Internal Geneva Mechanism

AIM: To create the 3D model of an internal Geneva mechanism and analyse its motion.

THEORY:

Geneva mechanism, also called Geneva Stop, one of the most commonly used devices for producing intermittent rotary motion, characterized by alternate periods of motion and rest.

An internal Geneva drive is a variant on the design. The axis of the drive wheel of the internal drive can have a bearing only on one side.

Uses:

• In Mechanical watches.
• In movie projectors and movie cameras.
• It is used for indexing (i.e., rotating a shaft through a prescribed angle).

OBJECTIVES:

1. To create 3D models for driver and driven wheels.
2. To perform motion analysis by rotating the driver wheel at 10rpm and 20rpm, and obtain the following plots
1. Contact force (between driving and the driven wheel) as a function of time.
2. Angular Displacement of the driven wheel.
3. To compare the contact forces with and without "Precise contact" and
1. Show image for precise contact selection.
2. Export the results to Excel and make the plots over there.

DESIGNING:

1. Driven Part

2D sketch of the driven component

2D sketch with driving component

3D model of the driven component

2. Driving Part

2D sketch of the driving component

3D model of the driving component

3. Assembly Design

Front view

Right side view

MOTION ANALYSIS:

Case 1:

Speed = 10 RPM

FPS = 60

a) Contact Force between Driver and Driven component without Precise Contact

b) Angular Displacement of the Driven Wheel

c) Contact Force between Driver and Driven component with Precise Contact

Case 2:

Speed = 20 RPM

FPS = 120

a) Contact Force between Driver and Driven component without Precise Contact

b) Angular Displacement of the Driven Wheel

c) Contact Force between Driver and Driven component with Precise Contact

COMPARISION OF CONTACT FORCES:

For 10 RPM:

For 20 RPM:

Image Showing Precise Contact Selection:

ANIMATION:

Animation of Internal Geneva Mechanism

CONCLUSION:

1. From the above plots, it is evident that at the entry to the slots the contact force increases suddenly which in turn faces a jerk.

2. As the speed increases the contact force also increases.

3. The Contact force with precise contact is found to be smaller than the contact force without precise contact at 10 RPM but it is nearly equivalent at 20 RPM.

CAD MODELS:

SolidWorks Models

REFERENCES:

https://en.wikipedia.org/wiki/Geneva_drive

https://www.britannica.com/technology/Geneva-mechanism