You’d be hard-pressed to find a single machine on a construction site that offers more versatility than a midsize excavator.
Offering more time-saving performance than a compact excavator and much easier to transport and far more agile than the large excavators, midsize excavators are right at home on a wide variety of residential, commercial and public works projects - from excavating basements and septic systems and digging footings and utility trenches to loading trucks, laying pipe, shaping slopes and grading roads. What’s more, they offer the latest in performance-boosting, comfort-enhancing and maintenance-reducing features - all in the name of making you more productive.
For example, Kobelco midsize excavators include an auto warm-up system. Activated when oil temperatures drop below 50 degrees F, it keeps both the engine and hydraulic oil at the proper operating temperature for maximum efficiency. A full-size cab, foot-operated boom swing circuit and an orange backlit monitor enhance operator comfort.
A power-boost button gives John Deere midsize excavators extra hydraulic muscle when needed. Large idlers, rollers and strutted links, and sealed and lubricated undercarriage increase reliability, while 500-hour engine oil and 5,000 hydraulic oil service intervals minimize maintenance costs.
Hyundai midsize excavator cabs come standard with comforts such as heated air-ride suspension seats, height-adjustable control consoles for optimal access to joysticks and transparent skylights for a better view of raised buckets
A WIDE SELECTION
Just how big is a midsize excavator? That depends. There’s no universal agreement among manufactures as to specific limits of this category in terms of engine horsepower, operating weight, digging depth, reach and the like. The Association of Equipment Manufacturers classifies excavators weighing no more than 6 metric tons (about 13,200 pounds) as compact machines.
Corey Rogers of Hyundai Construction Equipment considers excavators weighing between about 9 and 45 metric tons to be midsize machines. John Deere’s midsize models range in weight from 8 to 35 metric tons.
Within the 7-ton to 45-ton size, maximum digging depths can range from about 14 to 25 feet with a digging reach of about 25 to 40 feet. The smaller models can be towed on a trailer behind a tandem-axle dump truck for easy transport, even in rush hour traffic. Meanwhile, the larger midsize units can be hauled on a low-boy without requiring special permits.
“The 20-ton excavator is the bread-and-butter size of the mid-range machines,” says Matt Hendry, an excavator consultant for John Deere Construction & Forestry. “It’s the number one model, representing the largest amount of all midsize excavator sales. Most contractors who use midsize excavators will have a 20-ton machine in their lineup. This size is easy to transport, big enough to do substantial projects and small enough to handle smaller projects efficiently.”
A BIG ROLE
“A midsize excavator is the quarterback of the jobsite,” Hendry says. “Because of its ability to be a production tractor in many different applications, other machines support its operations. With the right operator, a midsize excavator can do a significant amount of work. You’re limited more by your imagination in how to use it than by the limitations of the machine itself.”
Consider John Deere’s 200D excavator, its 20-ton model. Able to handle a 42-inch bucket, it has a maximum digging reach of 32 feet, 7 inches to minimize the need to reposition when digging and loading. It can dig an 8-foot flat bottom trench as deep as 21 feet, 4 inches, for pipe installations. And, it has the strength to lift 36- to 42-inch diameter concrete pipe at full reach.
Equipped with a grading bucket, a midsize excavator can do many backfilling and grading jobs. In the tight confines of today’s residential developments, for example, this machine can reach between closely-spaced houses to cut grades and drainage swales where a dozer wouldn’t fit. Other uses for grading buckets include backfilling foundations, spreading dirt on a yard or grading a driveway.
Midsize models with a conventional tail swing are the most popular choice. However, those with a reduced tail swing - minimizing the length of the upper structure that extends beyond the side of the track when the house is rotated - are becoming more popular, especially in the tight quarters of urban construction projects. To compensate for the reduced stability of a short tail swing, manufacturers increase the amount of counterweight.
For example, John Deere’s 200D, with its conventional swing radius, weighs 49,000 pounds. The reduced tail swing version, the 225D, weighs an additional 5,000 pounds. Another difference is that the boom of the 225D is pinned farther back and higher on the house. This placement allows the boom to retract far enough for the house to rotate within the shorter radius. “You lose a little digging depth and reach with the reduced tail swing design, but you have the ability to work more efficiently in tight areas,” Hendry says.
