HETA

 

Mastering the backhoe-loader is a big job because it is really two machines in one. A good operator can improve productivity by employing many of the same principles that make excavators and wheel loaders more efficient. But the best backhoe-loader operators know how to set up for many tasks to take full advantage of the rubber-tired machine's unique size and weight.

"Approximately one-third of the total weight of a TLB is in the two-ton backhoe assembly," says Gary Ober, professional operator and author of the book, Operating Techniques For the Tractor-Loader-Backhoe. "Because of its location high above the ground and far behind the wheelbase, the backhoe's weight transfers the entire machine's center of gravity upward and to the rear. The positioning of this weight when maneuvering around a jobsite is a concern for all operators. . ."

With a backhoe boom tip rising 12 feet into the air, slopes shift the machine's center of gravity downhill. The backhoe-loader's tendency to tip in these conditions is greater than that of machines with lower centers of gravity. Swinging two tons of backhoe downhill moves the center of gravity farther down the slope. If the bucket is full of dirt and the outriggers aren't deployed, the center of gravity may well extend beyond the tires. The machine will roll onto its side.

A loader full of dirt can also compromise stability on slopes. For example, driving downhill with a full bucket shifts weight from the rear tires. On a two-wheel-drive machine, it's important to keep as much weight and traction as possible on the rear because they're the only wheels with brakes.

Conversely, a machine may be stable driving uphill with a full bucket of dirt, but when the load is dumped into a truck, the loss of ballast can cause the machine to tip backward. Again, the concern is not that the machine might roll over, but that it will lose its ability to steer.

The machine is most stable for backhoe work when it is set up in what can be called the tripod position. Stabilizers are spread for the widest platform possible — not necessarily fully extended, but down far enough to raise the rear tires. The machine should be leveled for normal digging, but stabilizers can also tilt the machine to dig around obstacles in the excavation, or to slope the walls.

Each stabilizer is one leg of the tripod, and the loader bucket is the third. The loader should be in solid contact with the ground. If the front tires are carrying even part of the machine's weight, it will bounce slightly as the backhoe works. That bouncing will be transmitted into the operator and amplified through the controls.

Maximum digging force is achieved by combining the hydraulic power of the boom, dipper and bucket. The best operators use all three functions at once while maintaining the best bucket angle.

"When trenching, the goal is to shave layers of soil off, rather than gouge out chunks," says the narrator in a training videotape called Tips From the Pros: Backhoe-Loader from VISTA Start Smart Training. "Let the bucket teeth and cutting edge work for you. The teeth do the initial cutting by breaking the soil into pieces. The crumbling spoil begins to fill the bucket and the curling action holds the spoil in the bucket."

In normal digging conditions, start with the bucket floor at about a 45-degree angle to the ground. On harder surfaces, a flatter angle of attack will generate more cutting force.

Concentrate on making the first cut exactly where the trench should be. It will guide all of the following passes, so make sure it's accurate. Digging a footing requires special precision because the walls of the excavation will be the form for the concrete pour.

"If it is dug too large, more concrete will be required; if it is dug too small, the reinforcing steel will not fit," says Ober. "Layout and digging techniques are extremely important because you only have one chance to get it right."

Pier-type footings require straight, plumb sides that are in exactly the right location. The excavation must first be precisely and clearly marked. Then the operator must align the backhoe so that long, straight strokes of the stick will align the excavation walls where the engineers want them.

Check the alignment by reaching out and touching the ground with the backhoe bucket's corner tooth next to the layout line. Boom up, stick in and touch the ground close to the machine. Do not swing the boom. The bucket should land as close to the layout line the second time as it did with the backhoe outstretched. If it doesn't, pivot the machine and check the alignment again until the boom is parallel to the layout.

Pivoting is a setup maneuver where the operator holds the stick vertically, digs the bucket teeth into the ground, and uses boom-down pressure to lift the rear end of the machine off the tires. Using the boom-swing cylinders, the operator can pivot the backhoe left or right on its loader bucket. Use the stabilizers as necessary to level the backhoe to dig plumb walls and a flat bottom.

After the guiding first cut is made, it's time to bale dirt. Each pass should be long and fairly flat, but the object is to move dirt as quickly and safely as possible until you're within six inches or a foot of the desired grade.

Cast the spoil as far from the trench as possible without wasted motion, placing spoil from the shallowest cuts furthest from the trench. OSHA requires a minimum of two feet between spoil pile and the edge of a trench. Unstable soils — whether it's because of sand or water or vibrations from nearby traffic — require more distance.

