AT THE HEART OF THE ROAD TRANSPORT INDUSTRY.

Call our Sales Team on 0208 912 2120

Promising Contribution to Nation', lood Productivity

10th January 1941
Page 22
Page 23
Page 24
Page 22, 10th January 1941 — Promising Contribution to Nation', lood Productivity
Close
Noticed an error?
If you've noticed an error in this article please click here to report it so we can fix it.

Which of the following most accurately describes the problem?

ABOUT 30 years have elapsed since the original introduction into agriculture of the practice of mounting the implement on the tractor instead of towing it. This neat arrangement is commonly described as " the 'unit principle.' '

One of its objects is to• achieve a better degree of constancy of depth in the line of draught than is possible • with a hauled implement. Variations in depth create a tendency for the implement to pull the tractor wheels into the ground or for the tractor to pull the implement out of the ground.

An undesirable feature, however, results from the fact that the mounting is rigid and overhangs the back axle by an appreciable distance. Accordingly, when the front wheels descend into a hollow the implement rises, whilst upward motion of the front wheels causes the implement to dig in more deeply. Even with close coupling of the implement to tractor, the fault has not hitherto wholly been eliminated.

The Ferguson tractor, built in this country for some years by the company which has since been renamed David Brown 'Tractors, Ltd., of Meltharn, near Huddersfield, represented an effort to overcome this difficUlty. Indeed, a considerable measure of success was achieved. A flexible mounting supported the implement and the position of the latter was regulated by hydraulic apparatus controlled by a valve automatically operated as the front wheels dipped. The mechanism functioned satisfactorily, and in the Main substantiated the claims made for it, but trials on a variety of types of land revealed certain shortcomings which have led to considerable modifications being effected,

Chief imperfection was time lag between the action of -the tractor and the corning into play of the -compenSatMg movement of the implement. In effect, the undulations of the surface were reproduced by the implement at the bottoms of the furrows, but at a difference in spacing equivalent to the distance travelled. by the tractor while the , dash-pot arrangement of the hydraulic 'gear was functioning.

„Reference to an accompanying diagram will explain what happened and its result. The illustration is, of course, exaggerated, and the fault could be kept within fairly reasonable bounds by running Slowly. One of the Main advantages of the tractor, therefore, namely, its speed, was thus sacrificed.

The uppermost of the. three diagrams shOws the effect when 'travelling slowly; that below it the-relation of furrow to surface at higher speed., 'and the lowest _ figure, the ideal, that is, a :furrow bottom which follows precisely the contour of the land immediately above.

Intensive research and a long period of experimenting have led to the development of a new scheme and to the introduction of a David Brown tractor with unit-principle implement control and a range of implements with a patented method of positive and accu rate 'depth control. These are now available, although supplies, both of tractor and equipment, are inevitably limited.

In order that the good features of the apparatus----indeed, the entire outfit— may be fully appreciated, it may be as well to run through the requirements that should be fulfilled by the efficient agrimotor. These have been summarized by the maker as follow :—

in respect of depth, from the „driving seat, and that maintain a constant pre" determined depth at all speeds and under all conditions,

Evidence is available to prove that the David Brown tractor and equipment conform with these condition's,

There is a new hydraulic unit, which is •a self-contained auxiliary and can easily be bolted on to the rear axle in place of the cover originally provided. Its presence does not interfere with the use of hauled implements. The unit also carries a power-take-off shaft extension' for power-driven implements. Its sole functions are lifting and lowering, not automatically controlling depth. This latter, operation is performed by an automatic depth-control wheel, clearly visible in some of he accompanying illustrations, Also well depicted is the general disposition of the Iuakage, which forms what may be described as a rhomboidal hitch. It will be appreciated that it definitely obviates any tendency for he implement to dip laterally. A levelling mechanism is provided to adjust the implement transversely to suit the con tour of the land. The handle for operating it is, roughly, between the• hydraulic unit and the top of the offside wheel. It can be seen clearly in the picture below.

Centrally situated are the handle and screw gear for regulating depth. They actuate, directly, the Upper end of the lever on which the depth-control wheel is mounted. The simplicity of the device is outstanding. If the operative desires a 8-in, cut, he just sets the wheel accordingly and it must maintain this depth.

As standard, a pneumatic-tyred wheel is used. For splitting ridges, however, this is replaced by a split depth-control wheel conforming with the dimensions of the ridges. It precludes any tendency for the implement to wander, and can be fitted in a matter of arfew minutes. For certain classes of work a steel wheel is preferable and in an illustration depicting ploughing, using the unit principle, will be seen bow the type and disposition of this wheel give accurate control.

Another point worthy of mention. relates to the stresses that are imposed, with former designs, when the tractor is driven quickly over rough surfaces with the implement lifted. These, not infrequently, have resulted in breakages. With the new arrangement the implement is still supported by the depth-control wheel, in such circumstances, and thus the linkage, etc., are relieved of excessive loading.

A. comment is called for about the picture of a tractor operating on a small area of land fenced off for a demonstration of its rnanceuvrability. The dimensions of this " field were actually 21 ft, by 14 ft. and the tractor, working with a spring-tine cultivator, left no part untouched, nor yet a wheel mark.

There are independent hand brakes to facilitate quick small-radius turns, and in view of the stresses that are imposed upon the mechanism by such treatment, it is of note that a gruelling series of tests is reported to have had not the slightest ill effects, which certainly constitutes a tribute to the design, workmanship arai materials of both tractor and equipment.

We mentioned earlier that production, at the David Brown works, is behind demand, but the company fully appreciates the national importance of accelerating and increasing the country's food-growing capacity, and the tractor's part therein.' It is taking all possible steps to speed-up output and is giving the earliest deliveries that present circumstances permit, taking all orders in strict rotation.

Tags

Organisations: compenSatMg
People: David Brown

comments powered by Disqus