Appendix A – Stability of Powered Industrial Truck

Stability of Powered Industrial Trucks (PIT)

The following definitions help to explain the principle of stability:

• 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.
• 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.
• 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).
• Lateral stability is a truck’s resistance to overturning sideways.
• 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.
• Longitudinal stability is the truck’s resistance to overturning forward or rearward.
• 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.