240 ONE MAN HOLE DIGGER, FORM GOM26010601, VERSION 2.0, AUTHORIZATION: DVR, PAGE: 15
auger will begin to rotate when the engine speed
reaches the centrifugal clutch initial engagement
speed.
3) Normal operating procedure for the Hole digger is to
d
ig with the engine operating at full speed. This will
allow the centrifugal clutch to become more firmly
engaged. This procedure will transmit more usable
power to the auger, resulting in greater productivity and
less component wear.
When digging in areas filled with known buried
obstructions such as tree roots, rocks and other
debris, operate the Hole Digger at less than full (an
intermediate) speed to insure a more rapid release
of the centrifugal clutch when an obstruction is
encountered. This is an industry wide operating
procedure.
4) The Hole Digger is equipped with a centrifugal clutch
assembly within the transmission, designed to slip
whenever overloaded or if the auger comes in contact
with a buried obstruction. Newtonʼs Laws of Physics
allow the centrifugal clutch assembly to ALWAYS slip
whenever overloaded or if the auger comes in direct
contact with a buried obstruction. The term slippage is
not intended to infer that the centrifugal clutch
assembly becomes fully disengaged with no
horsepower and torque is being transmitted to the
auger. In the slipping mode, a centrifugal clutch still
transmits a specific amount of horsepower and torque
to the auger. This specific amount of horsepower and
torque directly proportional to many factors including:
the mechanical condition of the centrifugal clutch
assembly and the rotational speed of the centrifugal
clutch assembly when the initial slippage occurs. The
response time for the centrifugal clutch assembly to
react to an overload condition is directly proportional to
its rotational speed. The higher the rotational speed
(RPM) of the centrifugal clutch at the time of overload,
the greater amount of time it requires to react and
actually slip. This phenomenon is inherent with all
centrifugal clutch assemblies. It is also inherent with all
powered equipment incorporating such a device.
STRIKING BURIED OBSTRUCTIONS SUCH AS
TREE ROOTS, ROCKS AND OTHER DEBRIS AT
ANY SPECIFIC ENGINE OPERATING SPEED CAN
CAUSE THE HOLE DIGGER TO TRANSMIT
REACTIONARY TYPE "IMPACT" LOADS TO THE
OPERATOR. THESE TYPES OF LOADS ARE
C
HARACTERIZED BY A SHARP, PULSATING
MOVEMENT OF THE HOLE DIGGER IN A
C
OUNTERCLOCKWISE DIRECTION (AS VIEWED
BY THE OPERATOR). SUCH LOADS CAN LEAD TO
THE LOSS OF OPERATOR CONTROL AND RESULT
IN PERSONAL INJURY. THE OPERATIONAL
EFFECTS ARE ALIKE TO THAT OF UTILIZING A
COMMON ELECTRIC DRILL AND OTHER,
ROTATION TYPE, POWERED EQUIPMENT. THE
RELATED PHENOMENON IS INHERENT WITH ALL
SUCH TYPES OF ROTATION TYPE, POWERED
EQUIPMENT AND IS TERMED AS KICKBACK.
UNDERSTANDING KICKBACK.
The operation of the Hole Digger involves engine
torque being transmitted and multiplied by the
transmission to the auger. The energy is then used to
dig holes. But to every force (action), there is always a
reaction force in the opposite direction. Thus, if the
auger contacts a buried obstruction, the operator will
feel the left side of the handle of the Hole Digger being
"thrusted" toward him. This "thrusting" force
experienced by the operator is called kickback. The
speed that the handle moves (and magnitude of the
resulting impact force) is directly proportional to the
amount/speed of the kickback force experienced by
the operator. The torque and kickback generated by
the digging process is inherent with a portable, one
man Hole Digger of this type. The operational effects
are alike to that of utilizing a common, electric drill and
other, rotation type, powered tools.
MINIMIZING KICKBACK FROM AN OPERATIONAL
STANDPOINT.
The operator should keep the left side of the handle as
close to his body (left hip and leg areas) as possible to
minimize machine "kickback" when a buried
obstruction is encountered by the auger. Assume
operating positions that allow exercising reactive "body
english" against the torque sensation created by the
digging process. Keep upper arms as close to the
upper body as possible to maximize mechanical
leverage. An operator should position his back as
vertical as possible by bending the legs as required
during the digging process. Positioning the left foot
ahead of the right foot at a comfortable distance will
enhance proper body position. Maintaining proper
operating position is one of the most IMPORTANT and
EFFECTIVE procedures for controlling kickback.
Improper operating positions only aggravate the effects
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