Figure 5.
Lifting a 5 lb box directly up has the
effect of lifting 5 lbs.
Figure 6. As the distance increases from the shoulder, the moment, or apparent
weight increases so that a 5 pound box seems to weigh 12 pounds.
View Animation 
The way in which weight is distributed changes the amount of weight the lift truck will safely carry. You
can experience this for yourself by doing the following activity:
Lift a 5 pound box. As you extend your arms, the center of the box’s weight
moves a greater distance from your body, so the box feels heavier and you will
tend to fall forward. The same idea of increasing the load center distance
applies to a playground seesaw: the farther you sit from the middle, the more
you increase the load center distance and the more force you put on that end.
The same principle—increasing the load center distance—can cause a forklift to tipover.
When the load center distance increases, it is actually increasing something
called the "Load Moment":
Load Moment is the product of the object's weight multiplied by the object’s
distance from the fulcrum, which is a fixed point that acts as the pivot point.
On a sitdown counterbalanced forklift, the fulcrum or pivot point is the axle
of the front wheels. It is this product, or Load Moment, which determines how
much overturning force is being applied to the forklift.
Load Moment = Weight X Distance
Because the overturning force depends on both the weight of the load and the
load’s distance from the pivot point, a forklift’s capacity is always stated in
terms of both: the load’s weight and its load center distance. For example, if a
forklift’s capacity as stated on its data plate is “3,000 pounds at a 24 inch
load center,” this means that the Load Moment cannot safely exceed 72,000
inchpounds (24in. x 3,000 lb = 72,000 inchpounds.) If the load center
distance for the actual load is greater than the standard 24 inches, the only
way to keep the Load Moment from exceeding 72,000 inchpounds is to reduce the
load. The easiest way to determine the maximum load when the load center
distance is greater than the distance stated on the data plate is to divide the
maximum Load Moment by the actual load center distance. For example:
If a load is 60
inches long (30inch load center) then the maximum that this load can weigh
is:
72,000 inchpounds / 30 inload center = 2,400 pounds
Figure 7. Improperly
distributed loads may tip the forklift if the maximum load moment is exceeded. 
Potential Hazards:
While carrying a load near the maximum allowable capacity, be aware of
the following:
 Danger of tipover
 Danger of losing load
 Danger of being struck by falling load
Requirements and Recommended Practices:
 Calculate a maximum allowable load moment to determine whether an unusual load, such as
one that is longer than 48 inches (i.e., the load center distance would be
greater than 24 inches) or that has an offset center of gravity (i.e., uneven
weight distribution) can be
handled safely.
 Minimize the load center distance measured from the back of the forks to the center of the load. This allows the
forklift to carry more weight.
As illustrated in Figure 7, a truck that has a 4,500 pound capacity at a 24inch
load center will tipover if a 60inch load is positioned lengthwise.
Positioning the load in this way increases the load center distance to 30 inches
and increases the load moment by 27,000 inchpounds.
In Figure 7 the forklift safely carries the 4,500 pound load at a load
center distance of 24 inches, but tips over when the load
center increases to 30 inches. Here's the calculation:
30 inches X 4,500 pounds = 135,000 inchpounds
24 inches X 4,500 pounds = 108,000 inchpounds
The load moment is increased by 27,000 inchpounds.
If the load center distance is 30 inches, the only way to keep the maximum
allowable load moment within 108,000 inchpounds is to limit the weight of the
load to 3600 pounds:
30 inches X 3600 pounds = 108,000 inchpounds
 Use extra caution when handling extra heavy loads that may approach the truck's maximum capacity. For example, when handling
a maximum load, the load should be carried at the lowest position possible, the truck should be accelerated slowly and evenly,
and the forks should be tilted forward cautiously. However, there is no one rule for all situations.
 Maintain control of the vehicle at all times. The operator is responsible for handling the truck.
Drive slower when carrying a load near the maximum allowable.
 Do not exceed the stated capacity of your truck. Know its mechanical limits.

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