DC Velocity - January 2016

high-lift trucks. It covers everything from fall protection and braking requirements to compliance testing and maintenance. The standard is not just for equipment manufacturers, though; it also defines safety requirements for users and has been adopted by the Occupational Safety and Health Administration (OSHA). (The B56 standards for all types of lift trucks are available at no charge at www.itsdf. org/ pB56.asp.)

With high-reach trucks, stability is the critical safety issue. Four main factors come into play here. The first is the vehicle’s legs, known as outriggers. With a standard sit-down counterbalanced truck, the higher you go, the less weight you can lift because the truck’s center of gravity shifts forward as the load ascends, says Tony Kordes, product manager at UniCarriers. But high-reach trucks generally can carry more consistent weights regardless of height because “they straddle the load with outriggers, so the center of gravity is close to the mast,” he says. Higher lifts call for wider outriggers, which also have to absorb lateral loads to prevent tipping as the truck leans left or right, Kordes adds.

The second element is the mast. As it rises by means of a series of stages, or sliding extensions, it becomes subject to twisting, swaying (particularly when the operator moves around), side bowing, and leaning forward (“deflection”). “This means the mast should be rigid enough to minimize sway and have the ability to evenly distribute load forces throughout the frame,” says Matt Barrow, product manager for Yale Materials Handling Corp. How effectively a mast does that varies with the manufacturer, the mast design, and the type of truck, but strong torsional rigidity is a must.

Some manufacturers have software that helps to keep the mast steady. Cat Lift Trucks, for example, says the Active Sway Control feature available on certain models of its reach trucks uses software to calculate mast sway; it then provides a compensating movement to control acceleration and braking so that the driver’s compartment remains stable at all heights.

The third stability factor is the flatness of the floor.
“Super-flat floors are required for turret and swing reach
trucks because neither their masts nor their carriages tilt
to help them compensate for the irregularities of common
warehouse floors,” says Bruce Dickey, vice president of
sales for Narrow Aisle Inc. “This requirement can add sig-
nificant cost to turret and swing reach truck installations,”
he notes, adding that flatness requirements for the articu-
lating narrow- and very-narrow-aisle trucks his company
provides are much less stringent.

Last is the weight of the battery, says Susan Comfort, product manager, narrow-aisle products, for The Raymond Corp. “The battery needs to be bigger because it has to function as a counterweight for the height. But there’s a trade-off: The bigger battery may mean a wider truck, which may limit the width of the aisles where the truck can work,” she says.

Because the tall mast may be called on to lift and lower loads (and in certain types of trucks, the operator, too) while the truck is moving, speed must be strictly controlled if stability is to be maintained. As the operator and/or load goes higher, the truck’s operating software will automatically reduce the vehicle’s speed, says Scott Carlin, electric product support manager at Toyota Material Handling U.S.A.