Geared Five-Bar Mechanisms

Geared Five-Part mechanisms are used to give:

Complex coupler curves
Complex output motions

It is usually easier to:

1.First add the Gear-Pair
2.Then add a Dyad:
a.Join the two Parts in the dyad to the two gears.
b.Join the two Parts in the dyad together.

tog_minus        Complex Coupler Curves

QST14-IGS-1

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

Dyad: RRR 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 RRR Dyad.

QST14-IGS-2

Step 1 is complete.

 

STEP 2: Add an RRR Dyad

To remind you:

2.a.Add two Parts

Step 2.a is complete.

 

QST14-IGS-3

2.b.Add three Joints1s-red2s3s between the Parts that are the Gear Pairs.

Step 2.b is complete.

 

Geared Five-Bar Mechanisms can give unusual motions and complex coupler curves.

QST14-IGS-4

You may want to be more flexible with the design

STEP 3: Edit the Part used for Gear 2

Instead of the R (Pin-Joint) at the end of the Part used for Gear 23s, add a Point (with a Line) in the Part.

Use the new Point for one of the Pin-Joints in the RRR Dyad4s. 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), Module to give centre distance
2.Phase between the Gears
3.Length of Gear 'Cranks'
4.Length of Dyad Parts
5.Position of Coupler Point

Geared-FiveBar-Ep5

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

Geared-Fivebar-Simple-1

Here is an interesting Coupler Curve.

 

In these Coupler Curves we are plotting the Point at the middle joint of the RRR Dyad.

You can add a Point to one of the Parts to give even more complex Coupler Curves.

tog_minus        Geared Five-Bars as Complex Function Generators

Geared-FiveBar-Ep1

Gear-Pair: 1:1, Orbiting-Centres, Internal Mesh

Dyad: RRR 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.

STEP 1: Add an Epicyclic Gear-Pair1s-red
STEP 2: Make the gear ratio 1:1 (for example 50:50 Gear Teeth)

Geared-FiveBar-Ep2

Step 2 is complete.

 

STEP 3: Add an RRR Dyad2s between the end the Geared Rocker and the Line in the Base-Part

 

Step 3 is complete.

Geared-FiveBar-Ep3

STEP 4: Measure the angular position of the output Part over a Machine Cycle with a Measurement FB3s
STEP 5: Add a Graph FB4s
STEP 6: Connect the Measurement FB to an input of the Graph FB

Step 6 is complete.

Add a Design-Set to give a quick way to edit the Part lengths.

Geared-FiveBar-Ep4

This Graph shows the Output Shaft Rotation as a Function of the Input, Constant Speed, Shaft Rotation.


Geared-FiveBar-Ep5

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

Geared-FiveBar-Ep6

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.

tog_minus        Geared Five-Bars: Pin-Joints and Slide-Joints

Geared-Fiveba-SG-Slide1

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

Dyad: RPR Dyad

Application: Coupler Curve

Geared-FiveBa-SG-Slide2

Gear-Pair, 2:1 Fixed-Centres with an RPR Dyad

Application: Coupler Curve

The Gear-Pair ratio changed to 60:40
The Crank must rotate twice for the mechanism to repeat a machine cycle.
To plot the complete Coupler Curve you should add a Gearing FB before the Motion-Dimension FB and make the Gearing Ratio parameter equal to 2.

Geared-Fiveba-SG-RRP1

Gear-Pair 1:1,  Fixed-Centres, RRP Dyad.

Application: Coupler Curve

Geared-Fiveba-EG-RPR1

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

Application: Function-Generation

Geared-Fiveba-EG-RPR1-graph

The 'Function' at the Rocker.

It has a reasonable dwell.

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