Bernet heads tit
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ALTHOUGH we are familiar with Berliet tractive units in the UK — though in fairly small numbers — few of the French maker's rigid vehicles are imported. However, Berliet main dealer Anderson Commercials (Newhouse) Ltd, of Wilson Road Garage, Newhouse, Motherwell, has brought in 30 GBH 260 6x4 dump truck chassis, and I was invited to test one of these, fitted with an alloy body, on an opencast coal mine in Scotland.
The GBH 260 is a naturally aspirated version of the GBH 280, and its 12-litre power unit produces 184kW (250bhp) at 2,200 rpm. This is more than enough to provide all the power required for site work, but with the gearing fitted to the 260, top speed is limited to around 35mph.
A ZF six-speed splitter box was fitted to my test truck, although Berliet's own eight-speed box is standard. Drive from the gearbox is transmitted to two double-reduction rear axles, which, on the test vehicle, incorporated inter-axle diff locks.
Tremendous
The differentials are located by massive retaining rods and 'single springs are used for the rear bogie. This set-up allows a tremendous degree of bogie articulation — vital for the sort of terrain encountered on an open cast coal mine. Anderson already has two of these dump trucks working on an opencast mine where they are completing about 45 journeys and tips a day per vehicle.
Non-stop The distance between loading and tipping is about three miles and each vehicle is loaded to 30 tons. The trucks work. more or less non-stop but are cleaned and serviced at weekends.
The gearbox is simple to use and the lever incorporates a change switch operating an electro-mechanical control, giving a high range top ratio of 0.835 to 1. Normal sixth is 1-to-1. Without body or load, the brakes were very sharp, pulling the vehicle up very quickly.
The steering was power-assisted and very low-geared. was able to appreciate these qualities, later, when drivin'g the laden vehicle across a very rough site.
When the 20cuyd body was loaded with coal to about 30 tons, the Berliet transported it effortlessly across fairly rough ground to the tipping point. Even with this weight, it pulled away without trouble and easily climbed a fairly steep gradient.
No feedback
The steering, which l had previously thought to be too low-geared, proved itself over the rough ground. There was no feedback and it was always possible to maintain course.
Bob Hunter, of Anderson Commercials, told me these open cast mines often get so muddy that the driver can't even get out to relock or clip up his tailgate without disappearing up to the tops of his wellies: Looking at the site, I could well believe it.
To keep the Berliets moving through these sorts of conditions, an inter-axle diff lock is fitted, and, in addition, an inter-wheel diff lock. This is controlled by a push button on the facia which is held in when complete locking is required, Once it is engaged though, the Berliet will not corner easily, if at all because there is no differential action.
The normal control cab fitted to the GBH series is similar to that used by a large number of other Berliet rigids and some tractive units, although these are seen only in France or occasionally, other Continental, countries. The cab is a comfortable enough workplace, though somewhat narrow.
Instrumentation, in a nacelle, consists of a speedo to the left of the column (optimistically calibrated to 120km /VI), rev counter, oil, water temperature, battery and pressure gauges. A fast-idle control is provided to the driver's right beside the slide-up stop control. Around the column to the left is the park-brake control.
On a tray
Several features have been built into the Berliet to improve accessibility for maintenance while protecting the components. The batteries, which slide out on a tray beneath the cab on the offside, are enclosed by an outer cover. Both engine side , panels can be removed completely to reach the power unit. To avoid damage by rocks on site, the rear brake chambers are mounted on a cross-bracket well out.of the way.
The Berliet is a very toughlooking truck which, if Ander son's experience is anything to go by, gives good service in the roughest conditions.
• Stephen Gray