JWN- SERIES • RIDE-ON POWER TROWEL — PARTS AND OPERATION MANUAL — REV. #7 (03/02/07) — PAGE 29
NEUTRAL
LOW SPEED
HIGH SPEED
DRIVE
PULLEY
DRIVEN
PULLEY
A
B
C
Figure 25. Pulley Conditions
JWN-SERIES— MAINTENANCE
The JWN-Series Ride-On Power Trowel is equipped with a "Torque
Converter" which supplies torque to both the left and right gearboxes.
The function of the torque converter is to automatically deliver the
correct amount of torque required by the trowel under all load
conditions. This enables the trowel to deliver the necessary torque
for float pan applications and the high rotor speeds required for
burnishing concrete.
The torque converter used in the JWN Series Ride-On Power Trowel
is a variable pitch pulley type (Figure 21) connected by a drive belt.
Fig. 21. Torque Converter/Variable Pitch Pulley
Drive Pulley
The "Drive Pulley" uses centrifugal force (Figures 22 and 23)
to create a belt squeeze force transmitted at the pulley faces.
This condition functions as an automatic clutch.
CENTRIFUGAL
FOR
CE
BE
LT
SQ
UEEZE
FOR
CE
FIXED
FACE
VARIABLE
FACE
DRIVE PULLEY
(TORQUE CONVERTER)
Figure 22. Torque Converter (Centrifugal Force)
The "Variable Pitch Pulleys" have one
fixed face, and one moveable
face. The drive pulley ( torque converter, Figure 24) moveable face
is controlled by roller weight arms and springs, which change
position according to engine speed. The
driven pulley moveable
face is controlled by a spring and belt tension.
Fig. 24. Variable Pitch Pulley
DRIVE
PULLEY
DRIVE
PULLEY
LOW OUTPUT
SPEED
DRIVEN PULLEY
LOW ENGINE RPM
HIGH ENGINE RPM
DRIVEN PULLEY
HIGH OUTPUT
SPEED
CENTRIFUGAL FORCE
DISTANCE
MOVEABLE
FACE
TRAVELS
MOVEABLE FACE
IS CONTROLLED
BY A SPRING
AND BELT TENSION
MOVABLE FACE IS
CONTROLLED BY
ROLLER WEIGHT ARMS
AND SPRINGS
Fig. 23. Pulley Interaction
As shown in Figure 23, centrifugal force pushes the roller arms (see
Figure 23 below) against the ramp plate, forcing moveable face
toward fixed face squeezing belt.
DRIVE V-BELT
VARIABLE PITCH
PULLEY
TORQUE
CONVERTER
WEIGHT
RAMP
PLATE
BUSHING
ROLLER ARM
SPRING
DRIVE PULLEY
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