With the ladder ditcher, excavating is done by
buckets attached to the bucket line chain; the chain
travels on the drive sprockets on the boom assembly.
Like the wheel ditcher, the ladder ditcher has a spoil
conveyor to carry the excavated material out to one side
or the other. The radius of a curve depends mainly on
the density of the soil to be excavated. Turns should be
made cautiously at a slow-digging speed and only to
where the boom starts binding between the trench walls.
The crumber shown in figure 9-68 has a major job
to clean out and smooth the ditch after the teeth have cut
the material. The crumber is adjustable and should be
adjusted so it will clean the ditch of loose materials
behind the teeth.
CHAIN DITCHER
The chain ditcher, as shown in figure 9-69, has teeth
attached to a chain similar to a chain saw. The chain teeth
pull or drag the cuttings to the surface, rather than lifting
them in a bucket. The cuttings are usually moved back
from the edge of the ditch by rotating augers.
Chain ditchers are ideal for lightweight work, such
as sprinkler systems, gas lines, and small waterlines.
Some of these machines can dig up to 10 inches wide
and 4 feet deep.
CAPABILITIES AND LIMITATIONS OF
DITCHERS
A ditcher can dig earth material ranging in texture
from soft to hard; however, as the material being
excavated increases in hardness, the production rate
decreases. Table 9-1 gives maximum trenching rates for
classes of soils in feet per minute.
A limitation of a wheel, ladder, or chain ditcher is
that ramps are left at the bottom of the trench ends and
around buried objects. To obtain a flat-bottom trench,
you must remove these ramps by hand. The wheel
ditcher digs faster in dense material and is preferred for
cross-country digging where speed is needed.
OPERATING TECHNIQUES
In most ditching work, keep the machine in line and
working at the proper depth. Unable to see the ditch
bottom, you (the operator) must use surface controls.
First, the ditch is surveyed and the depth of cut is
determined by the EAs from the blueprints. You, the EO,
establish a guideline at a fixed and constant distance
above the bottom grade of the trench and offset from the
center line of the trench beyond the track line of the
ditcher.
Figure 9-68.-Crumber.
9-32
