H. D Waterhouse
Flash boilers are of very small size for the power which they are capable of generating. Their value is due to the very high working pressure, and the instantaneous generation of steam, and light weight. Boilers of this type are capable of such power only because the entire energy of the fire is used on the volume of stoam required at the particular moment of intake of the engine. They do not keep a mass of water under steam for the sake of what the engine may require at any particular moment.
They are, however, unable to respond to sudden abnormal demands for power, because they have no considerable amount of super-heated water ready to burst into steam at once. That is to say, they do not contain any amount of stored power, as in the ease of the ordinary tubular boiler. For this reason the fire must be very closely regulated according to the amount of power needed.
In the construction of the boiler here described the materials necessary are: - 20ft. of seamless drawn copper pipe, Jin. iron pipe size, and walls l-16in. thick; also six brass couplings, 1-8 in. iron pipe size. These are sizes in name only, the pipe being actually a little over 1/4 in. internal diameter.
A force pump of small diameter is also needed; if one is not at hand it may easily be made. First make a piece of wood .F of the shape and one third larger than the drawing. Nail this in the middle of a piece of board. Take one end of the copper pipe and lay it against the straight side and drive a nail in to hold it at G. About 2 1/2 in. of pipe should be left for connections from the point H. Make a mould of wood for casting a strip of lead 1/4 in. wide, 1/2 in. high, and about 5 ft. long, with a little taper at one end. Next make one turn of the pipe around F, then place the tapered end of the lead strip between what would be the two inner sides of the first and second turns of pipe, and wind on the pipe and lead strip, keeping the lead strip placed with smallest diameter always between the turns of pipe. Make three concentric turns of the pipe and bring the ends together at the same side of the coil as in the elevation drawing.
Thread the ends and bend to the proper angle. The beginning of each coil J, and the ending K, should be threaded respectively with a right and left hand thread, fitting couplings. Make five coils in this way, and join tight with couplings. The boiler is then complete except for threading, at the delivery end, a steam gauge. safety valve and throttle. The intake end of the boiler is connected to the delivery of the force pump. The coils are then mounted in a shell or casing made of heavy sheet iron in two layers with a thick layer of asbestos between. The burner, which should be for gas, gasolene or kerosene is to be mounted under the coils. The pump is made as in drawing, No. 2; i. e., just an ordinaryforce pump with 1/2 in. piston, drivan by an eccentric on the engine shaft.
It differs, however, by having a spring between it and its eccentric of slightly less force than that in the safety valve. In this way only enough water is let in to make steam enough to pop the valve and no more, as when the steam is at that point, the spring C in the pump compresses, the collar B slides over the piston, and no water is forced ahead. The eccentric L is illustrated in the drawing, and has a 1/2 in. throw. It is located on the main shaft of the engine. The boiler may be heated in any way so long as there is heat enough. A good burner may be made by making coil of iron pipe like the boiler coil. This is for vaporizing the kerosene which is to be used for fuel. Underneath this is a coil of iron pipe single turn, in which very small holes have been drilled on the upper side about an inch apart.
To operate the boiler, pour a little kerosene in the base of the burner and let it burn out, this will heat the vaporizing coil. Now slowly turn on the kerosene which is under a pressure of about 15 lbs. and as it spurts up light it. When the lower tubes of the boiler get red hot, which will be in a very short time, give a few strokes of the pump slowly and steam will be raised to 300 or 400 lbs. pressure instantly. Then turn the engine over a few times by hand and open the throttle. The engine will then start. When engine is stopped the burner should be turned low.