Equipment Type

Your Next Backhoe Could Be A Mini Excavator

Buyer demand is growing the compact excavator from a shovel with a seat to a production digging machine

October 14, 2010

Mini excavators are so many different things to so many different buyers that the industry can’t agree on the size range that defines “mini.” Miraculously, diverse buying influences have unanimously brought about just two product-development trends.  

(See bottom of this page for specifications chart.) 

 

First, sophisticated hydraulic and control systems designed to make full-sized excavators more productive and efficient keep finding their way into 6-metric-ton (13,200-pound) and smaller machines—what has traditionally been thought of as mini excavators. Reflexively, features invented for mini excavators such as minimum swing radius and swing booms keep showing up on machines bigger than 6 metric tons.

It helps to remember that outside North America, for the most part, mini excavators replace skid steer loaders and backhoe loaders. Product development (by mostly off-shore manufacturers) tends to be geared toward a user who is more likely to move a lot of material most days with the mini rather than renting one occasionally to dig a hole they can’t reach with larger excavators or backhoes.

Transportation is more limited in most of the rest of the world, too, as 350-plus-horsepower pickup trucks are pretty much a North American phenomenon. So world mini excavator users want their 2- or 3-metric-ton minis to have some of the productivity enhancers seen on full-size machines.

Kubota, for example, uses variable-displacement pumps and increased pump capacity on its 3,800-pound (1.7 metric tons) U17 to boost productivity on the newest version of this model with 39-inch track width. Controls can be switched from ISO to SAE patterns—allowing the operator to use either hand to control the bucket or dipper—by throwing a pattern-selector lever.

Use of pilot hydraulic circuits has made the control-pattern selector a pretty common convenience on mini excavators. Pilot hydraulics relay the operator’s control inputs through a lower-pressure hydraulic circuit to the valve operating under full system pressure. Operators can use a softer touch to control the machine, and joysticks can be shifted around with the seat or armrest for a custom fit to the operator’s preferred seat position.

Other control refinements include moving the swing-boom and auxiliary-hydraulic controls off the operating-station floor. Bobcat’s M-Series machines, for example, position a swing-boom rocker switch in a joystick under the operator’s thumb. Joystick-mounted buttons or triggers are becoming common proportional controls for auxiliary hydraulics.

Bobcat M-Series machines, currently ranging from 7,000 to 19,000 pounds, employ cushioned boom, stick and bucket cylinders for smoother stops at the end of stroke. It’s another big-excavator feature that helps take a jolt out of less-experienced operators’ regular movements. Cushioned cylinders are still reasonably rare in mini excavators, but don’t be surprised if they start showing up in more competitors’ machines—it’s the kind of advance that helps operators stay productive through a long day in the seat.

In what may be the ultimate example of big-excavator hydraulics used on smaller machines, Caterpillar has added its boom-and-stick regeneration circuit to D Series mini excavators. The system saves the hydraulic energy generated as gravity pulls the boom and stick down into the hole and then reuses it to assist the boom-lift and stick-out segments of the digging cycle.

All diesel engines in 9-metric-ton and smaller excavators (they’re all less than 74 horsepower) have had to comply with the Environmental Protection Agency’s Tier 4-Interim emissions limits since 2008. Technology needed to satisfy the regulation encourages the use of an electronic governor. As has been the case with emissions thresholds that have brought electronic control to larger engines in full-sized construction machines, the addition of a computer to mini excavators has inspired increasingly sophisticated systems.

Electronics have allowed auto idle to be added to many mini excavators. The big-excavator feature drops engine speed to idle automatically after a few seconds of joystick inactivity.

“Normal engine speed resumes when a hydraulic function is activated,” says Brian Rabe, product manager for Gehl compact excavators. “This feature conserves fuel, up to 15 percent in some applications, and functions without input from the operator.”

Auto idle recently became a standard feature on Gehl’s 603, 753Z and 803. Some makers—Case and New Holland, for example—offer the operator a one-touch decelerator that reduces engine speed to idle with the tap of a button. A second touch returns the engine to the operator’s choice of working speed.

Electronics control work mode selections, which are making increasing appearance on mini excavators. Most commonly, the choices offer improved fuel economy in lighter-duty work or establish swing and boom priority for faster digging.

Caterpillar’s standard Cat Tool Control System offers similar interface between electronic controls and the hydraulic system. Tool Control allows the operator to set up the flows and pressures for up to 10 attachments using the in-cab monitor. Tools will then be ready to work at the touch of a button, without manually resetting the hydraulic system. Takeuchi, another leader in the category, offers similar auxiliary-hydraulic control.

Kubota makes a programmable-key electronic security system (similar to Caterpillar’s optional Machine Security System) standard equipment on its new 48-horsepower, 12,000-pound models: the tight-swing U55 and conventional KX057-4 excavators. Bobcat offers a keyless-start option on its Dakota-built M-Series machines (E32 through E50).

Komatsu is first in the industry to make telematic fleet-management electronics standard equipment on compact equipment. As with most versions of Komtrax (or Cat’s Product Link, or Deere’s Deere Trax, or others), the system uses the global positioning system (GPS) and cellular communication to enable users to pinpoint machine location and obtain real-time operating data.

Even the smallest mini excavators, such as Kubota’s 3,800-pound (1.7 metric tons) U17, are often equipped with electronic monitor panels for delivering operating temperature and pressure information.

