Four-wheel drive is the way to treat sods
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United Services Garage at Portsmouth specialises in 4x4 cross-country vehicles and Butser Turf makes good use of its Pathfinder conversions. Loam ranger Bryan Jarvis makes his field report
THERE WAS a time when the only four-wheel-drive vehicles available to the civilian market were based on ex-war department stock. Now, with increasing numbers of operators realising a need for off-road capability, converted vehicles are an obvious attraction.
One such version is the product of over seven years of continuous development and improvement by United Services Garages of Portsmouth, a member of the Wincanton Group.
In its special engineering department USG builds Pathfinder 4x4 cross-country vehicles based on Bedford TK or TL chassis. The complete UK range extends from 5.5 to 12.6 tonnes gvw.
A TL 1260 with 5.4-litre 101kW (135bhp) turbocharged engine provides the basis for the latest Pathfinder. It has a five-speed synchromesh gearbox, powersteering and comfortable tilt cab. The vehicle achieves further versatility by the fitting of suitably modified Bedford cornponents — a rebuilt J-type front axle with 7.38 to 1 ratio, a standard transfer gearbox and modified prop shafts.
Front stub axle assemblies are to USG's own design as are constant velocity joint housings, seals, hubs and drive shafts. Bedford's own constant velocity joints are used while the original brake assemblies and drums are also retained. By rebuilding the front axle to its own design USG has improved the 27 degree steering angle by five degrees.
Two and four-wheel-drive selector mechanisms on earlier conversions consisted of a long transfer gear lever in the cab connected through a mechanical linkage to the transfer box in the drive train.
On the latest Pathfinder, the mechanical systems have been replaced with air-operated cylinders. From a pneumatic control, located within easy reach in the facia panel to the left of the heater controls, the driver can select a two or four-wheel drive mode in the normal way. For this the vehicle must first be stationary.
The control unit consists of a central knob which turns through 90 degrees either way. To the left side of it, two indicators signal rear wheel and high ratio drive. To the right of the switch is four-wheel drive and low ratio. When the knob is turned in one position or the other, red eyelid-like indicators clearly show when the selected drive engages.
Martonair cylinders attached to the transfer casing operate the selector rods to engage two or four-wheel drive and high or low ratio. The system relies on an air feed from the vehicle's own compressed air supply to the brakes, but special check valves are fitted to ensure that the brakes always have command of the air supply. USG also fits a small regulator, a filter and a lubricating unit between the vehicle's air supply and the Martonair units. The latter provides a fine film of oil to lubricate the cylinders and help reduce the risk of corrosion.
The standard Bedford lends itself particularly well to this type of development and USG has attracted considerable interest with the latest Pathfinder. With the cost of the conversion at £6,990 bringing the overall price of the TL 1260 in four-wheel drive form to just below £21,000 excluding vat, this puts the Bedford conversion within the budget of many local authorities, electricity boards and private companies. One fairly local turf cutting company has used four-wheel drive conversions for a number of years and is currently operating a fleet of 10 4x4 Pathfinder vehicles based on the Bedford TL 1260.
Butser Turf of Horndean, Hampshire has changed from Bedford M1120 and improved its fleet payload by just over one tonne for each TL vehicle. NoSPIN differential locking mechanisms are specified on all of its vehicles. These units, which replace the conventional differentials, prevent driving torque from forcing one wheel to turn faster than the other. Thus, if one wheel loses traction the opposite wheel will still drive.
USG also supplies the vehicles with wide tyred single wheels on the rear axle, which is of particular benefit to Butser Turf because of the environment in which its vehicles operate.
Butser has recently celebrated 50 years in the agriculture business and although it gave up the timber side of its business a decade ago, its 170 acres of farmland still supply some turf. The majority of the grass, however, is bought-in from other farms or estates. It is sliced into 3 x 1 ft strips each about tin deep, folded in two, then delivered in 400sgyd loads.
Typical customers range from civil contractors and local councils to garden centres, even private buyers. Cutting-site conditions vary considerably from nearby flat meadows to almost inaccessible fields.
Rainy weather makes the tracks heavy and great care has to be taken not to damage the field when carrying the turf away.
visited a site set amid undulating woodlands near Liphook on the Hampshire/West Sussex border at the invitation of Butser's managing director Alan Smees. Over a quarter of the field had been cut, leaving a rich loamy top soil, heavy with rain.
Judging by the amount of tyre tread marks, vehicles had been making regular trips between the grassless area and the woodland tracks to the main road. Yet there were no ruts or signs of the ground cutting up. Despite the steady drizzle and occasional driving rain, one of the newest vehicles was halfladen with broken turf and loose top soil for me to give to a site at nearby Liss.
Although the conditions were by no means extreme, using four-wheel drive together with the NoSP1N positive locking differential, I drove out of the field without any wheel slip or fuss of any kind. The narrow tracks through the woods were of a different nature being muddy and severely rutted with large tree roots laying in wait across them. Here the Pathfinder gave a good ride with the long taper-leaf springs and progressive elliptical-nose bump stops combining well. I was left with the impression that the ride would be no different with the maximum permitted pay load.
Although the cab is relatively low for a cross-country vehicle it has fairly generous approach and departure angles, which would prove useful when traversing very rough ground.
The TL's modern cab also offers a good level of comfort for driver and passenger. Although there is a double passenger seat it could become cramped with three in the cab on the long delivery runs which Butser sometimes undertakes.
Before changing to two-wheel drive, high ratio, the vehicle had to be stopped and neutral gear selected. When the selector knob on the dash was turned through 90 degrees nothing happened, the vehicle's transmission remained in four-wheel drive. The change did not occur immediately because of pressure within the transmission. By moving the gear lever between first and second gear several times, disengagement was quickly achieved.
The eventual change to twowheel drive was signalled by air actuating the two red indicators to the left of the selector panel on the dash.
This system is a considerable improvement over the usual lever method found on earlier models and is more in keeping with a modern-cabbed vehicle.
On the road the converted TL 1260 drove well, giving a fair degree of feedback through the steering. Although there was no disguising that definite feel of a four-wheel-drive vehicle, it drove much more smoothly than I expected.
Butser has been using these vehicles for a number of years now, each covering between 7580,000 miles annually. Company policy is to keep the vehicles for two to three years before it sells them.
Md Alan Smees told me: "I have no problems in disposing of them. They are sold within the agricultural trade". Mr Smees assured me that the wide tread tyres generally last the life of the vehicle, thanks to recutting the treads.
As Butser Turf is a fairly local client, it is easier for USG to monitor closely the vehicle's capability and maintain a close liaison with the user. USG director Douglas Sharp is particularly pleased with the latest Pathfinder's performance, as well he might be. If the potential orders materialise, then the conversion section will be busy for months to come.