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Compact excavators are designed to solve just about any problem you face in digging efficiently and profitably in confined areas. Whether you want a basic solid machine or one equipped with the latest in hydraulic, electronic, and ergonomic sophistication, you have plenty of choices. By Greg Northcutt |
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If you haven't already noticed, compact excavators - those mini machines weighing no more than about 6-8 tons - are getting bigger. Not that they're growing in stature or engine size. Instead they're shouldering more and more of the work in the excavating business where working room is scarce and time is short. They're not only doing the work once done by larger equipment, such as tractor-loader-backhoes and labor crews, but they're doing it faster, easier, and more profitably. In North America, annual sales of compact excavators have increased probably four- to fivefold over the last half a dozen or so years to some 10,000 units, depending on where you draw the line for the largest such machines. One reason for their growing popularity is the shrinking size of job sites, as project owners repair and rebuild aging structures in crowded urban areas and developers squeeze more homes into ever more expensive land in the suburbs. What's more, compact excavators are becoming increasingly sophisticated in terms of digging and loading performance and operator comfort and convenience. The efficient size of these machines means they cost less to buy, operate, maintain, and transport than larger equipment. In addition, the compact machines operate more quietly and with less impact on sensitive surfaces than their larger brothers.
In short, these machines are proving that bigger isn't always better. "It's a question of efficiency on the job site," explains Pieter van den Assumm of Lely Corporation Inc. "While a machine costs you money when you buy it and maintain it, labors costs you money every day. Do you want a crew of four people waiting for a big excavator to show up and then finishing the job and repairing any disturbance to the site with hand tools? Or do you want a pair of two-person crews working with two smaller excavators who aren't standing around while the big machines travel to the job and who don't waste [time or money] doing much cleanup and repair work afterward?" The time, labor, and money-saving abilities of miniexcavators are paying off in a wide range of applications-digging trenches for power, cable TV, and fiber-optic lines; water mains; sanitary and storm sewers; building retaining walls; excavating for foundation repairs, footings, swimming pools, septic tanks, and drain fields; drilling holes for planting trees; removing tree stumps; and even finishing jobs started by larger excavators. More and more contractors are achieving even more job-site efficiencies by teaming up their small excavators with other compact machines." That trend is definitely increasing," says Chad Ellis, Daewoo's national service manager for compact equipment. "Contractors are replacing tractor-loader-backhoes with compact excavators and skid-steer loaders. They can buy both of the smaller machines for the same price as a traditional backhoe and benefit from the increased versatility of the compact equipment." These small machines earn their keep when the work site is too small for large-capacity equipment to work efficiently, if at all. Since they're easier to operate in such tight quarters, the compact machines also help reduce operator fatigue, increasing productivity even more. For example, while the miniexcavator is digging a trench in a tight passageway and using its 360( house rotation to dump spoil in the best spot, the skid-steer loader can be removing the spoil and loading it into a truck at the end of the narrow alley. In fact, some of the compact equipment is small enough to fit through normal doorways to tackle excavating jobs inside factories, stores, schools, and other buildings. In addition to compact size, miniexcavators offer other advantages over a center-mount backhoe: 360 degrees House and Work-Group Slew. The house (cab, engine compartment, and hydraulic system components) and the work group (boom, dipper or arm, and bucket or other attachment) can turn in a complete circle for unlimited spoil dumping and truck-loading possibilities. This also reduces operator head movement for more comfort without sacrificing visibility. Tracked Undercarriage. While some compact excavators travel on four wheels, most are equipped with tracks. Besides eliminating flat tires, tracks generally reduce ground pressure to less than 5 psi. That compares to around 35-40 psi exerted by a conventional backhoe or a skid-steer loader. This lower ground pressure eliminates ruts in soft ground, allowing a miniexcavator to work in muddy conditions where rubber-tired machines could bog down. Tracks also improve traction on hard, slick surfaces and enable the machine to run across open trenches. In addition, the counterrotating tracks allow an excavator to turn completely around within its own length for easy maneuvering in tight spaces.
