Safety Section
-21-
Avoiding Lift Truck Tipover
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,
are 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.
