Stabil-Trak™ Operation; Understanding The Stabil-Trak™ System - JLG sky trak mmv Service Manual

Stabil-TRAK™ System
11.3 STABIL-TRAK™ OPERATION
The rough terrain telescopic handler rarely operates on
ground that is a smooth, flat surface. As its name infers,
the "Construction Rough Terrain Telescopic Handler" is
typically found on worksites with numerous holes, trench-
es, rocks and slopes.
To negotiate this type of terrain, rough terrain telescopic
handlers are designed with a free oscillating rear axle.
This design enables the operator to drive over changes in
terrain with minimal concern for what the rear tires are go-
ing over.
With oscillation, the rear axle will rotate upward or down-
ward when a tire meets with anything causing it to raise
or lower. The rear of the vehicle moves up or down ap-
proximately one-half the distance of the tires movement,
while giving the vehicle minimal lateral movement. The
oscillation capability is necessary for traveling across
rough terrain.
The rear axle is capable of oscillation; the front axle is
normally locked to the vehicle frame by the frame sway
cylinder. The frame sway cylinder does allow for adjust-
ment of the frame and load to a level position when trav-
eling on a rough terrain worksite, or for leveling a load.
The least stable condition for the rough terrain telescopic
handler is when the boom is raised and the carriage is
empty. This is because the center of gravity is now high
and closest to the rear apex of the stability triangle.
11.3.1 Understanding the Stabil-TRAK™
System
The following information explains the difference between
a typical telescopic handler and the benefits that the
Stabil-TRAK™ system provides.
Most telescopic handlers operate within a 3-point stability
triangle (1) as defined by points A, B and C.
Point 2 in the illustration represents the center of gravity
of an unloaded vehicle. The load has its own center of
gravity represented by point 3. When the vehicle is load-
ed, the vehicle and load become one mass with a com-
bined center of gravity, represented by point 4.
As the boom is lowered or extended, point 4 will move for-
ward in the 3-point stability triangle, or backward in the
3-point stability triangle as the boom is raised. Point 4 can
also move left or right toward the edges of the stability tri-
angle if the frame is tilted. As long as point 4 remains in
the boundaries of the 3-point stability triangle (1), the ve-
hicle will remain stable. If point 4 ever goes beyond the
boundaries of the stability triangle, the vehicle can tip
over.
11.4
In the LOCKED MODE, the exclusive Stabil-TRAK™ Sys-
tem provides a 4-point stability rectangle (5) by positively
locking the frame to the rear axle through the stabilizer
cylinder. The vehicle is then supported at four points; A,
B, D and E. While in the LOCKED MODE, it is clear that
point 4 will remain within the entire boundary of the
4-point stability rectangle, giving the operator more flexi-
bility in positioning the load.
3
A
1
5
The following describes the three basic modes of the pat-
ented Stabil-TRAK™ system. The vehicle may operate in
any one of the following three modes.
a. Free Pivot Mode (6)
With the boom below 40°, the Stabil-TRAK™ system is in
the FREE PIVOT MODE and the rear axle is allowed to
pivot freely. The frame sway control will function normally.
Below
40°
FREE
PIVOT
MODE
B
4
2
C
E
6
Stabil-TRAK
Light
"OFF"
Model MMV Rev. 12/04
D
MT2780
OS01912