Gear trains are used to transmit motion from one shaft to another while enabling large speed reductions within a compact space. There are several main types of gear trains including simple, compound, reverted, and planetary or epicyclic gear trains. Planetary gear trains allow for relative motion of the gear axes and can provide large speed reductions, making them useful when space is limited.

1. SUBMITED BY
ANURAG PANDEY
131MC00234

2. Gear train is a combination of gears used to transmit the motion from one
shaft to another. It is required to obtain large speed reduction within a
small space.
The following main types of gear trains are
 Simple gear train
 Compound gear train
 Reverted gear train
 Planetary or epicyclic gear train

3.  Each shaft support one gear.
 A series of gears capable of receiving
and transmitting motion from one
gear axes remain fixed relative to the
frame and each gear is on separated
shaft.
 A simple gear train also have bevel
gear

4.  When the series of gears are
connected in such a way that two
or more gears rotate about an axis
with the same angular velocity ; it
is known as compound gear train.

5.  If the axis of the first and last
wheel of a compound gear
coincide it is called reverted gear
train.
 Such arrangement is used in clock
in simple lathe where ‘back gear’
is used to give slow speed to the
chuck.
 If r is the pitch circle radius of a
gear,
r1+ r2 = r3 + r4

6.  When there exist a relative
motion of axes in a gear train, it is
called an epicyclic gear train.
 In epicyclic gear train the axis of
at least one of the gears also
move to the relative frame.
 If arm ‘a’ is fixed. Turn ‘s’
through x revolution in the clock
wise direction. Assuming
clockwise motion of wheel as a
positive and counter clockwise
motion as negative.

7.  Revolution made by ‘a’ =0
 Revolution made by ‘s’=x
Revolution made by ‘p’ = -(Ts / Tp )x
Large speed reduction are possible with epicyclic gears.
In general gears trains have two degrees of freedom.