Internal Geneva Mechanism

Aim: To perform motion analysis on Internal Geneva Mechanism

Theory:

Geneva mechanism is a pair of rotating components which converts continuous rotary motion into intermittent rotary motion.

They are mainly of two types:

1)External Geneva Mechanism

2) Internal Geneva Mechanism

Motion Analysis:

Motion analysis is study of dynamic behaviour of interconnected rigid or flexible links which have a rotational or translation motion.

For performing motion anaylsis driving motion is defined for the driving member and then contact between driving and driven member is defined to study the effect of motion of driving member on driven member.

From the results the contact force between driving and driven member. reaction forces, displacement, velocity, acceleration etc. can be known.

The Internal Geneva Mechanism here is modeled in SolidWorks with following dimensions:

For motion analysis, rotary motion is defined for the driving member with constant RPM of 10. A dry contact between driving and driven member is defined with both being made of steel.

Analysis has been performed here for 10RPM and 20RPM with and without precise contact.

Using precise contact allows the use of analytically correct contact which gives accurate results but it takes more time for computation than approximate solution.

For 10RPM study, 60 Frame per sec have been used with precise contact.

For 10RPM study, 120 Frame per sec have been used with precise contact.

The following results are shown below in Graphs:

1) Angular displacement of Driven Member

2) Angular velocity of Driven Member

3) Contact Force between Driving and Driven member

4) Contact Force between Driving and Driven member with precise contact

Conclusion:

It can be noted from the angular displacement and angular velocity graphs that driven member is in motion for certain period and then it is stationary and again comes into motion and cycle repeats. Thus it can be concluded that driven member have an intermittent rotary motion.

From contact force graphs it can be noted that with precise contact the curve in graphs is smooth and there is very little noise and also there is change in contact force with and without precise contact. Also for precise contact it can be noted that curve is identical for each cycle. Thus it can concluded that precise contact gives accurate results.