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Completed Anemometer |
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Salem Clock Shop - 1085 Broadway Street NE, Salem, OR 97301 - (503) 581-3803 Fax: (503) 581-3331 |
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You can build a ping pong ball anemometer and use it to help make accurate local weather forecasts. |
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Ping Pong Ball Anemometer |
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Bill of Materials
· Regulation ping pong ball · Protractor · About 20” of 2 lb. test fishing line · Sewing needle · 16” long wooden dowel · Small screw · Small “stick-on” spirit level · Colored nail polish · Glue |
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Here is an instant reading anemometer you don’t have to mount on a pole somewhere. This is the answer for apartment dwellers and those uninterested in building a “whirligig” type of anemometer.
It is elegantly simple! Wind pressure on the ping pong ball changes the angle of the line from the vertical. Displacement of the line is read in degrees and a table is used to convert degrees to wind speed. Cute, huh? This gadget reportedly came from an old Scientific American magazine “Amateur Scientist” feature. |
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The “stick-on” spirit level can usually be obtained in the RV section of sports and “Big Box” stores.
The dowel is attached to the protractor along its baseline using a screw. You'll need to start a hole in the plastic protractor first with a knife or whatever.
Attach the stick-on spirit level on the side opposite the dowel. It must align exactly with the baseline of the protractor. You can test this later by making sure the fishing line hangs straight down through 90 degrees when the level reads horizontal.
There may already be a small hole in the protractor in the center, along the baseline. If so, wonderful! If not, then heat the needle with a match or lighter, and make a small hole in the protractor for the fishing line, right at the baseline midpoint.
Insert one end of the fishing line through the hole, tie a goodly knot, and seal all on the back side with some glue to anchor the line permanently in place.
To prepare the ping pong ball, heat the needle again and carefully poke a small hole on each side of the ball. Then thread the free end of the fishing line through the holes.
The length of the fishing line from its attachment point on the protractor to the top of the ball must be 11-7/8 inches (30 centimeters). Tie a knot in the line that protrudes through the bottom of the ball, and seal it with a small amount of glue. Then cut off any excess line. |
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Salem Clock Shop - 1085 Broadway Street NE, Salem, OR 97301 - (503) 581-3803 Fax: (503) 581-3331 |
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Using The Anemometer
It is easier to have one person holding the anemometer, and another person reading the scale on the protractor.
Hold the anemometer level, parallel to the direction of the wind, and well in front of you.
(The reason for the long dowel handle is to minimize turbulence from your
body, which could affect the reading.) Your partner can read the angle of displacement at the bottom of the protractor. This
can range anywhere from 90 degrees (no wind) to 20 degrees or less (lots of
wind). Of course, several measurements should be made, and the results
averaged. We have provided two different conversion tables to arrive at wind speed. Click on the link of your choice and print the page for later use.
· Degrees to Kilometers Per Hour
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