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HOW SEVEN PERFORM

27th September 1974
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Page 29, 27th September 1974 — HOW SEVEN PERFORM
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CM technical staff chose a variety of vehicles from the Earls Court demonstration park for brief road appraisals...

SEEING is believing but in the case of the gleaming new models on the Show stands a short demonstration drive can either confirm or dispel original impressions gained from inside the hall. CM staff had the opportunity to put seven of this year's demonstration models through their paces in the streets around Earls Court.

Graham Mon tgomerie says that:

ALTHOUGH the 1626 from Mercedes-Benz is intended to become the spearhead of its attack on the UK market, no such model was available in the demonstration park. Instead, an example of the higher-powered 1932 model with a fully laden Van fool trailer was tested. As this was similar to the vehicles I drove in Germany earlier this year, I was interested to see what improvements, if any, had been made in ansv to the various criticisms made at that time. In fact, the 1932 turned out to be a completely different truck.

When I first drove the 1932, in company with several other journalists, the Overall impression was one of a good basic design rather spoiled by braking and steering performance. These faults have been eradicated on the latest model. The steering was light and precise when cornering but still retained this precision in the straight-ahead position, which made the brief trip up M4 very enjoyable.

Nice and easy

Braking on the original vehicle was rather a dodgy business as they were either all-on or all-off and nothing in between. Whatever the reason for this, which nobody from MercedesBenz has not yet revealed, it has now been cured and the brakes are now as easy and progressive as a hydraulic system on a private car.

Now the bad news. The cab nod on the new truck caused great discomfort on dubious road surfaces, which is a prime example of progressing backwards — as the original ride was very good. Sometimes a design team just can't win!

I look forward to carrying out a full road test of the 1626 Mercedes-Benz but, if the higher-powered version is anything to go by, this is M-B's most serious attempt yet to re-establish itself on the British heavyweight market.

Trevor Longcroft tried:

AN INTERESTING addition to the urban delivery concept is the Fiat and Alexander Trailer linkup to produce a lightweight articulated vehicle combination which can he driven by a Class 4 hgv licence holder yet is able to carry a 6ton payload.

I was able to try the first prototype model, which features an all-aluminium tandem-axle semi-trailer which is 7.6m (25ft) long, coupled to a short 2.6m (8.5 ft) wheelbase Fiat 0M55 chassis-cab fitted with a fifth-wheel.

As driven, the combination had an unladen weight of just 3 tons and was loaded with 4.5 tons of timber ballast.

The busy traffic conditions around Earls Court were an ideal testing ground for the Fiat. The semi-trailer followed the tractive unit almost exactly and cornering could be completed safely almost without the need for checking the trailer through in the rear-view mirror.

The trailer was fitted with Feeny & Johnson three-line vacuum brakes, which had a delayed reaction. When the brake pedal was released a few seconds passed before the trailer brakes fully disengaged.

The tandem-running gear provided a harsh trailer ride and whenever I drove over rough roads I could hear the load bouncing on the trailer platform. If the trailer is to carry delicate cargoes, such as bottles, Alexander will need to take a closer look at the suspension.

Racing the clutch

The Fiat 0M55 tractive unit had covered only 1,120 km (700 miles) before the appraisal and it was noticeably stiff. The throttle jammed occasionally, especially during those gear changes which could not be completed without momentarily racing the clutch.

A wide gap between third and fourth gears spoilt an otherwise evenly spaced ratio spread, and I was particularly impressed with the engine's tractability at low engine speeds. In fifth (top) gear the outfit pulled away easily from 48.3 km/ h (30 mph).

The DAF FAD 2205 DU 30-ton eight-wheeler was introduced earlier this month and although models are not expected to be available until early next year I took the opportunity to drive the demonstration vehicle. It was loaded to its maximum 30.5 tonnes (30 tons) and with an unladen weight including Booker body of 10.2 tonnes, it carried an effective payload of 19.8 tonnes (19.5 tons).

The vehicle specification includes the 8.25-litre (503 cu in) turbocharged engine, 13-speed Fuller gearbox and standard twin-drive rear bogie with inter-axle differential lock.

Manoeuvrability in tight spaces was put to the test straight-away in edging the DAF from the ridiculously cramped underground car park. Although the eightwheeler has a tight turning circle, the engine revs must be kept above the idling to prevent any drop in power assistance. Lock to lock manipulation at engine idling speeds is hard work.

I selected a route that included sections of A4 and M4 and a short, busy section around the exhibition area. The DAF handled well; once on the move steering was light and accurate and small gaps could be negotiated with confidence.

On A4 and M4 the 13speed gearbox came into its own and by sensibly keeping the engine in the higher rev band, optimum speeds were easily maintained.

The cab was fitted to DA F's usually high standard, though I would criticize the position of the throttle pedal, which is too far forward and uncomfortable to keep flat on the floor for prolonged periods.

All the instruments are easily seen through the large diameter DAF steering wheel, though I would prefer a different indicator arm arrangement. I often, inadvertently sounded the horn while engaging the indicators.

