Option 2: Orbiting Gear-Pairs

A Gear-Pair with 'Orbiting Centres':

One gear centre revolves, or 'orbits', around another gear centre.
A gear 'carrier' connects the centres of the two gears.

Applications

Planetary Gears

The combination of an orbiting gear that engages with a sun gear and also an annular gear is called a planetary gear train.

Planetary Gears have a number of advantages over simple and compound Gear-Trains.

We can design:

Curve Generation and their Applications

The path of the centre of the revolving Gear - Gear 2 in both of the images - is a circle. This is not very useful, or interesting. However, the path of a different Point on the revolving gear is interesting and sometimes useful.

Points on a revolving gear rolling around the outside of a fixed gear. See top image (below)

Epicycloid: A curve given by a point on the pitch-circle of a gear that rolls around the outside of the stationary gear

Epitrochoid: A curve given by a Point that is not on the pitch-circle of the gear that rolls around the outside of a stationary gear

Points on a revolving gear rolling around the inside of a fixed gear. See bottom image (below)

Hypocycloid: A curve given by a point on the pitch-circle of a gear that rolls around the inside of the stationary gear

Hypotrochoid: A curve given by a Point that is not on the pitch-circle of the gear that rolls around the inside of a stationary gear.

Peritrochoid: A curve given by a Point on an orbiting gear, that is bigger than a fixed gear, and its centre is inside the pitch circle of the fixed gear.

Basic Arrangement of Orbiting Gear-Pair

Example Planetary or Epicyclic Gears

External Gear-Pair : The mesh is 'External'


Gear 11s-red : Fixed to the Frame - it does not rotate

Gear 22s : Rotates about its own centre AND Orbits around the centre of Gear 1

Line-of-centres3s : Rotates with the centre of rotation at the centre of Gear 1

Epicyclic-Internal

Internal Gear-Pair : The mesh is 'Internal'

Gear 11s-red : Fixed to the Frame - it does not rotate

Gear 22s : Rotates about its own centre AND Orbits around the centre of Gear1

Line-of-centres3s : Rotates with the centre of rotation at the centre of Gear 1

Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd