Page 265 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

Chapter 8 Combining Simple Machines for Work and Fun 243

Linkages
A linkage is a connection that transfers motion from one mechanical component to
another. Linkages are often the simplest, least expensive, and most efficient mechanism
to perform complicated motions. They come in many shapes and configurations, and
can do many jobs, such as the following:

• Change direction or otherwise alter path of motion
• Alter speed and/or acceleration
• Change timing of moving parts

• Apply a mechanical advantage
• Create elegant and efficient motion

Most linkages are planar, which means all the motion takes place in the same plane.
Linkages usually have only one job, regardless of the number of links: create a specific
output motion from a specific input motion.

Four-bar linkages are the simplest closed-loop linkage. They can create many different
output motions by varying the lengths and relationships of the four segments (see
Figure 8-6):

• Ground/frame The link that is kept stationary.

• Coupler/lever The link opposite the ground.

FIGURE 8-6 Types of four-bar linkages