The Foden AR28 / 38 tractive unit was fitted with the sleeper version of the S80 cab and was powered by a Rolls-Royce 280 engine driving through Foden's own nine-speed gearbox. It was coupled to a York platform skeletal semi-trailer loaded with two empty 20 ft ISO containers.

Adjustable steering column

I found it cramped getting into the driver's narrow door, but once inside there was ample room and I liked the adjustable steering column. It could be moved through a narrow angle in order to give a comfortable driving position.

But for the cab door hinge pillars all-round vision was good and the mirrors were vibration-free.

Because the vehicle was unladen it could be driven satisfactorily without resorting to the four ratios in the low range; -acceleration was brisk and steering was light almost to the extent of being vague. Careful use of the brakes was also required to avoid abrupt stops.

I was pleasantly surprised to find how easy it was to thread the maximum-length artic through the busy streets. I had only one anxious moment: when turning left I narrowly passed a road sign with the bogie wheels just inching over the kerb.

Finally, I took the opportunity to drive the Volvo F86 City artic unit coupled to the small 7m (23 ft) long semitrailer which forms the rear end of the Volvo/ Crane Fruehauf doubled-bottom outfit. It seemed the ideal time to put theory to test and see just how well the city vehicle fared in the environment it was designed for.

The outfit was operated at its maximum 26.4 tonnes (26 tons) gross and the unit was specified with the Volvo TD7OD 6.7-litre (409 cu in) environmental engine and the eight-speed fully synchromesh range-change gearbox.

The cab of the F86 is already well known from previous descriptions and I can add nothing to it except that it came up to the standards expected.

The engine is encapsulated in insulated material to reduce noise emission, and inside the cab it was pleasantly quiet regardless of engine load and speed condition.

As with the small Fiat outfit, the Volvo easily blended with the rest of the traffic. It moved fast enough not to cause any hold-ups and was easily guided around corners or through narrow streets strewn with parked cars.

The eight-speed synchromesh gearbox has a light and easy action. And as with most turbocharged engines the best performance was achieved by keeping the engine revs in the high range.

My last impression of the, Volvo was how simple it was to reverse into a confined space. Parking the vehicle in the demonstration area was easier than reversing a similar wheelbase rigid.

. . . And Martin Hayes went on the buses:

AN IMPORTANT model, new to Earls Court. which I was able to try from the demonstration park was the first production model of Tricentrol's Unibus 25 body on the Ford A-series chassis. When I first drove the prototype of this model earlier this year, the vehicle was petrol engined and had a coach interior. The demonstration vehicle was a bus model with a diesel engine.

Finish on the bus was much better than on the prototype, and I greatly liked its higher driving position. Floor level on the diesel is 150 mm (6in) higher than the petrol model and this helped a lot I was impressed by the smoothness of the engine when idling or driving at a constant speed and the noise level was quite acceptable.

Although the bus was very new I found the stiffness of the throttle rather unforgiveable and this made stop-start traffic conditions a series of jumps unless extreme care was taken. More worrying was the tendency of the vehicle to surge in the lower gears, even when throttle opening was delicately controlled. This is a feature I have noticed on other diesel A-series and is something which will need attention if the chassis is to be used successfully on heavily trafficked bus routes.

Another improvement made to the vehicle is the use of firmer rear springs and these make for a useful increase in vehicle stability. Fast corners no longer cause exaggerated roll angles and the vehicle feels comfortable at all speeds.

Suburban express

The second vehicle I was able to try was the Leyland National suburban • express which made its debut on the stand at last year's Scottish Show. Complete with semiluxury Chapman seats, anodized aluminium parcels racks and a flat floor the vehicle is quite significantly different from the standard National bus specification. On the technical front the bus has a version of the IN series engine which develops 149 kW (200 bhp) at 2,200 rpm. The rear axle ratio is 4.30 to 1 and a fivespeed semi-automatic gearbox is fitted.

The route I chose to try the vehicle — from Earls Court, along M4 to the London airport and back (about 40 km (25 miles) in all) — was a typical "surburban express" route. With the vehicle unladen performance was deceptively good in traffic using the four upper ratios. As usual with this gearbox a long pause between ratios is necessary to achieve smooth upward changes.

Once on the motorway I was a little surprised to find top speed, even with this "high" axle ratio, was only 93 km/ h (58mph). This would be barely adequate if the vehicle was including much urban motorway in its route, but at least at this speed the vehicle was very quiet with no wind noise.

The demonstration vehicle was fitted with an anti-roll bar in a bid to prevent excessive roll angles. This seemed to work well with the vehicle remaining flat even during the highspeed twists and turns of the Chiswick flyover.

However, there was a disturbing. by-product of the roll bar. This was a slight shimmy in the steering at high speed. Coupled with the ultra lightness of the steering and a certain deadness around the. straight-ahead position this called for rather more concentration at high speed than I thought desirable.

Tags

Organisations: Earls Court
Locations: York

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