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STRAPPING LIGHTWEIGHT

18th October 1986, Page 126
18th October 1986
Page 126
Page 128
Page 129
Page 126, 18th October 1986 — STRAPPING LIGHTWEIGHT
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The 609D is far from revolutionary — it has the heaviest chassis cab in its class and has a naturally-aspirated engine -but it is as robust as they come • The first model from Mercedes' new, confusingly coded 'T2 van and chassis cab range to be tested by CM was a 709D, 6.6-tonne GVW van (CM, September 6). We were impressed with its voluminous carrying capacity, superb suspension, and outstanding build quality but we were left wondering how lighter, chasiss-cab models in the T2 range compare with their major rivals, the Renault/ Dodge '50' Series and Volkswagen LTs. Now we have some answers.

Mercedes-Benz produces chassis cabs to match all its T2 vans except for 507D models at 3.6 and 4.6 tonne GVW. The 811D provides a 600kg lighter alternative to the equivalent 7.5 tonner from the LN2

truck range. A far as the cabs are concerned, there is no mistaking the family resemblance. Externally the T2s seem almost an enlargement of the smaller series.

Apart from the 507D, each version is offered with an alternative 4.25m wheelbase in place of the standard 3.7m one. This allows the operator a choice of bodywork up to 4.57 or 5.40m in length.

Our test vehicle, a 5.6-tonne GVW 609D chassis cab on the shorter 3.7m wheelbase, was supplied with a very neat aluminium dropside, tilt-canopied body, built and fitted by Brade-Leigh. Initially, the vehicle was supplied for road test without a roof deflector which left it presenting a high front and side profile.

This clearly affected the 609D's fuel consumption, especially at speeds of 8 km/h and above around both the and distribution routes.

The results bear this out as late were able to drive it over our route in dropside form without the o'l3structive tilt but with the same low-height . • load in the rear.

• DR1VEUNE

Unlike its main competitor, the Dodge S56 which uses a turbocharged Perkins , T4.38 engine, the 609D has a naturallyaspirated power unit-the four litre 0M364 engine which it shares with the 6.6 tonne GVW 709D models.

Its maximum power output of 66 kW (88 hp) is 8.0% up on the 0M314 engine used in the L68D 5.69-tormer and is delivered at a slightly lower speed of 2.80rom.

The 0M364's 266Nm (1961b/ft) of torque peaks out at 1,400rpm, and although this is nearly 18% below that of the Perkins 14.38, it still provides a healthy, if not sparkling, performance.

Mercedes fits the G2-27 five-speed synchromesh gearbox which has a very deep 7.36:1 first and a direct top gear.

With its standard 3.27:1 final drive and shod with 205/75 tyres, the 6091) surpassed its 1111tm/h (69mph) geared top speed by 11km/h, helped by a stiff breeze of equal strength and some governor runout.

Mercedes-Benz offers an optional 3.73:1 differential which reduces its geared top speed to 98km/h (61mph) but gives better gradeability.

• PERFORMANCE

At its maximum 5.6-tonne GVW the 609D's 66kW provides an 11.8kW/tonne (16hp/ton) power-to-weight ratio that looks impressive enough.

On the test track at MIRA its acceleration through the gears up to 961un/h was marginally slower than the turbocharged 50-series (CM July 26, 1986).

The consistency of the times however, suggests a certain parity considering that the 6091) had to contend with the extra wind resistance from its tilt body.

Like the 709D panel van tested last month, the 6091) feels short on acceleration, especially around the A-road section and on our inter-urban distribution route.

It pulled away quite strongly from rest on MIRA's 25% (lin4) test hill, underlining its excellent torque characteristics and also performed extremely well over the timed hill climbs.

Only at the top of its speed range in the upper gears, where its power seems to fall away, does it disappoint.

Comparing the 609D's two sets of overall average speeds with the 66.1km/h (41.1mph) of the 7091.) 6.6-tonner reveals a shared consistency, but its journey times are slightly slower than those of the 50-series, especially over the motorway section.

In dropside form, the 6091) achieved its best fuel consumption figures around the A-road section returning 14.6 lit/1001on (19.4mpg), which can be balanced against its worst of 17.4 lit/100km (16.2mpg) over the distribution route with the full tilt body.

Both these figures were attained at vir tually the same 44krrilh (37.5mph) average speed.

While the dropside's return seemed more representative to the accompanying M-B engineer, respective results of the 50-series, 11.61ft/100km (24.3mpg) on Aroads and 11.81it/100km (23.9mpg) look more impressive.

• SUSPENSION

One of the 6091)'s best features is its suspension.

Over MIRA's exacting ride and handling course the long (1,550mm) parabolic springs, two-leaf at the front and four-leaf at the rear, with anti-roll bars all round as standard, proved most effective.

The way it absorbs pot-holes, tram lines and adverse cambers at fast speeds emphasises the obvious engineering connections with the larger LN2 models.

What a pity that M-B specifies the T2 models up to the 6091) without the benefit of power steering as standard.

While the manual steering feels comfortable enough, on long fast motorway runs power steering transforms the task of in-town or depot manouvring.

For the time being, if you want power assistance it will cost another £470, says M-B, however, from January it will become standard. Having joined the frontdiscs brakes for 7.5-tonners' fraternity along with the early pioneer Iveco and . now Leyland and Renault, Daimler-Benz

has decided on fixed calipers for the 507D models and floating type on the larger T2 models, all having ventilated discs.

The vacuum servo-assisted brakes gave a good account on roads that were mainly dry. Full pressure stops on the test tracks showed a generally good rate of deceleration with the truck pulling up straight at 32km/h.

Stops at 48 and 641cm/h had the rear brakes locking up early, with a slight pull to the left and a feeling that the fronts were not working hard enough.

• CAB COMFORT

From the driver's point of view, the 12 takes over where the heavier range stops.

With the cab's short nose and entry position behind the front axle, access is good. The driver's seat, which is slightly off-set to the steering wheel is comfortable, giving a sufficient range of adjustment.

The deep windscreen, angled door windows and, for the dropside, rear windows, give drivers a broad field of vision.

Gauges are easy to read off in daylight and clearerstill at night, being back-lit to a translucent green which highlights the orange needles.

Parts vulnerable to damage from stones, such as wheel arches, valances, step inserts and the front grille are of plastic material. Both batteries are stowed in a sealed compartment beneath the seat which hinges upwards on a hydraulic strut for maintenance.

• SUMMARY

Against the modern trend of computerdesigned aerodynamic shapes, Mercedes-Benz has replaced its long-lived Dusseldorf vehicle range with another in the same blunt-nosed style. Like the 50series its squat shape is practical and of more interest to operators in the nonHGV middle-ground of between 3.5 and 7.5 tonnes than to design purists.

The 6091) is marginally the heaviest in a small group of trucks plated at 5.6 tonnes, and it is up against snappier and more fuel efficient turbocharged models. They have power steering as standard whereas M-B is not likely to include it as standard until next year.

Undoubtedly, the reputation of its predecessor will give much assurance to interested municipals or own-account distribution firms, but it is not the most competitive in price.

At £11,530 the 609D is £460 dearer than the equivalent 50-series, but if currency fluctuations continue M-B may have to follow VAG's lead which has recently increased the price of the LT 50D by 3.3% to become the most costly at £12,238. There is nothing revolutionary about the 609D but it has the hallmarks of a durable, reliable workhorse.

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Locations: Dusseldorf

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