Most concrete contractors don't do extensive earthwork prior to placing concrete. There are, however, many situations where you need to do some digging, and the invention of the rubber tracked compact (or mini) excavator has been a real boon for those times.
Compact excavators are generally defined as those with operating weights less than 6 tons, and they go as low as 0.9 ton. If you don't currently have a compact excavator and are thinking of buying, leasing, or renting one, there are a few advantages over the traditional loader backhoe that you should consider. “They have the ability to get into tighter spots,” says Luke Secrest with Advanced Foundation Solutions—The Basement Guys, in Columbus Ohio. “For a long time if you wanted to do anything around your house, you had to bring in a big piece of equipment. We have rubber tracks on our equipment because of the low pressure on the ground and because we go across a lot of driveways and parking lots where it could cause damage. Also, the maintenance is less; as you get into the smaller engines, they are a lot easier to maintain. We use a lot of the small Kubota machines, and nothing ever breaks. Although the operation is pretty much the same as on a full-sized machine, it's easier to train someone to use the small stuff because the hardest thing about training someone on equipment is depth perception. When you put someone on a small machine, it's easier for them to grow into the bigger equipment.”
Another big advantage with the compact excavators is the ability to dig in the offset position (see Glossary, p. 34, for an explanation of this). With the boom slewed one way and the carriage rotated the other, offset digging allows the operator to excavate directly adjacent to an existing structure. It also allows the tracks of the excavator to remain parallel to the trench for efficient repositioning.
The limitation with compact excavators, of course, is that you have a limited digging depth and force. “But you always have some limitations on any equipment,” says Secrest. “You're not going to do a major freeway project with one.”
If you are thinking about buying a compact excavator, the first thing to consider, of course, is whether you really need one—or you just want one because they are so cool. “But if a contractor is looking at a loader backhoe,” says Brian Rabe, product specialist for Mustang, “he might be able to get a compact excavator and a skid-steer loader that have much more flexibility for about the same cost.”
So if you are going to buy one, then the first decision is size (digging depth, digging force, dump height, reach), which directly relates to the applications you have now and expect in the future. Get a machine that is big enough to do the job, but don't go too big. “If you buy a 16-ton machine and finish the job in an hour and then it just sits there for the rest of the day, that's not a good use of your money,” says Ingersoll-Rand's Georg Seyrlehner, “when you could have bought a less expensive 6-ton machine that would have finished the job in three hours.”
There are many manufacturers making these machines today (see below). Some factors to consider when, comparing manufacturers and models are:
- Cycle time refers to the cycle time on the cylinders that control slew speed and boom speed; what kind of productivity do you need?
- Auxiliary hydraulic flow rates and pressures are relevant to attachment capacity and compatibility; make sure the machine has the flow and pressure you need.
- Travel speed is important on larger jobsites.
- Operator comfort and visibility
- Size/configuration of controls
- Accessibility of engine and hydraulic components
Zero swing (sometimes called zero tail swing or zero house swing) is the hottest thing in the compact excavator market today—but it adds some cost. “If you are buying a zero tail swing machine,” says Bobcat's Greg Rostberg, “make sure it is a true zero tail swing. Some companies sell a zero tail swing machine, yet the counterweight kits can extend outside the tracks. This could limit slew rotation (and minimize spoil placement opportunities) and increase the potential for damage to the machine and peripheral objects.”
Operator comfort can be a big issue. “I tell people to sit in the cab for a long time,” says Mustang's Doug Snorek. “Then you begin to get a feel for whether it is cramped and what kind of visibility the operator will have. Some of the zero swing machines had to sacrifice cab comfort and some are more difficult to service because of difficult accessibility to the engine compartment.”
So what does a compact excavator cost? The smallest machines start a little under $20,000. At the top end of this category (1.2 tons), prices range from $60,000 to $100,000.