Planetary Gear

Planetary gears

A 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.

Aim

The main aim of this project is to assemble a planetary gear train by importing the gears available in the design library of solidworks and to make a multi body dynamic analysis of the gear train for three different output cases.

Initial calculation and carrier design:

Module = Pitch Diameter / Number of Teeth

Ring gear:

Given: Module = 2.5

No. of Teeth = 46

Dr= 2.5 * 46

Therefore pitch diameter is 115 mm

Sun gear:

Given: Module = 2.5

No. of Teeth = 14

Ds = 2.5 * 14

Therefore pitch diameter is 35 mm

Planetary gear:

Pitch radius of ring gear = Pitch dia. of planetary gear + Pitch radius of sun gear

Dp= (115/2)-(35/2)

Therefore pitch diameter is 40 mm

Using these parameters, the inbuilt models of the spur gears from the design library of the Solidworks toolbox was used to modify the gears according to the required specifications.

Using these values, the carrier was also designed separately.

Motion study setup:

After checking for interference (as gear mate was not used), according the case a motor was introduced to the required axis. Solid body contacts were established between the gears. As the input speed was 200 rpm, 1200 frames per second were used for the motion analysis.

Results:

Case 1- Angular velocity of carrier - Ring gear fixed

Case 2 - Angular velocity of carrier - Sun gear fixed

Case 3 - Angular velocity of ring gear - Carrier fixed

Conclusion:

Thus the assembly of a planetary gear train was made using Solidworks and a motion study was setup to analyze the angular velocities of various components.

It could be seen that the angular velocity was almost constant with slight variations. This is attributed to the small gaps between the gear tooth which can be reduced by reducing backlash. The animations were uploaded to youtube.