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ANEMOMETER

There are two basic kinds of instrument designs used to
measure the speed of winds.

a. The first design requires you to turn the instrument into
the wind.

To make such an instrument, clean an empty milk carton
and remove both ends. Thumbtack the carton to a block
of wood to hold it steady. Cut an "H" in the middle
section of the top side of the carton, and open the
flaps. Push a cork to the center of a long knitting
needle, then push the needle through the flaps. Mount a
small needle vertically into the cork to serve as a
pointer. Cut a square piece of cardboard so that it fits
inside the carton.

Attach a second, smaller needle to it with tape or glue
and stick the needle into the bottom of the cork. You
may have to adjust the cork, the knitting needle, or the
card so that the card swings smoothly in the box.

When the wind is blowing, point the indicator into the
wind so that it blows through the box. The wind will
push against the square card, tilting the cork and moving
the needle pointer. The distance the needle tilts
indicates how fast the wind flows through the carton.

A card can be attached to the carton to make a gauge.
When the card has been attached, draw a line on the card
parallel to the needle when it is straight up. The gauge
can be calibrated using the Beaufort Scale.

The ("BO-fort") Scale is a scale of wind velocity (speed).
The U.S. National Weather Service uses an adaptation of this
scale. It employs numbers from 0 to 12, representing calm,
light air, light breeze, gentle breeze, moderate breeze,
fresh breeze, strong breeze, moderate gale, fresh gale,
strong gale, whole gale, storm, and hurricane. Zero (calm)
is a wind velocity of less than 1 mile per hour and 12
(hurricane) represents a velocity of over 75 miles per hour.
(Concise Columbia Encyclopedia)

b. A second type of anemometer rotates as the wind strikes
it. To make this type, nail two sticks 1 1/2 inch square
and 18 inches long at right angles to each other. After
the sticks have been nailed together, drill a hole
through their centers so that a small test tube or
medicine dropper tubing will fit snugly through the hole.
Medicine dropper tubing can be prepared by holding the
dropper by the rubber bulb, placing the tip of the
dropper in a flame, and rotating it slowly until the
opening is completely closed and rounded. When the glass
is cool, remove the rubber and insert the tubing through
the wood.

You might need to use some friction tape to keep the wood
from slipping off the tubing. Attach four paper cups,
halved rubber balls, tin cans, or other cupped objects to
the ends of the sticks. The instrument can be mounted on
a coat hanger.

Alternatively, a hole can be drilled into a block of
wood, a pencil placed in the hole, and the instrument set
over the pencil. Paint one of the cups so that you can
easily count the number of times it goes around in one
minute. The instrument can be calibrated by comparing
the number of turns with observations on the Beaufort
Scale.

When the instrument is mounted on the school grounds, the
speed can be determined by counting the number of turns in
one minute.

Keep a daily record of wind speed on a graph table. Measure-
ments should be made at the same time each day. Note whether
the sky is sunny, cloudy, rainy, etc.

After several weeks, study the table to see if there is any
relationship between the speed and direction of the wind and
the kind of weather that follows.

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