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By Greg Northcutt |
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If you're a hydraulic-excavator owner and ergonomics isn't a big concern when you buy a compact or midsize machine, it might pay to rethink your priorities. Such features as comfort, ease of operation, and convenience are high on the list for your operators and mechanics‹every time they stretch and strain to reach a lever, fumble with a switch, or crane their necks to see a guy on the ground hidden behind a pillar in the cab. Ergonomics also is a top-of-mind issue at the end of the day when aching backs, skinned knuckles, and banged-up shins testify to their struggles to muscle a machine around or climb up to reach a filter or a grease point.
Your employees aren't the only ones who suffer from such annoyances and irritations. Your profits suffer too. Repetitive motions can lead to injuries, and poor visibility can lead to accidents. Also uncomfortable operators and mechanics aren't fully productive ones, and they're more likely to bail out on you in favor of a competitor whose equipment is easier and more enjoyable to operate and service. "Ergonomics refers to the ability to adjust the work environment to better fit the operator," says David Wolf, excavator product manager for Case Construction Equipment. "The operator is key to making an excavator productive. If the operator doesn't fit the machine, the machine won't perform." That's why manufacturers continue to include more and more operator-friendly features and easy-to-service components on their excavator models. Improved technology has allowed manufacturers to include items, such as smoother controls and electronic engine monitoring, that weren't possible in the past. In some cases, public concerns also influence the way construction equipment is built. Noisy engines, for example, can bother neighbors of your job as much as your excavator operators. Wolf lists half a dozen areas involved with excavator ergonomics: noise levels for operators and other job-site personnel, adjustability of the cab and controls to fit the individual operator, location of hand and foot controls, support of the operator's body, visibility, and amount of effort required to operate controls. Two of the more obvious ergonomic features include comfortable seats and easy-to-reach controls. "When seated, the operator should be able to reach the controls for any routine‹work group, blade, or travel‹without stretching, and they should be easy to use," says Tom Connor, excavator product specialist for Bobcat Company. "The goal is to minimize operator movements and the thought processes required to use the machine for a specific function." Other ergonomic features, which reflect a better understanding of biomechanics, acoustics, and the like, can be subtler. That can mean adding curves to the cab to help dissipate sound waves, designing controls that fit the natural curves of the operator's hand, or redesigning the stroke of a joystick to reduce the range of motion required to operate the control from perhaps 40° to 20° for less stress on the wrist. The process of improving ergonomics can extend beyond the cab. Cushioned-boom hydraulic cylinders, for example, dampen shocks to the operator and the excavator when the machine is subjected to a sudden quick movement or a heavy load. But the machine's dynamic stability is even more critical, says Sungmo Yang, excavator product marketing manager for Volvo. "Weight balance of the machine from front to back and side to side is very important," he notes. "When you're working, the center of gravity of the bucket or other attachment is changing continually. The degree to which that movement affects the operator's comfort depends on such factors as the design of the boom and arm and the density of material in the bucket. To reduce shocks, the weight of the machine has to be well matched to that kind of movement." Progressive Improvements
Advances in ergonomics can stem from advances in other areas of excavator technology, such as sound-insulation materials or electronics. For example, one of the most significant improvements in excavator ergonomics was the switch from the use of cables and other mechanical linkages to connect the levers to the hydraulic valves that controlled the work group to the use of low-pressure, low-volume hydraulic pilot lines to control the valves. The mechanical system not only required a fair amount of muscle power but also was prone to wear, producing sloppy controls and adding to maintenance costs. In contrast, the hydraulic-over-hydraulic pilot-control joystick offers much easier, smoother operation and much greater reliability, allowing the operator to move a hand or a wrist instead of a whole arm. Not content with that, most manufacturers have improved on these pilot controls with proportional hydraulics. The faster you move the joystick to, say, raise the boom or curl the bucket, the wider the valve assembly opens to increase the flow of hydraulic oil for a faster response and more productivity. Move the joystick slow enough, and flow of the hydraulic oil reduces to a trickle, allowing for very precise control of the boom. Either way, it makes the operator's job easier and the results more productive. Kubota Tractor Corporation's newest compact excavator, the