WITH the name of Mr. S. J. Wright, M.A., Director,
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IV National Institute of Agricultural Engineering, behind it as the author, the paper entitled "The Versatility of the Modern Tractor," which was read at a recent London meeting of the Institution of Automobile Engineers held at the Royal Society of Arts, would, naturally, be expected to embody some important facts and figures relative to farming mechanization And the author does not disappoint us, although one may find cause for occasional criticism of a line of thought in a spate of agricultural wisdom.
As the average size of holding for the whole country is about 70 acres, Mr. Wright wisely limits the applicability of his subject matter to the small farm up to, say, 150 acres which, in pre-war days, would have been worked by not more than five horses, and upon being mechanized cannot economically employ more than one tractor of ordinary size. He backs his decision by a few figures. There are in England and Wales rather more than 300,000 agricultural holdings of over five acres; of these 85 per cent, occupy not more than 150 acres, rather less than I per cent, is over 500 acres, and only about 1 in 900 is over 1,000 acres in extent. As a further thought on this theme it is said " that until the. needs of the small farm are met, British agriculture cannot claim to be mechanized."
Despite the title of his paper, Mr. Wright does not blind himself to what, seemingly, are shortcomings of the tractor, and proceeds to state that although experience over the past 20 years has shoWn that the "average " tractor can effectively replace five or six work horses, the case is altogether different when, as on the small. farms, the Ultimate aim is to replace all the horses; the italics are the author's,' It is then, he says, that horses seem
to have virtues which no existing tractor possesses. Surely the words "seem to " could have been omitted if we concede that his subsequent remarks are 100 per cent. correct. He says, for example, that the tractive efficiency of horses is almost • completely independent of soil or weather. They can exert much the same pull whether the land be wet or dry, heavy or light, and; under all conditions, can contribute a substantial " overload " pull for a short time. They can also take transport loads straight from wet fields to public highways.
Let us admit that some of these assertions are substantially right, ignoring the factor of animal fatigue, but is the author arguing soundly when be says that "no one kind of tractor, whether steel-wheeled,. pneumatic-tyred or track-laying, can at present achieve a comparable performance "? Perhaps the use of "at present" does not completely obliteratethe possibility!
Work for the Small-farm Tractor Mr. Wright summarizes the general wok 'of the all-purpose small-farm tractor under four main headings, as follow:—
(1) Ploughing and heavy cultivations which call, in general, for a high drawbar pull all relatively slow speed, and which are carried out mainly at the wetter seasons of the year when good adhesion is a major technical requirement.
(2) Lighter ordinary cultivations, such. as harrowing, rolling, drilling, etc., which can, within limits, he carried out by any tractor, but in which it is often difficult to provide anything but the smallest tractor with a full load.
(3) Special inter-row cultivations of potatoei, root crops and vegetables which call for accurate work with tractor and implement exactly fitting a particular crop pattern. These are mainly light jobs to be done at relatively low speeds:, (4) Haymaking, harvesting and transport work in' which, for one reason or another, high speeds may be advantageous.
It is under the first and last of these headings that, generally speaking, the author thinks the tractor offers the farmer the most definite advantages in comparison with horses. In the case of ploughing, the benefit is that of
greater power, because the tractor enables one man to control power equivalent to that of an unmanageably large horsed team and affords a big saving on what would otherwise be the high labour costs of such operations. On this work the saving of time, as such, he regards as of secondary importance. In the fourth class, however, most of the advantages come from the fact that the tractor saves time in comparison with horses.
The author then discusses the intermediate classes of work—minor and inter-row cultivations—when the advantage will sometimes be with the tractor and sometimes with horses. He directs attention to the complicated wheel attachments which plague the owner of a row-crop tractor.
Mr. Wright emphasizes that small-farm economy will demand that, once bought, the tractor shall be used as extensively as possible, and in the long run tractor design must develop on these lines, that is, towards ever greater versatility. He qualifies this view by saying that in striving too much after. versatility, designers have sometimes, lost sight of the tractor's main functions and more important advantages, and 'illustrates this point in connection with wheel equipment.
Influence of Pnetimatic-tyre Equipment He recalls, for instance, that the pneumatic-tyred tractor wheel was first introduced in America rather more than 10 years ago, and soon became available here as an alterna
tive to the steel wheel. As might • be expected, -the advantage of pneumatics in a country where the farms, are nearly always intersected by at least 'one public road was quickly realized, and at the outbreak of war about:.one wheel_tractor out of 'every three sold in Great Britain was
pneumatic-tyred. In America, however, something like 95 per cent. of wheel tractors sold in I939—there were over 250,000 of them—were pneumatic-tyred.
Pneumatics swept the board because they made the
tractor more 'versatile, and for the-moment at any rate every other aspect of performance was forgotten. However, because tractors of normal weight on pneumatic' tyres simply could not transmit high enough drawbar pulls, under normal agricultural conditions, axle weights had to be increlsed. Under test conditions the weight of a pneumatic-tyred tractor had sometimes to be nearly doubled, by the addition of water ballast' and cast iron, before the full drawbar power could be developed, and even then performance in the lowest gears was not always satisfactory.
We are pleased to note that the author stresses, the
point that in discussing this question he does not intend to decry the merits of pneuraatit tyres. He has sought to illustrate how over-insistence on the virtues of versatility may result in the tractor becoming lees effective in its more essential functions.
In sketching the general outline of the small-farm trac tor, Mr. Wright thinks that consideration should first be given to the power or " capacity " that will be needed, and then proceeds to discuss the question of type. He will find all-round support for his, contention that the machine for a one-tractor farm cannot be a track-layer. This type is too expensive and, as a rule, unsuitable for high-speed transport work, because of the liability to track wear. Moreover, track-layers are not easily adaptable to varying raw widths. The author acknowledges, however, that their tractive efficiency cannot be equalled by any wheel machine.
He does not argue the relative merits of steel and pneu matic-tyred wheels, because he thinks that the small larm will need both, the former for general and heavy work and the latter for use when high speeds have a real advantage. On the question of three versus four wheels, he does hot takesides and points to minor advantages possessed by both arrangements.
The remainder of the paper is taken up by an examination of a few modern wheel tractors, with comments that arise in comparing them iti relation to the general picture. 'Six tractors are selected—an equal 'number of British and American origin.