PLANETARY GEAR

AIM: Design and motion analysis of Planetary Gear System

INTRODUCTION:

An epicyclic gear train (also known as planetary gear) consists of two gears mounted so that the center of one gear revolves around the center of the other. A carrier connects the centers of the two gears and rotates to carry one gear, called the planet gear or planet pinion, around the other, called the sun gear or sun wheel. The planet and sun gears mesh so that their pitch circles roll without slip. A point on the pitch circle of the planet gear traces an epicycloid curve. In this simplified case, the sun gear is fixed, and the planetary gear(s) roll around the sun gear.

OBJECTIVE:

1. To calculate the ‘Pitch Circle Diameter’ and the ‘Number of Teeth’ for the Planet Gear.
2. Performing motion analysis of the Planetary Gear System.
3. Obtaining plots of Angular Velocity for different outputs.

Simulation cases:

S. No	Input	Output	Fixed
1	Sun Gear	Carrier	Ring Gear
2	Ring Gear	Carrier	Sun Gear
3	Sun Gear	Ring Gear	Carrier

Given:

Ring gear:

Module = 2.5

No. of teeth = 46

Sun gear:

Module = 2.5

No. of teeth = 14

Input speed of the gear = 200rpm,

No. of Planetary gears = 4

Planetary gear specifications and calculation:

Module = 2.5

Pitch circle dia. = p

No. of teeth = N

m = p/N

p(r) = 115mm

p(s) = 35mm

Now, to calculate the Pitch circle dia. Of the planetary gear,

p(r)/2 = p(s)/2 + p(p)

p(p) = 40mm

N(p) = 40/2.5 = 16

PROCEDURE:

First open the assembly file and upload an internal spur gear from the Design library’s toolbox. Specify the dimensions and insert the component.

Similarly, the sun gear is also uploaded same as the internal gear from toolbox.

Then, the process is followed by inserting 4 planetary (by inserting dimensions only for one and copying it 3 times) form the toolbox.

The carrier is designed in a separate part file and is inserted into the part file where the all the gears have already been uploaded from the design library. The dimensions of the carrier depend on the shaft dia. of the planet gear.

The planet gear mechanism for motion study is created with proper and adequate no. of mates.

Animation: The link of the animations are:

RESULTS:

PLOTS FOR DIFFERENT CASES:

CASE 1 –

Input plot

The angular velocity is observed to be constant throughout because of the smooth engagement of gears and the transmission is highly efficient.

Output plot

The carrier velocity has sudden peaks due to the variable power transmitted in the output plot.

CASE 2 –

Input plot

Constant Angular Velocity of Ring gear is observed. The transmission is smooth, but the addition of idler gears make output variable.

Output plot

Plot depicts transmission anomalies that may exist due to out of order contact between the parts interconnected.

CASE 3 –

Input plot

The sun gear possesses constant input Angular Velocity with minimal variations.

Output plot

The output obtained in the form of movement of Ring Gear gives a perception of sudden increments and decrements projected in the result.

CONCLUSION: The motion study gives a clear sight about the functioning of the planetary gear system. The cases have been simulated accordingly with the most common being the fixed Ring gear case. With the variation of the parameters, the output can be varied.