• When Volvo Trucks (GB) revealed its M6 prototype recently
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it was doing more than signifying an interest in the military market. It was also signaling a change in the whole philosophy of building military trucks.
Instead of being a specialist military vehicle topped off by an adapted civil cab, the M6 is as close as possible to a civilian vehicle, with the minimum modifications needed to satisfy military requirements.
In Volvo's case, this does entail a move away from its long-established 'matched driveline' approach of using only Volvo parts, to one of using ready-developed and common components.
The M6 programme is still in its early stages (though the prototype which we drove has already undergone 6,000km of rigorous off-road testing) and there is certainly not a definitive specification yet. On this particular machine, the front and rear axles are based on Rockwell's new 125C unit. The gearbox is the wellproven ZF S6.36, .driving through the same manufacturer's transfer case.
DRIVELINE
Up front the engine is Volvo's tried and tested T1)61 unit, in this case in the un stressed 'G' specification. This gives 112kW (150hp) at 2,800rpm and 430Nm (317lb/ft) of torque at 1,600rpm.
The cab is lifted straight off the FL6 complete with dashboard and instruments, the major modification being the replacement of the standard roof with a flat, reinforced component incorporating a standard military ring hatch. The flat roof panel brings the overall vehicle height down to the level needed for the M6 to fit inside transport aircraft like the ubiquitious Lockheed Hercules. Underneath, the multileaf suspension of the FL6 is replaced by two-leaf parabolics with Aeon rubber helpers.
CAB COMFORT
Inside, this vehicle gives few hints that it is destined for off-road use. True, the standard seat is replaced by a lower, nonsuspension unit, and the steering wheel is lower, but there are no extra levers. The two-speed transfer case is controlled by three push-buttons which give the choice of 4x2 high-ratio, 4x4 high-ratio and 4x4 low-ratio via pneumatic relays.
Access to the cab is not the easiest: the big 1200R20 tyres (a new Goodyear design on this vehicle) lift the bottom step of the cab well off the ground, leaving a big stretch for those unwilling to trust the step ring on the wheel centre. The standard FL6 cab trim means that in-cab noise levels are low; a big change from the noisy interiors of traditional military vehicles. All that is missing at the moment is a set of grab handles to help passengers keep their seats over rough going.
HANDLING
Underway, most of the controls are light — the steering retains its usual power assistance, and seems to have lost little precision even with the big, soft tyres while giving good isolation from rough-road shocks. The least satisfactory control is the gear lever: with the lowered seating position, the lever — in its usual place on top of the engine cover — is awkwardly placed. On this still-young example, the synchromesh is rather obstructive as well, making `round-the-corner' changes from fourth to second, for instance, a bit of a chore.
PERFORMANCE
When we drove the vehicle, it was fitted with a C300 container body and laden to some 10.5 tonnes against its design weight of 12.5t. In this form it was happy trundling around quite severe gradients in the upper ratios of the low range, but gradients approaching 33% required a quick snatch back to low second. Although there is no interlock fitted at the moment, changing from high to low ratio and viceversa on the move is discouraged.
On the loose-surfaced hills over which we tried the M6 it would merrily spin all four wheels on such steep gradients, but there was never any threat of its failing to clear a hill with one gear — and the diff locks — to spare. As is essential for any off-road vehicle, the brakes are progressive, well-weighted and do not snatch on loose surfaces.
The lowered driving position does not seriously affect the driver's line of sight down to the front of the vehicle, and gives the added advantage of a greater angle of vision upwards — most useful when tackling steep up-and-down work.
Although the big tyres look almost as big as the wheelarches above them, there was no hint of fouling in any of the manouevres which we undertook, and the glass areas stayed surprising clear of filth during mud and water splashes. We were not able to try the M6 over any really sharp crests, but there would seem to be little chance of grounding the vehicle. When laden the lowest point underneath the chassis is the transfer case, from which the propellor shafts extend roughly horizontally.
SUMMARY
As a first attempt at a military 4x4 the M6 is certainly impressive, and much credit must go to Volvo's British subsidiary which has done all the development work.
Thanks to the civilian origins of the MS. Volvo may be able to get the benefits of volume production and offer a lower price than specialist military vehicle manufacturers. The cab will undoubtedly be familiar to anyone aquainted with the FL6 layout.
It is certainly far more civilised a vehicle than the traditional military truck, yet loses nothing obvious in off-road performance.
In that, it is a successful design: what remains to be seen is whether it will prove attractive enough to the world's armies to be a successful commercial venture.
0 by Allan Winn