The best-selling mini-excavator sizes in North America can dig about 10 feet deep and typically weigh 7,000 or 8,000 pounds (3 to 3.5 metric tons). It’s no coincidence that this is a reasonable conventional-trailer-hitch load for a ¾-ton pickup truck (F-250 or 2500 Series). An operator without a commercial drivers license can legally tow one of these on most North American roads. Contractors, builders, landscapers, facilities managers, ranchers and, most importantly, rental companies can usually come up with a ¾-ton pickup and somebody to acceptably tow a trailer with it.

Depending on the variable fleet-spending dispositions of rental firms, they buy about three out of four excavators weighing 6 metric tons (13,200 pounds) or less in North America. Nobody has more difficulty with operator skill, and the accompanying liability and machine damage, than rental firms. That’s one of the key reasons zero-tail-swing, or minimum-swing-radius machines have become so common among mini excavators.

The idea is that little to none of the excavator’s rotating upper section sticks out beyond the edge of the tracks when the house turns. Operators are less likely to hit jobsite obstacles with a minimum-swing excavator’s counterweight, so machine damage and risk of lawsuit are both nicely reduced.

The short-swing feature, swing boom and backfill blade have become distinguishing features of the traditional mini excavator, a category defined by the Association of Equipment Manufacturers as machines weighing 6 metric tons (13,200 pounds) or less. But those same features have proven attractive enough to help extend the mini-excavator category into larger machines.

When the excavator’s boom is mounted on a hinge at the base of the excavator upper, it is called a swing-boom or offset boom. The feature allows the operator to offset the boom and stick from the center line of the excavator so that it can dig a trench parallel with the tracks just at, or sometimes beyond, the outside edge of the track.

An excavator in offset position can expose a foundation or dig along a fence line like a backhoe loader. Better than a backhoe, once it digs all the trench it can reach from a location, the operator simply tracks forward to extend the trench. And the rotating, short-radius house gives the mini excavator a much broader range of reach for casting spoil further from the excavation or loading it into trucks. The mini with offset boom can also dig square footings of its own track width without repositioning.

Several makers offer power-angle backfill blades to further improve productivity. That fact was not overlooked by some utility, sitework and foundation contractors in North America.

“They (mini excavators) can fit in places where loader backhoes and mid-sized excavators can’t, and their rubber tracks (compared to wheels) provide very low ground pressure; so they won’t tear up the existing landscape,” says Curtis Goettel, marketing manager, Case Construction Equipment. “Their tracks provide the same benefit in operation on dirt, mud and wet areas, whether digging or grading. Their overall versatility allows them to be used in many different applications and essentially keeps them running while on a jobsite regardless of conditions. This tends to mean they pay for themselves quickly and operate at low costs per hour during their life cycle. In the end, the contractor can charge less to the customer and put more profit in his pocket.”

Until six or seven years ago, one limiting factor to the mini excavator’s North American spread was that the biggest models with offset digging capacity were 13,000-pound (6 metric ton) machines that could only dig about 12 or 13 feet deep. The traditional mini excavator size range is fine for rental firms, but most contractors who could use the combination of boom offset, minimum-swing-radius, and backfill blade were accustomed to backhoe loaders that can dig 14 feet deep or more.

In the first half of this decade, there weren’t many excavator models of any kind in the 15,000- to 20,000-pound (7- to 9-metric-ton) range. As manufacturers have filled that gap, they’ve tended to do it with machines that have the features smaller mini excavators had been using to displace backhoe loaders: swing booms, minimum swing radius, and backfill blades. Now there are models over 8 metric tons with maximum dig depths around 14 feet from Kubota, Bobcat, Caterpillar, Takeuchi, John Deere/Hitachi, Komatsu, Volvo, Yanmar and Case. Bobcat is talking about a refinement of the reduced-tail-swing concept as a market distinction. Most mini excavators are designed with the cylinder that adjusts the swing-boom angle on the right side of the boom.

“And most operators would love to be able to look through the door, rather than over the instrument panel to see where they’re digging,” says Tom Connor, Bobcat excavator product specialist. So they position the machine with the right track against jobsite obstacles, swing the boom to the left, rotate the cab right, and dig over the right track.

“On most machines, if you do that you have a boom-mount casting and the fully retracted cylinder sticking out beyond the right track,” says Connor. Depending on how close you position the machine to the obstacle, there can be contact. Bobcat moved its swing-boom cylinder to the left side of the boom, still offering the most boom swing to the left, and calls the feature an “in-track swing frame.”

Connor says it allows the excavators to actually dig a little beyond the right track width without the risk of hitting anything with the swing frame. Similarly, Yanmar describes its mini excavators with a “turning radius so small that the boom bracket stays entirely within the tracks.”

New mini excavators range in price from $19,000 to $90,000 for 6-ton models and significantly higher as you progress up to 9 metric tons. Cost-conscious buyers, particularly of the traditional under-6-ton models, can take advantage of great used deals spinning out of rental fleets; deals that get really juicy when rental firms are suffering in a housing-construction downturn.

Choice of steel or rubber tracks is common. Several makers offer small machines with minimum track widths narrower than 40 inches to help them squeeze through pedestrian gates and doorways, and systems that telescope the track width for a more stable footprint at work.

Two-speed travel motors are pretty common, and many now automatically shift between ranges depending on travel load.

Auxiliary hydraulic plumbing to the end of the stick is typically standard equipment on mini excavators. With bucket thumbs being prevalent in mini excavators, Caterpillar has made thumb-mounting brackets standard equipment. Komatsu sells select models thumb-ready.

The market is dense with mini-excavator offerings and rich with productive features. Anybody who carefully considers the reasonable limits of their own needs and the features available to meet them will inevitably find a cost-effective solution among today’s small excavators. It might make sense to buy big within the range and rely on ubiquitous rental fleets to supply machines under 8,000 pounds (3.5 metric tons).

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