Archive Article: 1997/09/20
AMONG the new introductions from John Deere is an 8000T Series range of rubber- tracked tractors, based on the corresponding wheeled models, with rated outputs of 185, 210, 230 and 260hp.
Targeted principally at the larger acreage arable farm with heavy soils, they are the first tractors in their power class to be offered with a choice of wheels or tracks.
With no wheels to support the over-hanging front of the tractor, the whole centre section has been beefed up to accommodate the track drive and idler assembly, and to cater for the redistributed loads along the length of the tractor.
To ensure good stability with mounted implements and help maintain the ideal weight distribution of 55% on the front idler and 45% on the rear drive wheel, the rear linkage mountings have also been moved forward so that equipment is transported and operated closer to the tractor.
New, stronger castings are used to carry the increased weight and greater forces at the rear.
Drive to the one-piece moulded rubber tracks is via a friction band around the circumference of the two rear drive wheels. A set of three mid rollers supports the centre of each track and the two front idler wheels are equipped with hydraulic track-tensioning cylinders which can be topped up from one of the tractors four external service outlets.
A conventional steering wheel is used to actuate electronically-controlled hydrostatic differential steering which provides forward or reverse rotation to the final drives.
The first movement of the steering wheel is the most sensitive, preventing over-reaction during precision work such as drilling.
Steering action is also proportional to ground speed – the faster one is driving, the slower the steering responds to the turning of the wheel, designed to make the tractor easier to control.
Centre to centre width of the standard 60cm (24in) wide tracks can be altered in 100mm (4in) increments between 1.72m and 2.23m (68in-88in) and the front idler incorporates a simple adjuster to maintain track alignment.
Mr Day says that all 8000T Series tractors come with appropriate front weights for the model, although extra ballast can be added at the front and between the drive and idler wheels to suit soil requirements and the implement being used.
The 8000T tractors will cost about £32,000 more than the equivalent wheeled models.