John Deere stx38 - Manual (Page 185)

3/21/97
5 - 21
POWER TRAIN THEORY OF OPERATION
CLUTCH PEDAL AND BELT
TRACTION DRIVE SYSTEM
OPERATION
STX38 (SN 210001— ) & STX46
Function:
The function of this system is to transfer power from
the engine to the 5-speed transaxle. This system also
allows the power transfer to be interrupted in order to
stop in gear, change to a different gear or direction,
engage power again, or shift to neutral and push the
unit with the engine on or off.
Major Components:
• Engine drive sheave
• Drive belt
• Clutch pedal and shaft
• Actuating spring assembly
• Bellcrank assembly
• Transaxle drive sheave
Theory of Operation:
With engine running and clutch engaged (clutch/brake
pedal (A) released), the engine drive sheave (B) pulls
the drive belt and transmits power to the transaxle
drive sheave (H). As clutch/brake pedal (A) is
depressed by the operator, clutch shaft (D) pulls the
clutch actuating spring assembly (G) forward. Initial
movement of the pedal compresses the spring in the
actuating spring assembly (G) and, once compressed,
pivots the bellcrank assembly (F). As the bellcrank
assembly pivots, the tensioning sheave (E) moves
rearward, releasing drive belt tension. This allows the
engine drive sheave to rotate without transferring any
power through the slackened drive belt.
As the bellcrank pivots rearward, belt tensioning spring
(C) is stretched, building additional tension in the
spring. As the operator begins to ease-up on the
clutch/brake pedal (A), tensioning spring (C) pulls the
bellcrank tensioning sheave (E) into the drive belt,
causing the belt to tighten and seat in the grooves of
the transaxle drive sheave (H) and the engine drive
sheave (B). This interaction of components results in
turning the transaxle drive sheave rapidly in a
clockwise direction, transferring power from the engine
to the 5-speed transaxle.
M42537
F
E
H
G
D
A
C
B