Digging requires horsepower. The faster, deeper and wider you want to dig, the more power you actually need. Ideally, you would like to get the job done as quickly as possible at the lowest possible cost. Yet, the cost portion of the equation means the solution isn't always the machine with the most horsepower.
Consider trencher selection. Mark Cooper, Vermeer, says you must compare the cost of operation and production in order to select the right machine for your operation. Machine size has the largest influence on these variables.
But it is a balancing act. "You should look at the job and determine how fast you need to get the trenching part done," says Brent Bolay, the Ditch Witch organization. "This helps you get into a size class of machine that will actually accomplish that."
Tires or tracks
While size is the primary criteria that determines which trencher is right for your application, you may also have a choice between rubber tires or a tracked undercarriage. There are a few compact ride-on trenchers under 25 hp that are equipped with rubber tracks, but the majority of trenchers under 115 hp are on rubber tires. From 115 to 185 hp, you will find trenchers equipped with either tracks or tires; and above 185 hp, the trenchers are almost exclusively on steel tracks.
Rubber tracks on compact trenchers offer low ground pressure for soft soils and minimal ground disturbance. "Compact trenchers that can be equipped with rubber tracks can be used in residential areas because they can move over asphalt or concrete without damaging the surface," says Bob Wren, ASTEC. This leads to lower rehabilitation costs.
Machine life may also be affected. "I believe that rubber tracks increase the life of a compact trencher because the tracks absorb some of the shock load that goes into the chassis while digging in tough ground," says Wren.
In the mid-size trenchers, however, the rubber-tired units dominate the market. "There is more of a horsepower selection in the rubber-tire range, which allows the contractor to choose a size unit best suited for his or her particular application," says Wren.
The benefits of rubber tires on mid-size machines are numerous, including the ability to handle curved trenching. "A rubber-tire trencher typically is more mobile; it has higher road speeds," says Cooper. "It is also easier on the ground, streets and grass."
The trencher turns by steering rather than skidding. "Rubber-tired machines can suit more applications without increasing the cost of restoration," says Wren.
Different tire sizes are available to suit specific applications. "At ASTEC, we offer a couple choices on some models, depending on whether the machine will be equipped with a trencher or a cable plow," notes Wren. "Those who are plowing cable usually want a larger footprint on the ground to increase tractive effort, and also improve flotation."
In some cases, suppliers offer a choice of tires or tracks in the same size machine. For example, Ditch Witch offers both the 115-hp rubber-tired RT115 and the HT115 on tracks. "In the case of the tracked model, you need to have an application that justifies the higher purchase price associated with a tracked unit," says Bolay.
Each option offers strengths and drawbacks. The tracked unit provides increased traction and flotation for cable plowing and straight line trenching. But the rubber-tired unit is more maneuverable for cutting curved trench, and it doesn't damage the surface as much, requiring less rehabilitation work.
"If you have a job that requires quite a bit of turning, a rubber-tire machine would be better because you would typically use the front axle, or steering axle, to guide the machine," says Bolay. "It is easier on the trencher [boom] with a rubber-tired machine than it would be with a track unit." When a tracked machine is turned, it tries to rotate the whole machine, similar to a skid-steer loader. "That forces the boom to move in the ground (against the side of the trench) faster than it really should."