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Gear Trains & Its Types


                                                                    
   

Gear Trains 


In mechanical system there are too many elements .One of the most important element is gear.

  • Gear is a teethed wheel which is used to transmit the power and motion through meshing of two such gears.




  • Gear Trains are combination of two or more gears made to mesh with each other in order to transmit the power and motion from one shaft to another shaft, in a mechanical system.


          The nature of the train depends upon the velocity ratio required,and the axes of the shaft on which they are mounted.


  • A Gear Train may be of following ➜
  1. Spur Gear
  2. Bevel Gear
  3. Spiral Gear
Let us explore more on this topic....

  • Types of Gear Trains ➜

Depending upon the arrangement of wheels there are 4 types of gear trains


  1. Simple Gear Train
  2. Compound Gear Train
  3. Reverted Gear Train
  4. Epicyclic Gear Train


1.Simple Gear Train

        If there is only one gear on each shaft of gear train system that simply known as Simple Gear Train.



SImple Gear Train     


 When the distance between the two gears is small , gear 1 (driver) drives gear 2 (driven)
and transmit the motion  


However , if distance between the two gears are large in such conditions following methods are used


  • By providing Intermediate gear. 
  • By providing large sized gear.
 If the no of intermediate gears are odd then the motion of two gear is like.
 If the no of intermediate gears are even then the motion of two gear is unlike.


Speed Ratio :
    
         The ratio of speed of driver to the speed of driven.

If   N1 - Speed of driver
     N2 - Speed of driven

Speed Ratio = N1/N2

                          
Train Ration :

          It is reciprocal of speed ratio.

If  T1 - Number of teeths on driver
    T2 - Number of teeths on driven

 Train value = N1/N2 = T2/T1

For intermediate gears -

                     N1/N2 = T2/T1

                     N2/N3 = T3/T2
                      
2 . Compound Gear Train →

     When there are more than one gear on each shaft then it is Compound Gear Train




Compound Gear Train


         Compound Gear Train is the solution for the drawback occured in simple gear train.
When the distance between two gear is large then its is required to bridged by intermediate gears between driver and driven , at the same time a great speed ratio is required . In such condition the compound gear provide large speed ratio by using more than one gear on each shaft.

        In compound gear train Gear 1(Driver) is mounted on shaft A,followed by compound Gear 2-3 on shaft B , and on shaft C Gear 4-5 is mounted, followed by last driven Gear 6.

Speed Ratio →

       Speed of the first driver           Product of no of teeth on driven
      ----------------------------------  =    -------------------------------------------
       Speed of the last driven           Product of no of teeth on driver
        
       N1         T2 x T4 x T6
       ------  =  ------------------
       N6          T1 x T3 x T5

Train Value →

       Speed of the last driven
     -----------------------------------
       Speed of the first driver

Advantages of compound gear train →


  • Large amount of speed reduction from first shaft to last shaft with small gear
  • High speed ratio compared to simple gear train
  • Intermediate gear are replaced by combination of two gears 
  • Compound gear train is employed for worm gearing 

 3. Reverted Gear Train →
    
          When the axes of the first gear (i.e first driver) and the last gear (i.e last driven )
are co-axial then it is Reverted Gear Train .



Reverted Gear Train


      The First driver (i.e Gear 1) drives Gear 2 in opposite direction ,since the gears are mounted on same shaft Gear 3 will also follow same motion as that of Gear 2 . Gear 3 is meshing with Gear 4 in the same direction as that of Gear 1, motion 1st and 4th gear is like .

Here motion is reverted back from Gear 1 to Gear 4 , hence it is referred as Reverted Gear Train. 

Speed Ratio →

       Product of no of teeths on driven
  =   --------------------------------------------
       Product of no of teeths on drivers

    N1       T2 x T4
   ------ =  ------------
    N4        T1 x T3

Applications →


  • Automotive Transmissions
  • Lathe back gears
  • Industrial speed reducers 

4. Epicyclic Gear Train →
            In Epicyclic gear train the axes of the shaft over which the gears are mounted may move relative to fixed axes  .


Epicyclic Gear Train

            In a simple epicyclic gear train the Gear A and Arm C have common axes at point O1 about which they can rotate . The Gear B meshes with Gear A and has its axis on the arm at O2 about which Gear B can rotate.


            By fixing on of the two elements i.e Gear or Arm we can produce an epicyclic motion.
If the arm is fixed then gear train is simple gear train i.e Gear A can drive Gear B or vice-versa , but if the Gear A is fixed and the arm is rotate about Gear A , then the Gear B is forced to rotate around Gear A .Such motion is called as Epicyclic 

The gear train are arranged in such a manner that one or more of their members move upon and around another member such type of arrangement is known as Epicyclic Gear Train.

Application →

  • Transmission of high velocity ratio with moderate size gears .
  • It is used in differential of automobile.
  • Back lathe of gears .
  • Hoist
  • Pulley Blocks
  • Wrist Watches
    
      Gear Trains | Fully Explained -|

                         
 




Thank You,
Student Helper 2020.

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