Brake.
1. (Railroad-engineering.) A contrivance for stopping the motion of a car-wheel by friction applied thereto. Car-brakes, until the advent of the atmospheric brake, were actuated by a winding drum, connecting chains and levers, the power of the brakeman being applied to a hand-wheel on the car platform. The principal modes of application of the hand-operated brake are explained under car-brake (which see). In the same article are detailed a number of devices for the use of air, steam, the colliding of the cars, friction, feet on the track, etc., for arresting the motion of the cars. The Westinghouse Atmospheric Brake, illustrated by the folding plate opposite, was patented in 1869, and has been adopted on many railway lines in the United States and in Europe. Its chief features are, first, the use of compressed atmospheric air as a means of applying the brakes; and, second, putting the whole braking-apparatus under the direct control of the locomotive engineer, so that he can apply the brakes at pleasure, instantaneously, or gradually, and with any desired power, limited only by the power of the air-compressing apparatus and the strength of the air-vessels. The construction of the apparatus is shown by elevation and section. A small but powerful direct-acting steam-engine A is secured to the frame of the locomotive above and between the driving-wheels. This engine operates the air-pump B, and thereby the air is compressed to any desired density into a receiver or reservoir Y, which is arranged under the cab. Each car is provided with a line of air-pipes p p, which are united between the cars by flexible hose r r, and suitable couplings. Each half-coupling contains a valve so constructed that, when the hose are coupled up, the valves are automatically unseated, so as to make an open continuous air-pipe through the train, and, when uncoupled, each valve will automatically resume its seat. Hence, the valve of the rear coupling of the rear car of a train will always be closed, and if, after the brakes are applied in view of actual or anticipated danger, a car jumps the track and becomes disconnected, the couplings will separate, the valves resume their seats, and the brakes be held “on” or “down” till the car comes to a full stop. See hose-coupling. The air-pipe p, under each car, makes connection by a branch with one end of a cast-metal brake-cylinder W, which is fitted with an ordinary piston. The stem w of this piston is connected directly (or indirectly by rods x xa, and “progressive lever” X) with the ordinary brake-levers in such a way that, with a forward thrust or throw of the piston, the brake-shoes will be applied to the car-wheels, and by a reverse movement they will be released or “let off.” A three-way cock M in the air-pipe, just outside the reservoir Y, is within reach of the locomotive engineer. In ordinary running all communication between the reservoir Y and the air-pipes p is closed. The engineer, at pleasure, turns the cock M, so as to open this communication, and permit the compressed air to flow back into the brake-cylinders W, either partially if he merely wishes to check the speed of his train on a down grade, or more completely for an ordinary stop, or instantaneously and fully in anticipation of immediate danger. By another adjustment of the cock, he closes the communication again, and opens a port for the escape of the compressed air from the brake-cylinders. The brakes are then “off,” and the wheels free. The construction is such as not to interfere with the ordinary operation of the brakes by hand. For ordinary passenger-trains, an air-pressure is commonly required of from 30 to 60 pounds per square inch. The capability of this brake is best shown by the following report of tests made. At a test on the Kansas Pacific Railway, May 12, 1871, a train going at the rate of 45 miles an hour was stopped within a distance of 250 feet. On September 18, 1869, a test was made on the Pennsylvania Railroad, at the famous “Horseshoe bend.” The train of six cars, running down a grade of 96 feet to the mile, at the rate of 30 miles an hour, was brought to a stand-still in 420 feet, — seven carlengths. The steam-ejector has also been employed by Mr. Westinghouse, under a patent granted to him in 1871, for exhausting the air from the brake-cylinders in front of the pistons, and thus applying the brakes by a “vacuum” or atmospheric pressure. See Giffard injector.
2. (Machinery.) A friction strap or band applied on the periphery of the drum of a hoisting-machine, crane, or crab. Or it may consist of a pivoted lever, having a shoe at one end, and a rope attached to the other, by pulling which the shoe is pressed against the rim of the wheel. Of this class is the rim of wood surrounding the inclined wheel attached to the sail-shaft of a windmill, and pressed down thereon by a lever to stop the mill.
3. (Vehicle.) a. A vehicle for breaking horses, consisting of the running-gears, and a driver's seat, without any carriage-body. b. A rubber pressed against the wheel of a vehicle, to impede its revolution, and so arrest the descent of the vehicle when going down hill. The old Herodes Atticus, the rhetorician, refers to [357] the fetter to the wheels, used when his chariot was descending a hill. It appears to have been only a stick put through the wheels.
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| Wagon-brake. |
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| Sled-brake. |
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| Pump-brake. |
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| Brake-shoe. |
4. (Husbandry.) a. A machine for separating the bark and pith from the fiber of hemp or flax; to loosen the boon and shives from the hare. See flax-brake; hemp-brake. b. An English term for a heavy harrow.
5. (Farriery.) a. A frame for confining refractory animals while being shod or undergoing operations. b. A sharp and heavy snaffle for breaking or subduing untrained or vicious horses. 6. A name for the ballista (which see).
7. (Hydraulics.) The extended handle of a fireengine or similar pump, by which the power is applied. Said especially of an extended handle at which a row of men can work together.
8. (Basket-making.) An iron crotch with a sharpedged reentering angle, adapted to peel the bark from osiers drawn therethrough. 9. The baker's kneading-machine; consisting, in some cases, of a pivoted lever operating on a bench; the name now including other machinery for effecting the same purpose.
