Load Handling, Stability, and Capacity
This domain tests the stability physics and capacity limits that explain why a forklift tips, and the load-handling habits that keep the combined centre of gravity inside the stability triangle.
Stability and capacity
- A counterbalanced truck is stable when its combined centre of gravity (truck plus load) stays inside the stability triangle formed by the two front wheels and the centre of the steer axle.
- The data plate gives rated capacity at a stated load centre, commonly 24 inches, and sometimes at a stated lift height. Capacity falls as the load centre moves outward, as lift height increases, and when an attachment is fitted.
- Keep loads centred, against the backrest, and tilted back slightly during travel. Keep the load low; raising it moves the combined centre of gravity upward and reduces margin.
- Avoid dynamic loads: braking, turning, and shock loading increase the effective load on the truck.
- Never exceed the plate rating. If load weight or centre is unknown, stop and verify; do not guess.
Worked example
A truck is rated 5,000 lb at 24 in. The load weighs 4,500 lb but its centre is 36 in from the fork face. Using the common proportionality approximation, capacity at 36 in is about 5,000 x 24/36 = 3,333 lb. The 4,500 lb load therefore exceeds capacity, even though it is below the 5,000 lb figure on the plate. The operator must not lift it; the correct action is to reduce the load, use a larger truck, or obtain the manufacturer's derating chart for the actual attachment and height.
Traps
Reading the data plate as a single maximum weight; ignoring load centre, lift height, or attachment derating; travelling with the load raised 'to see better'; side-shifting or turning with an elevated load.