Art. 11. THE DEVELOPMENT OF THE AGRICULTURAL MOTOR.

THE influence of the war upon the development of the agricultural motor has been somewhat complex, inasmuch as its effects have in a sense been beneficial, and in another sense detrimental. Without fully endorsing the general opinion that farmers are extremely conservative, it is at least safe to contend that as a class they are not much inclined to indulge in expensive experiments of a speculative character. They are more impressed by the actual experiences of other farmers of their acquaintance than by the theoretical advantages of any new invention, even if these advantages are demonstrated in a practical manner. They are, moreover, inclined to be very critical, and perhaps to lay undue stress upon the comparatively weak points of some fresh idea, and not enough upon the compensating advantages.

It would be futile to deny that, in his endeavours to convince the farmer, the motor engineer has in past years not been able to put forward a very strong case. The application of motor power to agriculture has proved extremely difficult. The conditions under which a farm tractor has to work are incomparably more severe than those which accompany the use of an ordinary motorcar, or even of a heavy commercial vehicle. While a tractor is ploughing or doing other heavy work upon the land, it is obliged to develope its full power for long consecutive periods, whereas the engine of a motor-car is only extended to the full occasionally, and there are long intervals during which its work is comparatively light. Another essential difference between the two classes of machine is to be found in the fact that the farm motor has to develope its power at very low speed. A large amount of work can be got out of a light machine, provided the speed at which it operates is high enough; but, when the speed is low, very substantial construction becomes necessary, since the stresses experienced by the parts which transmit the power are in inverse proportion to the rate of motion. It follows that parts constructed for use in motor vehicles, and quite strong enough for their work, are not necessarily adequate when embodied

in an agricultural tractor. Unfortunately, many designers have been slow to recognise this primary fact, and numerous failures have resulted from the neglect of it. Attempts have been made to employ ordinary motorcars, only slightly modified, for the haulage of farm implements upon the land; and the consequences have been disastrous to the prestige of motor transport in this application. In other instances, lack of success has been traceable to a want of appreciation of the fact that a farm motor is handled, as a rule, by men of no great engineering knowledge or mechanical aptitude. Not infrequently, it suffers from neglect, not only in respect of proper repair and maintenance, but even as regards the ordinary precaution of cleaning and lubricating the moving parts.

The conditions under which farming is carried on in Great Britain differ widely from those prevalent, for example, in the greater part of the United States or in the West of Canada. There, the problem is generally to cultivate enormous areas of open lands; and it is often deemed sufficient to plough to a depth which, in the opinion of the British farmer, would amount merely to a scratching of the soil. Where land is cheap and limitless in extent, there is not the same need to study the art of obtaining the maximum production from a given acreage. Where the country is open and merely undulating, with a soil homogeneous over large areas, it is possible to employ a comparatively cumbrous engine which would be almost, if not quite, useless in confined fields often involving heavy gradients and frequent changes in the consistency and nature of the soil. For these reasons, the British farmer has quite rightly refused to consider the whole-hearted adoption of agricultural motors built primarily to work under American or Colonial conditions. His attitude in this matter has been rendered all the firmer by the fact that, even in districts where all the circumstances favour the big farm tractor, expensive failures have been extremely numerous.

In Great Britain, the manufacture of agricultural motors has not been carried on upon a large scale. The demand has been small and uncertain, and very difficult to nurse into a healthy development. The more substantial engineering firms have in general preferred to

expand along lines of less resistance, and in some cases, after tentative experiments, have come to the conclusion that the farm motor is a dangerous affair which, in the interests of shareholders, had better be left alone. Meanwhile, pioneers have laboured under many disadvantages, the principal of which has been the lack of funds to support them through an unexpectedly prolonged period of experiment and qualified success. At the time of the outbreak of war, the British industry had not attained considerable proportions, but there had been developed, year by year, machines which had become thoroughly practical and well suited in principle to the average British farmer's requirements. The quality of the workmanship and material put into them was not always above reproach. The supply could only improve materially if the demand were correspondingly enlarged ; and this seemed likely to happen only very gradually, because, as already indicated, the supply did not represent anything approaching the farmer's ideal. Meanwhile, labour and horses remained available in adequate quantities and at reasonable prices.

