Planetary Gear
PLANETARY GEAR
AIM:
- To analyze the motion analysis on a planetary gear under given conditions and explain about the Planetary Gear and discuss the plots obtained in the three cases.
- Input- Rotary Motion given to that part as input.
- Output- After motion analysis, the Angular velocity of that part is plotted as a graph.
- Fixed-Make that particular component as a fixed part.
- You should not use the Gear Mate.
- The module is the same for all the gears.
- You need to calculate the pitch circle diameter and the number of teeth for the planet gear.
| Sl.No | Input | Output | Fixed |
| 1 | Sun Gear | Carrier | Ring Gear |
| 2 | Ring Gear | Carrier | Sun Gear |
| 3 | Sun Gear | Ring Gear | Carrier |
INTRODUCTION:
Epicyclic gearing or planetary gearing is a gear system consisting of one or more outer, or planet, gears or pinions, revolving about a central sun gear or sun wheel. Typically, the planet gears are mounted on a movable arm or carrier, which itself may rotate relative to the sun gear. Epicyclic gearing systems also incorporate the use of an outer ring gear or annulus, which meshes with the planet gears.
THEORY:
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.
An epicyclic gear train can be assembled so the planet gear rolls on the inside of the pitch circle of a fixed, outer gear ring, or ring gear sometimes called an annular gear. In this case, the curve traced by a point on the pitch circle of the planet is a hypocycloid.
The combination of epicycle gear trains with a planet engaging both a sun gear and a ring gear is called a planetary gear train. In this case, the ring gear is usually fixed and the sun gear is driven.
Planetary gears (or epicyclic gears) are typically classified as
- simple planetary gears.
- compound planetary gears.
- Simple planetary gears have one sun, one ring, one carrier, and one planet set.
- Compound planetary gears involve one or more of the following three types of structures: meshed-planet (there are at least two more planets in mesh with each other in each planet train), stepped-planet (there exists a shaft connection between two planets in each planet train), and multi-stage structures (the system contains two or more planet sets)
CALCULATION:
- To calculate the pitch circle diameter(PCD) of the planet gear
- PCD of planet gear = (PCD of ring gear - PCD of sun gear)/2
= ((115 - 35)/2)
= 40 mm
- No of Teeth in planet gear = PCD of planet gear / Module of planet gear
= 40/2.5
= 16
- To calculate the pitch circle diameter(PCD) of the sun gear
Module = 2.5
No of teeth = 14
PCD of sun gear = Module * No of teeth
= 35 mm
- To calculate the pitch circle diameter(PCD) of the ring gear
Module = 2.5
No of teeth = 46
PCD of ring gear = Module * No of teeth
= 115 mm
CREATING THE 3D MODEL:
For creating gear go to
Design library -> Toolbox -> ANSI metric -> Power transmission -> For choosing sun and planet gears use Spur gear whereas use internal spur gear for choosing ring gear.
The models are represented below.
Face width = 20mm
Pressure angle = 20 mm
SUN GEAR (i.e SPUR GEAR)
PLANET GEAR (i.e SPUR GEAR)
RING GEAR (i.e iNTERNAL SPUR GEAR)
CARRIER MODEL
FINAL ASSEMBLY
The sun gear, planet gear, ring gear and carrier are assembled as shown below. Here we are not using mechanical gear mates as we have to analyze the motion of three cases.
MOTION ANALYSIS
In motion study, we make contacts between the following:
- Carrier and the planet gears.
- Sun and the planet gears.
- Ring and the planet gears.
The material for each contact is Steel (Dry)
The three cases are:
| Sl.No | Input | Output | Fixed |
| 1 | Sun Gear | Carrier | Ring Gear |
| 2 | Ring Gear | Carrier | Sun Gear |
| 3 | Sun Gear | Ring Gear | Carrier |
The input speed to the motor in each case is 200 RPM.
RESULTS AND PLOTS
-> CASE 1:
The plot of the angular velocity of the carrier is shown below.
-> CASE 2:
The plot of the angular velocity of the carrier is shown below.
-> CASE 3:
The plot of the angular velocity of the ring is shown below.
ANIMATION
-> CASE 1
-> CASE 2
-> CASE 3