Although the machine is gradually run upward and downward, it is always blocked level after each forward move before beginning work, to insure quick and easy swinging of the crane, as previously explained. Most machines will cut 5 ft. below the main track and load on a flat car with 18 ins. side boards. Some machines will cut as low as 8 ft., and they are preferred to others on railways where much work of this kind is done, as their use often avoids making an extra cut.
After the first cut has been completed, the pit track, A 1, Fig. 36, becomes the temporary main and loading track; the main track is taken up from C to H, and the steam shovel run back to C to begin the second cut, Fig. 42, excavating it in the same way as the first, and loading on the temporary main track. This track again is taken up after the second cut, the machine begins at D and ends at G for the third cut and loads on the pit track in the second cut; the fourth cut is made in a similar way, the machine beginning at E and ending at F, Fig. 36. The fifth and last cut is merely a widening cut, made by loading on the track in the pit of the fourth cut. The material of each cut after the first is loaded on the track laid in the preceding cut. After the completion of the last cut, the permanent subgrade having been reached, the main track is laid on the permanent line, and the small quantity of material obtained from cutting the ditches loaded on cars by hand and taken away for unloading. The most frequent depth of cut made at the summit of grades is about 10 ft. (two cuts), Figs. 38 and 39.
When the main track is on a curve, as frequently happens, an extra cut can often be avoided by slightly changing the alinement of the new main track, and at the same time reducing the degree of curvature, as shown by Figs. 42-1/2 and 43. This is particularly applicable where an odd number of cuts must be taken to reach the bottom of the new grades. The dipper will cut to a slope of about 1 to 1. When greater slopes are required, it must be done by hand or undercutting resorted to. Sloping by hand is slow and expensive work, impracticably so in all tenacious materials; it has therefore become the exception, and undercutting the rule. Cuts made in the latter manner sometimes present a rather ragged appearance when just completed, but the irregularities soon merge into a smooth surface as the action of the elements produces the natural slope of the material; the smaller cost amply compensates for the temporary lack of finished appearances. The amount of hand labor necessary where undercutting is not practiced is shown by the sections A in Figs. 38 and 41. This can be entirely avoided by undercutting the slopes, as shown in Figs. 39 and 42; the sections B will slough off within a year or two and most of the material lodge in the spaces C; a small part of this material may roll to the bottom of the cut, and can be removed by loading on cars by hand, or space may be provided for it by making the cut a few feet wider at the bottom. In most cuts for reducing grades this extra width must be cut out anyhow to provide room for both steam shovel and loading track.