Planetary Gear

Aim: To analyze the motion of Planetary Gear Systems and plot Angular Velocity for different cases with time

Theory: The Planetary Gear System consists of 4 parts namely:

1. The Sun gear, a spur gear present at the center of the systems mated with all the planet gears.
2. The Planet Gear, also a spur gear mated with sun gear as well as the ring gear. These spins and turns (revolve around sun gear) transferring the motion between the two. Their axes revolve around the central axis.
3. The Ring Gear, an internal spur gear mated with all the planet gears. It is the outermost component of the assembly.
4. The carrier, it houses the planet gears providing a shaft to all along with connecting the planet gears to one single shaft (axis).

The module of all the aforementioned gears should be the same in order to mate with each other.

Components Used: The module used is 2.5 for all the gears. The pitch circle diameters for sun gear, planet gears, and ring gear are 35mm, 40mm, and 115mm respectively.

Motion Study Setup: The material for all the gears is used as Steel (Dry) with the static friction coefficient of 0.3 and the kinematic friction coefficient of 0.25.

Case 1: Input: Sun Gear

Output: Carrier

Fixed: Ring Gear

Case 2: Input: Ring Gear

Output: Carrier

Fixed: Sun Gear

Case 3: Input: Sun Gear

Output: Ring Gear

Fixed: Carrier

Results: Case 2 results in comparatively quick rotations with respect to Case 1, whereas Case 3 resulted in reversed output.

Input	Fixed	Output	Max Output Angular Velocity (deg/sec)	Approx. Avg. Output Angular Velocity (deg/sec)
Sun Gear	Ring Gear	Carrier	312	287
Ring Gear	Sun Gear	Carrier	1007	928
Sun Gear	Carrier	Ring Gear	387	365

Case1: The fixed ring gear makes the planet gears spin and revolve simultaneously which in turn makes the carrier output shaft rotate.

Case2: Here also the carrier is being rotated due to stationary sun gear. But the higher angular velocity is the result of the input at the ring gear.

The same input of 200 RPM means the same angular velocity but the tangential velocity depends on radius also. The Ring Gear provides more velocity to the planet gears as compared to the same input at sun gear. Hence more angular velocity at the carrier.

Case3: Making the carrier fix, we are allowing the planet gears to rotate but not revolve. To maintain the gear mating planet gears' rotation produce the reverse effect. The same result (direction of rotation, not velocity) would have been obtained if the input and output were interchanged.

Animations, Part files, Assembly files, plots:

https://drive.google.com/open?id=1Am5T5OHTDqq-c7VB_nhzRQlWdQamd7Tk