Fig. 72.
The brakes are placed on one side of the car, as shown in [Figs. 74] and [75]. When boulders, loose rock, etc., are to be unloaded, the brake staff is set in a socket, [Fig. 76], and taken out before the plow is started. This avoids bending or breaking the staff in case any stone should be wedged between it and the moving plow. Sometimes the socket is used with the brake at its ordinary place at the end of the car; in such a case it must always be taken out before the plow reaches it.
The plow, [Fig. 70], is built of heavy plate and angle iron, strongly braced, and headed by a cast steel point, to which the cable is attached. The sides are curved outward at the bottom, working under the material and pushing it aside as the plow is drawn along, and held down on the car by the weight of the material and the partly downward pull of the cable at its point. Short pieces of old rails and other scrap iron are also often placed on the plow to help hold it down on the car when very tenacious materials are to be unloaded. The groove extending along the center line on the bottom fits over the ridge timber on the car, and forms the guide by which its movement is directed. Small stones, protruding bolts, slivered ridge timbers and other obstructions in the groove of the plow sometimes wedge the point fast, and before the engine can be stopped, the plow is turned up on its point, and falling to either side, tumbles off the car. The weight and elasticity of the cable is often sufficient to draw the plow half a car-length after the engine has been stopped, and it is often difficult to stop the plow quick enough to prevent upsetting when obstructions occur, although the speed is usually only two to three miles per hour. The unloading nearly always occurs on trestles or embankments, and when the plow is thrown off the car, its replacement often requires much time and labor, sometimes even making the services of the wrecking car necessary. This difficulty is very likely to occur when unloading on curves, where one side of the point of the groove presses against the ridge timber. This plow unloads the material equally on both sides of the car, as it is wanted in filling trestles, raising embankments, tracks, etc.; but it cannot be used to advantage where the material is wanted on one side only, as in widening embankments for double track, side tracks, yards, station grounds, etc.
Fig. 74.
Fig. 75.