Clean up the area around the trench before final grading. "By sliding the bucket flat on the surface, the spoil will either be pushed toward the spoil pile or fall into the trench," says VISTA's Tips video narrator. "Also, now is the best time to remove any exposed rocks from the trench walls that may be a fall hazard."

A backhoe with extendible stick will dig more trench with fewer setups, but the benefits of additional reach come with limits.

"The machine isn't designed to work all the time in the extended position," says Dave Littlepage, product demonstrator/instructor at Caterpillar. "And don't forget to place the lockout pin in the stick when using hydraulic tools — the EStick is not designed to be fully extended while using things like hammers and plate tamps."

The Caterpillar Equipment Training Program for backhoe-loaders adds to the list of don'ts for extendible booms. "When the stick is extended, don't strike the ground with the bucket, fully extend the swing cylinder, backfill with the side of the bucket, use a large bucket, swing the load downhill, or reposition the machine (using the backhoe)."

Ober recommends digging most of the excavation — all except the finish grading — in two stages. Extend the stick and dig everything from the surface cut down to just above the finished grade. Then retract the stick and repeat the process closer to the machine. Fine grade the excavation in two stages as well.

For more details on excavator and wheel-loader productivity, which can be applied to backhoe and loader work, see the stories "Production Heroes Take the Textbook to the Trench" and "Take-Charge Loader Operators Fill Trucks Faster" at www.ConstructionEquipment.com. Keep in mind, though, that there are many features unique to backhoe-loaders.

For example, when digging or loading from a stockpile, drive the bucket into the material and raise the loader arms to put down pressure on the front axle and get more traction from a four-wheel-drive unit. But in a two-wheel-drive machine, down pressure on the front axle unloads the rear drive wheels, reducing traction.

When working with the loader on the side of a hill, swing the backhoe uphill to stabilize the machine.

A four-way, or clamshell, bucket can unload sticky material better. Just open the jaw of the bucket and most materials will fall out without requiring a full dump cycle. This maneuver can also help backhoe-loaders reach trucks that are a little too tall for a full dump cycle.

 

It's too easy to settle for the usual way of digging trench when soil conditions or limited right of way challenge the textbook prescription for setting up a job. It's a mistake to throw out the textbook in less-than-ideal conditions, though, because even tiny improvements in production can add up to significant profit gains.


Almost anybody can improve their productivity by 5 percent. Programs such as Standards Based Operator Training (SBOT) from Caterpillar Equipment Training (CET) and VISTA Training's TIPS from the Pros videotape series recognize the value of refining experienced operators' skills. They focus on advice that will improve production with each cycle, but emphasize how to do it safely.

It's clear that any excavator operator should get OSHA's competent-person certification for trenching. The operator will be first to notice variations in soil conditions that require a change in trench shoring or sloping to keep people safe.

Before starting work on any site, the utilities need to be located and potholed to confirm their depth. VISTA's TIPS From the Pros series recommends walking the site to look for hazards like drop-offs, soft spots, and power lines. Climb down from the machine every now and then during the day to look at what's around behind.

Merle Hermsen, operator trainer at John Deere, pays particular attention to maintaining solid footing.

"Make sure the machine's setting level," he warns. "If you're working across a slope, bench up the downhill side so the trench walls will be straight up and down. If there's a hole behind you, swing around with a bucket full of dirt and level it off before you move back."

Everybody recommends inspecting a machine before starting to work. But Tom Brady, training coordinator for Cat's SBOT program, suggests that the best time for a really thorough once-over is probably at the end of the day. If you find a leak or a loose or broken part, there's a chance to fix the machine before the next morning. Grease will flow into warm joints much more easily, too. Then morning walk-arounds boil down to checking cold fluid levels and making sure the machine hasn't been damaged in the night.

When you're ready to start moving dirt (seat belt buckled, hydraulic fluid warmed up, gauges in the green) make sure excavators with work-mode choices are set at full power and boom priority. Approach the trench with the track idlers forward. Keeping the final drives behind you protects their bearings and seals from digging and lifting stress, and they provide extra counterweight.

Digging within the machine's power band makes maximum use of all that counterweight. The boom and stick are most powerful working in an arc that starts with the stick extended 35 to 45 degrees ahead of vertical and ends when the stick returns to vertical.

"It's typical for operators to work in one spot too long," says Brady. "They'll reach too far forward and pull back to within 2 feet of the tracks. It takes too long to fill the bucket.

