Wm. Foster and Co., Limited.
Page 18
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Exhibit : —1907 Model Tractor.
Being amongst the oldest manufacturers of traction engines and road locomotives, one naturally looks to William Foster and Company, Limited, of Lincoln, to turn out a really welldesigned and businesslike steam tractor. This company was one of the first to design a tractor to come within the requirements of the new Act dealing with road locomotives, and the resultingmachine has been well received by users of steam as a motive power. The boiler is of the loco.-multitubular type with large heating surface and grate area, and it is constructed for a working pressure of 2 rolb, per square inch. The tubes are it inch in internal diameter, are made of iron, and are lap-welded. The barrel-plates are of the best Siemens-Martin mild steel, and the edges of these are all planed. Mud-holes are provided at all corners of the lire-box, and are fitted with suitable plugs and bolts. In the crown of the fire-box there is a brass plug with a fusible metal centre. All the usual lit
tings are supplied, including two sets of heavy asbestos-packed water gauges. An efficient, continuous-action, slowspeed, boiler feed-pump is worked by gearing from the crankshaft. One of the special features of the water system is the feed-water, controlling, and by pass valve; this we illustrate. The quantity of water delivered to the boiler is regulated minutely by a new and improved " controlling " valve, which can be set to deliver a constant quantity of water to the boiler, a quantity suitable for the nominal requirements of the engine. Should a larger quantity
of feed-water be required, the by-pess cock can be closed, when all the ater goes to the boiler, but, should the water rise above the normal water level, the by-pass cock can be opened and will then allow all the water to return to the tank. An injector is also provided, and both the pump and injector deliveries to the boiler are fatal with non-return valves with shut-off cocks enabling them to be examined
while the boiler is under steam. A feed-water heater is fitted to this tractor. The construction of this will be understood if a reference is made to
the illustration on this page. There are two concentric tubes, the annular space between the two being filled by the feed water, at the same pressure as that of the boiler. The inner tube is a length of " Row's," copper, indented tubing, which has a large surface area, and a part of the exhaust passes through this tube. Cold water is pumped into the end of the heater adjacent to the steam outlet and, flowing counter to the flow of the steam, gives the maximum efficiency. The curious shape of the inner tube causes an un. dulating motion of the water and assists in the deposit of scale in the heater, where it can easily be reached. The steam, after passing through the heater, is carried to a coil, or receiverbox, in the ash-pan. A small hole in the bottom of this box allows any condensation to drip on to the road whilst all steam rises up through the fire-bars, keeping them cool, and, generating water gas, assists combustion.
The engine is a compound one with a high-pressure cylinder zth inches in diameter and a low-pressure cylinder 62 inches in diameter of bore ; the piston stroke is g inches. The cylinders are,
as shown in our illustration, bolted to a saddle bracket which is securely riveted to the boiler plate. This saddle is truly planed and can be made a permanent fixing to the shell, thus obviating the necessity of passing bolts into to steam space. The piston is secured to a steel piston-rod, II inches in diameter, by a nut. Ordinary slide-valves are employed and are placed on the top of the cylinders in a very accessible position. Stevenson link-motion is used, and all parts are of the best wroughtiron and have ample wearing surfaces and, wherever necessary, are casehardened. The crankshaft is forged out of solid mild steel and is 2i inches in diameter with bearings 31 inches long; the four keys for driving the twospeed pinions are forged with the shaft and machined out of the solid. A disc fly-wheel, 2 feet 7 inches diameter by 31 inches wide, is used and this is turned on the face and edges.
The change-speed gear allows of two speeds of 3 and 6 miles an hour. The gears are of crucible cast-steel moulded from machine-cut patterns and are inches in pitch, and al inches in width of tooth. They are moved in and out of gear by two levers, arranged so as to allow only one pillion to be in gear at one time. The intermediate pinion is shrouded ; its pitch is 2 inches, ana
it is 2+ inches in width of face. It meshes with the spur ring on the rearaxle, differential-gear spider. The differential gear can be locked from the outside of one of the driving wheels. A screw brake, operating wood blocks acting on the inside of the rear wheel rims, is fitted. The steering gear is of the usual traction type. The address of Win. Foster and Comip.any, Limited, is Wellington Foundry, Lincoln.