KX41-3, illustrates another example of how improved machine performance can lead to an ergonomic bonus. "Redesigning the hydraulic system by replacing the gear pump of previous models with a new, more efficient piston pump allowed us to downsize from a 21-horsepower engine to a smaller, 17-horsepower engine," says Keith Rohrbacker, construction equipment product manager for Kubota. "This smaller engine takes up less space in the engine compartment. As a result, we were able to move the operator seat farther back to provide more room in the cab." Ergonomics, however, involves more than designing comfortable armrests or wristrests, adding air conditioning, or providing a convenient place to hold your morning cup of coffee. "It's about making it easier for the operator to interact with the machine," says Mark Wall, excavator product marketing manager for John Deere and its North American distribution partner, Hitachi. "It's putting controls in smart locations, making operation of the machine an intuitive process, and giving the operator a clear view all around the machine. You want to feel like you could operate that machine all day without getting tired and do exactly what you want to do with the excavator when you want to do it." Ergonomics by Design Depending on the manufacturer, deciding how to improve comfort, ease of operation, and other ergonomic features can involve both formal and informal surveys of customers and lab studies. Like other manufacturers, Bobcat engineers will conduct focus-group sessions in which they might ask operators to evaluate ergonomic features, such as different contours or textures of joystick controls. Tom Connor, Bobcat excavator product specialist, reports some of the results. "Most prefer a basic form for the handle, with a soft touch rather than a hard feel in their hands," he says. "We've also found that too many switches can overwhelm operators, and they want to be able to work a switch easily when they're wearing gloves."
Operator feedback also is important to Komatsu America Corporation engineers. "It's difficult to measure comfort," says Erik Wilde, senior product manager for Komatsu. "To test the comfort level, we'll bring in operators that represent a wide spectrum of physical sizes and operating preferences. We try to find a happy medium between, maybe, a 6-foot, 2-inch, 250-pound guy and a 5-foot, 4-inch, 115-pound operator. The end result may not satisfy every operator 100%, but there aren't many complaints either." Before John Deere engineers begin designing an excavator, the company holds a best-in-class exercise where operators compare different brands of machines and report their findings. "This indicates the directions we need to go," Wall explains. "After building a prototype, we bring the customers back and ask them what they think of it. Then we use those results in building the final product." The designing process also includes virtual reality checks. "Operators sit in the seat of a cab mockup and, using a virtual reality device that fits over their eyes, they can experience what it's like to actually operate the machine. For example, they can determine how easy it is to put their hands on a switch, reach the foot pedal, and look outside the cab to see the bucket in different positions." The feedback from these operators and engineering tests then are used to finalize the design of the new model. Some of the features various manufacturers offer to reduce the time and effort it takes to operate and service excavators follow. Hands-On Controls Most excavator operators find it easier to operate levers, switches, and other controls with their hands or fingers rather than the ball or heel of their foot. Bobcat has replaced a foot pedal, typically used on compact excavators for controlling auxiliary hydraulics, with an electric-over-hydraulic thumb switch on the right joystick. "That way it's easy to hit the switch to open or close a hydraulic clamp or to activate an auger or other hydraulic attachment as you operate the boom," Connor says. "You click the button to engage the hydraulic flow and click it again to shut it off."
Liebherr Construction Equipment Company lets operators choose between hand controls and foot pedals for steering the excavator right or left or for straight travel. Hand levers can be screwed into the foot controls or stored behind the operator's seat. "The hand controls are designed for operators who feel more comfortable using their hands than their feet to steer the machine," says Bob Fiorenza, a district manager for Liebherr. "That can be important when you want good control of the machine in situations where a few inches right or left can make a big difference, like loading the excavator onto a trailer or unloading it or working in tight areas." More Convenience Manufacturers have devised various ways to make excavator operation more convenient, from electrical ports to power cell phones to flip-up, lockable hoods. To eliminate the need for a special tool or to access a compartment to change joystick control movements, Bobcat excavators feature a lever below the operator's right leg to select standard or International Organization for Standardization control patterns. "I've seen operators use control patterns that they weren't familiar with because they didn't know how to change them," says Connor.