"You never catch a break," he adds. "A steady stream of trucks really adds to the stress. Utilizing that power band will allow you to cycle faster, and it makes your life a lot easier."

In reasonable conditions, trenches should be dug from the top down, peeling material off in long layers just thick enough to fill the bucket by the time the stick is vertical. Start with the bucket floor at about a 45-degree angle to grade. The teeth will do the initial cutting by breaking the soil into pieces, but curl the bucket as the stick moves toward you. Use bucket breakout force to quickly penetrate to the desired depth of cut.

VISTA's new tape, "TIPS From the Pros: Excavators," points out that you will get a flatter trench bottom if you finish the cut with the bucket flat. Begin to boom up out of the trench before you curl the bucket, and only close it enough to retain the load. It saves time and helps avoid hooking utilities.

"It's easier to dig a level trench when you're slicing 6 inches deep and 8 feet long," says Hermsen. "You're almost practicing finish grading all the way down."

Don't use more finesse than you need, though.

"Know when to do precise work, and when to just bale dirt," urges the VISTA videotape narrator. "Don't waste time trying to make every pass a finishing pass."

Move dirt as quickly as is safely possible down to within 6 inches of the desired grade, or until the trench box should be pulled forward. At that point you may want to clean up spillage around the edge of the trench and pluck out any exposed rocks that might fall from the sidewalls. Then move the box into position and finish the trench.

Try to pile spoil over a corner of the tracks, where swing time is minimized and the excavator is still quite stable. But spoil must be a safe distance from the trench (minimum of 2 feet, according to OSHA). Some jobs will be more profitable with an oversized excavator that can reach further without sacrificing productivity.

"If you're digging material that weighs 2,700 to 3,300 pounds per cubic yard with a 2-yard excavator," says Brady, "you have a few tons of material coming out of the bucket every cycle. You want that spoil as far away as you can get it and still be productive."

One way he recommends to get better distance without swinging farther is to dump through the spoil pile. He describes the motion as laying the bottom of the bucket on the pile and using it to push the pile away from the trench as you uncurl the bucket and stick out. You're moving the previous load back and replacing it with the load in the bucket.

Deere's Merle Hermsen recommends refining cycles by extending the stick only about 40 degrees when dumping the bucket.

"It leaves the arm in position to start digging when you come back to trench," he says.

Great time savings can be gained in truck placement when you're loading spoil to be hauled away. In the rare textbook example, off-road haul units back up close to the trench and the excavator swings less than 45 degrees through their open end gates to dump.

Loading over the end gate requires the least amount of booming up to put the bucket over the truck, and allows you to dump while swinging over the length of the bed. You don't have to stop swinging to dump over a narrow target, which is what happens when loading over the truck's side rails. Hitting the target is easier on the machine, too, because the swing brake doesn't have to stop 3 tons of material.

Of course, most construction jobs use highway trucks with tailgates to haul spoil. But the tailgate of an on-highway truck is lower than its sideboards, so you still save some booming-up time working over the rear. And there's serious motivation to dump while swinging the length of the truck because the dump body is generally narrower than an off-road hauler's. Loading a highway truck over the side rails presents a small target.

"Any time you can dump while you're swinging, you will reduce cycle times 6 to 9 percent compared to loading over the side," says Brady. "The best arrangement on a construction site is usually to have the truck beside you, where you can swing 90 degrees and be over the tailgate.

"If you have to swing more than 90 degrees, switch the machine over to swing-priority mode," Brady adds. "You'll swing faster, and still have plenty of time to get the boom up over the truck bed. But remember: If you're not blending three functions, you get no benefit from work modes. The machine is designed to work most efficiently when you're using three functions at once."

When limited right-of-way forces trucks to back in behind the excavator, you must blend functions to get the bucket ready to dump and dig while swinging. It's one of the only time savers available.

Limited right-of-way seldom offers the opportunity to slip trucks in at an advantageous angle, but watch for it. Any time you can load over the tailgates you'll be a hero.

Safe improvements in production are within everybody's grasp, especially with programs like Cat's SBOT, other manufacturers' training efforts, and third parties such as VISTA's TIPS from the Pros. In light of today's razor-thin margins, a little productivity can earn big profitability.

"One point we make when we train operators is that all of the profit for a day on most jobs is made in half an hour," says Rich Deeds, fleet manager at Brubacher Excavating, an eastern-Pennsylvania firm with about $30 million worth of equipment in the field. "If they're unproductive for half an hour, the job loses money for the day. But if they can find a way to improve productivity just a little, they can easily double the profit."