Page 322 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

You need to pull the muscle out straight when empty

So it can shorten when full of air

16.1 Drawing of air muscle being stretched
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When air pressure is applied, the muscle contracts by the following
mechanism. When the air muscle is pressurized, the soft inner tube
expands. The inner tube pushes against the black plastic mesh and
causes it to expand also. When the plastic mesh expands, it shortens
in length in proportion to the expansion of its diameter. This
causes the air muscle to contract. However, it is essential that the
air muscle be in a stretched or elongated position when it’s deacti-
vated or in a resting state in order for it to operate properly. If not,
there will not be any movement or contraction when it is activated
(see Fig. 16.1).

Components of the air muscle system
Figure 16.2 illustrates the components needed to use the air muscle.
Item 1 is the air muscle itself (of course). Item 2 is a three-way air
valve. The three-way air valve allows one to manually operate the
air muscle (see Fig. 16.3).
Item 3 is a bottle top adapter, with a pressure release valve (set
around 60 psi). The bottle top adapter allows one to use a standard
plastic PET soda bottle for air storage. The pressure release valve
automatically releases excess air when preset pressure is exceeded.

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