'THERE is every indication that the most popular maximum". capacity
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four-axle artic operated in the UK will be the 30tons-gross outfit. More and more are appearing on our roads and the Magirus-Deutz model in this category is reported to be in good demand. An acceptable delivery situation could be an important reason for this, but operators who may be expecting to forfeit something for the benefits of quick delivery need have no worries. A full road test of a Magirus-Deutz 200 D 16FS coupled to a Merriworth tandem-axle semi-trailer and running at just under 30 tons a.t.w. showed fuel consumption to be at an acceptable level, performance and handling to be commendable and, despite a suspected incomplete bedding-in of the brakes, braking performance up to a reasonable standard.
These results were not surprising as the model was originally designed for operation at 32 tons gross, and presumably this could be so in the UK in conjunction with a triple-axle semi-trailer. Now that the maximum-weight limit in Germany has been increased to 38 tons the model has been superseded by the 210 D 16FS, which is basically the same, but has a 210 b.h.p. directinjection V8 air-cooled engine instead of the 200 b.h.p. indirectinjection unit as in the test vehicle.
New cab A new cab is employed, similar to that on the Magirus-Deutz six-wheeler tested by COMMERCIAL MOTOR on October 8, 1965. But, wisely, the German manufacturer does not export newly introduced models until they have proved themselves on their home ground. For this reason none of the new models introduced
at the Frankfurt Show is yet exported, but it can be expected that eventually the later-design cab will appear here, and in a tilting form.
In spite of the considerable difference in external appearance between the new cab and the unit fitted on the test vehicle there is hardly any difference in interior size. The standard of fittings is very high and comfortable seating is provided for three passengers as well as the driver. Access is easy, although there are two steps to be climbed to reach the relatively high floor, and even though the seats go over the engine the driving position did not seem to be unduly high and the unit seemed fairly compact.
Air-cooled V8 engine
The Deutz air-cooled V8 engine in the test vehicle could be termed a shortened version—by one pair of cylinders—of the VIO in the six-wheeler tested previously. Bore and stroke dimensions are the same and, like the V10, the bores and heads are individual components. Cooling air is drawn into trunking which directs it past each bore through a hydraulically-controlled, high-capacity fan mounted in the vee at the front end. The work done by the fan is dependent on the engine temperature. Cubic capacity of the engine is 11.67 litres and the maximum output of 200 b.h.p. net is produced at 2,300 r.p.m. Maximum net torque is 521 lb. ft. at 1,300 r.p.m.
It is interesting that the latest direct-injection V8 has a capacity of only 11.63 litres but produces 10 b.h.p. more at the same maximum speed. It is also worth while to note the Deutz method of quoting firing order, given in our table as 1.8.4.5.7.3.6.2. For this the cylinders are numbered 1 to 4 in the right-hand bank (when
facing the engine from the front) with No. I closest to the flywheel, and 5 to 8 in the other bank with No. 8 at the flywheel end.
Drive from the engine is transmitted through a 15-in.-diameter clutch to the ZF six-speed gearbox—an AK 6-70 as against a 6-80 in the six-wheeler tested previously. Primary drive in the rear axle is by spiral-bevel gearing and there is secondary reduction by spur gears in the hubs.
Modifications for UK Market
The wheelbase of the tractive unit tested, at 9 ft. 10.1 in. (3 metres), is longer than most comparable British tractive units but even this is a reduction from the German standard of 3.5 m. (11 ft. 5.5 in.). Original imports of the model were shortened from the latter dimension but now chassis with the shorter wheelbase are being produced especially for Britain. Also slightly modified for the UK is the braking system. The basic layout is unaltered and it is rather unusual to British eyes to have air/hydraulic two-leading-shoe brakes for the front axle and direct-air cam brakes for the rear. Application of the rear brakes is by a single spring/diaphragm brake chamber acting through a compensating linkage to each side. This provides for the main and secondary brakes, air being released to allow the spring pressure to apply the brakes at the same time as the auxiliary line to the semi-trailer is pressurized for the secondary system. The spring-brake unit is manufactured by the German Westinghouse company. A mechanical handbrake is an additional fitting for Britain.
Another unusual feature of the test outfit was a fifth-wheel coupling centre 2 ft. 2 in. forward of the rear axle centreline. On British designs, I ft. 6 in. is about the maximum and, in fact, there was a good weight distribution over the four axles. For the tests, the outfit was loaded with concrete blocks—fairly evenly over the 33 ft.-long platform, but with about 2 tons extra in the area of the semi-trailer bogie.
The load amounted to exactly 20 tons, and as will be seen from the specification table, the driving axle and semi-trailer bogie were both about 1 ton within the legal maximum. There was no excessive loading orthe front axle, which carried 7.5 cwt. less than the 6 tons that front axles of 16-ton-gross four-wheelers have to carry. On the test chassis the power steering was virtually an essential fitting.
33 ft. long semi-trailer
The semi-trailer supplied for the tests was a Merriworth 33 ft.long unit with fabricated I-beam side-members, 20 in. deep in the area between the landing gear and bogie, reducing to 15 in. at the rear. Suspension and running gear were Rubery Owen and brake application was through Berg piston/diaphragm dual chambers. The frame design has now been superseded and the. latest Merriworth models have 18 in.-deep straight-through side-members. As on the unit tested, the frame depth at the neck area is kept at 9 in.
