Planetary Gear

Aim: Designing the Planetary Gear and run a simulation on the given cases.

Introduction: Use the following inputs for designing the Planetary Gear

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

The dimensions of the carrier depend on the shaft diameter of the planet gear.

With the above input parameters, you are going to run a simulation on the following cases,

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

Basic theory on the motion study:

motion study as the “Science of eliminating wastefulness resulting from ill-directed and inefficient motions”. The main aim of motion study is to find the scheme of least wastage of labour. Subsequently, the scope of Motion Study was enlarged and it was named as Method Study.

Planetary Gear :

So,What are Planetary Gears?

A planetary gear set is made up of three types of gears; a sun gear, planet gears, and a ring gear. The sun gear is located at the center (yellow), and transmits torque to the planet gears (blue) which are typically mounted on a moveable carrier (green). The planet gears orbit around the sun gear and mesh with an outer ring gear (pink). Planetary gear systems can vary in complexity from very simple to intricate compound systems, depending on the application.

Image credit: Wikipedia

Where are Planetary Gear Systems Used?

Planetary gears are often used when space and weight are an issue, but a large amount of speed reduction and torque are needed. This requirement applies to a variety of industries, including tractors and construction equipment where a large amount of torque is needed to drive the wheels. Other places you will find planetary gear sets include turbine engines, automatic transmissions, and even electric screwdrivers.

Planetary gear systems are able to produce a lot of torque because the load is shared among multiple planet gears. This arrangement also creates more contact surfaces and a larger contact area between the gears than a traditional parallel axis gear system. Because of this, in the load is more evenly distributed and therefore the gears are more resistant to damage.

Entire motion study setup:

we have to calculate the planetary gear pitch circle diameter and no.of teeths.

The diameter of the Planet gear :

The radius of Ring gear= Diameter of the Planet gear + radius of the sun gear

Rr = Dp + Rs

So, Dp =Rr - Rs

Dp=115/2 - 35/2 = 40mm

Number of teeths of Planet gear:

Pitch diameter, D=m*T (m=D/T)

where , m=module

T= Number of teeth

so, T=D/m = 40/2.5 = 16

Gear type	module	pitch diameter	no.of teeth
Ring	2.5	115	46
Sun	2.5	35	14
Planet	2.5	40	16

There after,

Ready your every parts and assemble them.

Switching to SolidWorks Motion Manager Switch to SolidWorks Motion by clicking the motion analysis tab in the bottom left hand corner.

SolidWorks Assembly Mates.

Specifying the Input Motion and

Under Motor Type selet Rotary Motor. In our case i have used 200 rpm constant motor

Select contact between parts. Between Sungear – planet gear-ring gear

Go to settings and set frames per seconds as per our requirements. I have used defaults

Select Simulation time.i have choosed 5 sec

Running the Simulation.

Looking at the Results. And select plots as per our requirements.

Let’s go through one by one,

Model Description:

Ring gear :

Sun gear :

Planet gear :

Carrier :

Final assembly :

Results for case1:

Input	Output	Fixed
Sun Gear	Carrier	Ring Gear

Animation :

Youtube video link : https://youtu.be/MYPXWEDO0NM

Angular velocity plot for Carrier :

Results for case2:

Input	Output	Fixed
Ring Gear	Carrier	Sun Gear

Animation :

youtube video link:https://youtu.be/cm9qAiNGwZU

Angular velocity plot for Carrier :

Results for case3:

Input	Output	Fixed
Sun Gear	Ring Gear	Carrier

Animation :

Youtube video link : https://youtu.be/oBHm6miZHrE

Angular velocity plot for Ring gear :

Conclusion :

• In the first case, the planet gear not only rotates about their axis but are also forced to roll on the inside of the ring gear along with the carrier as the Ring gear is fixed.
• In the second case,The angular velocity achieved is maximum since the internal gear is big and planet gears are small comparatively so when a large gear meshes with a small gear the velocity achieved from the small gear is high because the velocity ratio is high.
• In the third case,All the gears rotate about their axis. The planet gears rotate only about their axis and transmit motion from sun to the ring and since the ring gear is big in diameter the angular velocity achieved is less. The deviations that are visible in the graphs show that there are points where sliding is occurring between the gears.