Fig. 84.
Fig 85.
On hauls exceeding 25 miles the full number of cars and engines required can seldom be obtained, and the output of the steam shovel is correspondingly decreased. The delay in returning empty cars due to detentions from other trains is the great trouble most keenly felt in steam shovel work on railways in operation. The so-called "mud train" is generally considered an outcast, and is usually the last train to receive the dispatcher's attention for an order to the road. These delays are daily occurrences, and it is quite an exceptional case when the machine is amply supplied with empty cars. The record of most steam shovels on such work is therefore a rather poor one, when the machine really made a good showing for the crippled condition of its car service. Some of these delays can be avoided or shortened by stationing a telegraph operator at the outgoing end of the pit, and on all but very small pieces of work his wages will be many times balanced by the time gained in keeping the whole plant moving, by obtaining train orders quicker, and remaining constantly informed of the whereabouts of the construction and other trains, and regulating the work in the pit accordingly.
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 2½ or 3 ft., sometimes 2 ft. or even 1½ 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.