Diseases of the air brake system; their causes, symptoms and cure . d forstraight air being made to do service by using the handlein the reverse This cock was simply a brassvalve with three connections, one from the main drum,one to the train-pipe, and one an exhaust to the atmos-phere. In one position of the handle, called the releaseposition, there was communication between the maindrum and the train-pipe, the exhaust being closed ; inanother position of the handle, called the , the exhaust from the train-pipe was open, thecommunication from the drum being shu
Diseases of the air brake system; their causes, symptoms and cure . d forstraight air being made to do service by using the handlein the reverse This cock was simply a brassvalve with three connections, one from the main drum,one to the train-pipe, and one an exhaust to the atmos-phere. In one position of the handle, called the releaseposition, there was communication between the maindrum and the train-pipe, the exhaust being closed ; inanother position of the handle, called the , the exhaust from the train-pipe was open, thecommunication from the drum being shut; while the thirdposition was midway between these two, and as it blankedall the ports, it was termed the lap. These three positions form the foundation for nearly allthe engineers valves since designed to operate automaticcompressed air-brakes. The main difficulty w^th the old three-way cock wasthat it had such a large port opening as to make too sud-den a reduction when a ser\ice stop was desired. Anothertrouble was, that unless closed with very great care the. Plate 9. Diseases of the Air Brahe System. 41 stoppage of the opening was very apt to release the headbrakes from the recoil of the train-pipe pressure. Besides this there was no provision in the originalthree-way cock for storing any excess pressure in themain drum, and this made it difficult at times toproperlyrelease the brakes. This old valve, being in the shape of a plug-cock, wasY^ry liable to leak after a short period of service, asgrit and dirt which got into the valves would cut groovesaround the bearing. If it was screwed together tootightly it was very hard to move, and if it was left looseit was constantly leaking. BRASS ENGIXEERS VALVE. The next valve to come into general use was a smallbrass valve with a rotary disk as the main operative had an excess pressure valve and a spring devicefor cushioning the valve, which cut off the exhaust of airin applications of the brakes. This valve had several
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Keywords: ., bookcentury1800, bookdecade1890, bookiddiseasesofai, bookyear1894
