DRAWING A VACUUM
Thoroughly grease the bell jar lip and place it on
the bell jar plate, centered over the vacuum port.
The three-way valve controls the connection
between the bell jar, the atmosphere, and the
pump cylinder. Before you push the piston
down, the valve handle must be positioned so
that connection is between the atmosphere and
the cylinder. When you pull up, the valve must
connect the bell jar to the cylinder.
To draw a vacuum, follow this procedure:
• Start with the piston at the bottom of the
cylinder. Just before operating the piston, turn
the valve handle so the valve connects the
cylinder and the bell jar.
• Pull up on the piston. When the piston is at
the top of the cylinder, turn the handle on the
three-way valve. This isolates the bell jar and
simultaneously makes a connection between
the cylinder and the atmosphere, so the air
removed from the bell jar can be exhausted
when you …
• Push down on the piston on the return stroke.
With each pull stroke, you’re evacuating one
cylinder volume of air from the bell jar. The first
few pulls will be easy but pulling will become
more difficult with each additional stroke as the
vacuum inside the bell jar increases.
Continue pumping until you reach the level of
vacuum you desire.
VACUUM GAUGE
To measure the pressure inside the bell jar, add
a vacuum gauge. Drill a hole in a rubber stopper,
insert the gauge into the hole, and then plug the
top hole of the bell jar with the stopper. For tips
on using it, see makezine.com/projects/skill-
builder-quick-tips-for-using-vacuum-gauges.
LEAKS AND PATIENCE
Without doubt, the hardest thing about building
a Boyle-style vacuum pump is handling the air
leaks that inevitably occur. Boyle himself wrote
often and bitterly about his problems with leaks.
I pretty much guarantee that if you build an air
pump, you will have leaks too. Eventually you can
stop the leakage, but it will take time.
A prolific writer, Boyle wrote a great deal
about his vacuum-related experiments. Many
of these explored the effects of vacuum upon
the physiology of small animals, and his notes
make for some pretty disturbing reading. Other
experiments are friendlier to modern sensibilities
and involve the behavior of gases under differing
volumes and pressures, the transmission of
sound and heat through air and vacuum, and
ultimately, the nature of matter itself.
What can you do with your own vacuum pump?
There are dozens of interesting projects and
experiments, including the propagation of sound
through vacuum, heat transfer through vacuum,
the respiration of plants, vacuum preservation of
foods, and much more.
83
make.co
INTO THE VACUUM
Find more cool vacuum projects from the
pages of Make: at makezine.com/projects.
MAGDEBURG
HEMISPHERES
Pull a vacuum so
strong two horses
— or interns — can’t
separate the halves.
The trick? Fire..
VENTURI-STYLE
VACUUM PUMP
Make a pump based
on fluid dynamics
and the famous
Venturi effect.
NUCLEAR FUSOR
Build a high-voltage
“star in a jar” to
explore nuclear
fusion.
UNIVERSAL ROBOT
GRIPPER
Air pump + coffee
+ balloon = a
“jamming” gripper
that molds itself to
any object.
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