Compact excavators with operating weights of 3 to 4 metric tons deliver powerful digging capabilities in the most confined areas. While they can lift the occasional odd-sized object, these machines do best lending a helping hand with site development, landscaping, and demolition or utility work, such as trenching for wires, cables or pipes.
“As long as the compact excavator is matched to a specific application, it can do many of the same tasks as a skid-steer loader, track loader and backhoe, and in many cases it will do so more efficiently,” says Eric Brown, Bobcat excavator product specialist.
“We would argue that higher horsepower in an excavator can sometimes be a disadvantage,” says Bill Gearhart, marketing and product manager, Yanmar Construction Equipment. Hydraulic components distribute power to the boom, arm and bucket, or the “muscles” of compact excavators, to get the job done, Gearhart says. “If an engine supplies enough power to maximize the capabilities of the hydraulic system, adding more horsepower won’t necessarily help. It will only serve to increase fuel use and noise,” Gearhart claims.
Bobcat, however, disagrees. By increasing the engine’s horsepower, the company says its compact excavators are able to produce more hydraulic horsepower under maximum flow and pressure. The ability to use this flow at high pressures makes faster cycle times possible, the company says. “More power means more production for the operator,” Brown adds.
Today’s advanced hydraulic systems feature variable displacement piston pumps so these machines can perform multiple hydraulic functions simultaneously without lessening speed or power.
“Variable displacement pressure compensating piston pumps let the operator feel and control the machine’s pulling power, leading to increased breakout forces,” says Allen Rudd, national marketing manager, Takeuchi.
Komatsu offers HydrauMind – a closed load-sensing system – on its MR Series to monitor simultaneous functions and to ensure each function works according to its control input regardless of the load. “This gives the operator precise control, greater responsiveness, reduced operator fatigue and it enhances overall efficiency,” says David Caldwell, product manager for compact hydraulic excavators, Komatsu utility division.
Reach for it
Not only do compact excavators excel at excavating and grading with their powerful hydraulics, they also compete with backhoes in terms of maneuverability and productivity.
Compact hydraulic excavators exhibit an advantage in their ability to work in restricted areas and the limited number of times they must be repositioned while digging a trench or footer. So reach is an area that shouldn’t be overlooked. “An excavator with more reach means you don’t have to reposition the machine as often,” says Caldwell. “This applies to trenching, digging footers and picking up and placing objects.”
A compact excavator’s independent boom swing helps permit offset digging capabilities, enabling operators to dig square holes, or dig on each side of a buried utility. “This is much more difficult with a backhoe because of its size and limited visibility,” Brown says.
The offset boom design on an excavator also gives the operator optimal visibility of the arm, bucket and excavated area when digging next to buildings, fences, sidewalks or walls.
Add an attachment, such as a hydraulic thumb, and you can achieve a number of tasks, such as grabbing and securing rocks, tree limbs, pipes or debris, without having to move the machine. Landscapers may also benefit by coupling a smaller sized excavator with a bucket thumb to place decorative stone in backyards.
Another option: Use a backfill blade and watch your compact excavator backfill trenches faster than a backhoe, Caldwell says.
A compact excavator’s tracked undercarriage makes flotation possible by evenly distributing machine weight and rubber undercarriages reduce the need for repairs after positioning the machine on established surfaces.
“Tracks provide better grip and traction with less slippage in sloped or muddy areas, and increase machine stability when digging over the side of the tracks,” Rudd,says.
Most compact excavator manufacturers offer rubber or steel tracks. In addition, Komatsu’s road liner track shoes work as an alternative to purely rubber shoes, as they allow the machine to travel over asphalt and concrete without damage. “The road liner track shoes consist of composite rubber with a steel insert for added strength and rigidity,” Caldwell notes. “Due to the material used, the road liner track system has a longer life expectancy than rubber band tracks.”
Although the initial cost is higher than rubber track, road liner track shoes may be replaced one pad at a time if damaged. In comparison, cut or damaged rubber track shoes require replacement of the entire track. “Therefore, over time the replacement cost of the rubber track is much higher than the road liner track shoes,” Caldwell says. If the machine’s going to be in areas with sharp rocks or debris, an undercarriage composed partly of steel may improve your chances of minimal wear and tear.
Still making an impact
Over the past several years, zero-tail-swing compact excavators have allowed users to experience reduced rear collisions once common with conventional excavators and focus more on the work in front of them.
“Conventional excavators can do serious damage to buildings or other equipment on jobsites with the counterweight,” Gearhart explains. Not only do you improve chances of missing obstacles with a zero-tail-swing machine, it also lessens chances of pinning workers between a building or another obstruction and the machine’s counterweight.
Some companies achieve zero tail swing by widening the track gauge Gearhart says, which limits the machine’s ability to fit into narrow passageways and tight spots on jobsites. Yanmar chose to not widen the gauge to keep maneuverability key.
Limitations do exist, though. As excavators become more compact and cabins get larger for comfort purposes it becomes harder for manufacturers to increase service accessibility. “There is only so much we can do in that regard because we’re dealing with small machines and the zero-tail-swing design,” Gearhart says.
Compact excavator advancements
- Bobcat’s 430 and 435 FastTrack models offer all hydrostatic drive systems with separate piston pumps and high-torque drive motors to power the left and right tracks independently and separate from the rest of the hydraulic system.
- Yanmar’s ViO Crawler Technology with Advanced Stability (or VICTAS) track system adds stability and lift capacity over the side by moving the drive sprocket out from the center of the track. This moves the fulcrum point of each track outboard and widens the track gauge without widening the overall machine width.
- Takeuchi’s FR Series offer tilt-up operator platform for quick access to valves, pumps and the engine. The models also feature remote slew lubricating systems, automatic fuel bleed systems and conveniently located hydraulic pressure test ports
- Komatsu’s PC27MR-2 and PC35MR-2 have canopy units that use a two-post ROPS canopy instead of the commonly seen four-post ROPS canopy. The two-post canopy helps the operator maintain a clear, unobstructed view and affords easier entry and egress.