An Irish challenge to the conventional tractor design was unveiled over 40 years ago, in the form of an all-hydraulic, four-wheel drive, variable-clearance articulated tractor, developed by farmer and engineer John Wilkinson from Dunboyne, Co Meath.

The tractor was launched to the media on a wet day in Dunboyne in September 1983, but unfortunately, it never went much further than that.

The design team for the tractor included John Wilkinson, who also operated an engineering company called Standish Ltd and could be said to have initiated the concept; John Bielenberg, the consulting engineer who carried out much of the design work; and Terry Nolan of Turmec Engineering, Rathcairn, Athboy, Co Meath, who carried out all of the engineering and fabrication work. The project received some funding from FBD Insurance at the time.

The most unique feature of the tractor was its variable clearance function, which was operated from the tractor seat and gave the operator the opportunity to vary the ground clearance from 0.45m (18in) at its lowest position, to over 1m (40in) at its highest.

The tractor, which at the time was called the Tructor, was powered by a 98hp (72kW) four-cylinder, air-cooled, diesel engine made by VM of Italy. At that time these engines were used widely in Ireland for industrial installations, such as driving generators and pump generators as well as pumps.

The engine, through a large splitter box, drove three large hydraulic pumps, which provided power for the transmission and PTO. There were two additional hydraulic pumps driven from the front-end of the engine crankshaft and one of these provided the power for the three-point linkage and external hydraulics, while the second smaller one operated the centre pivot steering system.

Two of the three pumps on the splitter box end provided power for the wheel motors. The flow from each pump to the wheel motors was routed in a diagonal path which meant that one pump provided oil for the front right and back left wheel motor while the other pump supplied the other two wheel motors.

This claimed to give a differential effect with the aim of reducing wheel slip. Each wheel motor was rated at about 60hp (45kW) and they were all high torque motors which were rated to have good pulling characteristics. The wheel motors were piston-operated units and by varying the piston displacement, the speed and torque characteristics of the tractor could be changed, to give either a low or high range.

Although the flow to the wheel motors was in a diagonal pattern, the displacement of the pistons in the wheel motors were operated by a separate hydraulic circuit and the front or back wheels could be varied in speed and torque, independently or together.

Speed

Because the transmission was hydraulic, there were just two speed ranges, high and low, and within each range there was a variable forward and reverse speed operated by a lever on the dashboard.

The forward speed was monitored by an RDS speed area meter mounted to the left-hand side of the tractor. The wheel track widths could also be varied in width from about 1.52m (60in) to about 1.93m (76in). The wheel track widths can be varied, not alone by changing the wheel centres, like in traditional tractors, but also by moving in or out the complete arm which carries each wheel and wheel motor.

Power

The third hydraulic pump on the splitter box provided power for the PTO shaft by means of a 90hp (52kW) motor. A standard 540 rpm six-spline, 35mm (13/8in) shaft was used, as well as 540 rpm an additional 800rpm speed was available for high-speed low torque work.

The PTO shaft speed was monitored directly by means of a RDS shaft rev. monitor unit and the shaft was engaged and disengaged by means of a lever to the left of the driver’s seat.

The three-point linkage was French made Trac-Equipe TE 2000 unit with a 2t lift capacity. The linkage with quick coupling lower link ends was a standard front-mounting unit, which in this case was bolted to the rear.

Instead of three-point linkage sensing, the TracEquipe unit had a depth gauge which was electrically operated and based on a resistor unit attached to the linkage cross-shaft. The actual depth or position of the linkage was read from a dial in the cab beside the linkage operating lever.

The complete back-end, which comprised the three-point linkage, the PTO shaft and the motor, the motor and the two double acting auxiliary services spool valves, were all mounted onto a plate, which was in turn bolted to sliding box section units.

It was planned that the entire back-end would have a total of six different positions and on the production of models it was planned that this would be varied hydraulically. It was envisaged that this could also be removed and replaced by the front-end loader type of attachment.

The sliding back-end concept was a useful feature, as it left a good deal of space for mounting sprayer tanks or additional fertiliser hoppers to cut down on the amount of time wasted at filling during both spraying and fertiliser spreading.

The cab and operation

The relatively small tractor cab was centrally positioned on rubber bushings for a smooth ride. The steering wheel, controls, console, seat and hydraulic levers were all mounted on a turn-table operating unit, which could be turned through 180 degrees to give a reverse drive or dual drive tractor.

As this was an all-hydraulic tractor, a good deal of oil was being used and two large oil reservoirs formed the cladding on either side of the engine housing. Two front-mounted, thermostatically controlled fans were included to cool the oil. In future production models, part of the frame unit which provided the basic structure of the tractor was planned to be used as an oil reservoir, in an effort to reduce the machine’s overall weight.

The tractor was originally designed to solve the problem of low clearance at spraying with standard machines. It then developed into a multi-use machine. Ireland would provide only a small market for such a variable clearance tractor, so the concept was aimed at both British and continental European markets.

The tractor never made it to the market, despite great enthusiasm for the project at the time. It probably tried to be more multi-functional than the market was prepared for at the time.

Turmec, which had begun as a turf machinery manufacturing company in the early 1980s and today is a world-leading recycling machinery manufacturing company, provided a significant part of the engineering funding for the project.

Despite a number of farmer demonstrations, there was no clear marketing plan to take the project further. The short life of Ireland’s only variable height, reverse drive tractor, came to a relatively quick end.