Safety Section
-21-
Avoiding Lift Truck Tipovers
Lift Truck Stability
Counterbalanced lift truck design is based on the
balance of two weights on opposite sides of a fulcrum
(the front axle). The load on the forks must be balanced
by the weight of the lift truck.
The location of the center of gravity of both the truck and
the load is also a factor. This basic principle is used for
picking up a load. The ability of the lift truck to handle a
load is discussed in terms of center of gravity and both
forward and sideways stability.
Center of Gravity (CG)
The point within an object, at which the whole weight of
the object may be regarded as being concentrated, is
called the center of gravity or CG. If the object is uniform,
its geometric center will coincide with its CG. If it is not
uniform, the CG could be at a point outside of the object.
When the lift truck picks up a load, the truck and load
have a new combined CG.
Stability and Center of Gravity
The stability of the lift truck is determined by the location
of its CG; or, if the truck is loaded, the combined CG of
the truck and load. The lift truck has moving parts and,
therefore, has a CG that moves. The CG moves forward
or backward as the mast is tilted forward or backward.
The CG moves up or down as the mast moves up or
down. The CG and, therefore, the stability of the loaded
lift truck, is affected by a number of factors such as:
z
the size, weight, shape and position of the load
z
the height to which the load is lifted
z
the amount of forward or backward tilt
z
tire pressure
z
dynamic forces created when the lift truck is
accelerated, braked or turned
z
condition and grade of surfaces on which the lift
truck is operated
These same factors are also important for unloaded lift
trucks. They tip over sideways easier than a loaded lift
truck carrying its load in the lowered position.
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