Page 329 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

16.10 First mechanical device

looped around the bottom screw. The rubber band stretches the
air muscle when it is in its relaxed state.
Connect the balance of components as shown in Fig. 16.4. At
5
times I’ve had difficulty connecting the / 32"-diameter tubing to
some of the components. Here are a few tips. First, if the tube re-
fuses to go onto an adapter, place the tubing under running hot
water from the faucet. This softens the plastic, making it easier to
fit onto the components. Another trick is to use some clear plas-
tic tubing. The plastic tubing is snug enough to fit onto the
adapter nozzles properly (see Fig. 16.11). In addition it is pliable
308 enough to fit the / 32"-diameter tubing inside the tubing itself (see
5
Fig. 16.12). The soft tubing acts like an adapter and quick release
for changing air muscle devices.

To operate the device, first pressurize the system using the foot
pump. It only takes about four strokes to reach 50 psi. Your
mileage may vary depending upon the size of the PET bottle you
are using.
Open the three-way air valve to charge the air muscle. The muscle
should immediately contract. You can measure the distance it
moves in proportion to the psi gauge on the pump. You should be
able to operate the muscle through four or five contractions and
expansions before you need to refill the PET bottle. The air muscle
doesn’t use much air.
Notice that the air muscle stays in the contracted position until
the three-way valve is turned to release the air from the muscle. It
doesn’t cost any energy to keep the air muscle contracted. This is
in contrast to servo motors and solenoids that must be supplied
electric energy continuously to maintain their push or pull.
If the muscle doesn’t appear to contract, then it probably wasn’t
stretched far enough. Remember the muscle must be stretched in
order for it to contract (operate).
Team LRN
Chapter sixteen