BRP ski-doo MACH Z 1000 SDI, Руководство пользователя

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06-10
MMC2005-001_06A.FM
SECTION 06 - DRIVE SYSTEM
EFFECTS OF THE DRIVE PULLEY
SPRING
The purpose of the clutch release spring is to re-
turn the sliding half of the engine pulley and the
associated moving parts to the disengaged or neu-
tral position at low engine RPM. The spring ten-
sion is calibrated to work with the pressure levers
and ramp angles to allow clutch engagement at
the desired RPM. As the engine speed increases,
centrifugal forces increase and eventually over-
come the tension of the release spring and allow
the pulley halves to contact the drive belt. As en-
gine speed decreases, centrifugal forces de-
crease and the clutch spring returns the sliding
half toward the neutral position.
As the clutch shifts out to a higher ratio, the spring
balances the shift forces being generated by the
levers and ramps.
The spring tension will affect the entire shifting se-
quence of the engine pulley. The effect that it has
will depend upon the construction of the spring.
Three things must be known about the spring to be
able to predict its effect in the clutch: 1. The spring
free length; 2. The spring pressure when com-
pressed to 74 mm (2.9 in); 3. The spring pressure
when compressed to 41 mm (1.6 in). These three
factors are listed on the accompanying sheet.
The spring free length will give you an idea of the
condition of the spring. If the spring has lost more
than 6.35 mm (1/4 in) of its listed free length, the
spring is fatigued or has taken too great a set. The
spring should be replaced. The free length of the
spring is its overall length when resting freely on
a table top.
In the TRA clutch, the installed length of the clutch
release spring is 74 mm (2.9 in) This is the length
of the spring when the pulley is in its neutral posi-
tion. The pressure that the spring applies at this
length is the factor that controls the engagement
speed (all other things kept constant). When the
engine pulley is in its highest ratio position, the
spring will be compressed to 41 mm (1.6 in). The
pressure the spring applies at this length will de-
termine the RPM required to reach high gear;
again, with all other tunable factors kept constant.
As you look through the spring chart, you will see
that springs are available with equal pressures at
74 mm (2.9 in), but very different pressures at
41 mm (1.6 in). You will also note varying pres-
sures at 74 mm (2.9 in) and equal pressures at
41 mm (1.6 in). Simply by working with the spring
charts, one can easily see how the shift speed (the
speed with which the change from one gear ratio
to the next is made) and the engagement speed
can be altered.
As the pressure of the spring when 74 mm (2.9 in)
long is increased, the clutch engagement speed
will increase. As the spring rate is increased, the
engine will be required to turn more RPM to
achieve a given gear ratio. Again, these facts hold
true when all other tunable components are kept
constant.
On chart 1, spring A has a pressure of 311 N (70 Ib)
at 74 mm (2.9 in) and a pressure of 1157 N (260 Ib)
when compressed to 41 mm (1.6 in). With no oth-
er changes made in the clutch, spring
B was in-
stalled. The spring has a preload of 712 N (160 Ib)
at 74 mm (2.9 in) and a pressure of 1201 N (270 Ib)
at 41 mm (1.6 in). As the chart indicated, the en-
gagement RPM increased 1000 RPM while the
shift curve from 30 MPH up remained relatively
unchanged.
Chart 2 illustrates the effect of keeping the spring
preload pressure at 74 mm (2.9 in) constant and
increasing the pressure at the 41 mm (1.6 in)
length. In this example, spring
A has a pressure of
311 N (70 Ib) at 74 mm (2.9 in) and a pressure of
756 N (170 Ib) at 41 mm (1.6 in). Spring
B also has
a pressure of 311 N (70 Ib) at 74 mm (2.9 in) but in-
creases to 1157 N (260 Ib) at 41 mm (1.6 in). The
projected effect of this spring change is shown on
chart 2. Since the preload pressure at 74 mm (2.9 in)
is equal for springs
A and B , the engagement
speed is not affected. At 95 MPH, however, there
is a loss of RPM with spring
A in place.