Compact excavators also have experienced bracket creep; the category was once capped at machines weighing 6 tons, then went up to 8 tons, and currently includes units weighing 10 tons and lower. The range is now broad enough that some in the industry are defining subsets as micro, mini, midi, and compact with no adjective for bigger units.
Why the steady increase? It was partly customer demand, partly OEM one-upmanship, and partly because the market wanted to classify machines more accurately. A lot of 8-ton machines, for instance, really were significantly bigger than 8 tons.
Overall performance
To meet Tier 4 Final requirements, many models that had 35- to-40-horsepower engines now have engines of less than 25 horsepower. At the same time, hydraulic systems have become much more efficient. “We’re getting more hydraulic horsepower per unit of engine horsepower,” says
Customers need to be mindful of the relationship between engine power and hydraulic power, says Mark Wall, product marketing manager, John Deere. “The important thing is to have enough engine power and torque to drive the hydraulics,” he says. “Any more than that is wasted.” Demo the machine in your application with your operators and with any attachments you plan to use.
RELATED >> Caterpillar’s new 304.5E2 XTC is half excavator, half skid steer
Also check that the machine performs multiple simultaneous functions smoothly at the same time. This requires hydraulics that are not only powerful but sophisticated. Terex uses axial piston, variable displacement hydraulic pumps and motors to provide both load-sensing and load independent flow division (LUDV). “With a load-sensing system, the pump senses the operator’s commands and directs oil flow to that function without stopping the other functions,” says Gregg Warfel, compact division sales manager, Terex Construction Americas.
Manufacturers typically list breakout and lift figures using the standard configuration for a machine and usually cite a reference bucket used in obtaining these specs. Connor says customers need to be aware of how these requirements influence specs. A machine that comes standard with a quick-attach may show lower lift capacity because of the added weight. And lift capacities will vary depending on whether a bucket was used in calculating those values. “It’s also important to remember that breakout forces are theoretical values derived from mathematics that assume 100 percent efficiency. They’re helpful for comparison but don’t reflect the absolute performance of a machine on a jobsite,” Connor says.
Attachments
If you know you’ll be using your compact excavator with attachments, make sure it’s spec’d right. “The most important aspect is to ensure you have the correct auxiliary lines,” says Jordan Dey, compact excavator specialist, JCB. “Is there a need for high or low flow? Single or bi-directional flow?”
Some attachments have multiple circuits with dissimilar flow requirements. David Steger, national sales manager for Takeuchi, says these typically fall into two categories: positioning and work. He cites shears as an example. A shear would need low flow for rotation (a positioning function) and high flow for the shearing action (a work function).
Swapping attachments and buckets is much easier with a quick-attach, but because a quick attach increases the distance from the pin to the cutting edge of the bucket it reduces breakout force.
In theory a quick-attach allows the operator to change attachments from the comfort of the cab. In practice, says Steger, this isn’t necessarily so. “A secondary lock or the need to make hydraulic connections will still require that the operator get on the ground.”
Applications
Comrie says many of the attachments he’s seen in these specialty applications are one-offs, made by the owners. “Oil and gas contractors are making their own pipe clamps, specialty buckets, boring tools, and winches for pulling oilfield hardware. They have tasks for which no commercially-made products exist.”
Among the mass-produced attachments are a variety of buckets, including some that tilt and rotate. But even with a stock bucket a compact excavator offers excellent digging performance. Compared to a backhoe, Comrie says an 8-ton compact excavator has comparable dig depth of around 14 feet, is easier to maneuver, and has 360 degrees of use. “It will simply out-dig the backhoe.” He says contractors often pair a compact excavator with a skid steer loader.
Comfort
Electronics are used to manage engines and pumps, but are not used in controls. Pilot hydraulic controls are used instead. They’re favored for their simplicity, low cost, and good feedback.
Kurt Moncini, senior product manager for excavators and crawler dozers, Komatsu, says ease of entry and exit are important comfort features since operators are in and out of the cab several times during the day. Key features are flip-up foot pedals, a tilt-up left arm rest, and a sliding door that, unlike a hinged door, opens fully even in confined spaces. “In addition the sliding door resists rattling and is less likely to be blown closed by high winds,” says Moncini.
Because “compact” now covers such a wide range of machine sizes, not all comfort features are available on all sizes of machines. Corey Rogers, marketing manager, Hyundai Construction
Serviceability
The development of long-life coolants, synthetic lubricants, and advances in additive packages for engine oils as well as cleaner-burning engines greatly extended PM intervals in the recent past. But that extension has leveled off and isn’t likely to dramatically increase anytime soon.
Right sizing
Since the development of features has occurred across the full range of compact excavators, the choice comes back to size. But be careful of basing the choice on size category alone, says Katie
Pullen says for customers it all comes down to profitability which at its simplest is production revenue minus cost of ownership. “The right choice is the machine that meets all your needs and provides the best overall performance, regardless of how it is categorized.”