As will be seen from the layout drawing, the test outfit was found to be 1 ft. above the maximum legal length of 42 ft. 7.75 in. and, in practice, use of a 33 ft.-long semi-trailer is not possible with the 200D tractive unit. The main reason is the relatively long front overhang of 5 ft. 6.6 in. (Another make of tractive unit tested, with a 33 ft.-long semi-trailer and coming within the legal overall dimension had a front overhang of only 4 ft. 2 in. This is about the same as on the newer Magirus-Deutz tractive unit, so when this is imported into the UK it will be possible to use 33 ft.-long semi-trailers with a Magirus-Deutz two-axle tractive unit.)
Only one comparable British outfit has yet been tested by COMMERCIAL MOTOR at 30 tons gross. The fuel consumption obtained with the Magirus-Deutz was worse than this on normalroad running—the usual section of A6 south of Luton was used. On the other hand, the consumption on a high-speed run on M 1—a return trip between the A6 and A4147 junctions—was marginally better. It is difficult, if not impossible, W make comparisons between the two machines because the British outfit was tested in the north of England. But certainly the section of M1 used is probably the most hilly stretch of motorway in the country.
Very good performance
Acceleration tests showed the Magirus-Deutz to have a very good performance for a vehicle in its weight class; the times obtained would not have disgraced many rigid four-wheelers. In the direct-drive tests the engine showed little distress at speeds as low as 8 m.p.h. and there was a very good pull-away when the road speed reached 10 m.p.h.
I was a little disappointed with the braking tests, not because the results were unacceptable in themselves but because I felt the outfit was capable of better. There was some locking of the offside driving wheel and the offside wheel on the forward axle of the semi-trailer. None of the other tyres marked the road and this leads to the conclusion that the brakes were not fully bedded-in. The tractive unit had only 500 miles on the clock and this would not have included much brake work as the trip from the German factory accounted for most of it. It, is more than likely that the semi-trailer had completed an even lower mileage.
Braking figures
The figures obtained for the maximum-pressure braking stops were almost the same as those with the 30-ton artic previously tested and represent actual efficiencies of around 43 to 46 per cent. The best Tapley-meter readings for maximum deceleration on the stops were 66 per cent from 20 m.p.h. and 63 per cent from 30 m.p.h. Initial tractive-unit handbrake tests gave poor results but after adjustment the satisfactory figure of 23 per cent was obtained.
It can be expected that there will be an appreciable delay in the application of artic secondary systems where the feed to the semi-trailer has to travel something like 30 ft., but this was not too bad on the Magirus-Deutz. There was at any rate the "feeling" of braking as soon as the hand-reaction valve was operated; this emanating from the driving axle. But the best Tapley-meter reading obtained was only 28 per cent. With fully bedded-in semi-trailer brakes this could probably improve. It is likely that it will have to if the proposals for changes in the C. and U. Regula
dons go through in their present form. The figure is satisfactory for a vehicle in service, but 30 per cent is going to be required of "new" vehicles.
Bison Hill on Dunstable Downs was used for tests to assess hill-climbing performance and brake fade and the handbrake checks. The hill is 0.75 miles long and has an average gradient of I in 10.5 with the maximum 1 in 6.5. A maximum-power ascent was made in 5 mm. 29.6 sec., for 2 mm. 13 sec. of which' first gear was necessary. Minimum speed on the climb was 4 m.p.h. The return down the hill was used to assess brake fade. Instead of making the descent in neutral it was decided to keep direct drive engaged due to the weight of the outfit and the wet road conditions. The run was made at 20 m.p.h. and towards the bottom, where the hill is not so steep, the vehicle was driven against the brakes with full throttle applied to keep to the same speed. A maximum-pressure stop at the bottom produced a Tapley-meter reading of 58 per cent, showing that there had been virtually no reduction in efficiency due to the heating of the drums and linings. The trip down the bill had taken 2 min. 51.6 sec. with 31 sec. spent driving against the brakes.
Returning up the hill to the 1 in 6.5 section, the handbrake held the outfit both facing up and facing down the slope and an easy uphill restart was made in first gear. But when facing down the hill, clutch slip prevented a restart in reverse.
Pleasing to drive
I found the Magirus-Deutz pleasing to drive, with easy steering, good "feel" to the brakes, efficient suspension and a relatively lively performance. Noise in the cab was not unduly high and comfortable seating and an efficient heater were welcome, the latter more particularly because the outside temperature never rose above freezing during the test. Yet io much heat was being pumped into the cab that it was frequently necessary to open the windows. Most of the comments made in my road test of the Magirus-Deutz six-wheeler can be repeated, and on one point the tractive unit showed an improvement—there was no tendency towards front-end bouncing on some road surfaces.
I was surprised to find that a light-laden valve was not fitted to the chassis, as• this is a requirement in Germany to prevent overbraking when empty. Apparently the vehicle manufacturers decided that this unit could be dangerous because a similar unit was not fitted on the semi-trailer. Unladen runs with the outfit which had been planned were unfortunately impossible because the empty semi-trailer brought to the test circuit was not of the right dimensions to couple to the test tractive unit.