Doosan D50S-5 Operation & Maintenance Manual page 22

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