Post on 30-Oct-2014
Transmission system
INTRODUCTION
• Mechanism that transmits the power from the engine crankshaft to the rear wheels
• Gear box (manual transmission)
• Automatic transmission
Functions of transmission
• To provide a means to vary the torque ratio between the engine and the road wheels as required.
• Provides a neutral position so that the engine and the road wheels are disconnected even with the clutch in the engaged position.
• Provides means to back the car by reversing the direction of rotation of the drive
Location
Types of transmission
• Manual transmission (gear box)– Sliding mesh type gear box– Constant mesh gear box– Synchromesh type gear box
• Automatic transmission
Sliding mesh type of gear box
• Simplest type of gear box
• All the gears on the lay shaft are fixed to it
• Three direct and one reverse speeds are attained on suitably moving the gear on the main shaft by means of selector mechanism.
Constant mesh gear box
• All gears are in constant mesh with the corresponding gears on the layshaft.
• The gears on the main shaft are free.• The dog clutches are provided which are free to
slide on the main shaft.• The gears on the layshaft are fixed.• Weakness: Double declutching(for smooth engagement of the dog clutches it is necessary that the
speed of mainshaft gear and the sliding dog must be equal)
Synchromesh gear box
• Used for smooth meshing• Works like a friction clutch
Advantage
• In constant mesh gear box, the dog clutches connect the gears of the main shaft. This produces noise and jerk. To avoid this the synchromesh gear box is used.