Forklifts work on the principle of a cantilever. A load on the forks (a beam) supported by the front wheels (a fulcrum) is counterbalanced by the forklift’s body and counterweight built into it. Comparing the “moment” of each determines whether a forklift will safely carry a load or tip forward. In other words, the driver must consider the load and the forklift’s center of gravity together. And to complicate matters the center of gravity moves as the load is moved with the forklift traveling over rough and inclined surfaces.Understanding the principle of a cantilever is an essential part of reducing the risk of forklift overturn, collision and loss of load. It’s also helpful to understand a forklift’s stability triangle. This triangle is formed by the center of each front wheel and the center of the rear wheel (or center of the two rear wheels’ axel). Imagine a vertical line extending from the center of gravity of the vehicle-load combination. If that vertical line is inside the stability triangle, you’ll prevent the forklift from tipping forward, falling sideways or dropping the load.
Here are some scenarios that illustrate how the center of gravity moves on a forklift. The center of gravity moves toward the front axle when a driver tilts the load forward, raises the load while tilted forward, drives on an incline with the load downhill, stops forward travel or accelerates backward. The center of gravity moves toward the rear axle when a driver tilts the load back, raises the load while tilted back, drives on an incline with the load uphill, accelerates forward or stops backward travel. When driving a forklift across an inclined surface, the center of gravity will move toward the downhill side of the forklift’s stability triangle. If you drive across a rough or uneven surface, the center of gravity will move toward the rut or low side of the forklift’s stability triangle. And when you’re turning a forklift, its center of center of gravity moves toward the side now facing the original direction of travel.
You can reduce the risk of forklift overturn, collision and loss of load by having a firm understanding of how a forklift load combination can move outside the stability triangle. This can happen when the load is picked up on the tips of the forks, when the load is tilted forward, when the load is tilted too far back when raised, when the load is wide or when forklift movement causes the center of gravity to shift.
There are several ways to prevent your forklift from dropping its load, falling sideways or tipping over. Be sure a load is stable and safely arranged on the forks. Avoid tilting the forks forward except when depositing a load or picking one up. When tilting a load backward only do so enough to stabilize the load. When traveling, keep the load just above the pavement with the forks tilted back. If you need to cross railroad tracks, cross them diagonally when possible. When it comes to elevators, enter the forklift into the elevator squarely. When going up or down and incline, keep the load uphill. Make sure you drive your forklift at a speed that allows you to stop safely within the stability triangle. Be sure to slow down on slippery or wet surfaces. You’ll want to slow down when making turns. And, lastly, avoid driving on surfaces with holes or ruts and over loose objects.