The Royal Agricultural Society of England had apparently approached the subject with some reluctance. The only set of competitive trials that had been organised and carried through by that body had produced very little valuable information, and had suffered from a number of restrictive regulations, which had prevented the entries from being representative. In these trials, steam tractors weighing about five tons had shown up much better than the lighter motor tractors using petrol or paraffin. Apparent results had been too much dependent upon fuel costs, which, though important, are not really the main consideration. Such difficulties as those connected with bringing up supplies of water and fuel to steam tractors at work upon the land had not been taken into account. Undoubtedly, the steam tractor is a very valuable implement for direct ploughing under some conditions, but it is certain that sooner or later the internal combustion engine will predominate.

In France, more energy had been shown in the matter of organising trials and demonstrations; and some valuable statistics had been collected. The real test of an agricultural motor is not the intrinsic beauty of the furrow

turned by it, but the yield of the land which it has cultivated. Nothing really conclusive is likely to follow from trials, unless these are taken in hand by centres of agricultural research. At such centres, samples of various types of farm motors ought to be collected, and each type employed for the whole of the cultivating processes required on certain stretches of land, which should be as nearly as possible identical in position and composition. The crops ultimately obtained from these stretches should be carefully measured and analysed, and compared with those yielded by similar stretches cultivated entirely by means of horse-drawn implements. In any one centre such trials would serve to establish with fair accuracy the relative advantages of motor and horse-drawn implements on land of the same quality. If contemporary tests of a similar nature were also made at other centres, the aggregate result would be the collection of data of the highest possible value. The cost of the whole of this procedure would amount only to a few thousand pounds; and the results, in their possible influence upon the problem of bringing more land under the plough and encouraging intensive culture, would almost certainly be of inestimable value. In certain instances, the makers of agricultural motors have set seriously to work to enlarge their experience by cultivating farms of their own with power-driven machinery, and keeping exact accounts over a period of years. plan should, in any given case, lead to the rapid improvement of the type of motor manufactured. It does not, however, provide results available as a basis for comparison of the various types upon the market.

This

Wherever agricultural motor trials are held, one hears many and diverse opinions expressed as to the effects of the machines upon the land. It is quite conceivable that one motor may turn very clean, straight furrows, while another may do what appears to be slip-shod work, and yet that the second may produce a better yield than the first. Such a result might be influenced, for example, by the difference of pressure upon the ground of the driving wheels of the two machines. Then again, some machines run with both driving wheels upon the unploughed land; in others, the wheel supporting the bulk of the weight runs in the

furrow. Assuming that compression of the soil is in any case detrimental, it still remains an open question whether it is worse to compress the surface before turning it, or to compress the bottom of the furrow, afterwards turning the unpacked land on to the top of what quite conceivably might tend to forma sort of subterranean watercourse. The French have developed a number of motor implements, which aim at the abandonment of ploughing proper in favour of cultivation by a large number of rotary digging implements, which break up the soil into fairly uniform and small pieces. From the mechanical standpoint, this scheme has the disadvantage of introducing comparatively delicate cutting implements, which must certainly be more liable to fracture than the ordinary plough, if stones or heavy roots are encountered. On the other hand, it has the great advantage of making the implements themselves do their share in the propulsion of the machine, which they drive forward while kicking up the earth backward. They thus solve the troublesome problem of securing adequate adhesion on greasy and hilly land, and this without introducing weight so considerable as to make serious packing of the soil inevitable.

The pioneer work of the French has, in fact, been of very wide scope. In addition to these motor cultivators, our Allies have developed independent motor tractors and also self-contained motor ploughs, in some cases having the cutting implements so arranged that the machine itself does not have to turn on the headland after completing each furrow. Another method tried with some success in France is to employ a tractor, with a wire rope gear connecting it to the plough or other implement. The tractor itself runs forward light until the whole of the wire rope is unwound. It is then anchored by means of some sort of sprag, and the wire rope is wound in by the power of the tractor's engine, dragging the plough forward with it. In a small field, a complete set of furrows can be turned in one reach. In larger areas, the operation of unwinding and drawing in the wire rope may have to be repeated several times in turning a single set of furrows. The basic idea is that power and weight, which would not be adequate to propel the tractor and draw the plough simultaneously,