The usefulness – and profitability – of an excavator directly corresponds to a correct sizing of the machine to the jobs it is expected to perform. Underestimating this particular bit of alchemy can be disastrous for a contractor: Spec a machine too small, and you get to watch it underperform and – worse – tear itself apart in the process. Get a machine that’s too big, and it sits idle because you can’t get it into the places you need to work or because it’s out-produced its support equipment.
The bottom line for a successful equipment strategy is utilization. There are lots of high-falutin’ ways of charting equipment use, but they can all be summed up easily: If a machine is in action on your jobsite, odds are it’s making you money. If another machine is sitting idle in your yard, shop or on a job, it’s costing you money (unless it’s old and you paid it off years ago – but that’s another story altogether).
It’s these basic equipment use principles that make excavators in the 45- to 50-metric-ton class so desirable to contractors. These machines are slightly larger than the most popular class of excavators currently used in North America. So, in many ways, they’re not much different from the machines you’re probably using on your jobs – they’re a bit bigger, more expensive and can dig and lift more, but it’s not like you’re moving into a mining-class machine. So what’re the advantages of moving up in size from machines in the 30- to 40-ton class?
Productivity, as it turns out. “If a contractor’s not using these machines now, he’s certainly thinking about or dreaming of the day when he will,” says Carl Heggen, product manager, hydraulic excavators, Komatsu America. “Generally, when a contractor upgrades from 20- to 40-ton excavators, he’s looking for the capability of loading slightly bigger trucks, bidding on larger mass-excavation jobs or larger size pipeline work. He can tackle these new applications because excavators in the 45- to 50-ton class have the ability to move more material per hour, lift larger pipe and structures, and power through more severe digging conditions. And hopefully, this additional performance will provide an edge on his competition not available if he were bidding work with smaller excavators.”
Getting through current projects quicker and at a higher production level is also an undeniable competitive advantage. “The idea is that a larger machine, through basic economies of scale, lowers your operating costs per yard and therefore makes you more competitive on the jobs you’re already bidding,” Heggen says.
A 45- to 50-ton excavator has additional weight and higher engine horsepower and more powerful hydraulics to enhance its digging forces, Heggen notes. This means higher production when you encounter tougher digging conditions. A larger machine will allow your operators to break through tough areas more quickly with less stress on the machine than if you struggled along with a machine one or two size classes smaller.
“You’ve got to remember, though, that the acquisition cost is higher than a machine in the 20-ton size class,” Heggen adds. “So a hard, cold look at your business – where it is now and where you predict it’s going – is absolutely essential when you’re considering adding a 45- or 50-ton excavator to your fleet. They can do a lot to enhance your profitability, provided high utilization can be maintained.”
Beware of physics
One reason excavators in this class are so productive in such a wide array of applications is they have the size and power to handle a range of different boom arm and stick configurations. “These machines are great all-around performers,” notes Dave Hardwick, product manager, JCB. “They are powerful digging machines, but can also be spec’d with long dippers, making them ideal for long-reach or below-grade digging applications, or high-reach demolition work with hammers. Other machines can use grapples to place rocks in shoreline or harbor protection work.”
But, Hardwick warns, any attempt to configure an excavator for long-reach work requires careful site assessment first. “Depending on the application, dipper length, track pad width and auxiliary pipe work must all be configured to meet the job at hand,” he explains. “Because these machines move such large amounts of material, adverse movements or incorrect geometry will magnify these loads and cause tipping or other unwanted movements if things are not configured correctly.”
“A lot of times, contractors think if they simply put the longest arm and the biggest bucket they can find on these machines, they’re going to get instant super-productivity and that’s not necessarily the case,” says Mark Wall, product marketing manager, John Deere Construction & Forestry. “There are basic geometrical rules that you simply cannot ignore or you’ll end up with an unstable machine.”
Generally speaking, Wall says a shorter arm usually allows you to move up a bucket size since the arm will keep the heavier load closer to the machine’s center of gravity. For those same reasons, a shorter arm will also give you better breakout forces when you’re digging with the machine.
“Cycle time is the key to all of this,” Wall adds. “You want to keep your cycle times as fast as possible. So if you put a long arm on the machine, then add a coupler, a thumb and a big bucket too, the machine may be powerful enough to give you a full bucket each pass, but it’s going to be working really hard to do it.”
Worse, you’ve compromised the machine’s inherent stability. “That’s why you’re better off with a short arm if you don’t need a lot of excess reach,” Wall explains. “You’ll have a more stable machine that’s more productive because your digging forces are going to be a lot higher. That’s why I always urge contractors to talk to their dealers to make sure the arm and bucket configurations they’re using in certain types of material are going to give them maximum cycle times.”
Caterpillar, like many OEMs, offers a variety of front linkage and undercarriage configurations to meet different needs of different applications. “The 345C L has sufficient weight, horsepower and hydraulic capability to effectively work in a wide range of applications – from traditional site development to sewer and water to specialty applications like demolition,” says John Walker, heavy construction consultant, Caterpillar. “For even more versatility, the 345C L has multiple auxiliary hydraulics available from the factory. “The optional hydraulic system includes hammer, thumb and Tool Control System options.”
Couplers are increasingly important on excavators of all sizes because they allow a high degree of versatility, particularly valued by utility contractors in water and sewer applications. “These guys have to move a lot of dirt when they start a trench and need to install a trench box,” Wall notes. “So they may start out with a 54- or 60-inch bucket on the machine. Once that’s done, they’ll switch to a 42- or 48-inch bucket so they can get down inside the trench box to spread bedding material.”
