Steam Tractors and Road Trains.
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It. is found, in some trades and subdivisions of haulage contracting, that the power unit must be divorced from the load-carrier, It is analogous to the steam tug, for river ami estuary work, in competition with the steam barge, and not a few readers of these pages will know that the steam barge is out of favour in shipping circles. The heavier types of road engine weigh far too much to allow of their employment, in all parts of old and developed countries, owing to their damaging effects upon both roads aud bridges, and any loss due to this inherent fault is accentuated in new countries. Military limitations have much in cummon with the factors that control traffic upon the inferior roadways of numerous Colonies and Protectorates, and evidence of the correctness of this view is contained in the Blue Book of the British Colonial Office, in respect of mechanical road transport, which we had occasion to review a few months ago. The lower axle-weights of the tractor and its one or two wagons go far to give it a claim, in certain cases, which cannot be rivalled by the self-contained wagon. The former does not exceed four tons, as a rule, on ally axle, whereas the latter reaches double that weight. Again, the wheel-diameters are much larger in the ease of the tractor, say, 5 ft. compared with 3 ft. for a wagon. This increased diameter, of course, greatly facilitates the crossing of soft or yielding grmmd. Water and fuel considerations, with a steam tractor, are much the same as for a steam wagon, and the locomotivetype boilers are usually a little more economical in feel. Roughly, for the same useful load, a tractor will consume slightly less of both, whilst the freedom of access to the tubes and the water-legs is at least as good. With careful driving, the standard tanks of a modern tractor are large enough, without condensing, for a run of 20 miles, and the machine can have extra. tanks added to extend this range. They can he handled, readily, by a single man, and their one drawback, so far as manwowing, goes, is the inability to back the trailers which they customarily The normal weekly mileage for a tractor is not so high, on paved roads. as for a motor wagon. On macadamised or other " metalled and bound " roads, however, they have fully as good a range of action, and they can do more in a day when travelling is over "dirt" roads. The working value of a tractor, in England, is often taken at 3s. per hour, in exchange for which expenditure the owner is able to move five or six tons of useful load a distance of five or six miles. As, however, it is not safe to reckon that one can at all times obtain loads without losing some time, this figure ought., to be increased by at least 25 per cent. before rates per ton are considered. We are prepared to admit that the tractor is cheaper and more economical than the steam wagon where the special conditions suit it, and most of all on macadam roads with moderate gradients, but it must be conceded that town conditions run up the cost of labour and repair.;, owing to the greater vibration upon paved surfaces. Several makers, and at least 20 important users in England, have made extended trials with wooden treads of different types, and a measure of successful application has resulted. The first cost of such wooden treads need not exceed £6 or £7 per driving wheel, but their durability in service is entirely dependent upon weather conditions aunt the nature of the surface covered : we have known treads which behaved satisfactorily in dry weather to last only 300 miles in wet weather. Depot-to-depot haulage, where the tractor can pick up a trailer which has previously been drawn by a horse through the weary round of collection, is regarded by many as an ideal method of working. Contrariwise, when the tractor brings in a trailer to such a depot, the delivery round is completed by animal draught. Such a system, when elaborated, has undoubted advantages, not the least of which is the ability to provide for the mechanical plant to work at the maximum, and also to allow a few hours of latitude when the road conditions are troublesome. The standard machines, of which we illustrate a number, are reckoned, in England, to be able to haul a gross weight of eight tons up one in ten. Amongst the notable makers, who have brought themselves into line with modern needs. are : Aveling and Porter ; Burrell ; Foster ; Fowler ; Ransomes and Tasker. The Foster system, in particular, has constructional features which call for special mention, and we regard that maker's new outside-spring suspension as of the utmost value for Colonial work. The Wellington Foundry, at Lincoln, where this tractor is made, has the advantage, in common with other old-established factories, of an intimate knowledge of export requirements, by reason of its big sales to South America in particular, and it also enjoys a large turnover, both with owners and other makers, in respect of wheels and trailers. Another maker, Brown and May, Ltd., of Devizes, whose principals were showing some Al testimonials at the Smithfield Show, deserves mention.
We give, herewith, a graphic and typical illustration of a modern tractor, and the non-technical reader will be able to comprehend its distinctive points. A compromise between tractor and wagon, we may add, in which the necessary adhesion is derived from a twoton load or that weight of ballast, is sold by the Mann Co., of Leeds.
A tractor system which is of unique merit, is known as the Renard. In this, the power unit is essentially of the tractor class, yet it does not haul the following trailers. A portion of the power is communicated, by means of an articulated longitudinal driving shaft and suitable connections, to a pair of driving wheels on each truck or passenger coach. Thus, instead of being hauled, the train propels itself, whilst the wear and tear on the roadway, by reason of the lessened intensities of tractive effort and imposed load, is reduced very much. This distribution of the power is of far-reaching importance from every stand-point, and the Daimler Motor Co., Ltd., of Coventry, which is specializing in the manufacture of these trains, has done much to render their successful operation assured. The universal joints on the propeller shaft have been perfected, the steering connections have been lightened and simplified, and the cost of production has been brought down. Hence, for work which presents the necessary loads, say, not less than 12 tons, or two passenger-coaches, these Renard trains deserve to be given first consideration by any persons or authorities. Trains of this type are already in use in India, Australia, :Jamaica, Burma, Canary Islands, Manchuria and Turkey, and amongst the Governments who have voted sums to experiment in this direction are those of Tasmania, Queensland, Natal, Russia and Ceylon_ Steam trains on the Renard system are working in Argentina and California.
The working cost of a Renard train, with power unit and three " followers," is found to be between 2s. and 2s. 6d_ As it can take 15 tons of net load, this approximates 2d. per ton-mile, and furnishes a figure which cannot be excelled for the peculiar fields of application in which this system is unrivalled. We refer to countries where roads are not strong enough to carry either a traction engine or a steam wagon. For passenger conveyance, in such circumstances, it appears to provide the solution to a problem of world-wide concern. The improvement and development of internal communication is second in importance to production only.