OUTFITTING CONSIDERATIONS
Because midsize excavators use tracks primarily to move the machine rather than to provide traction, most are equipped with triple grouser tracks. This style of track causes less damage to sensitive surfaces than a single grouser design that offers more traction. Most manufactures offer two or three choices of track widths. A narrow width is better suited for working in hard, rocky conditions, while the wider track provides more flotation for working in soft conditions.
Demand for rubber tracks on smaller midsize excavators is growing, reports Paul Golevicz of Kobelco Construction Machinery America. “They’re popular with owners who drive across roads and curbs and don’t want to mark up the pavement,” he says. “Steel tracks with replaceable rubber shoes are also becoming more popular. That way, if a rubber shoe gets damaged, you don’t have to replace the whole track.”
It’s important to match a midsize machine with the right size of bucket or other attachment. Otherwise, production may suffer,
“Many contractors mistakenly believe that the bigger the bucket the higher the production,” Hendry says. “However, the critical factor is how fast you can complete a digging cycle. With the right size bucket, one that makes most efficient use of your arm and bucket breakout force, you can minimize cycle times to complete more work in a day than you could with a larger bucket that slows your machine down. That’s true of any excavator.”
FEATURES AND BENEFITS
The latest midsize excavators offer a broad array of technological advances. Here are just a few examples:
More productivity
The first such excavator in the United States, Kubota’s KX080-3 8-ton utility class model, features an expandable boom. Called the Super Double Boom, it allows you to work closer to the machine, reach farther, dig deeper and level wider ranges than a standard boom machine. “It provides a wider working range than many larger excavators,” says Keith Rohrbacker, Kubota product manager. It also offers a dumping height of just over 20 feet, and a digging depth of slightly more than 15 feet.
A foot pedal controls boom extension and retraction. “The boom brings the bucket more than three feet closer to the machine, making it easy to hold soil in front of the blade when leveling, while eliminating the small piles of rocks and rubble often left by a standard boom,” he says.
Easier, more precise control
John Deere midsize excavators are equipped with a single mode hydraulic system. Instead of dialing in mode and hydraulic settings to get the desired level of machine performance this system does it for you. “The more you pull on the control levers the more power this system provides,” explains Hendry. “For example, you can pick up a box culvert, crane it over to a trench and put it in place without touching any settings. By making precision control easy, it makes you more productive.”
The auto-deceleration on Hyundai machines reduces engine speed in three stages for faster engine speed recovery and better fuel economy. When hydraulic control levers are left in neutral position for one second, engine speed drops 100 rpm. After another four seconds in neutral, engine speed drops to high idle and, a minute later to low idle. Also, the new Posi-Nega hydraulic control system gives operators extra precision for controlling boom, arm and swing functions.
Quieter operation
The advanced air flow technology of the Integrated Noise and Dust Reduction feature on Kobelco midsize excavators draws cool outside air through integrated vents. This air is pre-filtered before entering a two-stage engine air filter. High volume air cools the radiator, hydraulic oil cooler, turbo intercooler and engine compartment before it’s exhausted through the upper rear vents of the excavator. “It makes the 70SR and 80CS models quieter than many compact excavators,” Golevicz says. “What’s more it increases fuel efficiency up to 10 percent.”
At the same time, the hydraulic proportional control system on John Deere’s D series midsize machines makes them 7 decibels quieter than the previous series.
Fuel-saving features
Hyundai’s new 9 Series midsize excavators feature engine, electronic and hydraulic technologies to boost fuel efficiency. Those advances include a variable speed fan clutch that reduces fuel consumption up to 10 percent.
Kobelco’s Intelligent Total Control System maximizes engine and hydraulic performance to conserve fuel and optimize power management. It manages hydraulic output to the swing, travel and implement circuits with proportional control, Golevicz notes. Also, it enhances digging capability and provides smoother control for fine grading and leveling work.
