Planetary Gear

The following inputs were used for designing the Planetary Gear

• Ring Gear
• Module = 2.5 (metric system)
• Number of teeth = 46
• Sun Gear
• Number of teeth = 14
• Input Speed of the Gear = 200 rpm.
• Number of planet gears = 4

Calculating the number of teeth in planet gear:

(Module is same for all gears)

Pitch diameter of Ring gear = Module * Number of teeth = 2.5 * 46 = 115 mm

Pitch diameter of Sun gear = Module * Number of teeth = 2.5 * 14 = 35 mm

Pitch diameter of planet gear = (P.Dia of Ring – P.Dia of Sun)/2 = 40 mm

Therefore, number of teeth of planet gear = Pitch diameter of planet gear / Module = 40/2.5 = 16

The carrier was made appropriately considering the shaft diameter of planet gear.

The number of planet gears used were 4.

After making the parts and doing its assembly, ‘Solidworks motion’ was loaded to do the motion analysis for 3 scenarios:

• Input: Sun gear, Output: Carrier, Fixed: Ring gear
• Input: Ring gear, Output: Carrier, Fixed: Sun gear
• Input: Sun gear, Output: Ring gear, Fixed: Carrier

The input was always 200 rpm which equals to angular velocity of 1200 deg/sec

The results are as follows:

Scenario 1:

Average angular velocity of carrier = 280 deg/sec (from excel file)

Not only do the planet gears rotate about their own axis but also about the carrier axis.

Scenario 2:

Average angular velocity of carrier = 915 deg/sec (from excel file)

Not only do the planet gears rotate about their own axis but also about the carrier axis.

Scenario 3:

Average angular velocity of ring gear = 365 deg/sec (from excel file)

The planet gears rotate only about their own axis.

The rotation of ring gear is reverse of ring gear.

We observe that in different scenarios, the output angular velocity changes.

The gear ratio in scenario 1 = Input angular velocity/ output angular velocity

= 1200/280 = 4.28

The gear ratio in scenario 2 = 1200/915 = 1.31

The gear ratio in scenario 3 = 1200/365 = -3.28 (reverse)

About Planetary gears:

The Planetary Gear can generate multiple gear ratios based upon which gear is fixed.

After one gear is fixed, there are two options for input.

Thus, total 6 gear ratios can be generated.

This type of planetary gear is used in the automatic gear automobiles and other applications.

Number of planet gears do not affect the gear ratios.

However, increasing the number of planet gears decreases the stress on individual component.

Also it helps in distributing the forces on sun and ring gear more evenly.

This increases the life of the system.

Part and result files (Incase the submission file can\'t be accessed):

https://drive.google.com/file/d/14bnNcrta3ibQNRxZzCWUUduhRNFDaZcX/view?usp=sharing