Trenching Through the Deep Freeze

Frost conditions vary throughout the country and from year to year. An early snow might mean a well-insulated ground and little frost. But a rainy season followed by a cold snap with little snow cover could mean frost as deep as 4 ft.

With winter just around the corner, it's important to know how to equip your trenchers for whatever cold-weather soil conditions they may encounter.

Choose the right outfit
Trenching through frost can be nearly as difficult as trenching through rock. Weight and horsepower are important considerations for tackling frozen ground conditions. A ride-on trencher is viewed as the minimum for regular frost trenching.

Stu Senska at Vermeer Midwest Inc. in Aurora, IL, says the majority of trenchers rented out for winter trenching are in the 14,000-lb. and 90-hp range. "The heavier the machine and the more horsepower, the easier it is on the operator, especially if you're in frozen soils with rock, because the machine will want to bounce or buck," he explains. Minimizing the bounce with a heavier machine will also reduce wear and tear on the trencher.

Properly outfitting the chain and tooth assembly is also essential for working in frost conditions.

"In any condition, not using the proper digging chain and tooth arrangement can cause premature wear on teeth, chain and sprockets," says Bob Wren at Astec Underground. "In addition, it takes horsepower and torque to run the digging chains. Not using the proper setup can also cause elevated wear on the prime mover."

The standard summer digging tooth is a cup tooth, which scoops the soil out of the ground. In frost conditions, however, the cup tooth is ineffective.

"A cup tooth takes too much of a bite at that frozen ground — it wants to grab and it causes more problems. So we typically switch to a carbide bit that has a definite point, and it chips away [at the soil]," says Brent Bolay, senior product manager at the Ditch Witch organization.

The bullet-shaped carbide bits rotate and are self-sharpening. They are also replaceable when they become worn or damaged.

The shark tooth bit is another tooth style that was introduced to the industry about five years ago. "It has carbide on the end, but it's stationary," Bolay says. "You don't have to replace it — whatever wear life you get out of it is what you get from a particular chain."

The chain is also an important element when outfitting a trencher for winter work. In most cases, you will want to use what is known as a frost chain. "The difference between it and a standard chain is that it has a sidebar on every station, which means you end up with a tooth on every station," Bolay explains. "Typically, more teeth on a chain means they're taking a smaller bite of the material you're trying to cut rather than a large bite. In frost, you want to chip away at it."

Al Chancellor, Ballantine, Inc., says his company's Trench-All chain line is specifically engineered for the most severe digging conditions, including trenching through frost or rock. It features a raised rivet design, which provides more wear area on the bottom of the chain; anti-back-flex, which minimizes the force driven back into the cutter; and a low profile.

"A low profile is extremely important when you build these rock-style chains," says Chancellor. "We build what we call a low-profile, H-plate style chain. The higher a tooth stands, the more load it forces back onto the trencher itself, and that will accelerate the wear on all the other components. So what you do is use a low-profile style of chain and it keeps the tooth down closer to the power source. When it engages properly at the right attack angle, it then basically reduces that load and kickback."

Rod Bendit is regional fleet manager for the central region at Henkels & McCoy, Inc., a national contractor performing all types of utility construction. He oversees about 50 trenchers of varying sizes and brands in the central fleet.