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104
FIAT· 850 PASSENGER CARS
Engagement of 2nd, 3rd and 4th Gears.
Fig. 165 • Transmission synchromesh gears.
1. Slip sleeve hub.· 2. Third and fourth slip sleeve. - 3. Third speed
gear with synchronizer.
fig. 166) have been designed to work one on over-
ride and the other on underride.
As
a matter of fact the speader spring is com-
pressed between the thrust plate (5, fig. 166) and
the stop plate (3), so that it spreads out against the
synchromesh ring.
Thus the synchronizing action resulting of the
tension of the ring itseU
is
boosted gradually from
the end pressure exercised by the spreader spring.
The task of the synchronizer
will
stop as soon
as
the slip sleeve and the gear affected are brought
to spin at the same speed; the spreader spring
relaxes and the synchromesh ring retracts itself.
This condition corresponds to the final step of
the tripping movement of the slip sleeve, so that
it
comes into mesh with the mating teeth of the
gear with minimum strain.
3
1
Fig. 167 • Third speed gear and synchronizer components.
1. Synchromesh ring. - 2. Synchronizer spreader springs. - 3. Slop
plate•• 4. Third speed gear with toothed crown for synchromesh.•
5. Thrust plate•• 6. Snap ring.
NOTE· The synchromesh device shown in figs. 166
and 167 applies to the 2nd, 3rd and 4th gear, being
just identical, whereas the device for the 1st gear
differs in design (fig. 168).
Synchromesh of 2nd, 3Id and 4th gears
is
obtained
thanks
to the use of the items shown in figures 165,
166 and 167.
The slip sleeve (2, fig. 165) is serrated internally
for proper mesh
with
the toothed crown of the
gear (3), turning idle on the output shaft.
In
this
way the gear will be rigidly locked
with
the driv-
ing hub.
As the slip sleeve is moving on, the synchromesh
ring
(I,
fig.
167)
gradually equalizes rotation speeds.
Under the action of the slip sleeve, the syn-
chromesh ring (I, fig. 167) is dragged to abut
with one end, both on acceleration and deceleration,
against the thrust plate (5, fig. 166), which causes
such a wrapping effect as a quick mesh is obtained.
For a better adherence of the synchromesh ring
against the slip sleeve, two spreader springs (2,
Fig. 1&6 • Third speed gear synchronizer in place in gear.
1. Synchromesh ring.• 2. Ring spreader springs.• 3. Stop plate. _
4. Third speed gear. - 5. Thrust plale.
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