Page 163 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

142 Making Things Move

Types of Linear Actuators
Linear motors are far less common than rotary motors. There are quite a few other
ways to create linear output from rotary input (see Chapter 7 for more on this).
However, linear motors can be handy when you have a specific need. Figure 6-14
shows the two main types of linear actuators: linear motors and solenoids.

Linear Motors

Linear motors, like the ones from ServoCity shown in Figure 6-14, are DC gearhead
motors that interact with an Acme or ball screw assembly to push a plunger in and
out. We’ll talk more about these kinds of screws in the next chapter.
Linear motors can do a great deal of work, but you will pay the price for the
convenient packaging (they start at around $130). A former student of mine used
them to create lifting shoe mechanisms strong enough to hold and lift her weight (see
Figure 6-15).
On data sheets for these motors, you’ll see a lot of terms that should look familiar by
now: operating voltage, no load current, and so on. Since the action is linear, you’ll
see speed in inches per second instead of rpm. You should also see ratings for static
load and dynamic thrust. Static load is the weight of something you can put on the

FIGURE 6-14 Linear motors (left) (image used with permission from ServoCity) and solenoid
(right)