Backhoe loaders: 4 to <15 foot dig depth
| June 12, 2007 |
In many ways, you could say the whole versatility revolution in construction equipment started with the backhoe loader. Before the backhoe first appeared in the late 1950s, construction equipment was, for the most part, designed, built and used for single-purpose applications. The backhoe loader, however, was different: One half dedicated loader, and one half digging machine, it did both jobs equally well, with rubber-tire mobility to boot. And it was easy to trailer longer distances. Small contracting firms – including single-man operations – took to backhoes in droves because of the huge amount of diversity they offered.
Today, backhoes remain popular among North American contractors. In addition to the features that first attracted contractors 50 years ago, modern backhoes offer a host of performance-enhancing features, modern comforts and powerful front-and-rear attachment versatility that have allowed them to stave off a host of newer and smaller machines seeking to steal the jobsite spotlight.
Side-shift and extenda-dig options increase backhoe flexibility
Backhoe loaders in the 14- to <15-foot-dig-depth class are used in a wide variety of construction applications including truck loading, grading, backfilling, material handling, site preparation and cleanup, trenching, craning, demolition, etc.
Most manufacturers today say the rear portion of the backhoe is used slightly more than the front loader. Chris Giorgianni, midrange product sales manager for JCB, thinks this usage split is roughly 60 percent backhoe and 40 percent front loader. "That's why we're targeting both the front and rear cab areas for ergonomic upgrades and productivity-enhancing features," he says. "Some of these enhancements include improved operator comfort, better sightlines to the boom and bucket and our new Precision Control System."
Pilot hydraulic control systems and open- or closed-center piston pumps are also standard backhoe offerings. Pilot controls offer contractors greater flexibility as they can be easily switched from backhoe- to excavator-control patterns, usually with a simple flip of a lever. This reduces the amount of training and adjustment time needed when an operator schooled on one type of pattern climbs into the seat and starts to dig.
Both open- and closed-center hydraulic systems offer productive digging and lifting characteristics. Open-system hydraulics use gear-driven hydraulic pumps to propel oil through the hydraulic system. Closed-center systems use piston-driven hydraulic pumps. "Closed-center piston pumps provide full digging and breakout force at any engine speed," explains Paul Grohsmeyer, marketing manager, Caterpillar. "They also give backhoe operators more stick 'feel,' thanks to the feathered hydraulic profile. They allow more precision for tasks like setting pipe when the machine is idling, letting the operator communicate with the ground crew. "Piston pumps also generate less heat and wear due to their design. This helps increase pump efficiency and life, as well as extend hydraulic oil life."
But other OEMs say there are equally important advantages to open-center hydraulic systems, namely lower cost and better hydraulic "feel." "Open-center hydraulic systems use fixed-displacement hydraulic gear pumps," explains Rusty Schaefer, product manager, Case. "These pumps provide maximum feel while maintaining full hydraulic flows at high pressure. This characteristic gives you increased productivity because the pumps provide an optimal balance of power and precision for delicate operations like working around buried utility lines. Gear pumps are also less sensitive to contamination so they're more durable in the field and they're easier and less costly to rebuild, both of which contribute to their lower overall operating costs for backhoes equipped with them."
"Closed-center piston pump hydraulic systems give more precise control, and they also allow an operator to input multiple functions at the same time, without compromising other hydraulic circuits," notes Paul Kindelspire, district sales manager, Midwest region, Komatsu. "These closed-center systems are even more precise and efficient when they are tied in and managed by an onboard electronics system. These systems offer various work modes to exactly match the hydraulics system to the task being performed. On a Komatsu backhoe, for example, selecting the 'power' mode cuts boom movement flow in half, while optimizing lift circuits. This ensures adequate power for the lift and precise placing of materials."
Older rear machine options remain popular. None more so than the extenda-dig option, which allows operators to hydraulically extend a backhoe boom via a foot pedal in the cab. "Very simply, extenda-dig gives you more dig depth and more reach almost instantly," Giorgianni says. "Our model gives up to 4 feet of additional reach, which can make a world of difference if unforeseen obstacles arise. It also decreases the number of times the backhoe has to be repositioned in standard trenching applications."
Although extenda-dig backhoes offer enhanced productivity, maintenance on them is vital to ensure long life. Be sure and keep it well lubricated and check it periodically to ensure that tolerances are tight. If you don't over time it will get loose and start to deliver sloppy performance.
Ride control is among the best options available for backhoe loaders engaged in high-volume, load-and-carry operations.
Ride control and autoshift excellent in load-and-carry work
Load-and-carry work is the most common application for the front end of a backhoe. For that reason, most machines in this class are fitted with loader buckets ranging in the 1.1- to 1.32-cubic-yard range. “Ride control is probably the best option available for a backhoe engaged in heavy load-and-carry work,” says Schaeffer. “It works by allowing a small of amount of hydraulic oil to meter into the front loader arm cylinders and act as a shock absorber when the machine is on the move. Because this system isolates heavy bucket loads from the rest of the machine, it presents the operator with a smoother ride and protects the backhoe’s frame, drivetrain and components from potentially damaging impact shocks. At the same time, ride control helps keep a load in the bucket during transport.”
