Underground Infrastructure - May 2023 - 17

lower-horsepower machines are more
effective with soil trenching, but as the
relative hardness of the material increases,
so do the demands on the machine. "
According to Van Roekel, crews can
usually get by with a smaller trencher in
soft or loose rock formations. However,
harder rock formations require more
horsepower.
" Using a small trencher in solid rock
will take more time, and crews will go
through more teeth in the process.
Similarly, choosing a large trencher for
digging in softer rocks will not increase
production rates and can limit how
narrow a trench crews may be able to
dig, " he said.
Trencher teeth
To get the most performance from these
powerful machines, there are a few critical
steps Van Roekel and Scieszinski
recommend, from their work with hundreds
of contractors in the field.
" First, the contractor should be aware
that different-sized trenchers take different-sized
teeth, " said Scieszinski. " The
tooth shank for small- to mid-sized trenchers
typically measures about 1 inch
in diameter from the base of the tooth
to the retainer. And larger trenchers
require the 1½-inch tooth shank to
support the higher horsepower of those
powerful trenchers. "
Next, it's important to select the appropriate
style of tooth for the ground
conditions.
" The tip of a trencher's tooth can
range from rounded, dull surfaces to
pointed, spiked styles, " said Van Roekel.
" The rounded-face teeth, with a larger
carbide surface, can hold up longer than
more aggressive, smaller, carbide-tipped
teeth. The teeth with a larger surface area
are effective at breaking up softer rock
formations like sandstone and limestone.
" For harder rocks, contractors should
employ a more aggressive tooth style for
deeper rock penetration. "
Once the tooth style has been chosen,
it will be necessary to select a
tooth pattern.
Trencher chains usually come with
a standard V digging pattern, and the
number of chevrons varies by the boom
length and chain width. On wider chains,
a chevron may start with a single center
tooth and build to as many as three teeth
on the outer plates. Each tooth bites off
between 2 and 4 inches of material, depending
on the rock's density.
" Crews working in very hard rock may
want to consider using a staggered pattern
that incorporates short and long teeth, "
Scieszinski explained. " For this pattern,
longer teeth are placed in the middle of
the chevron to make the initial impact,
and then shorter teeth are used at the outer
edges to pull the chips out of the way.
" Using a combination of smaller carbide-tipped
teeth
and larger-surfaced
carbide teeth is also another combination
often employed. This configuration
mimics the way people chew their food.
Teeth in the middle cut and the outer
teeth grind and reduce the particle size. "
Buying versus renting
Once a contractor determines which trencher
is right for the project at-hand and
selects the proper configuration, the next
decision is more financial or budgetary.
If intended to be operated on a consistent
basis, especially when the contractor
owns, operates and maintains a larger
fleet of equipment, outright ownership is
most likely the best fit.
Another factor is whether the trencher
will be used frequently in the same
ground conditions. If so, the contractor,
regardless of size, should consider buying.
On the other hand, renting from the
dealer may be a practical strategy if the
company uses the trencher more sporadically
or are usually working in different
ground conditions. These trenchers are
highly specialized, so a dealer may be the
only source for rental. UI
UndergroundInfrastructure.com | MAY 2023 17
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Underground Infrastructure - May 2023

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