The operation of this valve is as follows: The handle 8 being placed in the release posi tion, the air passes from the main reservoir, through the port a, cavities h and c, and port 1, to the train bnike-pipe. and releases the brakes, At the same time the air also pusses through the ports J awl e to the chamber I), thus placing piston 17 iu equilibrium. The handle S Description of Tests.-1. Emergency stop, train running 20 miles an hour. 2. Emer gency stop, train running .10 miles an hour. 3. Applying brakes while train is standing still, to show quickness of application. 4. Emergency stop, with passengers aboard ; speed. 40 miles per hoar. 5. Service stop, and time 1,f release. Showing the kind of stop made when a smitten stop is not necessary, and how pros aptly the brakes can be released. 0. land-brake stop, nettle at 20 miles an hour, with five brakemen at their posts (at Buffalo there were swell brakemen). 7. Breaking train in two. All the above stops were made with the braking power so low that it would not slide the wheels of empty ears in regular service. By using greater power, quicker stops could he made, but there would be more or less sliding of wheels, and it was not thought that the advantage gained would be enough to make up for the damage done in freight service. 8. Train running 20 miles an hour; the brake leverage having been increased to give the quickest stop possible. 9. Train running 40 miles an hour ; leverage as in No. 8. 10. A train of 20 freight-ears and a train of 12 ordinary passenger-coaches were run alongside of each other, on parallel tracks, and the brakes applied at the same time. This test showed the relative stopping power of the old and the new brakes.
is then moved to the position for running. Cavities b and c are thus separated. and the air from the main reservoir now has to pass to the train brake-pipe through ports j, f, and /. To pass through the port f the valve 21 must be forced from its seat, and, it being seated by the spring 20 of the proper resistance, a proportionally greater pressure is thus carried in the main reservoir. In this position of the handle, the piston 17 remains in equilibrium, the train brake-pipe and chamber D being in open communication, through port 1, cavity c, and port g. Figs. 5, 6, 7. 8 show parts in detail.
To apply the brakes for any ordinary purpose the handle 8 is moved to the position for "service stop." All communication with the main reservoir is thus destroyed, and the air in chamber D is cut off from the train brake-pipe. The cavity p of the rotary valve 13 con nects ports eau(' h, and air from the chamber D discharges to the atmosphere. A pressure gauge, connected to the chamber D at W indicates when the pressure has been sufficiently reduced by the discharge of air, and the handle 8 is then moved back as far as the position on lap." Here all ports are covered. Accompanying the reduction of pressure in chamber D, the equilibrium of piston 17 being destroyed, it is forced upward by the greater pressure in the train brake-pipe, and the port a is opened. The aperture of the port a is so gauged that the air is discharged from the train brake-pipe through the ports en and a at such a rate that the brakes are all applied gradually and uniformly. The discharge of air from the train brake-pipe through the port n continues until the reduced pressure becomes a little less than that remaining in chamber D, when piston 17 is forced downward and cuts off further discharge from the train brake-pipe. The volume of chamber D being constant, the reduction of pressure invariably corresponds to the quantity of air discharged from it, without reference to the volume of air in the train brake-pipe; the manipulation of the brake-valve, to apply each brake with any particular force, is the same, therefore, for trains of any length.
To effect a quick stop the handle 8 is moved directly to the position for emergency stop." The cavity c then connects ports 1 and A-. and, a large direct avenue for the escape of the air from the train brake-pipe being presented, a violent reduction of pressure occurs, causing the quick action of the triple valves and a sudden, full application of all the brakes.
On page 89 is given a tabulated statement of the results of a series of tests of the quick action automatic brake upon a train of 50 freight-cars.
Bran Duster: sec Milling Machinery, Grain.
Breaker : see Coal-Breaker, Ore-Crushing Machines, and Rope-Making Machines.