The Four-bar Chain Unit is used to generate oscillating motions from a rotary motion

Swinburne University of Technology

School of Engineering and Science

HES 5310 Machine Dynamics 2

Lab Sheet: Four-bar Linkage Assembly

Name: ..

Student ID: .

Group Number: .

Date performed experiment: .

Lab supervisor:

1. Introduction

The Four-bar Chain Unit is used to generate oscillating motions from a rotary motion. Similar mechanisms are often applied in packaging technologies or Ackermann steering, for example. The angle of the rotary motion input and the oscillating motion can be read on scales.

2. Description of Apparatus

3. Theoretical principles

Four-bar linkages

Four-bar linkages are straight-line mechanisms. They can be divided into three groups, namely:

Rotating

Non-rotating and

Reversible four-bar linkages

1. Rotating Four-bar linkage

A four-bar linkage can rotate when the Grashof condition is met:

The sum of the lengths of the longest and shortest bars must be less than the sum of the two remaining bars, and there may only be a single shortest bar. There are three types of rotating linkages:

Crank-and-rocker (lmin = a, c)

Double-rocker (lmin = b)

Double crank (lmin = d)

2. Non-rotating four-bar linkage

(total oscillation)

This type contains only one longest bar. The relative oscillating motions always take place symmetrically with respect to the adjacent bar.

3. Reversible four-bar linkage

The requirement for reversible four-bar linkage is the equal lengths of the two bar pairs.

4. Experimental Procedure

1. Crank and rocker linkage

In the following section, two examples are taken from the number of possible settings of the hinge points.

1. The hinge points are set according to the figure as follows:

C-5-III2. With the input angle set to zero read the corresponding output angle and record in table.

3. Complete the table by reading the output angle corresponding to 20( input increments

4. Using the protractor supplied, measure the transmission angle between the coupler link, b, and output link, c.

5. Set the corresponding hinge configuration to:

C-1- III

6. Repeat steps 2 to 4

7. Set the corresponding hinge configuration to:

A-1- III

8. Repeat steps 2 to 4

2. Non-rotating four-bar linkage

This is a non-Grashof case. Identify at least 5 non-grashof situations and study one of the cases for the following points.

- toggle position, -angle with respect to the input angle in toggle position and

-input/output angle for 3600 rotation of link 2.-limitation of the experiment3. Reversible four-bar linkage

This is a special grashof case.

-identify the special grashof situation and -observe the motion of the linkage5. Results

1. Crank and rocker linkage

Fill in the attached tables.

2. Non-rotating four-bar linkage

- Non grashof situations occur at following hinge configurationa.

b.

c.

d.

f.

-Toggle position at

-Fill in the attached table3. Reversible four-bar linkage

Special grashof situations occur at the following hinge configuration

a.

b.

6. Discussion

1. Crank and rocker linkage

For the three cases

1. Determine whether the grashof criteria is meet.

2. State the minimum transmission angle for each case.

3. Plot the graphs of output angle versus input angle.

4. Discuss the effects of the differing bar lengths for the different situations, ie ouput angle and transmission angle.

2. Non-rotating four-bar linkage

-plot the graphs of the output angle vs input angle and find minimum and maximum transmission angle

-Is there any discontinuity of the motion? If there is, find the range of the discontinuity.

3. Reversible fourbar linkage

- Discuss the nature of the motion of the linkage.

7. Reference

Norton, RL 2004, Design of Machinery, An introduction to the synthesis and analysis of mechanisms of machines, 3rd edn, Mc Graw Hill, Singapore

8. Technical Data

Adjustable crank radii:

Hinge point A:

25mm

Hinge point B:

37.5mm

Hinge point C:

50mm

Adjustable connecting rod lengths:

Hinge point 1:

60mm

Hinge point 2:

160mm

Hinge point 3:

180mm

Hinge point 4:

200mm

Hinge point 5:

220mm

Adjustable lever lengths:

Hinge point I:

50mm

Hinge point II:

100mm

Hinge point III:

200mm

Interval between rotating axes200mm

2. Non-rotating four-bar linkage

Name of Hinge Configuration-

2

020406080100120140160180200220240260280300320340360

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