Table 9-1.—Crawler Ditcher Maximum Trenching RatesFigure 9-69.—Chain ditcher.The guideline should be established at a height thatwill put it at least a few inches above the ground at allpoints, stakes driven along it, and the exact height ordepth of the cut marked. Then a string line is stretchedalong the stakes on these markings.A rigid bar is fastened to the front of the power unitof the ditcher with one end over the string when theditcher is centered on the ditch line. A plumb bob orother weight is fastened to the bar, so it hangs directlyover the string. The operator can then keep the machineon center of the trench, cut by keeping the plumbbob just over the string. If the ground is irregular andcauses the ditcher to go up and down, the cord holdingthe plumb bob can be run through eyes or pulleys, sothe operator can reach an end of the cord to raise andlower it.The same device (plumb bob or other weight) canbe fastened on the side beam of the boom or wheel witha fixed length of string to control the depth of cut andcenter line travel of the ditcher.9-33Cutting CurvesThe radius of a curve cut while excavating a trenchwith the ditcher depends mainly on the density of thesoil excavated. In sandy or loose soil, the radius can bemuch less than in hard, compacted, and rocky soil. Theturn for the ditcher should be made cautiously at a slowdigging speed and only to where the boom starts bindingbetween the trench walls.Muddy TrenchingThe two major problems when trenching in muddymaterials are loss of traction and a buildup of materialin the buckets. The traction can be increased by puttingplanking under the tracks or by adding wider crawlerpads. To cope with material sticking to the teeth andbuckets, you can run the digging chain faster, so thematerial will not be forced into the cut. In this way, youdo not force and pack wet, sticky material into the bucketand between the teeth; otherwise, the material in thebucket gets stuck and cannot empty completely.TransportingA ditcher is slow and must be hauled betweenjobsites. It must be loaded and unloaded safely andproperly. The design of the ditcher requires that it beused on a smooth, gradual incline. When loading on atilt-bed trailer, you must be careful; the sharp incline ofthe trailer could make the ditcher hang up. Additionally,the smooth tracks of the ditcher tend to slip.
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