Fig. 1.—General Arrangement of a Gas Engine and Accessories.
Further reference will be made to this in another chapter, and, although this is not a necessity on a small engine, it is always employed on engines over 2 B.H.P. In fig. 1, HW is the cooling water outlet and CW the inlet. A small drain cock is shown at DC, through which the water in the cylinder water-jacket may be drawn off when required. The pipes leading to the inlet and outlet of this supply are connected to the cooling water tank by means of a couple of broad, flat nuts and lead washers, one inside and the other outside the tank, the latter, when clamped up well, making a perfectly water-tight joint. The outlet pipe making an acute angle with the side of tank, the washers used there should be wedge-shape in section. It is also desirable to fit a stop-cock SC, so that the pipes can be disconnected from the engine entirely, or the water-jacket emptied without running the whole of the water out of the tank. The exhaust pipe EP is made up of gas-barrel. It should lead from the engine to the silencer or exhaust box (if one is found to be necessary) as directly as possible, i.e., with no more bends than are needed, and what there are should not be acute. The silencer can be inside or outside the engine-room, whichever is most convenient; but both it and the exhaust piping should be kept from all direct contact with wood-work, and at the same time in a readily accessible position.
Beyond the exhaust-pipe and box and the water-tank, the gas bag GB and gas meter (where small powers are concerned, the ordinary house or workshop lighting meter may be used without inconvenience) are the only other accessories which are included in a small installation.
Fig. 2.—A Section of a Gas Engine.