1. I speed gear
2. II speed gear
3. Main shaft
4. Outer engaging unit
5. Inner engaging unit
7. Main drive gear
8. Top gear synchronising
cones
9. Counter shaft
Introduction:
•
Gears on the main shaft are free to rotate
•
Gears on the counter shaft also rigidly fixed
•
The main shaft gears and counter shaft gears are always remain meshed with each other
•
Engaging of the gears are done by the synchronizer
•
As we are using synchronizing device, it is called as synchromesh gear box
Synchromesh
Device:
• Synchromesh
disengaged, Gear running freely on main shaft
• Conical
synchromesh faces mate causing gear to rotate at the same speed as
synchromesh unit
• Further
movement of selector lever results in teeth of sleeve engaging dog teeth on
gear
locking drive
Construction
of the Synchro Mesh
Gear Box:
• This
type of gear box is employed modern vehicles
• Construction
of this gear box is similar to constant mesh gear box
• In
place of dog clutches synchronizing devices are used
Working:
• When
the gear lever is moved the synchronizer cone contacts with a similar cone on
the
gear
• Due
to friction, the speed of the rotating
gear gets synchronised to
the speed of the
synchromesh unit
• A
slight delay is required before engaging the dog teeth so that cones have a
chance to
bring the synchronizer and pinion to the same speed
• Then
the synchronizer sleeve engages dog teeth
on the gear
• Since
both pinion and synchromesh units are moving at same speed, this engagement is
done with out noise
• A
slight delay is required before engaging the dog teeth so that cones have a
chance to
bring the synchronizer and pinion to the same speed
Advantages:
• As
the engaging of the gears are very smoothly, there is no noise
• No
damage will occurred to the gears or dogs
• It
prevents the jerky motion
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