Snorkel TB65J - Manual (Page 51)

Chapter 8 – Operation
TB65J – 0084248 47
• Use low range (turtle) for driving on loading ramps
or other steep grades and when safety consider-
ations demand slow deliberate machine move-
ment. Low range is for low speed, high torque
operation.
2. Step down on the platform foot switch.
3. Push the drive joystick forward to move the chas-
sis forward, the direction of the blue arrow. Pull the
joystick backward to move the chassis backward,
the direction of the yellow arrow. The drive speed is
proportional to the joystick position.
4. To stop drive motion, return the joystick to neutral.
5. Push the drive joystick to the right to steer to the right,
the direction of the yellow arrow. Push the joystick
to the left to steer to the left, the direction of the blue
arrow.
Note
The steering wheels are not self-centering. Set the steer-
ing wheels straight ahead after completing a turn.
6. After driving to the desired location, release the foot
switch, or push the emergency stop button to apply
the parking brakes.
Drive Speeds
The drive speed is proportional to the joystick position.
The farther the joystick is moved, the faster the travel
speed.
Always slow down and shift the drive system to low
range before traveling over rough terrain or any sloped
surface.
Drive speed ranges are interlocked through a limit switch
that senses the main and intermediate boom position.
• When the maim 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 0.6
miles per hour (0.8 km/h) [26 feet (7.9 m) in 30 seconds]
when any of the booms are out of the stowed position.
Gradeability
Gradeability refers to the maximum slope that the aerial
platform is capable of travel. Gradeability can be de-
scribed 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,
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 condi-
tions. 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.
The value for actual gradeability will always be lower
than the theoretical gradeability value. The perception
then is that the machine can not climb a slope as steep
as it should.
Percent vs. Degree of Slope
Gradeability is most often referenced as a percentage.
That value is based on a slope angle of 45° representing
00% grade.
Angle indicators, or inclinometers, often measure the
angle of the slope in degrees not the percent slope.
Because of that, it may be useful to understand the re-
lationship between percent slope and the degree of the
slope angle as shown in Figure 8.5.
Driving on a Slope
The machine should only be driven on a slope or load-
ing ramp in the stowed position with the platform on the
downhill side.