British Tractor Development

Press, Volume CIII, Issue 30378, 29 February 1964, Page 7

British Tractor Development

ONE of the biggest surprises at the Royal Smithfield Show held in London recently was the quiet entry of Britain’s first farm tractor with hydrostatic transmission, writes Maurice Swift.

This great design advance has been on the manufacturer’s shelf for at least five years, but, to date, the larger tractor manufacturers have been reluctant to disrupt their production runs to introduce a model which will

cost £4OO or £5OO more than its geared counterpart in the early stages. The responsibility for this break-through lies with the makers of the Roadless Ploughmaster Hydrostatic 6/4, a six-cylinder diesel tractor with a near 90 b;h.p. engine, an infinitely variable hydrostatic transmission, and fourwheel drive.

The hydrostatic unit—the Lucas 100—is a back-to-back drop-in pack which fits neatly into the transmission housing in place of clutch and the normal gearbox. Both pump and motor employ tilting swash plates so that a greater range of speeds can be achieved simply. The Ploughmaster can travel at speeds from 0.2 miles to 18 miles an hour with the engine running at its rated speed of 2250 r.p.m. A single lever controls forward and backward travel to give stepless speed variation, and when in the neutral position it applies positive, balanced braking, which is a safety feature. It is virtually impossible to damage the hydrostatic system by operating the speed control lever too rapidly or by changing directly into reverse. A hydraulic blow-off valve is incorporated and maintains the operating pressure below a predetermined limit.