LBX Company's Link-Belt 240 LX and larger excavators offer single-pedal travel, designed for straight-line trenching and traveling longer distances. When pushed down, it keeps the machine traveling in a straight direction without having to use the right- and left-hand steering controls. Instead of swinging out to open, the door on the cab of the Caterpillar 321C LCR excavator slides back for easy entry and exit when working next to buildings or other obstructions. More Precise Hydraulics The PowerWize II engine hydraulic management system on John Deere excavators is designed to improve the predictability of the machine's response to joystick movements, notes Wall. "The hydraulic metering compensates for changes in the temperature of the hydraulic oil," he says. "So whether the oil is cool or hot, the boom will stop exactly where you want it time after time. If you're placing pipe in a trench, for example, this feature prevents overshooting the trench the first time and then having to swing the boom back before you can lower the pipe." Easier Tool Operation The optional Tool Control System on the Cat 321C LCR excavator reduces the operator's workload by eliminating the need to calibrate the hydraulic system when switching from one work tool to another. The system configures hydraulic flow, hydraulic pressure, and operator controls to match a specific tool, including hammers, compactors, thumbs, and grapples. In addition, the operator can program five different tool settings and select the appropriate one when changing tools. Fewer Jolts and Bumps Excavator manufacturers have tackled the jolting forces transmitted through the frame to the operator when abruptly stopping action of the work group. For example, Link-Belt excavators include a selectable attachment cushion. Activated by a push button, it's designed to reduce or eliminate the jarring effect when operating the boom or stick. "This is accomplished by precise flow control in the pilot system utilizing a special cushion control valve," say Larry McAdoo, hydraulic excavator product specialist for LBX Company. This is so they don't come to an abrupt stop when raising or lowering the boom and moving the stick in and out."
A similar feature on Komatsu Dash-7 series excavators is the shockless boom option. As Wilde points out, it does more than reduce wear and tear on both the machine and the operator. "It improves productivity by reducing spillage from the bucket," he says. Sudden stops and starts when swinging the house also can add to an operator's discomfort. To solve that problem, Link-Belt excavators are equipped with a feature called Selectable Free Swing Control. Instead of releasing the joystick to apply the brake and immediately stop the house swing, the operator can push a button, allowing the upper structure to slow to a smooth stop. "When you stop the swing, the momentum can jolt the operator," McAdoo says. "The free-swing feature is also helpful when using a chain to lift and place a load of pipe. When lifting, the boom will stay centered over the load, preventing the pipe from swinging back and forth." Liebherr's 934 and larger excavators feature three instead of the typical two pumps in the hydraulic circuit of the house swing. "It's a closed-loop system that prevents the undercarriage from jumping around and results in very smooth stops," says Fiorenza. More and Easier Visibility Visibility both inside and outside the cab is critical to fast, efficient, and safe operation of an excavator. To that end, manufacturers continue to refine the location of switches, gauges, and display panels so the operator can see them quickly and easily. They also have expanded the operator's view of attachments and the area around the machine by moving and reducing the size of cab posts and adding more glass. Komatsu Dash-7 series excavators feature a solid, pressed cab. Stronger than a conventional design, it provides more interior room and better visibility than previous models do. "This design allowed us to use smaller front pillars and to remove the pillar on the right-hand window for a wider field of vision," he says. Meanwhile, manufacturers are making windows easier to open. Caterpillar, Komatsu, and Link-Belt, for example, offer quick-release systems to reduce the effort required to open the upper-front windshield and handles on the middle-lower part to simplify opening or removal. Comfort-Loaded Seats Suspension seats are the norm on many lines of compact excavators and just about every make of midsize excavators. They're designed to adjust to meet the comfort needs of most operators, regardless of height or weight. The seat in Link-Belt LX-series excavators adjusts in nine different ways. The operator can slide the control console forward and backward for the best foot position, move the seat forward and backward for a comfortable hand position on the joysticks, adjust the suspension, tip the seat forward or backward, recline or incline the backrest, move the position of the joysticks up or down, adjust the armrest and headrest, and with a hand pump set the lumbar support for comfort. Unique among manufacturers, Volvo offers a heated air-suspension seat. Cool Cabs Air-conditioned cabs are available on some brands of compact excavators and are standard on most larger excavators. In many cases, this air conditioning is comparable to that found on top-end automobiles with such features as set-and-forget temperature controls. Some have pressurized cabs to keep out external air and dust for more efficient cooling and cleaner air filters. Quieter Operation Besides increasing interior space of cabs, manufacturers are decreasing the sound levels inside them. Their techniques include installing more and better decibel-deadening insulation inside the cabs and engine compartments, using tighter door seals, and placing the cabs on silicone-filled mounts to help isolate the operator from shocks and vibrations reverberating through the frame. The engines are being tweaked too. One approach is to reduce the sound of the engine-cooling fan, a major source of noise. Kubota, for example, uses specially shaped fan blades to move air more quietly. Link-Belt combines a slower fan-speed with a fan shroud that dampens noise levels and increases cooling efficiency by forcing air to be pulled through the oil cooler rather than by allowing it to be drawn in on the backside. Volvo reduces the amount of noise escaping from the engine compartment by reducing the size of air intakes. To compensate for the reduction in the amount of cool air being drawn into the compartment, the engines feature a high-capacity engine radiator and a separate, hydraulic, oil-cooling system. Easier Servicing Engineers are reducing maintenance time and costs by making it easier to reach components that require regular servicing. Electronic monitoring of engines and hydraulics and diagnosing problems also are helping lower repair bills.
