Echo SRM series, Safety Manual

Page: 32 / 52

ENGLISH
REACTION FORCES
Push/Pull - Kickback/Kickout
During normal use, operating a brushcutter with a circular metal blade can
produce sudden strong reaction forces that are difficult to control. Strong
reaction forces can cause a loss of balance or loss of control of the unit,
resulting in serious injury to operator and bystanders.
Understanding what causes these reactive forces may help you to avoid them,
and can help you to maintain control of the unit if you experience a sudden
reaction during cutting. Reactive forces occur when the force being applied
by the cutting teeth of a blade meet resistance, and some of the cutting force
is directed back toward the unit. The greater the cutting force or the amount of
resistance, the greater the reactive force.
Push and Pull Forces
Push and pull forces are reactive forces that
push the unit directly toward the operator,
or that pull the unit directly away from the
operator. These forces are the result of cutting
on the sides of the blade. The direction of the
force depends on the side of the blade being
used, and the direction of blade rotation at
the point of contact. The reactive force is in
the opposite direction of blade rotation at the
contact point, regardless of where the contact
is being made. These types of reactive forces
are also called “Blade Thrust.”
As shown in the illustration, a blade turning
counterclockwise will cause the unit to pull
away from the operator if the point of cutting
resistance is on the left side of the blade. If the
point of cutting resistance is on the right side
of the blade, the unit will push back toward the
operator. In both examples, the reactive force
is in the opposite direction of blade rotation at
the contact point where resistance occurs.
PULL
PUSH
Contact
Point
Contact
Point
32
OPERATION