Planetary Gear

Aim: To perform motion analysis on Planetary Gear Mechanism

Theory:

A planetary gear mechanism consists of a ring gear, a sun gear, planet gears and a carrier.

The dimensions of the gears are as follows:

Modulus = 2.5mm

Sun Gear:

Number of Teeth = 14

Pitch Circle Diameter = 14*2.5 = 35mm

Ring Gear:

Number of Teeth = 46

Pitch Circle Diameter = 46*2.5 = 115mm

Planet Gear:

Pitch circle diameter of planet gear can be calculated using geometry.

For smooth motion between two mating gears, there pitch circles should be tangent to each other. This principle would be used to find pitch cirlce diameter of planet gear.

Two concentric circles with pitch diameter of ring gear and sun gear are drawn and then a new circle in annular space is drawn which is tangent to both the previous circle.

The diameter of that new circle is the pitch circle diameter of planet gear.

From geometery,

Pitch Circle Diameter = 40mm

Number of teeth = 40/2.5 = 16

Planetary Gear Mechanism Assembly:

The components shown in assembly are:

Carrier `->` Green

Ring Gear `->` Red

Sun Gear `->` Blue

Planet Gear `->` Yellow

Note: Gear mates haven't been used in assembly. Instead components are arranged in such a manner that they won't overlap.

The study have been performed for three different cases.

Case 1:

Input: Sun Gear `->` 200RPM

Output: Carrier

Fixed: Ring Gear

The output angular velocity is as shown in graph:

Case 2:

Input: Ring Gear `->` 200RPM

Output: Carrier

Fixed: Sun Gear

The output angular velocity is as shown in graph:

Case 3:

Input: Sun Gear `->` 200RPM

Output: Ring Gear

Fixed: Carrier

The output angular velocity is as shown in graph:

Conclusion:

1. From the results it can be noted that case 1 given the lowest speed output among three cases. Thus when the ring gear is kept fixed and an input speed is applied to sun gear then output speed at the carrier is lower than other cases.

2. it can also be noted that case 2 given the highest speed output among three cases. Thus when the sun gear is kept fixed and an input speed is applied to ring gear then output speed at the carrier is higher than other cases.

3. From the motion study it was noted that during first two cases input and output rotation is in same direction but in the third cases the direction of input and output is reversed i.e when clockwise rotation is applied at input then output is anticlockwise.