Among the serviceability features of Bobcat excavators are a swing-open tailgate for quick access to the engine and a cover on the right side of the machine that tips forward one position for fueling or daily maintenance checks. Opening it to the second position provides access to hydraulic components. A central location on the front of the machine for the swing pinion, swing bearing, and offset cylinder simplifies the job of servicing these items. The electronic monitor on the Cat 321C LCR excavator allows the operator to check coolant, hydraulic oil, and engine oil levels from the cab seat before starting the engine. Service doors on both sides of the upper structure make it easy to reach such maintenance items as engine, radiator, or hydraulic components from the ground. Meanwhile, a concentrated, remote greasing block on the boom delivers grease to hard-to-reach locations, and oil-free bearings lengthen the greasing interval of the front linkage to 1,000 hours. Beneficial Combinations In come cases, features designed primarily to improve an excavator's productivity also add to its operator-friendliness. Excavator models that reduce or eliminate tail swing beyond the width of the tracks are one example. Designed for working in close quarters, such as alleys or other urban sites, they reduce the chance of damaging the machine or nearby structures as the house swings around. "You don't have to worry about what's behind the machine," explains Wall. "You're more relaxed so you can pay full attention to what's in front of you, like overhead wires or a trench." Some excavator manufacturers have taken the zero-tail-swing concept one step further with zero-house-swing models. On these machines, the right- and left-front corners of the upper structure and the right- and left-rear corners stay within the width of the tracks when the house swings. Plenty of breakout power also makes an operator's job easier. "When you're digging, you want the arm and bucket moving forward in one motion without stalling," Wall adds. "Strong digging forces allow you to do that. Otherwise you have to raise the boom or curl the bucket to complete the movement, which requires you to move your arms and hands more." Most midrange excavators allow the operator to select different operating modes to match hydraulic power to the job by pushing a button on the joystick. That also can make work easier. For example, in addition to a "power" mode for peak performance in heavy digging and lifting applications and an "econo" mode that reduces engine output by about 25% to improve fuel efficiency, Liebherr excavators allow the operator to choose a "fine-grade" or a "super-finish" mode for slower, more precise control of attachments. This can come in handy for such jobs as cleaning out ditches with a grading bucket or using a thumb to gently grasp decorative rock. Caterpillar takes a different approach with its 318C L and 318C LN excavators. Instead of work-mode and power-mode switches, these models automatically adjust hydraulic flow to the boom and swing functions for optimum performance based on movements of the joystick. These are just a few of the ways today's excavators are allowing operators and mechanics to do more work in less time and with less effort, and there's no end in sight to more ergonomic advances. In the not-too-distant future, they could range from more electric-over-hydraulic controls for even quieter, smoother, and more responsive operation to rear-view cameras, such as the blind-area surveillance systems already found on some of the largest trucks, dozers, and other construction equipment. It's all part of the continuous quest to help contractors drive costs down and push profits up. Author Greg Northcutt writes frequently on construction and business issues.
GEC - March/April 2004
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