Track trenchers can also create a challenge on rough terrain. "Because of the design of track trenchers, I would say they are more difficult to operate on rough terrain," says Wren. "They all have a rigid frame, which means the operator may be constantly raising and lowering the boom to maintain proper cover depth. Rubber-tired machines will have at least one axle that will oscillate to maintain ground contact."
Typically, the strength of tracked trenchers is straight line trenching for long runs. The low ground pressure of the tracks allows the trencher to traverse varying soil conditions.
When trenchers reach a certain physical size, the tracks become necessary to provide adequate flotation. "When you get up to a 40,000-lb. machine, you just have to have a tracked undercarriage underneath it to handle that weight and still do the job," says Bolay.
"The bigger the trench and the harder the material lead you to track trenchers," says Cooper. For instance, consider trenching in rocky soils. "Typically, track trenchers are much larger and heavier, and are used to cut rock. This is because they are more stable — they do not bounce cutting rock. They also provide better flotation and traction."
Track machines can also be beneficial when trenching on slopes. When equipped with a tilt frame, they can make vertical cuts on sloped surfaces. "That is a feature we offer that lets you work in those areas a little easier by keeping the frame level," says Bolay. The Ditch Witch models typically tilt 7° left or right. "We put a little level up on the dash so it will give you some guidance as to where you are at."
Track trenchers tend to cost more to run over the life of the machine due to the expense of undercarriage components. But the low ground speed and minimal force generated while trenching translate into a long life expectancy. There is not a lot of pulling force exerted on the track. "The majority of the horsepower goes through the trencher chain," says Cooper. "The final drive has a pretty easy life. The biggest thing it has to handle is the static load."
Trenching vs. cable plowing
If you are going to use a machine for vibratory cable plowing, the selection criterion changes. Bolay explains that traction is actually a bigger issue when cable plowing than it is with trenching. The trencher chain cuts away the material before the machine really starts to pull. "It doesn't really require a lot of traction," he notes. "On the other hand, with the vibratory plow, since we are not removing that soil, it has to have enough traction to pull the plow blade through the ground."
Cable plowing is an application where tracks can be very beneficial. "In many applications, such as burying cable along side the right of way, a track cable plow will have more tractive effort and, at the same time, have less ground pressure per square inch on the ground," says Wren. "I would say there are more track machines equipped with cable plows than with trenchers."
Features add productivity
All of the manufacturers have developed features that will help you get the job done a little easier. For instance, Ditch Witch can provide the operator with a digital readout of trenching boom depth from the operator's seat. "He can take the digging boom down and have confidence of digging deep enough to have his cable or pipe placed at the right depth," says Bolay. If you are going over rough terrain, it will indicate whether the operator manually needs to raise or lower the boom.
Electronics have also made it possible to automate functions, such as with cruise control. "It allows an operator to set a ground speed while trenching, and then it maintains the engine speed to operate within a certain parameter," says Bolay. "It gives you optimum performance out of the engine by maintaining a constant speed. It maximizes your feet per minute — your production on any given job."