Principle and operation of sliding mesh gear box

  

Sliding Mesh Gear Box:

   

•  Gears on the main shaft slide to engage and disengage with the lay shaft gears

•  Meshing of the gears are done by the sliding of the gears

•  So it is called as sliding mesh gear box

 

 

1.Main drive gear

 

2.Counter shaft

 

3.Main shaft

 

4.I gear

 

5.II gear

 

6.III gear

 

7.Top speed engaging dogs

  

8.Idler gear

  

Construction of the Sliding Mesh Gear Box:

• It is the simplest type of gear box

• Clutch gear is rigidly fixed to the clutch shaft and always remain meshed to counter shaft

• Gears on counter shaft are  rigidly fixed

• Main shaft is a splined shaft 

• Three gears are mounted on the main shaft 

• These are slide by the shifter yoke 

• The yokes are connected to shifting lever 

• Idler gear is mounted on the another shaft 

• It is always connected to the reverse gear of the counter shaft 

• Idler gear is provided for obtaining reverse gear

Neutral Position:

   

• When Engine is in running position and clutch is in engaged position, clutch shaft gear 

  drives the lay shaft or counter shaft  drive gear

• Counter shaft rotates

• As the gears on main shaft are not meshed with any gear of the lay shaft, hence gear box 

  main shaft does not rotate

• Hence the power is not transmitted to main shaft

• The vehicle is stationary

 

Gear in First Speed:

 

• Operate the gear shift lever 

• This lever slides the larger gear on the main shaft towards the smaller gear on the lay 

   shaft 

• Then main shaft turns in opposite direction to the lay shaft

• That is in the direction of the clutch shaft 

• Here we obtain gear reduction of 3:1

 

Gear in Second Speed: 

 

• Operate the gear shift lever to demesh the first gear and to engage the second gear 

• Smaller gear of the main shaft meshes with the second gear of the counter shaft

• Then main shaft turns in opposite direction to the lay shaft with second speed, in the 

  direction of the clutch shaft

• Here we obtain gear reduction of 2:1

 
Gear in Third or Top Speed:

 

• Operate the gear shift lever to demesh second gear and engage third gear

• Smaller gear of the main shaft meshes with the clutch gear directly with the dog teeth

• Then main shaft turns in opposite direction to the lay shaft in the direction of the 

  clutchshaft 

• Here we obtain no gear reduction and transmits 1:1

 

Gear in Reverse Speed: 

 

• Operate the gear shift lever to demesh third gear and engage reverse gear 

• This lever slides the larger gear on the main shaft to mesh with the idler gear on the lay 

  shaft

• The idler gear is in turn meshed with lay shaft gear 

• Main shaft rotates in reverse direction of clutch shaft

 

GEAR SYSTEM