Gradeability; Theoretical Gradeability; Actual Gradeability - Snorkel A46JRT Operator's Manual

Chapter 8 – Operation
Drive speed ranges are interlocked through limit switches
that sense the main and riser boom position.
• When either boom is elevated or extended, only the
slowest drive speed will work regardless of the drive
range switch position.
• To avoid a sudden speed change from high to low
elevated boom speed, always bring the machine to
a stop before raising the booms from the stowed
position.
Warning
The potential for an accident increases when safety
devices do not function properly. Death or serious
injury could result from such accidents. Do not alter,
disable, or override any safety device.
Do not use the aerial platform if it drives faster than 0.8
miles per hour (35 feet in 30 seconds) when any of the
booms are out of the stowed position.

Gradeability

Gradeability refers to the maximum slope that the ae-
rial platform is capable of travel. Gradeability can be
described as "theoretical" or "actual" with the slope, or
grade, measured in percent of slope or degree of slope.

Theoretical Gradeability

Theoretical machine gradeability refers to the maximum
slope that the machine is capable of travel under perfect,
34
Angle of Slope
in Degrees
Figure 8.4 – Slope Percent/Degree Conversion
or theoretical, conditions. It is based on mathematical
calculation, not practical application.
Some of the factors taken into consideration when cal-
culating theoretical gradeability include:
• Drive motor efficiency
• Machine weight
• Machine center of gravity
• Tire traction
• Tire contact
• Condition of slope
The value for theoretical gradeability will most always be
high when compared to the actual gradeability value. The
perception then is that the machine can climb a steeper
slope than is actually practical.

Actual Gradeability

Actual machine gradeability refers to the maximum slope
that the machine is capable of travel under practical con-
ditions. It, too, is based on mathematical calculation, but
it also takes into account the practical application.
At any given moment when driving the machine on a
slope, at least one, if not all, of the factors contributing
to achieving theoretical gradeabilty will not be at optimal
performance. For example, tire contact may not be the
same at each drive wheel or the slope conditions may
not be optimal, which would then allow for loss of traction.
45°
40°
35°
30°
25°
20°
15°
10°
5°
0
100%
95%
90%
85%
80%
75%
70%
65%
60%
55%
Percent of
50%
45% Grade
40%
35%
30%
25%
20%
15%
10%
5%
A46JRT – 0261169