MBD of Internal Geneva Mechanism

Aim: To create the 3D model of the internal Geneva mechanism.

Tasks

1. Create 3D models for driver and driven wheels.
2. Perform motion analysis by rotating the driver wheel at 10rpm.
3. Obtain the following plots
4. Contact force (between driving and the driven wheel) as a function of time.
5. Angular Displacement of the driven wheel.
6. Compare the contact forces with and without "Precise contact"
7. Show image for precise contact selection
8. Export the results that you get to Excel and make the plots over there
9. To navigate to the "Precise Contact" follow the steps given below
10. 10. Use 60 Frames per second for 10 rpm and then 120 Frames per second for 20 Rpm
11. 11. Once you have completed the previous study, change the rpm to 20
12. 12. Make a plot of the driver wheel's angular velocity and discuss the results

Solution:

Process Flow 1-3D CAD Modelling of the sketch

• Driven Wheel

This wheel will be driven by another internal wheel.

2. Driving Wheel:

This wheel will be driven by a motor which in turn rotates the driving wheel.

Assembly:

The parts are assembled as per the tangential sketch show in the above assembly.

Motion Analysis:

1. Motor is set up at 10 rpm and 20rpm to the axis of driving wheel.
2. Establishing the contacts between the driven and driving wheel.

Case 1: No precise Contact, 60fps , 10 RPM

Contact force between both wheels:

Angular displacement of Driven Wheel:

Case 2: precise Contact, 60fps, 10 RPM

Contact force between both wheels:

Angular displacement of Driven Wheel:

Case 3: No precise contact, 120fps, 20 RPM

Contact force between both wheels:

Angular displacement of Driven Wheel:

Case 4: precise contact, 120fps, 20RPM

Contact force between both wheels:

Angular displacement of Driven Wheel:

Angular Velocity plot at 20RPM:

Inference from the plots:

• It is clear that the peak values of plots are more accurate in precise contact enabled analysis.
• Increasing the rpm, results in peaks on contact forces at a shorter period of time which is obvious.
• Increasing the rpm, results in decrease of angular displacement at a faster rate.
• Change of precise contacts provide good resolution into the plot such as high peaks etc but does not impart any role in accuracy of the system.