🚀 go-pugleaf

        A real monkey and hunter demo is a lot of fun for kids to see.  We have
        a semi-permanent set up here at Lincoln-Sudbury HS if anyone in the
        area wants to come and take a look.  It's entirely homemade and works
        pretty well, with a bit of adjusting before class time.
        We have a metal tube aobut 70 cm long with a diameter of about 1.5 cm-
        just wide enough to accommodate a marble.  This is the blow gun.
        Diagonally across the room, hanging from the ceiling, is a solenoid.
        The leads from the solenoid run along the ceiling to the corner of the
        room where I set up the blow gun.  One of the power supply leads is
        attached to a wire wrapped around the gun a few inches from its exit,
        so that the gun itself is in the circuit.  A trip switch is set up in
        the following way:  insulating tape is wrapped around the gun near the
        exit.  A flexible metal strip is taped over this wrapping, and bent so
        that it just goes over the exit and contacts the gun only at the edge
        of the exit.  This metal strip is attached to a lead of the solenoid.
        The other solenoid lead returns to the power supply to close the
        circuit.
        When a marble is blown through the gun, it pushes the metal strip out
        of the way as it exits the gun, breaking the circuit.  The target we
        used to use was a soda can, but now of course they are made of aluminum
        and not steel.  So now we are using a steel vegetable grater, which
        also makes a larger target.
When the circuit is closed, the solenoid holds the target in place.  As the
marble exits the blow gun, the target begins to fall, as that is the
instant that the circuit is broken.  If you are careful about aiming (this
is the pre-class set up part of the job) and if you can blow hard (I always
ask a sturdy boy to do it for me, after cleaning the blow gun mouth with
isopropyl alcohol) the marble will hit the target with a clang.

Connie



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Constance Patten
Lincoln-Sudbury Regional High School    *
390 Lincoln Rd
Sudbury MA 01776

Fax: 508 443 8824
e-mail cpatten@copernicus.bbn.com       *
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