Independent Boom Swing. A swing frame allows the work group to pivot hydraulically 50-90( left or right, depending on excavator make and model. This feature—coupled with house swing-enables the excavator to dig around obstacles or alongside buildings, fences, and other structures. This reduces repositioning time by allowing the tracks to remain parallel to the trench. Using the full range offset, it allows the machine to dig a square hole the width of the excavator, for example. In extreme working conditions, it can be used to cycle the work equipment where there's not enough room to rotate the cab. Backfill Blade. This multipurpose tool can be used for more than backfilling a trench or grading a job site. It also serves as a stabilizer. This blade can be used to level the machine in uneven terrain and to increase digging depth or dumping height. Also, when combined with the bucket, it can pry out and move large rocks and other objects. Hydraulic Joystick Controls. These pilot-assisted controls minimize arm effort and movements to reduce operator fatigue. When it comes to shopping for one of these nimble machines, you can select from a number of models produced by more than two dozen manufacturers. However, all those choices can complicate the task of finding the excavator that best fits your needs. In fact, at first glance, except for size, the various models now on the market might look pretty much the same. So look closely when comparing machines, advises Dan Klug, excavator product marketing manager for Bobcat. "Despite all the apparent similarities, there are big differences among compact excavators when it comes to productivity and operator comfort and convenience," he says. Among the decisions you'll face: Size Versatility
Maybe you need a machine with extra reach or one with an expandable undercarriage or a telescoping arm to meet varying job requirements. Perhaps a zero-swing cab is a better choice than one in which the rotating cab overhangs the tracks. And talk about versatility: The Orbiter, manufactured by Flannegan Western in Emmetsburg, IA, is a two- or four-wheel-drive compact unit with a rotating house and an optional telescoping boom that accepts excavating tools and a variety of skid-steer loader attachments on the front and rear of the machine. Undercarriage Operator Comfort
LCD monitors that display oil pressure, battery status, and fuel level at a glance; digital readout for engine hours, job hours, and engine rpm; alarms for various conditions such as low engine oil pressure, high hydraulic oil temperature, and plugged hydraulic filter; and diagnostic functions. One 5-ton all-terrain all-wheel-steer excavator can work in deep water and mud, cling to steep hillsides, straddle streams, and even scramble over walls. Here are some tips to help you narrow your search for the ideal compact excavator for your work: Job Needs. Much of the suitability of a particular compact excavator depends on the type of work you do. If most of your work involves shallow trenching or truck loading, you might be better off with a machine that offers a long reach. Some mini-models offer a maximum reach at a ground level of 20 ft. or more. Such stretching abilities mean you'll spend less time repositioning and more time excavating and moving payload. On the other hand, if you dig at a variety of depths, a machine with a more conventional reach and greater digging depth might be the best choice. Options can range from maximum digging depths of about 5 ft. to as much as around 13 ft. Site Conditions. The need to get through gates or other narrow openings or to slip under low ceilings calls for smaller machines. Several compact excavators measure no more than 2 ft., 8 in. from side to side and stand less than 7 ft. tall. The largest ones can be close to 7 ft. wide and 9 ft. tall. Performance Factors. A number of features and specifications can be used to gauge the productivity of a particular model. But keep focused on why you want a compact excavator, suggests Keith Rohrbacker, product manager with Kubota Tractor Corporation. "No machine offers you the most of everything. Somewhere along the line you have to make tradeoffs, like between a machine that will give you the highest production and one that will fit into your work spaces. Remember why you're buying the machine and beware of the tendency to buy more than you really need. At the same time, keep your future plans in mind so that your excavator can continue to meet your needs as your work changes. A compact excavator can easily last you five to seven years." Engine Power
Higher engine horsepower ratings don't equate to increased performance when it comes to compact excavators. Depending on how a machine is engineered, one model, which uses available horsepower more efficiently, can outperform another model with a larger engine. Also, since there are no transmissions or driveshafts, the engine on a compact excavator powers only hydraulic motors. So it's more important that the engine is matched properly to the hydraulic pumps. "Otherwise you could overload an engine, resulting in increased fuel consumption and overheating," says Rohrbacker. "That, in turn, can increase operating and maintenance costs." Also, keep in mind that most construction equipment, including compact excavators, operate most efficiently within a certain performance envelope. "A diesel engine operates most effectively when its running at about 80% to 90% of its maximum capability," Rohrbacker notes. "Many people like big machines with lots of power," adds Harry Lao, president of Pine Brook Construction Equipment, Inc., which manufacturers miniexcavators. "That could be a costly mistake with compact excavators. You need to look at the intended use of the machine. The price difference among the different sizes of miniexcavators can be quite significant." Digging Depth
The rated maximum digging depth is designed to provide a 2-ft. length of flat bottom when digging a trench. To dig more flat bottom, you have to move the excavator. Consequently, using an excavator capable of digging 10 ft. deep to dig a 6-ft.-deep trench will allow you to dig about 8 ft. of flat trench bottom before you need to reposition. Still, you might need to allow for exceptions. "Even if you're not digging deep but you're working in hard, rocky soil, you may need an excavator with a greater digging depth to obtain the power you need to do the job," says Klug. Digging Power Cycle Time Type of Hydraulic