There are two main transmission types found on backhoe loaders. Each is designed for specific needs, from economical acquisition and operating costs, to making operating the loader as easy as driving the family car. The top-of-the-line transmissions are autoshift units, which Grohsmeyer says really bring out the full potential offered by ride-control systems. “Essentially, autoshift transmissions semi-automate loader operation, and let the operator concentrate on loader functions,” he explains. “These are full-featured transmissions with five speeds forward and reverse and full automatic shifting up to, and down from, the highest gear selected by the operator. If desired, the operator can also deactivate the autoshift function and manually shift through the gears.”
When used in conjunction with ride control, Grohsmeyer says an autoshift transmission can be programmed to automatically engage ride control as the machine’s speed increases, and automatic downshifting and ride control disengagement as its speed reduces or as you approach the load or unload point. “This gives you both faster travel speeds to and from the loading area and decreased cycle times since the transmission takes a lot of the guesswork out of gear selections when loading and unloading the front bucket.”
Autoshift transmissions also deliver more road speed, says Giorgianni, around 25 mph. “A lot of contractors will fit their backhoes with radial tires for better wear and a smooth ride on the road,” he adds. “But again, application should be the primary focus when you’re selecting a transmission. If you’re buying a backhoe and you know you’re going to be on your stabilizers 90 percent of the time and you’re going to trailer the machine everywhere you go, maybe the extra cost of powershift won’t benefit you.”
Manual transmissions can be as productive as autoshift units in certain applications and are a boon for contractors interested in low equipment and operating costs, says Joel Powell, product marketing manager, backhoe loaders, Volvo. “With four standard forward and reverse gears, they’re a good choice for rental houses, entry-level contractors and companies with large equipment fleets,” he adds. “In addition, they’re more fuel efficient than autoshift transmissions, easy to maintain and extremely durable in harsh construction applications.”
Pilot-operated hydraulic controls can switch from backhoe- to excavator-style control patterns with the flip of a switch.
Limit four-wheel drive use to extend drivetrain life
Equal-size tires are a noticeable departure from standard backhoes (with smaller-diameter front wheels) and offer higher flotation for traversing sloppy or uneven terrain. Again, these machines cost more than conventional backhoes, and may not be a good application match if you’re working in urban areas or rarely have to contend with sloppy ground conditions.
Four-wheel-drive systems have long been common on backhoes, and their advantages are obvious, namely easier movement through mud or deep snow. But continuous four-wheel-drive can be hard on a drivetrain, which is why Grohsmeyer suggests limiting its use to appropriate situations only.
If you plan to use four-wheel drive on your backhoe often, Kent Stickler, product consultant, backhoes, John Deere, says tire selection is crucial for good productivity. “Your front tires need to match the machine’s drivetrain ratio to ensure they work together with the rear tires,” he says. “If speed is not an option, spec bias tires instead of radials. They cost less and have a more durable sidewall, which can be an advantage in severe off-road conditions. Radial tires have a softer sidewall, which is what gives them a gentler ride on the road.”
Electronically controlled steering modes can also be a boost, particularly if you are working in confined areas. Generally speaking, three separate modes are available:
· Conventional steer, where only the backhoe’s front wheels can be turned.
· All-wheel steer allows the front and rear machine wheels to cut in opposite directions and greatly reduces a machine’s turning radius and increases maneuverability.
· Crab steer cants the front and rear wheels in the same direction, allowing a backhoe to move sideways at an angle. It is primarily useful for positioning the machine to work in areas with difficult or limited access routes.
Narrow buckets best for harsh ground
One application that demands total operator concentration is lifting, whether with the front or rear of the machine. “Never lift any load when the backhoe is not level,” Grohsmeyer cautions. “And never swing heavy loads side-to-side excessively. In addition to the obvious safety issues, this action can put excessive lateral twisting forces on the boom and pin structures and cause them to fail prematurely.”
“Ground engaging tools are the biggest wear items on backhoes,” Stickler says. To extend their life, he recommends properly adjusting return-to-dig settings for optimal surface penetration and hard surfacing the loader bucket to extend its life and its cutting edge effectiveness. “Make sure you’re using the right bucket when digging with the backhoe,” he adds. “Move up to a heavy-duty bucket in harsh ground conditions, and spec the correct bucket teeth to lower your operating costs. And remember that narrower buckets tend to work better in tough digging conditions since they cut through the earth more efficiently.”
Stickler says operators should always be attentive when applications call for continuous hard cycles when compacting with the bottom of the bucket. These hard blows can cause stress to the pins and bushings on the backhoe. “Hammers can be another application that is hard on components,” he notes. “Always be alert for abnormal boom or arm movement when you’re operating the machine. Inspect the boom and arm frequently for signs of stress.”