The Locomotive Of Today

The Tender, Brakes, etc. : Condensing Arrangements. 175 age groove is also provided at the bottom of the cylinder, so that any water that should collect in the cylinder above the piston may escape by it through the drain hole and escape valve. This latter is fitted with a ball valve which closes when steam is applied, but when the brake is released and steam allowed to pass up through the operating cock, the pressure is removed and the ball falis back, allowing the water to escape. The operating cock on the firebox front has ports in it so that when the brake is to be applied steam enters the cylinder. For release the cock is given a partial turn, and the steam is shut off from the boiler, and that in the cylinder allowed to escape through the cock. It is thus impossible for the pressure to gradually accumulate in the cylinders and apply the brakes against the driver’s wishes. Under various conditions of service, locomotives of special types are employed, but in this book, so far, only ordinary classes have been dealt with. We may, however, briefly mention a few of the chief departures from the orthodox. In tunnels and on underground lines the emission ot steam from the chimney would be intolerable, therefore some means have to be adopted to obviate this. The engines on these services are usually of the tank variety, with the biast arrangements modified as underto suit the special requirements. A pair of hinged flap valves are fitted in a chamber or valve box at the base of the biast pipe, between it and the exhaust opening' from the cylinders, from this valve box two branch pipes lead on either side to the water tanks of the engine. The arrangement is such that when the flaps are moved outwards they close the outlet to the side pipes, and allow a free passage directly up the biast pipe and chimney when the engine is doing ordinary work in the open ; when running in tunnels, etc., the flap valves are, by means ot levers and rods from the cab, simultaneously moved inwards and brought together on their lower sides, meeting on the centre line and closing the exit up the biast pipe, but opening the passages for steam to pass to the two side branch pipes leading to the water tanks in which it is condensed. Fig. 37 gives several views of an engine fitted with such an arrangement. At A a lialf front elevation with smokebox door removed, shows the biast pipe, valve box and side branch pipes leading up through the outside conducting pipes to the water tanks. B, which is a side elevation, shows all the pipes by which the condensation of the steam is performed. The large conducting pipe above the tank is fitted with an expansion joint at the elbow, which is fixed to the top of the