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 centers
2.Dyad: use one of the five dyads: RRR, RRP, 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-centers, External Mesh Dyad: R-R-R Dyad Application: Coupler Curve In a Geared Five-bar, three Parts are the •Base-Part, Input Crank, and Geared-Rocker The other two Parts are joined as a Dyad. Typically, the Dyad is an R-R-R Dyad. STEP 1: Add a Simple Gear-Pair - Option 1 |
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STEP 2: Add an R-R-R Dyad To remind you: 2.a. Add two Parts 2.b. Add three Joints between the Parts that are the Gear Pairs. Geared Five-Bar Mechanisms can give unusual motions and complex coupler curves. You may want to be more flexible with the design STEP 3: Edit the Part used for Gear 2 As an alternative to the R (Pin-Joint) at the end of the Part used for Gear 2, add a Point (with a Line) in the Part. Use the new Point for one of the Pin-Joints in the R-R-R Dyad. You can edit the phase of the Gear 2 relative to Gear 1. The design parameter options are: 1.Gear Ratio between Gear 1 and 2 (Number-of-Teeth); Phase between the Gears; Length of Gear 'Cranks'; Length of Dyad Parts. Position of Coupler Point in the Geared Coupler. |
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STEP 4: Change the number-of-teeth with the Gear-Pair dialog-box - for example 60:40. 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. STEP 5: Add a Gearing FB; make the Gear ratio = 2 STEP 6: Connect the wire between the Linear-Motion FB, Gearing FB and the Motion-Dimension FB STEP 7: Connect the Output from the Motion-Dimension FB to the X input of the Graph FB |
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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-centers, 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 center. The output motion is a function of the input constant speed motion and is therefore called a Function-Generator. STEP 1: Add an Epicyclic Gear-Pair STEP 2: Make the gear ratio 1:1 (for example 50:50 Gear Teeth) |
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STEP 3: Add an R-R-R Dyad between the end the Geared Rocker and the Line in the Base-Part
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STEP 4: Measure the angular position of the output Part over a Machine Cycle with a Measurement FB STEP 5: Add a Graph FB STEP 6: Connect the Measurement FB to an input of the Graph FB Add a Design-Set to give a quick way to edit the Part lengths. 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 vs input relationship is given. Then a mechanism is found to provide the function. Four-bar mechanism Function-Generators are limited. For example, it is not easy to synthesize 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. |
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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. STEP 7: Change the Gear ratio - for example 60:40. In this case, it takes two rotations of the input crank to complete the function at the output shaft STEP 8: Add a Gearing FB; make the Gear ratio 2 STEP 9: Connect the wire between the Linear-Motion FB, Gearing FB and the Motion-Dimension FB STEP 10: Connect the Output from the Motion-Dimension FB to the X input of the Graph FB |
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The Graph will shows 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-centers, Internal Mesh Dyad: RPR Dyad Application: Coupler Curve
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Gear-Pair, 2:1 Fixed-centers with an RPR Dyad Application: Coupler Curve •The Gear-Pair ratio changed to 60:40 •The Crank must rotate tow times to complete the Trace-Path •To plot the complete Coupler Curve you should add a Gearing FB before the Motion-Dimension FB and make the Gearing Ratio = 2. |
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Gear-Pair 1:1, Fixed-centers, R-R-P Dyad. Application: Coupler Curve
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Gear-Pair 1: 1, Orbiting-center, 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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