For general construction work where the excavated material is not loaded on standard gage railway cars, small dump cars, Figs. 84 and 85, are generally used. They are more economical than wagons or carts, which are employed only in special cases, mostly in cities, where the material must be hauled some distance over several intersecting streets, and where a track will not be allowed; or for very small jobs with a long haul which would not justify building a track.
The gage of these tracks is usually 2-1/2 or 3 ft., sometimes 2 ft. or even 1-1/2 ft. only; the latter gages are not often used, and the 3-ft. gage is usually preferred.
The rails most generally used weigh 20 lbs. per yd. Although these tracks are only temporary their construction should be fairly substantial; but they are often built in an exceedingly careless and insecure manner, causing a great waste of power in pulling the cars over them, and resulting in frequent delays, due to derailments. The grade is usually arranged so that the loaded cars will run downhill by gravity, and only the empty cars need be drawn back to the pit. On small work, horses or mules are used to pull the cars, but on large jobs small locomotives are employed. Small dump cars vary in capacity from 1 to 3 cu. yds., the latter size being most generally used. The side dump car, Fig. 84, dumps on either side. The rotary dump car, Fig. 85, unloads on either side or end; the box can be turned around horizontally, revolving about a vertical pin in a turntable on the frame; they are used mostly in dumping off the end of a fill.
In making fills it is nearly always the best plan to build a temporary trestle of round pieces of beech, cottonwood or other cheap trees, old bridge or building timber, or other second-class lumber, and then filling in with the side dump cars. By adopting this plan the unloading will progress much more rapidly than by dumping from the end of a fill, where only one car at a time can be unloaded. These trestles are inexpensive, and the saving in labor and time in making the fill will amply repay their cost.
Unloading the Material.--On railways the unloading is seldom done by slow and expensive hand labor with the shovel; sometimes dump cars are employed, but in most cases flat cars and the plow are used. The trains consist of 10 to 30 cars. The car carrying the plow is attached to the rear of the train at the nearest side track to the unloading place, if it is not over 10 miles from the steam shovel pit this car is generally carried back and forth to avoid an extra stop to couple it on the train at the side track. One end of a steel wire cable is then hooked to the plow and the other end (which is attached to an ordinary car coupling link) coupled to a car or the engine. Usually this cable is about 400 ft. long and extends over 12 cars. The brakes on these cars are then set up tight and the engine started with the forward cars, Fig. 86. In very tenacious or partially frozen material the rear cars are sometimes pulled along by the plow; the wheels are then blocked with pieces of wood or with stones; sometimes it is even necessary to chain a few of these cars to the track to prevent the rear lot of cars from moving. After the plow has been started, it is drawn along slowly until it arrives on the last car, Fig. 87. The engine is then stopped and backed up a few feet to permit the cable to be thrown on one side of the track, Fig. 88. The train is then backed up again and coupled to the unloaded cars, when four to six men throw the cable on the next loaded cars, Fig. 89, coupling its forward end to a car or to the engine if the cable is long enough. The operation is then repeated until all but the car next to the engine is unloaded; this car carries the plow and is the first car to be unloaded by the next train. The ends of the cable are then detached from engine and plow, thrown to one side of the track, and left there for the next train to pick up and use in the same manner.