Know your lift capacity limitations
Miller emphasizes the need to read and understand lift capacity charts for long boom and stick configurations. They provide the maximum acceptable lift at a given reach.
If a lift capacity chart is not available, there is a simple formula to approximate lift capacity at various boom and stick lengths. "A good rule of thumb is 2% loss for every 1 ft. of extra reach based on the original manufacturer?s brochure," says Wever. "This is a calculation of distance and moment arm. That is a safe number."
But estimating lift capacities can be a risky proposition. "Contractors should never estimate the lifting forces for any attachment," Jacobson asserts. "In every case, a lifting chart valid for the attachment on the machine should be placed in the operator?s cab and in documentation of the machine. This is the best way to prevent accidents on the jobsite due to overloading."
As a general rule, the longer the attachment, the smaller the bucket that can be used. "However, this is largely dependent upon the specific weight of the material," Jacobson notes. "The operator must always stay at or below the lifting capacity of the machine with a full bucket."
Resist the temptation to push lift capacity limits in the hopes of increased productivity. "Over bucketing a LF machine will cause machine stability problems and significantly slow machine cycle times, eliminating any perceived increases in production," says Hendry.
When calculating lift capacity, you must first know the exact length of your excavator front, says Hendry. "Second, you must know the exact weights of the material you intend to pick up," he states. "Third, you must know the exact maximum load your LF machine can lift at maximum reach ? over the front and, more critical, over the side.
"These numbers dictate what you can safely lift without exceeding the stability limits of the machine," he adds. "Then you can properly size the attachment." For example, if the machine can lift 10,000 lbs. and the grapple you?re using weighs 5,000 lbs., you will be limited to 5,000 lbs. of material per cycle.
"In general, the combined weight of the tool and any material to be handled should never exceed the published lifting capacity of the machine," Jacobson emphasizes. "If there is any doubt in the contractor?s mind about the suitability of an attachment for a particular boom and stick combination, the manufacturer should be contacted for a suitability study."
No replacement for experience
When it comes to LF excavators, only skilled operators need apply. "Super LF excavators are unique machines that require a skilled operator who is properly trained in long-front operation," says Hendry. "Any side sweeping motion of the boom/arm can and does cause twisting damage. LF excavators are designed to be used in an ?in and out? motion or, more directly, a ?pulling? motion. The boom/arm is not designed for heavy digging like a standard boom/arm machine. Super LFs have to be operated with great care and finesse."
This calls for an experienced operator who can maintain precise, deliberate movements. "Depth perception with the long fronts will be very different than a standard machine; operator concentration is imperative," says Hendry. "Banging the bucket on the ground while swinging will cause severe damage to the boom/arm. The long boom/arm configuration changes the center of gravity of the machine, so an operator will need to understand the difference between a regular machine and the LF machine."
The operator must also understand the difference in the range of motion. "In some cases, the attachment or the working tool on an excavator equipped with a long boom or stick could come into contact with the operator?s cab, some other part of the uppercarriage or the undercarriage of the machine," says Jacobson. Optional stick limiter kits are available from most manufacturers to prevent contact with the machine.