﻿ Getting Started Tutorials - MechDesigner > Tutorial 14: Gear-Pairs > Fixed Gear and Orbiting Gear Arrangements > Geared Five-Bar Mechanisms

# Geared Five-Bar Mechanisms

## Geared Five-Bar Mechanisms

Geared Five-bar mechanisms are usually built with:

One Gear-Pair

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#### 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: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 Gear-Pair: 1:1, Fixed-centers, Internal Mesh Dyad: R-R-R Dyad Application: Coupler Curve In a Geared Five-bar, three Parts are the •Base-Part, Input Crank, and Geared-RockerThe other two Parts are joined as a Dyad. Typically, the Dyad is an R-R-R Dyad. STEP 1: Step 1 is complete.   STEP 2: Add an R-R-R DyadTo remind you: 2.a.Add two PartsStep 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 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), Module to give center distance 2.Phase between the Gears3.Length of Gear 'Cranks'4.Length of Dyad Parts5.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 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 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) Step 2 is complete.   STEP 3: Add an R-R-R 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 FBStep 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. 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. 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-centers, Internal Mesh Dyad: RPR Dyad Application: Coupler Curve 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 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. Gear-Pair 1:1,  Fixed-centers, R-R-P Dyad. Application: Coupler Curve Gear-Pair 1: 1, Orbiting-center, RPR Dyad Application: Function-Generation The motion of the output Rocker as a function of the input-rocker. It has a reasonable dwell.