Rubber-tired trenchers — Cowboys finish sooner, but they pay more accordingly

Unlike dozers or excavators that crank up in the morning and run steady until quittin’ time, a trencher may be used at as many as a half dozen different jobsites on a busy day. Add to that the fact that soil conditions can change from easy-digging dirt to hard rock or cobble – sometimes in the middle of one job – and you’ve got a machine that requires a flexible and knowledgeable response to maintenance needs.

Taking the time to assess these needs, and if necessary change teeth or chains and do a job the right way, may seem like a waste of time. But in many cases, the faster you go, the smaller your profit margin shrinks.

Different users, different lifecycles
Usage on rubber-tired trenchers varies from about 1,000 hours to as little as 350 to 500 hours. Full-time trenching contractors put the greatest number of hours on a machine, while public utility companies often put on the fewest. Full-time trenching contractors typically trade or sell their used machines every two to three years. “There is a point where the trade-in value starts getting away from you,” says Mark Cooper, trenching product manager for Vermeer. “So you want to trade them off while they still have a strong portion of their value.”

For this type of contractor, uptime is profit. Maintenance chores beyond the regularly scheduled service checks can spell lost business. Utilities or contractors who put fewer annual hours on a trencher can often extend their trencher lifecycles to eight or 10 years. “The power, gas and telephone companies have defined maintenance programs and they look at their machines as a long-term investment,” says Brent Bolay, trencher product manager for Ditch Witch.

It’s a dirty world, but keeping your trencher clean and checking the fluids and filters regularly will help lower your owning and operating costs.

Correct spec’ing of cutting teeth
Aside from fuel, fluids and filters, a trencher’s digging/cutting teeth represent the biggest owning and operating cost for consumable components. Hard rock or abrasive sand can grind up even the best conical carbide teeth in less than a day. Yet cup teeth in soft, loamy soil can go as long as 500 hours.

You can’t change the soil conditions you’re asked to operate in, but you can lower the cost of replacing cutting teeth by carefully matching the teeth to the conditions at hand. Often the best sources of information on cutting teeth and soils are your equipment dealers. “When you step up to the parts counter, you’ve got people who know the local conditions,” Bolay says. Dealers will also help you choose the best teeth for the job, whether that be a cup tooth, a conical configuration, a specialized tooth or a combination of different teeth.
Spec’ing the right teeth not only reduces consumable costs and downtime, it helps keep your trencher digging at peak efficiency. “The more wear you have on its teeth, the less productive you get,” Cooper says.

Neglecting broken or damaged conical teeth can lead to bigger repair expenses and additional downtime as well. “If you let the tooth wear out or run broken, eventually you may have to weld the pocket back,” Cooper says.

Another expensive shortcut is to use the standard chain rather than spend an hour or so to change to the configuration the job calls for. Two examples would be using a wide chain when a narrow trench is called for and using a rock chain rather than changing to a dirt chain. The time it takes to change to the right configuration creates some downtime, but using the wrong setup also puts unnecessary stress on the engine and hydraulics and accelerates wear on the components.

Costly operations
Trenchers make it easy to be a cowboy. And with the time pressures contractors face, it can be tempting to just lower the boom and go. But failure to use the right techniques can add to your costs and lower your profit margins.

How hard you turn with the chain in the ground makes a big difference, especially if you are wrenching the thing around and you bind the chain, Cooper says.

Running with a too-shallow boom angle is also a profit snatcher. This typically happens when an operator has been digging with a 4-foot boom and comes to a job that needs a 2-foot-deep trench. Rather than switch to a 2-foot boom, he just adjusts the angle of the 4-foot boom. “You’re going to get your best performance at around a 60-degree angle, Cooper says. “When you go shallower, the dirt doesn’t come up out of the trench as well, so it’s more wear and tear on the machine.”

Even with the best operating techniques, haste and benign neglect are still the top enemies of a trencher’s lifecycle and ownership costs. “It’s easy to think ‘I’ve only got a couple more hours to finish a job, so I won’t worry about greasing or lubricating this time,'” Bolay says. “So it doesn’t get done.” These short cuts and skipped maintenance procedures rarely cause any immediate problems. Over time, however, neglecting the small and inexpensive maintenance needs can add up to expensive and unforeseen breakdowns, he says.

Hydrostatics change the equation
Over the past 10 years or so, most trencher manufacturers have been introducing more hydrostatic ground- and chain-drive models into their product lineups. Now mechanical-drive machines are rare except in the largest machines. Hydrostatics were first introduced as a ground-drive mechanism and gave the machines good creep control capability. Then, rather than have two power systems (hydraulics to the wheels and mechanical drive to the chain), manufacturers decided to use hydraulic systems to push both.

“Hydrostatic machines can take care of themselves,” Cooper says. “When you stall the chain, a hydrostatic machine can go over relief and it can protect itself. When a mechanical machine stalls, you can kill the engine or do some damage to the driveline, loading the gears each time you stall it.”

Hydrostatics also allow manufacturers to offer booms that can be offset and combination plow-trencher machines.

Aside from the performance differences, one of the main benefits of hydrostatic systems is that they require less maintenance. “Hydraulics use a closed-loop system so you don’t have to mess with it as long as it is functioning,” Bolay says. Mechanical drives have open chains and belts and allow you to clearly see components that need adjusting or replacing. And most owners and operators could do this work themselves. “Hydrostatics require more technical expertise,” he says. “But in the long run I think it’s been good for the owner-operator due to the performance he’s getting and the life of the machine.”

Cooper agrees: “I recommend taking hydrostatic systems to the shop for repairs. I’m sure there are guys out there who are going to repair their own machine, but if you are making a living with this machine it needs to run.”

Diagnosis of hydraulic system problems is particularly challenging. “A problem could be in the motor, the pump or the shuttle valve, and pinpointing where the problem is can take the contractor a lot of time,” Cooper says.

Keeping a clean machine
Trenchers don’t need a lot of elaborate or time-consuming service, just regular and consistent maintenance, correctly done. “Make sure you do the daily things,” Cooper says. “Grease it. Make sure it has a grease decal on it. Read the maintenance and service manual to find out where the zerks are, not just where you think they are. And find out what the amount is. There are times when you don’t want to over-grease it.”

Cleanliness also helps. “If you clean the machine at the end of the day you’re going to notice a wire off here or a leak there,” Cooper says. Keeping fluids and filters clean, especially in the dusty world of trenching, is also key, especially given the high-pressure hydrostatic systems used on most trenchers.

“Every time I go out and find a machine down, it’s always more than one thing,” Cooper says. “You can usually fix the first thing. But when two or three things stack up you can’t figure it out. The more you take care of the daily maintenance, the better off you’re going to be.”