An underground report

The loader-backhoe, regarded as the primary multipurpose excavation machine for construction projects, has performed many functions on the job site. The dual-purpose, tractor-mounted loader-backhoe (TLB) is highly mobile and can dig trench and other excavations; load excavated spoil into trucks; and efficiently move spoil, gravel and other materials around.

However, compact excavators are becoming just as visible as TLBs on many U.S. project sites, and many electrical contractors routinely use them to install underground electric conduit and cable to serve residential and commercial areas, for roadside lighting, for traffic signals, and to bury telecommunications duct and cable.

An obvious advantage to compact excavators—generally defined as machines with an operating weight of 16,000 pounds or less—is they can work in spaces where larger equipment can’t go. Their rubber tracks are suited for most surface conditions, their hydraulics operate smoothly and cycle quickly, and the machines are surprisingly powerful for their size.

What sets the compact excavator apart from conventional excavation equipment is its ability to offset trench next to buildings, fences and other obstacles (something no backhoe can do). This capability is made possible by a cab that rotates independently of the digging boom’s left-right pivot point, enabling the operator to offset the boom and bucket to dig adjacent to obstacles. Models can come equipped with zero tail swing—no part of the cab extends outside the width or length of the machine’s tracks allowing unrestricted rotation of the cab—which makes these machines even more versatile, especially when working in small spaces containing obstacles.

With the broad selection of attachments available, a compact excavator actually is a multipurpose tool carrier, useful for a wide range of construction applications. They are found on a growing number of electrical projects today, even though little effort has been made to promote the machines to electrical markets.

However, that may be changing.

Bobcat, best known for skid-steer loaders, is also a manufacturer of compact excavators. The company exhibited the product at the 2006 NECA Show last month in Boston.

Mark Teckenburg, Bobcat marketing manager, said key features emphasized to NECA attendees were compact size; digging performance, including breakout force, depth and spoil placement; zero cab swing on selected models; attachment capabilities; minimal ground disturbance with rubber track undercarriage; and excellent operator station ergonomics, including comfort, suspension seat, joystick controls and optional enclosed cab with heat and air conditioning.

“Compact excavators,” said Teckenburg, “are used both for new electrical construction and for repair and maintenance work. Because of their small size, they can fit in areas where larger equipment cannot go, such as between houses or buildings, and they can access back yards through gates, saving time and reducing labor costs that would be incurred if the excavations had to be dug by hand. Many Bobcat compact excavators sold to electrical contractors are long-arm models, which provide operators with excellent digging depths in a compact size machine.”

Experienced compact excavator operators say they like the feel of the hydraulic controls, which is smoother than hydraulic systems of most small backhoes—a feature that can be important for inexperienced/new operators or when digging near surface improvements or buried utilities.

Most models are equipped with a standard dozer blade, and optional attachments can quickly convert the machine to do a variety of special jobs. Among popular attachments for electrical and telecom work are buckets of various sizes and types, augers for digging holes for light and sign poles, breakers, and plate compactors.

“Another useful attachment is a hydraulic clamp designed for use with a trenching bucket,” said Teckenburg. “The clamp firmly grips broken concrete and other irregular-shaped objects for easy handling.”

Some brands offer trencher attachments. Universal quick-couple connectors facilitate changing the attachments and allow machines to use attachments made by several manufacturers.

Sizes of larger excavators are classified by operating weight stated in metric tons (1,000 kilograms or 2,205 pounds) and when the first compact imports arrived in the United States, their weights were also stated in metric tons. As the machines became more popular, some manufacturers began using pounds.

Size and weight varies with brand and model, but the smallest compact excavators are approximately 1,500 pounds—about 0.7 metric ton. The line separating top-end compacts from the smallest standard machines is about 16,000 pounds—slightly more than 7 metric tons. Popular machines for utility work are in the 4 to 5 metric ton—8,800 to 11,000 pound—range.

Compact excavator proponents point out that a loader-backhoe can only perform one primary function at a time. If a machine is moving gravel and excavation is needed, it has to stop loading in order to start digging. An alternative is two machines: a compact excavator and skid-steer loader with the cost for both, depending on sizes and models, being about the same as a standard TLB.

Bobcat actively promotes a two-machine package of compact excavator-skid-steer loaders promoted as the Bobcat System, and Teckenburg said the concept is very well received.

“The two-machine system allows the excavator and loader to work simultaneously for optimal productivity,” he said. “And if a machine is no longer needed at one job site, it can be moved to another site to maximize efficiency.”

But do not expect the TLB to disappear from job sites any time in the near future.

A 2004 Underground Construction magazine report considered whether compact excavators were impacting TLB sales. The consensus of representatives of Case, Caterpillar, and John Deere—all companies that market both products—was that demand remains strong for both types of machines with each offering specific advantages.

However, the popularity of compact excavators shows no sign of slowing.Teckenburg believes the use of compact excavators will increase among electrical contractors for several reasons.

“Perhaps their strongest appeal,” he said, “is their combination of compact size and digging and reach capabilities. Weight is another important factor; compact excavators generally weigh less than larger loader backhoes and can work in tighter areas without sacrificing digging performance. Maintaining compact excavators can be less expensive than larger equipment, and they also are more fuel efficient.”

The wide selection of available attachments is another plus for compact excavators. Teckenburg said Bobcat offers more than 40 attachments. A compact excavator and assortment of attachments can be transported on a trailer pulled by a vehicle that does not require a commercial operator’s license.

It’s easy to try out a compact excavator without investing in one. They are among the most rented categories of construction equipment. Most general rental centers have at least a couple of the smooth-operating compacts. Equipment rental specialists—including the large rental chains like United Rentals—have compact excavator fleets with models in several sizes to meet the needs of customers doing a variety of construction, maintenance, landscaping and demolition projects.                EC

GRIFFIN, a construction and tools writer from Oklahoma City, can be reached at 405.748.5256 or up-front@cox.net