Geared Five-Bar Mechanisms
Contents
Geared Five-Bar Mechanisms
Geared Five-bar mechanisms are usually built with:
| • | One Gear-Pair |
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| • | One Dyad |
Applications
Geared five-bar mechanisms are very interesting...to some people. They can give:
| • | Complex Coupler Curves |
| • | Complex Function Generators |
Geared Five-bar Mechanism Configurations
There are four ways to edit 'Geared Five-bar Mechanisms':
| 1. | Gear-Pair: Use fixed or orbiting gear centres |
| 2. | Dyad: use one of the five dyads:R-R-R, R-R-P, RPR, RPP, or PRP. |
| 3. | Gear Mesh: Use an external or internal gear-mesh |
| 4. | Basic Design: Edit the number of teeth on each gear. |
Typical Geared Five-bar Mechanism Configurations
Complex Coupler Curves
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Gear-Pair: 1:1, Fixed-Centres, Internal Mesh Dyad: R-R-R Dyad Application: Coupler Curve In a Geared Five-bar, three Parts are the
The other two Parts are joined as a Dyad. Typically, the Dyad is an R-R-R Dyad.
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Step 1 is complete.
To remind you:
Step 2.a is complete.
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Step 2.b is complete.
Geared Five-Bar Mechanisms can give unusual motions and complex coupler curves. |
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You may want to be more flexible with the design
As an alternative to the R (Pin-Joint) at the end of the Part used for Gear 2 Use the new Point for one of the Pin-Joints in the R-R-R Dyad The design parameter options are:
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In this case, it takes two rotations of the input crank to complete the function at the output shaft To plot the complete Trace-Point ,you must rotate the input crank two times faster.
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Here is an 'interesting' Coupler Curve.
In these Coupler Curves we are plotting the motion of the middle joint of the R-R-R Dyad. You can add a Point to one of the Parts to give even more complex Coupler Curves. |
Geared Five-Bars as Complex Function Generators
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Gear-Pair: 1:1, Orbiting-Centres, Internal Mesh Dyad: R-R-R Dyad Application: Function-Generation Typically, you can get interesting motions from a Geared Five-bar that has a Gear-Pair with an Orbiting Centre. The output motion is a function of the input constant speed motion and is therefore called a Function-Generator.
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Step 2 is complete.
Step 3 is complete. |
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Step 6 is complete. Add a Design-Set to give a quick way to edit the Part lengths.
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This Graph shows the Output Shaft Rotation as a Function of the Input, Constant Speed, Shaft Rotation. Notes about Mechanism Synthesis It is typical that an output to input relationship is given. Then a mechanism is found to repeats the function. Four-bar mechanism Function-Generators are limited. For example, it is not easy to synthesise a mechanism that oscillates the output shaft more than one time in a machine cycle. It is clear from this graph that more complex functions are possible. However, it is far more easy to synthesise a mechanism for a function. I will not suggest how you do. |
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Change the Gear Ratio to give more interesting Function Generation You can change the gear ratio of the Gear-Pair to give more complex function generation.
In this case, it takes two rotations of the input crank to complete the function at the output shaft
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The Graph will show the Y-axis for two rotations of the crank to give the complete Function-Generation for the 60:40 gearing ratio. |
Geared Five-Bars: Pin-Joints and Slide-Joints
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Gear-Pair: 1:1, Fixed-Centres, Internal Mesh Dyad: RPR Dyad Application: Coupler Curve
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Gear-Pair, 2:1 Fixed-Centres with an RPR Dyad Application: Coupler Curve
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Gear-Pair 1:1, Fixed-Centres, R-R-P Dyad. Application: Coupler Curve
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Gear-Pair 1: 1, Orbiting-Centre, RPR Dyad Application: Function-Generation |
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The motion of the output Rocker as a function of the input-rocker. It has a reasonable dwell.
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