Avoiding Lift Truck Tipovers - Doosan GC15S-5 Operation & Maintenance Manual

Safety Section

Avoiding Lift Truck Tipovers

Lift Truck Stability
Counterbalanced lift truck design is based on the bal-
ance of two weights on opposite sides of a fulcrum
(the front axle). The load on the forks must be bal-
anced 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 dis-cussed 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 uni-
form, 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 :
• the size, weight, shape and position of the load
• the height to which the load is lifted
• the amount of forward or backward tilt
• tire pressure
• dynamic forces created when the lift truck is
accelerated, braked or turned
• 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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