Species of Excavation
Dedicated Trenchers vs. CUL Trencher
Attachments in Your Natural Habitat
By Jason Morgan

The pedestrian trencher is the pygmy breed of digging machines. These small, walk-behind trenchers have been adapted over half a century to work in confined work environments. While it has a small stature, it also has large teeth that can channel a powerful digging action into a precise and evasive package. At about 4 to 5 ft in length and 2 to 3 ft in height, the walk-behind trencher (a.k.a. pedestrian trencher) has ruled the construction jungle for nearly 50 years.

Yet, those dedicated digging days are changing, as new competition migrates to the utility market in the form of species such as Dingos, Boxers and Ramrods. These are models of compact utility loader (CUL), and these compact machines not only trench, but they also wield a host of interchangeable attachments (buckets, pallet forks, brooms, backhoes, trenchers and everything in between). But do these CULs dig as fast and focused as a dedicated pedestrian trencher? Are they as small and unobtrusive as their trenching cousins?

“Jobs that require faster production or jobs that are in confined work areas, where a compact utility loader and attachment could be too large, a contractor can use a dedicated machine and perform the job quickly,” says Shaun Fritchey, solutions specialist for Vermeer. “If a contractor is renting the equipment, it is cheaper to rent a dedicated unit vs. a compact utility loader and attachments.”

When it comes down to picking between the two, you have to ask yourself if you’re ready to settle down with a trencher or if you need a bit more freedom. Obviously, the job is going to play a large role in your trencher system selection, but your personal needs are also a part of the equation. Familiarize yourself with the host of advantages, disadvantages and possibilities each machine offers, before you are going to choose your next earth eater.

“On a compact utility loader, a trencher attachment can easily be removed and replaced by a trench filling attachment that speeds up the overall trenching job,” says Greg Lawrence, Toro’s marketing product manager. “Traditional trench back filling is done by hand, but with a trench filler, it can be done in a fraction of the time. If the job requires additional digging, hauling, landscaping and other functionality, a compact utility loader would be a better investment.”

Attached to Trenching

Gone are the days of “one job, one machine” thinking. Tool carriers have opened up the construction, landscaping and utility work markets with machines that are designed to tackle every task (although not necessarily as efficiently as a dedicated unit). The smallest of these tool carrying creatures is the CUL (sometimes called a mini skid steer). Not only can they carry over 50 different implements (from breakers to box rakes), but they’re also excellent trenchers. This means that these multitasking machines are encroaching on dedicated machine territory.

By pinning a trencher attachment to a CUL, you effectively create a machine capable of trenching depths up to 24, 36 or 48 in. at widths between 2 and 8 in., depending on the attachment. Typically, you’ll find that most trencher attachments require between 10 and 14 gpm of hydraulic flow with around 2,750 psi from the carrier. All the big brands offer a variety of trencher attachment options — Ditch Witch, Bobcat, Vermeer, Toro, Ramrod and Compact Power. Trencher attachments are also offered from third-party OEMs like CEAttachments and Lowe.

Like dedicated trenchers, the range of options and features focus on steely teeth — from carbide-tip cutting edges to sharpened shark teeth (which cut through the toughest terra firma). There are also other options. Toro, for example, offers a 2-ft boom for depths up to 29 in., as well as a crumber that helps to remove excess material from the trench.

“To ensure that your trencher attachment will perform at peak performance with your compact utility loader, it is best to consult your dealer,” advises Lawrence. “Your dealer will help make sure that your compact utility loader has the right interface and hydraulic flow to perform with a particular attachment. Another important thing to check out when selecting a trencher attachment is the visibility to the trencher boom.”

As far as safety is concerned, most trencher attachments come equipped with a personnel restraint bar, located over the digging chain, for operator protection. Additionally, many CULs offer an operator’s presence system, which disables the attachment (i.e. trencher) controls and/or the drive control if the operator is not in the correct position on the unit.
Obviously, if you don’t have a CUL, then you are looking at a $10,000 to $20,000 price tag on top of the trencher price, depending on the manufacturer and features. If you already own a unit, a trencher attachment is a natural extension of your existing machine and will set you back about $3,000 to $7,000.

Dedicated to Digging

While keeping your options open and being able to change tasks at the click of a quick-attach plate is great for some, others are looking for a dedicated machine that knows its craft and gets the job done quickly. Dedicated walk-behind trenchers are made with only digging in mind, so they typically have higher production rates and are a bit easier to maneuver in the trench.

“Dedicated units usually gain a contractor additional production because it is a dedicated unit, meaning that all horsepower and hydraulic flow is going to the trencher itself,” says Fritchey. “Whereas, in the CUL and attachment scenario we have horsepower and hydraulic flow being utilized not only by the trencher attachment, but also wheel motors and track drives.”

