Planetary Gear

AIM:

• To design planetary gears, ring gear,sun gear and carrier by giving required constraints.
• To run the simulation and study the motion analysis of the whole assembly.

Theory:

A planetary gearbox is a gearbox with the input shaft and the output shaft aligned. A planetary gearbox is used to transfer the largest torque in the most compact form (known as torque density).

The bicycle’s acceleration hub is a great example of a planet-wheel mechanism: Have you ever wondered how you can get so much power and capabilities in such a little hub? For a three-speed hub, a one-stage planetary gear system is used, for a five-speed hub a 2-stage. Each planet gear system has a reduction state, a direct coupling and an acceleration mode.

In mathematical terms, the smallest reduction ratio is 3: 1, the largest is 10: 1. At a ratio of less than 3, the sun gear becomes too big against the planet gears. At a ratio greater than 10 the sun wheel becomes too small and the torque will drop. The ratios are usually absolute i.e. an integer number.

Formula Used:

Radius of Ring Gear = Diameter of sun gear+Diameter of planet gear

Pitch Diameter = Module * Number of teeth

Ring gear Parameters:

Module= 2.5

No. Of teeth= 46

Face Width= 20mm

Pressure angle= 20°

Pitch diameter= (2.5*46)= 115mm

Sun gear parameters:

Module= 2.5

No. of teeth= 14

Nominal shaft diameter= 20mm

Face Width= 20mm

Pressure angle= 20°

Pitch Diameter=35mm

Planet gear parameters:

Module=2.5

No. of teeth= 16

Face Width= 20mm

Pressure angle= 20°

Pitch Diameter= 40mm

Nominal shaft diameter= 25mm

Procedure:

• Using toolbox design sun gear, planet gear, Ring gear using ANSI metric.
• Design carrier according to gear assembly as given below.

• Assemble gear with carrier with proper constraints.

Motion study:

CASE 1:

• when the Carrier is fixed
• Input is given to sun gear
• Output is taken through Ring gear

Angular velocity vs time graph.

CASE 2:

• When the Ring gear is fixed.
• Input is given to sun gear.
• Output is taken through Carrier.

• CASE 3:

• When the Sun gear is fixed.
• Input is given to Ring gear.
• Output is taken through Carrier.

Conclusion:

Angular velocity is least when sun gear is fixed.

Based on arrangement these planet gear can be used in different arrangement.

Ring Fixed Youtube link:

https://youtu.be/_1H8ZE3QMJU

Sun gear fixed Youtube Link:

https://youtu.be/tafm_Q2Gtug

Carrier fixed youtube link:

https://youtu.be/mdjNuHnD80c