Machine Matters – September 20091
| September 29, 2009 |
14-to-15-foot-dig-depth-class backhoes address control preferences
With backhoes, it’s all about the hydraulics, especially in the production-minded 14- and 15-foot dig depth size classes.
Still-popular manual controls, mechanically connected to the hydraulic spool in the valve block, give operators a sense of feel, but also have longer throws, requiring more effort. And so another option appeared in the earlier part of this decade. Joystick-operated pilot controls – also called servo controls – have shorter throws, leading to less operator fatigue. Detractors of pilot controls, however, cite their lack of operator “feel” – that hard-to-describe feedback that an experienced operator gets from the mechanical levers – and slower speed.
Because of strong operator preferences, backhoe manufacturers offer both mechanical and pilot controls, and it depends on the manufacturer which type is standard. There have been a number of tweaks to these systems, including:
· Case’s Pro Control System designed to eliminate over-swing, or situations where the boom dipper and bucket are in motion and then brought to a rapid stop, causing a tendency to over-swing like a pendulum. The PCS anti-rebound system cushions these quick backhoe stops.
· Terex backhoes use tandem gear pumps, a system it says provides both reliability and a lower cost replacement than piston pumps. This system incorporates closed-center control valves, which in addition to giving multi-functionality and controllability to machines equipped with pilot controls, offers low lever efforts in a manual control machine, says Lowell Stout, Terex senior product manager.
· Cat’s load-sensing hydraulic system, which uses the same technology seen on its excavators, gives full lifting capability at any engine speed, which can come in handy when communicating with co-workers on the ground, according to Kevin Hershberger, Caterpillar backhoe loader marketing manager.
Expanded pilot controls
And two manufacturers offer what we’ll call expanded pilot controls, both mounted in the operator’s seat: JCB with its Easycontrol system and Deere’s Total Machine Control.
Out in the United States this past April, JCB’s Easycontrol is designed to improve backhoe speed and operator feel by changing the machine’s valve block from a pilot control’s typical flow-sharing block to a full-flow one similar to those seen on manual machines. Flow-sharing valve blocks only allow 50 percent of the hydraulic oil to come out of one of the ports in the block, says Jim Blower, JCB’s mid-range product marketing manager. “While this helps the operator pay more attention to the task at hand rather than manually determining where the hydraulic oil flow should go, it’s still only 50 percent of the available hydraulic power, which tends to slow things down,” he says.
With the Easycontrol open-circuit hydraulics, neutral circuit oil flows through the valves any time the engine is running and turning the pumps, making hydraulic power available on demand. The result, says JCB, is up to a 10 percent increase in backhoe cycle times.
Deere’s Total Machine Control – standard on its 310SJ TMC – really comes into play in “leapfrogging,” a technique used for years by operators to get out of the mud. On manual machines, seasoned operators are able to use a combination of both hands and an elbow to operate both ends of the backhoe at once, required in the push-pull of leapfrogging.
But, says Bob Tyler, backhoe product marketing manager for Deere, that process became more difficult with the advent of pilot controls, which are typically mounted on towers at the backhoe end. Unlike the manual levers, which are grouped together, the pilot control towers are placed on the left and right side of the backhoe operating position.
During TMC’s development, Deere concentrated on lower lever efforts and armrest controls but customers had an additional request – they wanted to be able to operate both the loader and the backhoe at the same time. Deere’s solution: to put what it calls a “mini-joystick” in front of the right joystick. Operators run the loader with the mini-joystick, usually with their little finger, while their hands on the main joysticks run the backhoe. The mini-joystick can be operated either while facing the backhoe or at any point up to 90 degrees from the rear position.
Manufacturers have long been able to take advantage of the similarities between these machines and wheel loaders. Wheel loader technology that’s made its way into backhoes includes boom height kickout, which allows you to set a maximum dump height; and return-to-carry and return-to-dig, which return to a lowered boom and bucket position, especially helpful in repetitive loading.
Another loader option is ride control, giving extra suspension for rough terrain or higher speeds. Operators can either manually switch to ride control, or put it on automatic, which turns the feature on and off as the machine’s travel speed changes.
Toolcarrier options are also common, allowing backhoes to efficiently load and handle materials such as pallets.
Cabs are always in the backhoe forefront.
“In the past few years there’s been a significant increase in the popularity of fully-fitted cabs, as opposed to open canopy machines,” says Marcello Bargellini, product specialist for backhoe loaders, Volvo Construction Equipment. “But the loader and backhoe attachment quick hitches have been perhaps most valuable.”
Joyce Szulc, Case brand marketing manager, adds that the Case hydraulic quick coupler option offers easy-to-use, push-button operation from inside the cab. “Plus there is no loss of breakout force,” she says.
New Holland has addressed visibility with a narrow 9.5-inch curved backhoe boom, giving the operator an unobstructed view of the work area even in confined spaces. Other visibility features include a flat glass rear window that moves up and out of the way and the cab’s four narrow posts.
Komatsu standardized four-wheel drive on all its backhoes, a feature it says gives operators more traction when pushing into the pile with the loader, four-wheel braking at road speeds, and the decreased likelihood of becoming stuck in muddy conditions. Other benefits include tighter turning radius and less environmental damage due to decreased wheel slippage on soft ground.
Caterpillar’s E Series backhoes offer either factory-installed hydraulic thumbs or sticks that are thumb-ready. “Thumbs are versatile for clearing and demolition, placing large block retaining walls and moving material,” says Greg Worley, Caterpillar market development engineer. And they add to the versatility of the backhoe – an aspect that can’t be overlooked in today’s economy.
Getting the most out of your backhoe
Our experts gave us these operating tips:
There’s no need to hot dog it. Turning the engine to its full rpm just wastes fuel. Most backhoes are tuned to run optimally at 1,800 rpms, and the speed and power comes through the hydraulic system flow, not through direct drive from the engine. On some machines, you can even run the machine at idle and still have full hydraulic power. And when you do try to run it at maximum rpms the hydraulic system cannot take the extra flow, so all you’re doing is turning the pumps quicker and wasting energy trying to overfill the system, says JCB’s Blower.
Take the time to properly stabilize the backhoe. Unlike an excavator, which has a more stable platform, backhoes perform best when properly stabilized, Cat’s Worley says. Aim for the machine to be square on the ground, flat and stable.
Don’t give up breakout force. This is actually the second part to the tip above. Any time you’re in a dig cycle with the backhoe, if the machine moves toward the hole as you bring the stick toward the machine, then you’re giving up breakout force. You can help keep your machine from moving by repositioning the loader bucket: take the bucket up in the air and put it in a full dump position, and then lower it back to the ground so the bucket cutting edge is firmly embedded. With multipurpose buckets, open the bucket jaws before you lower it to the ground, a technique that offers additional edges for gripping the ground.
Be knowledgeable of your surroundings, says Ben Cott, New Holland Construction’s platform product marketing manager – loader backhoes. Have a clear understanding what lies below as well as above ground.
Realize that backhoes dig differently than excavators. Excavators are bucket digging machines – operators reach out and grab a bucketful of material and dump it to one side. Backhoes, however, are more stick digging machines, and excavate best horizontally. Efficient operators use the whole length of the trench to dig out a 4-inch layer at a time, bringing the stick in and keeping the bucket flat until it’s close to the machine. This method also gives you a flat bottom on your trench.
Use your boom and stick to “bounce” material out of the bucket at the end of a pass. Rather than fully opening the bucket up during a dump, only partially open your bucket and then use your boom and stick bounce the remaining material out of the bucket. Your bucket is then in the right position to start digging again, which creates a more efficient dig cycle. Sticky material, however, will require a full bucket dump.
Take time to correctly position the backhoe’s controls. Make sure you position yourself in a way that supports your arms and wrists during a day’s work. Also adjust the seat to the correct height and position for your frame.
Maintain proper tire inflation. Over inflation, according to Volvo’s Bargellini, causes the machine to feel bouncy and unstable, plus it can affect ride comfort. Check regularly to make sure tire pressures meet manufacturer’s specs.
When transporting a load in the loader bucket, never engage the diff-lock when wheels are spinning, which can cause serious damage to the rear axle. Only engage the diff lock when wheels are not spinning to help extricate a machine from the mud. If your backhoe is equipped with a boom suspension system, use it when transporting a load since it will reduce machine bouncing and help bucket material retention.
When working in loose soil types, says Randy Bauserman, Komatsu America’s backhoe loader product manager, use the machine’s economy mode to lower pump output and reduce fuel consumption in easy digging.
Safety must be the top priority. Dennis Drake, owner of Drake Excavating, and working supervisor for Drake Homes, both in Charleston, Illinois, advises operators to know where everyone is around you. “The guy in the machine is always the eyes for the guys in the hole, watching the banks,” says this Case Backhoe Rodeo finalist. “And there are a lot of blind spots to be aware of, especially if you’re running a 54-inch bucket.”
Consider the benefits of loading on the options. Drake is a firm believer he gets a productivity payback in what he calls “deluxe equipment.” He adds the ride control, power shift and comfort steer options and then makes sure his operators fully understand how each feature is operated and what it adds to productivity.
Remember that speed comes with smoothness. “When you get to be smooth, you don’t have to worry about speed, it just happens,” says Drake, who estimates he has put more than 12,000 hours on a backhoe.
Don’t forget the value of a quick-coupler system on the loader end. While most attachment attention is on the back end, the addition of such attachments as a set of forks, a sweeper or a truss boom can open up your machine to even more work.
When craning a load with a backhoe, first ensure the machine is level and on a firm footing. Make sure the weight to be lifted does not exceed the machine’s maximum permissible load and the machine is on stabilizers. Secure the lifting device to the load, retract any extendible dippers and fully curl the bucket. Attach clevis and chains only on the lift-eye of the bucket linkage, and place the boom at maximum height, approximately 65 degrees from the ground. Crane the weight only with the dipper.
Check for ease of maintenance, including access to the engine compartment and radiator/cooling area at the front of the machine. Visual inspections should be possible while standing on the ground. “The easier the daily checks are the more likely they are to be completed,” says Terex’s Stout.
Know the limits of your machine, especially when lifting. When you use a too-small machine and then run it to its limits, you will wear out the machine more quickly. Make sure the machine can handle what you’re asking it to do.