Planetary Gear
AIM: To designed a Planetary Gear System.
Objectives of the project:
- Constructing a Planetary gear system with four planet gears.
- Plot angular velocity for an output part as a result for three different cases.
Introduction:
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. In this simplified case, the sun gear is fixed and the planetary gears 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.
Fig. Planetary Gear system.
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.
Planetary gears (or epicyclic gears) are typically classified as:
- Simple planetary gears.
- Compound planetary gears.
Fig. Simple Planetary gear Fig. Compound Planetary gear
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). Compared to simple planetary gears, compound planetary gears have the advantages of larger reduction ratio, higher torque-to-weight ratio, and more flexible configurations.
Calculation:
To satisfy the law of gearing, module needs to be same for each gear.
Input Speed Given to a gear part=200RPM
Ring Gear:
Module=2.5
No. of teeth=46
Sun Gear:
Module=2.5
No. of teeth=14
We know that, Pitch circle diameter(PCD)=module(m)* no. of teeth(t)
i.e PCD=m*t
Therefore,
For Ring gear, PCD=2.5*46=115
For Sun gear, PCD=2.5*14=35
Planet Gear:
From Planetary gear system, it is observed that
(PCD)Ring gear=2*(PCD)Planet gear+(PCD)Sun gear
Now, by substituting values of PCD, we get (PCD)Planet gear=40
No. of teeth=(PCD)Planet gear/module
=40/2.5=16
3D Models of Gear and Assembly of Planetary Gear System:
Ring Gear:
Sun Gear:
Planet Gear:
Carrier:
Assembly:
Analysis of Motion Study:
Results:
- Plot for Case 1: Fixing the ring gear, input is given to sun gear and receiving output at a carrier.
Angular velocity of the Carrier
Animation link for above condition:https://youtu.be/OmSdhswjpV8
- Plot for Case 2: Fixing the sun gear, input is given to ring gear and receiving output at a carrier.
Angular velocity of the Carrier
Animation link for above condition:https://youtu.be/Y_GNAJbvCdA
- Plot for Case 3: Fixing the carrier, input is given to sun gear and receiving output at ring gear.
Angular velocity of the Ring gear
Animation link for above condition:https://youtu.be/QoG_-52raoo
Conclusion:
It is observed from the above plot that the angular velocity of the part remains constant during motion and this is consistent with the input rotary motion given to a part at a constant speed (200rpm).
Drive link for Parts and Assembly:
https://drive.google.com/file/d/1OJzZ2u1Sg2JGPX6La4_5v-iB6NA51VTK/view?usp=sharing
https://drive.google.com/file/d/1J64fw2RRj3rRHZj216txV4bScI2L9LET/view?usp=sharing