Foster' s New Hornsby-engined Agrimotor.
Page 4
Page 5
Page 6
If you've noticed an error in this article please click here to report it so we can fix it.
The First-published Account of a New Overseas Type of Internal-combustionengined Tractor which has been Constructed by William Foster and Co., Ltd.
Few weeks go by nowadays during which the attention of THE COMMERCIAL MOTOR is not requested for some new development in which the internal-combustion engine plays a prominent part. There are few spheres in which the horse has been left in uninterrupted possession in regard to draught work. An internal-combustion engine, as we recorded in a recent issue, is now actually challenging the plough horse—surely one of the most difficult cases in which to effect economy of operation. But the mechanically-propelled cultivator and plough, both of large and small type, are rapidly securing approval at the hands of farmers and agriculturists at home and abroad. In the nature of things, progress has, so far, been more rapid in the latter case, especially in territories where there are vast areas under cultivation, and where the employment of machinery of any feasible type obviously is bound to effect economies of a startling nature, England has for many years led the world in the construction of the larger classes of steam road-haulage plant. The steam traction engine built in English shops is found in all parts of the world, and there appears to be no immediate likelihood of home producers being ousted from this special field of activity. Cable-ploughing plant, of which similar classes of prime movers are the principal units, is largely employed in many other countries than that of their own origin.
It is, therefore, fitting that the English manufacturer of steam plant should be taking a prominent part in regard to the development of mechanical haulage by internalcombustion engine for ploughing and cultivating tackle. We find, indeed, that several of the foremost makers of steam traction engines and similar machines have already produced practical petrol-driven or paraffin-driven tractors for directhaulage work, or for cable operation in the fields.
We now have to record the results of yet another old-established English manufacturer's developments in this direction. William Foster and Co., Ltd., of Lincoln, which concern has figured prominently, during the last few years, in regard to the progressive design and construction of its small steam tractor, has recently turned its attention to the nroduc
tion of an internal-combustionengined tractor which shall be suitable for ploughing and similar operations overseas. At the invitation of Mr. W. A.
Tritton, the managing director of the company, we lastweek journeyed to Lincoln to witness some field trials with the first of the new models, which, by the way, is to be hurried out to South America as quickly as the tests can be finished, as the demand for this class of plant is so rapidly growing, especially in that particular quarter of the world.
The new Foster tractor is a huge machine weighing something under 14 tons, and as its prime mover it has built into it a fine two-cylinder, horizontal petrol engine constructed for Foster's by Richard Hornsby
and Sons, Ltd. This engine in no way conveys the impression that it is an adaptation for the purpose. Our photographs bear excellent evi
dence of the very substantial class of design which B.ornsby's have embodied in this engine.
The two side-by-side cylinders have a bore of A in., and the stroke of the engine is 17 in. ; at 270 revs. it gives 55 b.h.p. The heavy castiron crankcase, with large inspection doors at the front end, encloses a massive crankshaft, on one end of which is carried 'the flywheel of 62 in. in diameter, whilst the other end accommodates a special form of internal-expanding parallel clutch and epicyclic reverse gear. The power is transmitted from this end of the shaft by way of a spur-gear train, through a layshaft carried right across the frame under the engine, to a large spur wheel, which surrounds the differential gear that is embodied in the finaldrive shafts. These last two shafts have on their outer ends, respectively, two small spur pinions, which engage with the huge internally-toothed rack S which are bolted by brackets to the outer rims of the 8 ft. driving wheels.
We trust it will be realized from this description that the whole of the mechanism of the new Foster agritnotor is of the simplest possible kind. There are no bevel gears in the whole of the transmission, so that the high efficiency of the drive is almost a foregone conclusion.
The new machine is constructed on these simple lines, and is en tirely devoid of more or less unnecessary refinements. The Foster and the Hornsby concerns have between them embodied
a remarkable method of starting this huge engine. We witnessed most satisfactory demonstrations of a system of which the principal characteristics are its utmost simplicity and its apparent entire reliability. We are not at liberty, at the present time, however, to describe the ingenious method which is adopted. We are, as is usual in such cases, astonished that it has not occurred to others before.
The cylinders have substantial but simple combustion-chamber castings, and these each accommodate an air valve in the top, a, gas valve at the back end, and an exhaust valve underneath. The whole of these valves are actuated by rocking arms, which take their motion from a side-driven camshaft. This shaft, which, of course, is in the position that is commonly adopted by gas-engine designers, is driven by skew gear from the near side of the crankshaft, in close proximity to the flywheel, which we have already mentioned.
Room is also found on this shaft for the eccentrics which operate the rocking type of Bosch magnetos, and at its extreme back end for the small spur gear driving an inertia type of governor. This latter fitting controls the supply of gas to the cylinders. An interesting part of this arrangement, however, is the fact that the gas valve alone is cut out when the governor comes into operation, so that all idle strokes of either piston draw in fresh, cool air, and thus effect very thorough scavenging, a feature which will make a distinct appeal to all those who know the excellent advantages it entails, especially in respect of these large-bore, slow-running engines for continuous running.
One of the ordinary sizes of the Longuemare carburetter is fitted to this first machine, but there is, of course, no reason why any other well-tried similar type of vaporizer should not be used. The exhaust pipes are laid under the engine, and then up into a silencer, which is situated just behind the big cooler in front pf the tractor. The cooling water is circulated through large pipes by means of a centrifugal pump, which is belt driven from the crankshaft and is situated immediately below the after end of the engine.
The cooler is an interesting type ; it has about 1000 sq. ft. of effective
area, and in bulk is about 3 ft. Gin. square in side elevation. It consists of a large number of sheet-metal plates melded at their edges and forming a number of pockets, in parallel, through which the water circulates on its way from and to the engine. These sheet-metal units are separated by vertical strips of wood, which serve to prevent the flat metal areas from bulging, and also, at the same time, to induce the vertical currents of air which are drawn up through the chimney stack on account of the turning of the exhaust blast upwards therein,
The frame is of massive channel steel, and is, of course, of exceptional strength, on account of the heavy draught work which it has to sustain. The back of the tractor has a stiffly-constructed draught frame, to which drawbars or chains may be attached and suitably adjusted. The front axle is of unusual design for this class of work, it consists of a stiff steel plate bent over into an inverted U section ; the front wheels are 54 in, diameter. A compact design of swivel bearing carries the front of the agrimotor on this component, and it is steadied by a stiff steel perch bar, of which the after end is anchored to the steering-gear cross-framing, carried amidships.
Steering is, of course, by chain in the usual way, and check chains are provided to the outer ends of the front axle. The back axle is built right across the main frame in heavy housings, the wheels being mounted free on the outer journals in the usual manner. Light steel guards are arranged to protect the internally-toothed final drive as far as possible.
No brakes are found to be necessary for agrimotor work, as a, rule, but the epicyclic and dutch reverse gear can be employed to check the machine if necessary. The whole of the control is conveniently arranged round the foot plate, and this, of course, includes the necessary levers and handles for engine and ignition adjustment, for the reverse and clutch operation, and for the steering gear. A large circular tank is located on the near side behind the driver, and an interesting feature of this is, that it has been found possible to dispense with all petrol joints other than the exhaust outlet pipe to the engine. The method of filling the tank is by a semi-rotary Wilcox pump through a, pipe running into the top plate of this tank.