Page:Collier's New Encyclopedia v. 03.djvu/128

LEFT COMPRESSED AIB 94 tubes, railway-brakes, etc. The use of compressed air by railroads began with the introduction of the Westinghouse air brake on passenger trains, about 1869. See Air Brake. A few years later the Denver, and Rio Grande, the Union Pacific, and the Cen- tral Pacific railroads began equipping freight cars with the air brake. For some time sleeping cars have used com- pressed air to force water from a tank under the car to the wash bowls in the toilet rooms. The train signal is op- erated by compressed air; pulling the bell cord in any of the cars blows a small whistle in the locomotive cab. Au- tomatic bell ringers on the locomotives are run by compressed air. It has also been applied to shake the grates in the fire-box of a locomotive, and to open and close the furnace door. For some years railroad crossing gates have been raised and lowered by it, the air being supplied by a hand pump op- erated by the crossing watchman. In 1891 its first application to car work was in cleaning the dust from the window sashes and blinds in coaches, and such parts of the inside that a duster could not reach. A round nozzle with a small opening was first used. This led to the use of a flat nozzle about two inches wide for cleaning cushions, seat backs, carpets, blankets and bedding. The sleeping car companies recognized its superiority for cleaning cars, and are using it very extensively. As its value in shops began to be appreciated, and the demand made by increased use ex- ceeded that which air pumps could sup- ply without an extravagant waste of fuel, air compressors were added to give an increased supply of air. This opened a new field for the use of compressed air.^ Pneumatic hoists began to replace chain hoists at all the heavy machines in the shops, driving wheel lathes were equipped to handle drivers in and out of the lathe, cranes were located in the yards for loading and unloading ma- terial, and in each instance a large sav- ing of labor and time was effected. The introduction of compressed air in shop practice has brought out by the shops themselves and by tool manufac- turers a number of very useful and val- uable tools — pneumatic drills, hammers, riveters, punches, and machines especi- ally designed for boiler work. The pneumatic drill performs a very im- portant part in the construction of new or the repair of old boilers. It has dis- placed the flexible shaft, and is now con- sidered an indispensable tool for fasten- ing the flues in a locomotive boiler. Air can be led to and run a number of ma- COMPRESSED AIR ENGINE chines where light power is required. The pneumatic hammer is used for chip- ping and caulking the seams of a boiler, beading over the ends of flues, chipping castings and driving rivets. The pneu- matic riveter is made either stationary or portable, and for all varieties of work, such as riveting locomotive boilers or locomotive tanks. Portable riveters are used for riveting locomotive mud rings, or car and tender trucks. Jacks for raising passenger and freight cars, and raising locomotives; machines for pull- ing down draft timbers from the car sills; shears for cutting off bolts, ham- mers for straightening bolts (the latter machine is usually located at the scrap pile) ; the sand blast for taking old paint from locomotive tanks; a machine for sandpapering the outside surface of a passenger cai". Aside f rom_ the number of useful tools compressed air has brought into service, it has been used in a number of ways in place of hand and steam power. A whitewashing machine run by air does better work than a man with a brush, and can do as much work in 10 hours as 30 men can do. It is also used for painting buildings and freight cars. Compressed air is also used in connec- tion with gas for burning paint off coaches. It is sometimes introduced into a barrel or a tank through a coil of gas pipe, for the purpose of mixing paint. It is used for kindling fires in loco- motives with oil fuel; elevating oil from tanks; elevating water; running trans- fer tables; copying letters; blowing out the steam passages in locomotive cylin- ders. It may be said the use of com- pressed air on railways will in the near future perform a large share of the work done by hand labor and steam. In 1893, John Wanamaker, as Post- master-General, opened the first pneu- matic mail-tube line, extending from the postoifice to the house in Philadelphia. Pneumatic mail tube lines are in opera- tion in most all large American cities. COMPRESSED AIR ENGINE, an engine which is actuated by air under pressure, which air has been compressed by mechanical means. Air under pres- sure is able to act as a piston of an engine in the same manner as steam, and an ordinary steam engine is capable of being operated by compressed air by merely changing a few connections. The average compressed air engine is small in size, and usually designed for some special use, and is generally located in some distance from the source of power, or in place where the discharge of ex- haust steam would be objectionable, as in a mine. Air under pressure can be