The full-time trencher tends to have a slightly larger range of cutting options — from 18 to 48 in. deep and 3 to 8 in. wide — and offers the typical types of raise, lower and engagement controls for easier operation. With the dawn of the hydraulic age, most dedicated trenchers have also gotten away from mechanical drives and are now hydraulic beasts of burden. Mechanical drives are a trenching symphony of gear boxes, shafts, pulleys, chains and sprockets to spin the chain and move the boom. Hydraulic drives, on the other hand, have fewer maintenance points, less controls for the operator and a seemingly infinite number of chain speeds to choose from. Hydraulic drives also tend to be more forgiving when taking big shock loads.

“A hydraulically-driven trencher allows for the chain to be operated in reverse mode, if the digger chain encounters an obstacle such as a tree root so that the chain can be removed from the obstacle to prevent wear and tear on the attachment,” Fritchey explains.

In the ever growing list of features and options each manufacturer has a unique system that sets its machines apart. For instance, Vermeer machines offer ground drive assist, which helps an operator trench a straight line, reducing the amount of physical labor required while trenching.

In Terms of Safety:

“Each manufacturer may take a little different approach, but we are all making every attempt to keep the operator back at the controls where he or she belongs,” says Bob Wren, training manager for Astec Underground. “Yet, we must combine this with ease of operation, a minimal amount of controls and machine balance. These features alone add to the safe operation.”

Maintaining the Digger

Routine maintenance on a trencher attachment can spell the difference between a productive, profitable attachment and an unexpected breakdown. Under proper use, the maintenance and repair costs of a trencher attachment are minimal compared to the amount of work you can accomplish with a well-maintained piece of equipment.

Because trencher attachments have many ground-engaging parts, it’s typical for some components to wear with use over time. The most commonly affected parts are the trencher chain and trencher bar. Although parts inevitably wear with time, the following routine maintenance tips can help extend their life.

Retain Proper Chain Tension — This is one of the most important maintenance procedures you can perform on your trencher attachment. When a chain is tensioned too loosely or too tightly, the trencher will not perform to full potential, prematurely wearing parts due to unnecessary stress. This stress can cause wear on the inside of the chain, trencher boom, roller and drive sprocket. Chain tension refers to the chain sag from the bottom of the trencher boom to the top of the chain. This ‘sag’ needs be maintained at 2” to 3”. When working in wet soil types that collect on the chain, the adjustment should be at 3”. Remember to clean the chain prior to making any adjustment. Chain adjustment is made by moving the boom by turning a threaded screw and lock nut. As a general rule, if the threaded screw is on the backside of the boom, turn counterclockwise to decrease chain sag. If the threaded bolt is in the boom, clockwise rotation will decrease the chain sag.

Check Chain Wear — Chains wear at each pivot point at each link. To properly check chain wear, the chain needs to be removed from the trencher and boom and laid out straight on a hard, level surface. Wear should not exceed 3% from when the chain is fully collapsed to fully extended. To calculate wear, lay out the chain and then push it together on each end so the chain is at its shortest length. Use a tape measure to measure the length of the chain from end to end, marking the points at which the chain is measured. Pull on each end of the chain until it is extended to its fullest length and measure at the same marked points. The chain should be replaced if there is more than a 3% difference between its collapsed length and fully extended length.

Examine Tooth Condition — Trencher teeth come in three basic styles: “cupped” for breaking up loose soil, “rock” used in loose rock, and “bullet” for use with solid rock. Many of these tooth styles include carbide inserts on their sides, tops or faces. When this carbide is worn flat or worn away, the tooth needs to be replaced. Teeth may look similar, but they can vary by height and the cup depth. Mismatched teeth to OEM specification can put additional load on a trencher or power unit and can shorten the life of a hydraulic system.

Grease All Moving Parts — Many types of attachments allow for greasing of moving parts such as the nose roller, trencher head, or parts of the drive mechanism. Routine greasing with a grease gun will improve the performance and life of the trencher attachment. In addition, check the oil level on the trencher power head to ensure it is full.

Chains Do Not Need Lubrication on a Regular Basis — If a chain is being placed into long-term storage, it needs to be cleaned, and the chain pivot points should be lubricated with a spray lubricant.

Dig In, Trench Out

A dedicated trencher and a trencher attached to a CUL are very similar creatures. Your prime objective is to dig a trench as easily and quickly as possible. Sure, the argument could be made that if you are trenching then you should get a dedicated trencher; it cuts down on the time it takes to swap attachments and connect hydraulic oil lines, especially since those lines are typically too hot to touch after operation. Yet, the CUL does offer prime jobsite versatility — and if you already have one, an attachment just makes sense.

When you cut right into it, you find what will be the best fit for you. Dedicated trenchers will run around $9,000 to $12,000, which is typically a bit less than a stand-alone CUL (without the trencher attachment). Being that the dedicated trencher is also no stranger to the rental market, trying out a trencher for a weekend might be the best idea.

Like a clawed mammal digging at the base of a rotten tree stump or into soft soil for grubs and termites, dedicated walk-behind trenchers and trencher attachments both have a tenacity for tearing into the earth. It’s just a matter of determining which breed of the trencher species fits your worksite habitat.

Jason Morgan is assistant editor of Compact Equipment.