Internal Geneva Mechanism

1. Aim:

• Create 3D models for driver and driven wheels.
• Perform motion analysis by rotating the driver wheel at 10rpm.
• Obtain the following plots
• Contact force (between driving and the driven wheel) as a function of time.
• Angular Displacement of the driven wheel.

2. Dimension and Parameters of Driver and Driven Wheel (All dimensions are in mm) :-

1) Driver Wheel Parameters

2) Driven Wheel Parameters

Note :- Contact between both the wheel is steel (dry)

3. Theory:

The Geneva drive or Maltese cross is a gear mechanism that translates a continuous rotation movement into intermittent rotary motion.

The Rotating drive wheel is usually equipped with a pin that reaches into a slot located in the other wheel (driven wheel) that advances it by one step at a time. The main wheel also has an elevated circular blocking disc that "locks" the rotating driven wheel in position between steps.

3D Model of Internal Geneva Mechanism :-

4. Result (Motion Analysis):

1) At the speed of 10rpm of the driver wheel (60 fps) :-

Fig :- Contact force between Driver and Driven wheel without precise contact

Fig :- Contact force between Driver and Driven wheel with precise contact

Fig :- Contact force between Driver and Driven wheel with precise contact

Fig :- Angular Displacement of driven wheel

Fig :- Angular velocity of Driven wheel

2) At the speed of 20rpm of the driver wheel (120 fps) :-

Fig :- Contact force between Driver and Driven wheel without precise contact

Fig :- Contact force between Driver and Driven wheel with precise contact

Fig :- Angular Displacement of driven wheel

Fig :- Angular velocity of Driven wheel

6. Animation: working of Geneva Mechanism

https://youtu.be/bbUZLXpfSQ0

7. Conclusions :-

• If the rpm of the driver wheel increases then the angular displacement of the driven wheel increases according to the time.
• In this geneva mechanism model if the driver wheel rotate 4 times then driven wheel rotate only 1 times. Its speed ratio is 4:1.
• When comparing the contact force between precise contact and without precise contact it shows that if the precise contact is considered then the value of contact force will increases and give much accurate result.
• By showing the angular displacement graph of the driven wheel it observe that for a few second driven wheel will at the rest position and again revolve upto 90 degree and this process will continued.
• By showing the angular velocity graph some jerk will observe at the begning of the motion of the driven wheel or intial contact between driver and driven wheel.

Reference:-

• www.wikipedia.com
• projects.skill-lync.com