Geared Five-Bar Mechanisms

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Geared Five-Bar Mechanisms

Geared Five-Bar Mechanisms

Geared Five-bar mechanisms are usually built with:

One Gear-Pair

+

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

GST-14-Cartwright1

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

GST-Geared5Bar-1

 

 

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.

GST-Geared5Bar-2

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

GST-Geared5Bar-3

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

GST-T14-Geared5Bar-A

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-PairRed-14-1b

STEP 2: Make the gear ratio 1:1 (for example 50:50 Gear Teeth)

GST-T14-Geared5Bar-B

 

STEP 3: Add an R-R-R Dyad between the end the Geared Rocker and the Line in the Base-Part

 

GST-T14-Geared5Bar-C

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.

GST-T14-Geared5Bar-D

GST-T14-Geared5Bar-E

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

GST-T14-Geared5Bar-F

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

GST-T14-Geared5Bar-G

Gear-Pair: 1:1, Fixed-centers, Internal Mesh

Dyad: RPR Dyad

Application: Coupler Curve

 

GST-T14-Geared5Bar-H

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.

GST-T14-Geared5Bar-J

Gear-Pair 1:1,  Fixed-centers, R-R-P Dyad.

Application: Coupler Curve

 

 

GST-T14-Geared5Bar-J

Gear-Pair 1: 1, Orbiting-center, RPR Dyad

Application: Function-Generation

GST-T14-Geared5Bar-L

The motion of the output Rocker as a function of the input-rocker.

It has a reasonable dwell.