The Field motorcycle was produced by Mr Alfred Wallington Field from 1908 to 1914 at Clacton-on-Sea, 80 miles NE of London.
The machine was steam-powered and had a single-acting two-cylinder engine. It would never be a popular choice as it took a long time to fire up the boiler.
Two are known to exist, both in the Netherlands, built in 1908 and 1914.
A Twin-cylinder Machine, the Result of Six Years' Experimental Work.
FLEXIBILITY is a point which is aimed at by all motor cycle designers, and is a much more difficult problem to deal with when internal combustion engines are the power units employed. By adopting a steam engine it is possible to utilise a better system from whence flexibility can be obtained. There are, of course, many difficulties which arise when such a source of power is applied to the motor cycle, as trouble is experienced in cutting down the overall dimensions and weight to really practical limits. At the same time, Mr. Field, of 101, Rosemary Road Clacton-on-Sea, has succeeded after six years' experimental work in building a steam motor cycle of a thoroughly practical nature.
His experience has led him to adopt a two-cylinder single-acting variable expansion high pressure engine. The bore and stroke are 45 mm. x 50 mm., and the cylinders are fitted with mushroom valves of special steel. The pistons are practically the same as those generally used in petrol motors, and are fitted with three rings The crankshaft is so designed that the crank pins are opposed - that is, at 180 ° - and the big end bearings of the connecting rods are split and are also similar to the usual type which are used in petrol engines. There are only two timing wheels in all, one being on the camshaft and the other on the crankshaft. The valves themselves are placed on one side, and are operated by ordinary tappets. It is possible to vary the lift of the valves by moving the cams, and if necessary the whole of the movement imparted to the valves can be eliminated. The action corresponds to the valve system employed on the motor cycle engine.
A steam generator of the instantaneous flash type is fitted, and is supplied with a feed water heater, the whole concern being housed in an asbestos-lined steel case which also contains the burner. This, it will be noticed on referring to the illustration, is placed in front of the engine.
Absence of Controls.
There are no hand pumps other than the ordinary pump used for lubrication, which is identical with that on a petrol-engined machine. The fuel supply is entirely automatic, and is carried out in the following way. There are two fuel tanks, one of which contains a small amount of fuel at a pressure of from about thirty-five to forty pounds to the square inch.
By means of this the fuel is conducted to the burners, and as it becomes used up means are provided by which a similar amount is supplied automatically. By such a system it is possible to fill up the main fuel tank whilst the engine is running. The water pump is housed behind the engine and takes up very little room.
It is possible with such an engine to utilise a very high gear, consequently the gear ratio is in the neighbourhood of 2 1/3 to 1. Even with a ratio such as is employed the machine can be started on the stiffest of gradients. Chain transmission is fitted from the engine to the countershaft, which is utilised for driving the pump mechanism as well as for conveying power to the rear wheel by means of a chain. The design of the machine generally is well carried out, and the designer has made a special point of getting the centre of gravity as low as practicable.
Power and Simplicity.
The engine is capable of developing from 6 to 8 h.p. owing to the high pressure of steam that can be used. It will, therefore, be seen that a motor cycle on these lines should be excellent for sidecar purposes. The total weight is 160 lb., and this, of course, compares favourably with petrol machines of similar horse-power. The machine is started up in the following way: a small quantity of methylated spirit is poured into the burner channel, and allowed, to burn for three or four minutes. When sufficient heat has been imparted to the burners the water and fuel regulators are opened, and by walking the machine for three yards starting can be effected. The control is on the burner and generator, and if an instantaneous stop is necessary the cutting off lever on the side of the tank puts out of action a cam and so stops the valves from opening.
The Motor Cycle, September 24th, 1914. p376
Graces Guide, The Motor Cycle
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