The boiler of a flash steam plant is extremely simple. Such a boiler is shown in [Fig. 133]. It consists merely of a coil of copper or Shelby steel tubing with an internal diameter of 1/4 inch. The boiler coils should be wound around a circular form of wood about 23/4 inches in diameter. In the case of copper it will not be found very difficult to do this, providing the copper is heated before being wound on the wooden form. If the copper is heated it is advisable to wind the wood with a layer of sheet asbestos before the copper tube is wound on. It is almost necessary to do this winding with a lathe, but if the mechanic does not have access to such a tool he may have to find other means of doing it, or possibly he can take it to a local machine shop and have the work done for a few cents. The boiler coil should be wound about 9 inches long.
A casing of Russian sheet iron is made to slip over the boiler, leaving sufficient space between. Ventilating holes or slots are cut in the cover to permit of a free circulation of air. The boiler covering is also provided with a funnel through which the exhaust gases from the blow-lamp pass.
The blow-lamp used operates on the same principle as the ordinary blow-torch. The details of such a lamp are given in [Fig. 134], and a finished torch is shown in [Fig. 135]. Instead of making the valves necessary for the blow-torch, it is advisable to purchase them, for they are very difficult to make accurately. The valve at the back of the torch regulates the gasolene supply that passes through the nipple. The hole in the nipple should be about twenty thousandths of an inch. Owing to the fact that the copper coil wound about the burner is short, the tube can be filled with molten resin before it is bent. In this way the tube will not kink or lose its shape while being wound. After it is wound it is placed in the fire and the molten resin forced out with a bicycle-pump. Such a blow-torch produces a tremendous heat and throws a hot flame far up into the boiler coils.