Flow of torque in Synchromesh Gear Box

Lay Out of the Gear Box:

 



 

 

Synchromesh Gear Box:

Neutral gear:

• In this position torque from the clutch gear flows to counter gear as both are 

  constantlymeshed

• From the counter shaft torque flows to main shaft as main shaft gear is constantly meshed 

  with counter shaft gear

• But as the synchromesh device is not engaged, the main shaft gear rotates freely on the 

  main shaft 

• It will not transfer the torque to the main shaft

First gear:

• In this position the first gear is slided to engage with the corresponding gear on lay shaft 

• In this position power flows from clutch shaft to lay shaft and from lay shaft to main shaft

  first speed gear 

• In this gear we obtain maximum torque with low speed 

• Here we get a gear ratio of 3:1

Second gear:

• The first gear is to be de meshed from the counter shaft gear to bring into neutral position 

• Synchromesh device is moved to the right side 

• Internal teeth of the Synchromesh device meshes with external teeth of the second speed

  gear

• In this position power flows from clutch shaft to lay shaft and from lay shaft to main shaft

  second speed gear 

• Here we get a gear ratio of 2:1

Top gear:

• The second gear is to be de meshed from the counter shaft gear to bring in to neutral 

  position 

• Dog clutch is moved to the left side 

• Internal teeth of the dog clutch meshes with external teeth of the main drive  gear

• Hence we obtain the third speed or top speed 

• In this position power flows from clutch shaft to main shaft 

• Here we get a gear ratio of 1:1

Reverse speed:

• The first gear of the main shaft is slide to mesh with the idler gear 

• In this position power flows from clutch shaft to lay shaft and from lay shaft to idler gear 

  and from idler gear to main shaft first speed gear 

• By using idler gear the power flows in opposite direction to the main gear 

• Hence we obtain reverse speed