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WE DO not often get the chance to try out crosscountry vehicles, so when Saviem told me of a demonstration SM8 4x4 vehicle available for a trial on a site at Dunipace in Scotland, I jumped at the opportunity to find out how it would perform.
The SM8 is a specialised 12.5-tonne vehicle intended for operation in areas where it would be impractical to use a conventional 4x2 tipper.
John Stewart, of Larbert, the local Saviem dealer, had been showing it to some of our nationalised industries and other government organisations a few days before my visit. If sales result from these trials Saviem will make the model a stock item for the UK.
In standard form it is fitted with lhd for the Continental market and must be specially ordered if rhd is required.
The vehicle as supplied is no e longer a current model, as the 5.3-litre (323cuin) type 597 engine has since been superseded by the more powerful 5.49-litre (325cuin) 98kW (130bhp) six-cylinder direct injection diesel engine which is also fitted to Saviem's J-series. In all other respects, though, the model is identical to those currently being produced.
Power is transmitted through a single-plate clutch by a fivespeed gearbox, with four synchromeshed gears manipulated by a dash mounted lever, to a two-speed transfer box, to each of the four wheels.
For normal road-going and easy cross-country use, the 1 to 1 ratio is selected in the transfer box, but when the going gets harder, the lower 1 to 1.72 cog can be engaged pneumatically as also can the differential lock, interlocking all four wheels.
Both front and rear axles are constantly engaged in drive, with the effort divided so that one-third goes to the front and the remaining two-thirds to the rear axle. The steered front axle uses cam and roller gear, assisted by an hydraulic ram.
A three-way tipping body, built by Decauville of France, was mounted on a chassis constructed from cold-drawn steel side-members joined together by welded cross-members. The suspension, comprising leaf springs front and rear with rubber bump stops located on the chassis, is backed up by hydraulic shock absorbers and, on the rear only, an anti-roll bar.
An all-steel forward control cab, mounted on Silentbloc rubber pads, may be tilted forward to an angle of 50 deg. Because this type of application creates greater distortion of the chassis than is experienced under a more stable environment, a secure locking arrangement is needed to hold the cab in the down position. Bolts, as used here, seem the ideal solution even though it may take a little longer than usual to release the cab.
For day-to-day inspections of oil and water this is not necessary, for a hatch, placed between the seats inside the cab, provides sufficient access to the engine compartment.
A basic cab interior includes two seats placed wide apart, rubber mat in the floor area and an instrument console housing a speedometer which is only calibrated in kilometres. Access to the high driving seat is unobstructed.
Left-hand-drive vehicles always seem a little strange at first, but on site at least I had no other traffic to worry about. The test site included a high bank inclined at about 30 deg, but nothing approaching the 1 to 1 gradient Saviem's claim the SM8 can climb.
Covered in soft, dry peaty earth, the hill looked a formidable obstacle, but loaded with a full 5.6 tons of dry soil, the SM8 made little fuss in climbing it. Further along, the bank appeared to be a bit steeper, but here the surface crust had been broken up.
This proved to be too much for the vehicle, even in the first low with the diff lock engaged. At such a steep attitude in soft going, the wheels, fitted with road-going patterned tyres, just rotated and began to dig in so we had to be content with the lesser incline where the surface was firmer.
Coming down again, grip was no problem at all. The whole descent was completed, without once touching the foot brake, simply by engaging the lowest gear and relying on the engine to provide the necessary restraint.
Again it was not possible to assess fully the maximum side tilt angle, but it was possible to run along the length of the steepest part of the hill where heavy ruts in places added to side forces.
Across more open country, full use was made of the gearbox to attain higher speeds. Neither the strangeness of the dashmounted gear levers, nor the fact that both the diff lock and lower gear range were engaged, prohibited smooth and easy gear changes.
The park brake can only be described as cumbersome to operate as two levers are employed to lock the rear telescopic cylinders.
On the return journey to the garage. I was able to make a detour which enabled me to drive the vehicle over A-roads and a local section of motorway. Before reaching the road, however, a narrow gate followed by a right turn showed up the limitations of steering lock and a shunt was needed to complete the manoeuvre.
On the open road there was little to indicate, from the feel of the steering or ride, that it was in constant four-wheel drive. Top speed on the motorway of just over 80krn /II (50mph) col be maintained only on the fla Within the limitations of test site, the SM8 perforrr well, hill-climbing showing one of its stronger points. 1 approach to steeper gradie should be treated with cautii however, as the vehicl, approach angle (36 deg loaf is less than the angle (45 deg climb claimed by the make Belly clearance of 528n (21 in) was more than adequ for the conditions encountere I should have liked to tr) through water, but there vi none nearby; however, witl chassis height of 103m (40.E in the laden condition, I quoted 90cm (36in) fordi height would seem to be a r sonable figure.
The poor steering lock i! rienalty of the front axle, and some extent, with this size vehicle, has to be accepted if1 undoubted advantages of I four-wheel drive are quired.