Rough terrain forklifts often have an oscillating
â€” or free-moving â€” rear axle that
allows the vehicle to better negotiate changing
grades. This added movement, combined
with the uneven terrain of a construction site,
plus the heavy weight and unusual shape and bulk of
construction loads, makes operating the rough terrain
forklift difficult. Here are seven safety tips:
In order to lift the load, the base of the vehicle
must be stable enough to avoid tipping over as the
load is raised or extended in the air. Rough terrain
forklifts weigh thousands of pounds more than any
automobile. In order to lift and move heavy loads, a
counterweight is mounted on the unit to keep everything
in balance. The mass of the vehicle itself provides
counterweight for extension and lifting.
A greater weight must be at the base of the lever in
order to raise a heavy load into the air. Forklifts are
basically levers supported on wheels, requiring force
on one side to lift the other side.
approach and negotiate
turns carefully. Steering
and stability go hand in
hand. Rough terrain vehicles
have the following
different steering modes:
3â€” Suspension, stability triangle, center of gravity
- Select steering
allows the operator to
select which wheels do
- Two-wheel steering
allows either the front or
back wheels to steer the forklift. Front-wheel steering
enables the forklift to operate like an automobile
and move at a faster speed over longer distances.
Back-wheel (rear-wheel) steering allows for increased
maneuverability in tight cornering situations.
- Four-wheel steering allows the rear wheels to
always follow the front ones and provides the tightest
- Crab steering allows for responsive steering that
aids in picking up an inconveniently positioned load.
This type of steering can turn
the wheels in the same direction,
enabling the machine to move
sideways or at a diagonal.
Today’s rough terrain forklifts
are being designed with four-point
suspension, but many continue to
be made using a three-point suspension
system where the vehicle
is supported at three points.
An imaginary line drawn
between these three points â€” the
two front tires and the pivot point
of the rear axle â€” makes up what
is known as the stability triangle.
The stability triangle is a reference
point; as long as the center
of gravity remains within this
imaginary area, the vehicle will
be stable. Unloaded and parked,
a forklift’s center of gravity will
remain centered in the stability
Once the vehicle is moving,
acceleration, braking, and turning
can affect this center of gravity.
That’s why operators should
avoid accelerating quickly and
should always take corners slowly.
Keeping the forks or attachments
at the lowest possible point for
traveling maximizes this center
of gravity. If the center of gravity
is shifted to the point outside the
stability triangle, the vehicle could
When the forks are loaded
there is even more to keep track
of. Besides the center of gravity
of the heavy vehicle
itself, each load has its
own center of gravity.
This is called the combined
center of gravity.
Because the load is
being constantly moved,
the combined center of
gravity is almost always
When moving a load,
the forklift’s stability
also depends on knowing
where the line of
action is. The line of action is an imaginary vertical
line that extends through the combined center of gravity.
If the line of action exits the triangle of stability,
the unit will become unstable and tip over. The line of
action is even more important when picking up a load
when parked on an incline.
4â€” Load handling and attachments
Before any load is handled, the operator must
know that the forklift can safely move, lift, or lower
it. This requires the employee to know the weight of
the load and the capacity of the vehicle. This information
can be found in several places â€” the identification
plate, operator’s manual and the load chart that
comes with the vehicle.
5â€” Load charts
The design and weight of the forklift determines
its load and lifting capacity. Since manufacturers
design their vehicles for specific applications,
different weights may make it necessary for
the operator to use a different forklift or split up
6â€” Load center
The load center is the center of gravity of the
load. It’s expressed as the horizontal distance from
the edge of the load at the front of the carriage, to the
center of gravity of the load.
Because construction loads are often irregularly
shaped with uneven centers of gravity, load centers
will vary depending on the size of the forks or
attachments. The stability of the load decreases the
farther the load center is from the face of the carriage.
Make sure the load center is appropriate for
the length of the fork or attachment.
7â€” Frame leveling
Always level the vehicle before raising the
boom. If the operator attempts to tilt the frame with
a raised load, the forklift could tip over. Adjust the
frame slowly until the ball is centered in the frame
level indicator for maximum stability.
If the surface grade is too steep or uneven to level
the frame, do not attempt to raise the boom. It will be
necessary to move the vehicle to a location that provides