Thumbs are also highly prized for their ability to clamp on and place hard-to-manage objects while doing land clearing or site prep work. In demolition applications, crushers and shears are the preferred attachments. “But regardless of what you have on the end of that machine, it’s got to be correctly matched with the stick and boom,” Wall warns. “If not, your productivity will suffer and – in extreme cases – the machine will become unstable.”
Track selection trade-offs
Boom and stick configurations aren’t the only things that can be specially spec’d on excavators in this class. Various track lengths and shoe and pad widths are available to ensure high flotation and traction in the wide array of ground conditions these machines traverse.
Many machines are offered with expandable undercarriages. “There are several reasons why you might want to expand or retract the undercarriage on a machine in this class,” explains Scott Sutherland, product manager, Link-Belt. “Most of the time it’s for transportation purposes: You can easily minimize overall machine width when moving it to a new jobsite.”
A wider undercarriage is inherently more stable than a narrow one. And it’s for that reason, Sutherland says, some contractors choose to spec expandable undercarriages. “We have a super wide, expandable version available for excavators in this class,” he notes. “It’s a highly stable machine platform specifically designed for material handling applications and it significantly improves over-the-side lifting performance.”
There are offsetting requirements that have to be considered when you’re spec’ing the machine’s undercarriage. If you’re going to be working primarily in muddy terrain, it’s best to choose the widest pad possible to guarantee adequate flotation. If hard pan and rock are the main areas of operation, a narrower pad is the best fit.
“Always keep in mind that your undercarriage life will be the best if you run the narrowest pad possible,” says Dave Wolf, product manager, Case. “Maintaining proper track tension is another crucial aspect for long-term track life. Many machines today have track tensioners so it’s easy to maintain the proper tension.”
Dirt and mud are abrasive materials. So Wolf suggests always spec’ing tapered track guards to assist in the cleaning of the tracks and the idler and sprocket areas that can fill with material when you’re working in soft or adverse ground conditions. “It’s a good idea to have your operators clean those areas out at the end of the day, regardless of whether the machine’s got track guards,” he adds. If you don’t, that material is going to dry overnight, then get ground into the tracks or onto the rollers and idlers the next day.”
Operators play a big part in track life, too. “It’s another one of those trade-offs you have to always keep in mind,” he says. “A narrow track is going to give you longer life because it’s got a smaller footprint on the ground and is less prone to twisting and tearing from uneven terrain. But all tracks – particularly narrow ones – don’t like abrupt turns. The more gradual a turn an operator makes with a machine the better it is for the tracks. You want to minimize the amount and affects of twisting, lateral torque that a turn puts on a track when it’s in contact with the ground.”
“It’s always a good idea to travel long distances with the drive motors to the rear,” adds Ed Hockenberry, product manager, Volvo Construction Equipment. “I recommend always digging with the drive motors to the rear and avoiding bouncing the machine at any time when you’re operating it. Shock waves cause excessive wear throughout the total machine structure, so you always want to minimize them. Drive motors, in particular, are sensitive to excessive shocks and vibrations, and keeping them behind the operator as much as possible is a good way to minimize the risk of component damage.”
Case CX460 & CX460 Extendable
Features include:
- Comfortable, ergonomic cab
- Low-effort pilot controls
- Case 6TAA-8304 turbo diesel engine
Caterpillar – nine models, including 345C L Long Reach 345C L Mass
Features include:
Doosan Infracore America Solar 470LC-V & dx480lc
Features include:
- Ergonomically designed cab
- Precision joystick controls
- Engine and hydraulic interface control system
Hitachi Zaxis 450LC & Zaxis 450LC ME
Features include:
- Auto acceleration
- Work mode
- Center-pillar-reinforced cab design
JCB JS460LC
Features include:
- Heavy-duty boom and reinforced dipper arm
- 305-horsepower, turbocharged, intercooled, six-cylinder diesel engine
- Cushion control reduces shock loads to operator and machine structure
John Deere 450D LC
Features include:
- Powerwise III engine and hydraulic management system
- Generous hydraulic flow for fast responses, powerful swing torque and drawbar pull
- Spacious, quiet operator’s station
Kobelco SK480LC-DA
Features include:
- Cab expanded 18 percent compared to previous model
- Total cab glass area increased 36 percent
- High-output Mitsubishi diesel engine rated at 315 horsepower
Komatsu PC400LC-7 Variable Gauge
Features include:
- High output, economical Komatsu SAA6D125E-3 diesel engine
- Improved lateral stability for enhanced lifting
- Increased arm and bucket digging forces
Liebherr 954B Li
Features include:
- Hydrostatically driven radiator fan
- Liebherr six-cylinder, inline diesel engine
- Computer-aided, robust design
Link-Belt 460LX Fixed Sideframes & 460LX Extendable Sideframes
Features include:
- Efficient hydraulic system for fast cycle times
- Automatic power up for tough digging conditions
Terex TXC 470LC-1
Features include:
- Powerful, fuel efficient and quiet
- Swing anti-rebound valve for smooth, precise boom movements
- Advanced graphic display LCD information monitor
Volvo EC460B LC ME, ECD460B LC & EC460B LC Retractable
Features include:
- Sealed track and pin bushings
- Planetary type swing reduction unit for high swing torque
- Joystick-mounted, one-touch power boost for 10-percent increase in breakout force
