Creating a Stable Load

Load instability is a major cause of forklift accidents, so operators need to know how to create a stable load. This requires understanding concepts related to the center of gravity, or the balance point of a load.

The following definitions help to explain the principle of stability:

The center of gravity is the point on an object at which all of the object's weight is concentrated. For symmetrical loads, the center of gravity is at the middle of the load. However, many loads are a mixture of items of different densities, weights, and distributions. For example, a pallet loaded with a variety of different materials will not have a consistently distributed load. The center of gravity will be on the side of the pallet that is loaded with the heaviest materials. The forklift operator should always pick up a load on the side that is closest to its center of gravity. This keeps the weight of the load closer to the forklift, which reduces the risk of the load falling off or causing the forklift to tip over.

Counterweight is the weight that is built into the truck's basic structure and is used to offset the load's weight and to maximize the vehicle's resistance to tipping over.

The fulcrum is the truck's axis of rotation when it tips over.

Grade is the slope of a surface, which is usually measured as the number of feet of rise or fall over a hundred-foot horizontal distance. (The slope is expressed as a percent.)

The line of action is an imaginary vertical line through an object's center of gravity.

Load center is the horizontal distance from the load's edge (or the fork's or other attachment's vertical face) to the line of action through the load's center of gravity.

Moment is the product of the object's weight times the distance from a fixed point (usually the fulcrum). In the case of a powered industrial truck, the distance is measured from the point at which the truck will tip over to the object's line of action. The distance is always measured perpendicular to the line of action.

Track is the distance between the wheels on the same axle of the truck.

Wheelbase is the distance between the centerline of the vehicle's front and rear wheels.

Stability types:

• Lateral stability is a truck's resistance to overturning sideways.
• Longitudinal stability is the truck's resistance to overturning forward or rearward.
• Dynamic stability is the truck's resistance to weight transfer and the resultant shift in the center of gravity due to the dynamic forces created when the machine is moving, braking, and cornering, as well as lifting, tilting, and lowering loads.

To learn more about Forklift Safety visit our Forklift Safety Online Training web page.