﻿ Gears and Five-Bars

# Gears and Five-Bars

## Geared Five-Bar Mechanisms

Geared Five-Part mechanisms are used to give:

 • Complex coupler curves
 • Complex output motions

It is usually easier to:

 a. Join the two Parts in the dyad to the two gears.
 b. Join the two Parts in the dyad together.

#### Complex Coupler Curves

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

Application: Coupler Curve

In a Geared Five-bar, three Parts are the

 • Base-Part, Input Crank, and Geared-Rocker

 STEP 1:

Step 1 is complete.

To remind you:

Step 2.a is complete.

 2.b. Add three Joints 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.

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 2, add a Point (with a Line) in the Part.

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

 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

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.

#### Geared Five-Bars as Complex Function Generators

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

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

Step 2 is complete.

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

Step 3 is complete.

 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

Step 6 is complete.

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.

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

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

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

Application: Coupler Curve

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.