gear. The ascent was made in an• ambient temperature of 5°C (41°F) and the temperature of the coolant in the cylinder head rose from 75°C (167°F) to 80°C (176°F).

To check the vehicle's performance on a steeper gradient, the outfit was taken up the hill from Wuppertal to Cronenberg, this being 1-25 mile long with an average gradient of 1 in 11 and steeper sections of up to 1 in 9 severity. This ascent took 8 minutes, of which 7 minutes were spent in second gear at nearly 12 m.p.h.—a quite remarkable performance on such a steep hill. The engine temperature rose from 70°C (174°F) to 84°C (183°F), indicating ample cooling-system latitude for prolonged hill climbing, as these temperatures are those on the engine side of the thermostat. No•exhaust smoking was observed during this or the other climb.

Because of the wet roads and the size of the unit, I did not attempt my usual type of fade test, which consists of descending the hill in neutral using the footbrake to keep the speed down to 20 m.p.h. Instead, the Cronenberg hill was descended using the exhaust brake. For the first part of the descent fourth gear was engaged, the road speed being 19 m.p.h., but towards the lower section of the hill the driver applied the footbrake for just long enough to get the speed down to 13 m.p.h., following which the rest of the descent was completed in third gear at this speed, again without the footbrake being used. This speaks volumes for the effectiveness of an exhaust brake, although it must be borne in mind that the trailer brakes also were being lightly applied automatically.

Impressive to Drive Quite apart from its exhilarating and economical performance, the DAF 2600 combination was extremely impressive to drive, and even I did not feel out of my depth at 50 m.p.h. on an autobahn, despite never having driven a vehicle nearly 54 ft. long and weighing nearly 32 tons at such speeds before. My confidence was mainly derived from knowing that I had good brakes and a slight edge as regards maximum speed over most of the German heavies on the same roads, but the delightful handling of the vehicle and its smooth, quiet operation were a great source of comfort also.

When cruising at nearly 50 m.p.h. on Autobahnen I was aware of slight trailer tugging, but was assured that this is usual with Continental outfits of this weight and is due mainly to the pitching of the short trailer: apparently longer, three-axle trailers give a smoother ride. I was also aware of slight front-suspension harshness over bad stretches of road, but this would be due partly to my not being accustomed to vehicles with a 6-ton front-axle load, and partly to the high-rate front springs used to give roll stiffness. At slower speeds over less erratic road surfaces the cab ride was smooth, and any roughness which was transmitted to the chassis frame was generally killed by the cab mountings and the generous upholstery of the seating.

The general quietness of the 2600 was praiseworthy, and I have never been in a vehicle powered by this Leyland unit in which so little noise penetrated the cab—this despite the fact that the model I tested was an early production version and had not got the full current under-cab insulation. Indeed, when sitting in the passenger seat—which has folding arm rests and a high squab—I felt more as if 1 were in the front seat of a luxury touring coach, rather than at the front end of a 32-ton commercial! Even the cab heating was way above the standard normally to be found on commercial vehicles, and its distribution was such that the whole cab was evenly heated, rather than just the area in the immediate vicinity of the toeboards.

My only adverse comment concerns the steering. Under normal conditions I felt perfectly happy with this, the effort required on the wheel being low without the steering becoming dangerously light. On Autobahnen, however, I could not avoid "sawing" slightly at the wheel when on the straight, to my mind there being a tendency for the front wheels to pull slightly to the right, a tendency which demanded correction. Watching German and Dutch drivers handle the 2600 I became convinced that the fault lay with me rather than with the vehicle for they, being accustomed to the steering, could hold the wheel steady.

All in all, however, there is no shadow of a doubt about the DAF 2600 combination being an extremely fine vehicle, and deserving of the highest praise for its design and performance. In Holland the chassis-cab as tested sells for the equivalent of £4,800, plus £467 for the body and superstructure, whilst the LVW 1616 trailer costs £1,065 basically, with an extra £411 for the bodywork. Equivalent prices in Germany are £4,520, £492, £1,392 and £385.

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