Pump In the past few years, however, more and more compact excavator manufacturers have been adopting the piston pumps, also called variable displacement pumps, at least for their larger models. Piston pumps feature more expensive technology, which provides variable hydraulic flow and better pressure control. This pump produces oil flow using a rotating assembly of small pistons, which controls the oil flow independently of engine rpm and pump shaft speed. The end result is a more efficient, smoother operating system. "A variable displacement pump gives you a very good feel for the machine," says Lao. "You can tell the difference between these pumps and gear pumps immediately." Rohbacker notes another advantage. "The variable displacement or piston pump automatically switches between low flow for power when you're digging and high flow for speed using other functions. That reduces cycle times and lets you get the job done faster." That's not all. "A piston pump requires less engine power compared to a gear pump to perform different functions efficiently," adds Lao. "For example, for the same weight class, a piston pump–equipped miniexcavator with a smaller engine can outperform a gear pump–equipped machine with a bigger engine." Zero Tail Swing
On conventional miniexcavators, the edge of the house typically extends past the side of the tracks by about 12-18 in. Those with a zero tail swing eliminate this overhang, allowing you put the track right next to a wall without hitting the structure as you rotate the house to dig and dump spoil. This feature changes the physics of the machine. The tracks of a zero tail swing machine are usually widened (placed farther apart) and lengthened to provide proper stability compared to a similar size excavator with a conventional tail swing. Tracks Auxiliary Hydraulics Operator Comfort and Convenience Manufacturers continue to improve operator comfort with such features as fully adjustable suspension seats, beverage cup holders, arm rests, storage compartments for grease guns, tools, or lunch boxes; ergonomic placement of control levers; instruments that are easy to see and read; and work lights. Most makes also offer a lever or a selector to switch the joystick control pattern between ISO (the typical pattern used with excavators in which the right-hand joystick raises and lowers the boom and the left-hand joystick moves the arm in and out) and standard (the pattern found in conventional backhoes, in which the two functions are reversed). Enclosed steel cabs with windshields, sliding windows, dome lights, heaters/defrosters and air conditioners, and factory-installed AM/FM stereo radio/cassette players are also available. Noise-reducing features, such as sound-absorption materials, an inlet silencer, a resonant muffler, and an engine bottom cover, can reduce operator fatigue and customer complaints. Other considerations are ease of entry and exit and amount of operator room. Also, check the two-speed travel control. On some brands, you push a button to switch between high and low ranges. Others use a foot pedal that must be kept depressed when operating in high range. Keyless ignition, which requires users to enter a password on a keypad to start the engine, can improve security of your machine.
One feature that can make servicing compact excavators easier is conveniently located zerk fittings that allow you to lubricate the swing pinion, swing bearing, and offset cylinder from one central location. Easy access to engine servicing points and to the fuel filler, hydraulic control valve, and associated plumbing can also help simplify your workday. In addition to digging and grading buckets of various widths, you can choose among several other tools to improve the versatility of compact excavators. Some are powered by auxiliary hydraulics. Attachment choices include hydraulic breakers for breaking up concrete and demolition jobs, and plate compactors for preparing grades and augers for drilling holes for posts and poles. A hydraulic thumb or clamp allows you to grasp rocks, tree stumps, and other oddly shaped objects, while a grapple makes it easy to handle brush and other bulky material. A rotating, wristlike device can increase versatility and efficiency of some attachments by allowing a tool, such as a bucket, to swivel and operate at various angles to the arm. Several features can increase productivity when using attachments. One is a quick-changing system that allows you to switch quickly and easily from one attachment to the other without having to remove pins. Another is variable-flow auxiliary hydraulics. Unlike auxiliary hydraulics, which are either full on or full off, this type of hydraulics allows you to change the rate of hydraulic flow between on and off. That can pay off when operating certain attachments, such as a hydraulic thumb or clamp. Instead of either completely open or closed, you can gradually squeeze or release objects for more precise control. Another handy feature is a detent mode. It provides continuous flow to the attachment without the need to keep a button or switch depressed. If your compact excavator doesn't have some of the features you want, you might be able to modify it to suit your needs. For example, former construction contractor Paul Wever, president of Paul Wever Construction Equipment Company Inc. in Goodfield, IL, has been enhancing performance of large and small construction equipment since 1987. One field-installed product, the Extendavator, replaces the original dipper to extend the digging depth and reach of the excavator. Available for 5,000-lb. and larger excavators, this tool is designed to work within the parameters of the original excavator, he notes. The company also produces other products for compact excavators, including outriggers to improve stability of wheel machines, rabbit valves to add an additional hydraulic function to the excavator for less cost than adding another pump, backup alarms, and remote controls. Specifications, features, options, and the like are great for helping to narrow your search for the best miniexcavator. However, there's nothing like comparing several different models on your work site to see just how well their actual speed, power, and smoothness on the job match your needs and desires. Most dealers offer demo models. Another option is to rent several different makes for several days. Among the things to check are the feel and balance of the machines and the speed of the hydraulic circuits operating the front working group, notes Rohrbacker. "When you operate the joysticks, the boom, arm, and bucket should all work together," he says. "You shouldn't have to wait if one circuit is faster than another. That will throw off your timing and lower your productivity. Also, check the balance with a heaped bucket of spoil. If the boom cylinder is really fast and balance fore and aft isn't correct, the machine will bounce. If that happens, some of the spoil can fall off, which needs to be cleaned up, further reducing productivity. Also, bouncing around all day will take its toll on you as an operator." Greg Northcutt is a frequent contributor to Grading & Excavation Contractor magazine.
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