Internal Geneva Mechanism

OBJECTIVES

• 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.
• Compare the contact forces with and without "Precise contact".
• Show image for precise contact selection.
• Export the results that you get to Excel and make the plots over there.
• Use 60 Frames per second for 10 rpm and then 120 Frames per second for 20 Rpm.
• Make a plot of the driver wheel's angular velocity and discuss the results.

THEORY

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. The angle by which the drive wheel has to rotate to effect one step rotation of the driven wheel is always smaller than 180° in an external Geneva drive and always greater than 180° in an internal one, where the switch time is therefore greater than the time the driven wheel stands still.

• Internal Geneva drive

• Animation showing an internal Geneva drive in operation

The external form is the more common, as it can be built smaller and can withstand higher mechanical stresses.

3 D model

The 3D models are created using the following dimensions

• Driver wheel dimension

• Driven wheel dimension

Created 3D model

• Driver wheel

• Driven wheel

• Assembled model

RESULTS

• For 10 RPM all the result given below

1. contact force without precise contact,

2. contact force with precise contact and 60 Frame,

3. angular displacement of driven without precise contact,

4. angular displacement of driven with precise contact and 60 frames,

5. angular displacement of the driver without precise contact,

6. angular velocity of the driver without precise contact,

7. angular velocity of the driver with precise contact,

8. Nangular velocity of the driven member without precise contact,

9. angular velocity of the driven member with precise contact,

• For the 20 RPM, all the result given below and 120 frames

1. contact force with precise contact,

2. angular displacement of the driven member with precise contact,

3. angular displacement for driver member with precise contact,

4. angular velocity of the Driver with precise contact,

5. angular velocity of the Driven with precise contact,

CONCLUSION:

Here I take the solution without precise contact and with precise contact for 10 RPM and60 frame in the precise contact. Where in the precise contact I got the less fluctuation and points were near to each other and accuracy of the result is higher. we also have the solution for 20 RPM precise contact I compare both of them over here.

first, if talk about the contact force graph where we got a peak in the graph at a different point because when the pin of driver moves inside the driven member slot there some clash occurs in between the driver and driven.

comparatively, we have a higher reaction force in the 20 RPM rotation speed. But in the same force decreases simultaneously. Whereas in the 10 RPM rotation speed from the starting to end our force is increasing.

Second, I determine the angular displacement of the driver and the driven member in the graph of 10 RPM and at 20 RPM, we can see a clear difference that at the higher RPM we get the higher angular displacement. In the precise contact graph, we got a smoother graph than the non-precise contact. In the 20 RPM graph, we have lines nearer to each other than the 10 RPM graph.

Third, I determine the angular velocity for the driver member its constant for the constant RPM but when we show in Excel graph we show the variation at some point. For 10 RPM angular velocity is 60 Deg/sec and for 20 RPM angular velocity is 120 Deg/sec.

Forth, I determine the angular velocity of the driven member its fluctuate from 0 to 25 for the 10 RPM graph, and from 0 to 50 for the 20 RPM graph. here also it is observed that the graph are smoother for the precise contact type solution.

Here also we got the peck point in the angular displacement graph of the driven member because when pin of the driver sudden come into the contact with driven its experience some jerk motion that is the reason that we got the peak in the graph.