The idea of a home-made wind speed meter must surely cross the mind of avid kite-fliers from time to time! Here are my own ideas and musings, after a quick look at one retail wind meter in particular.
Also called the anemometer (try saying that quickly!) or wind gauge, this kind of device is handy for a wide range of wind-powered sports. Some of these sports could be rather demanding on such a device, since it could be bumped or splashed with water. Or worse!
However, good old single-line kiting would have to be one of the safest environments for a wind speed meter. In comparison to many other sports and hobbies that is. Flying a kite like the ones in the ads over there is quite a genteel activity. Wouldn't you agree?
Before diving into some ideas for home-made devices, I have to admit that I don't actually use one! You see, a jolly red-coated gentleman with white beard supplied me with a you-beaut (Aussie expression) Windtronic 2 anemometer on the 25th of December not that long ago. However, before this ... ermmm wind-fall ... I certainly was considering making one for myself.
Shall we list them in order from practical right through to outright crazy? Start at whichever end of the list you wish ;-)
Of course, to calibrate any one of these devices, it would be necessary to hold it out the window of a moving car, at various speeds. Over here in Adelaide, South Australia, an appropriate approach might be to mark the scale in 5 kph intervals. 5 mph in the U.S.
In fact, to do a really good job of it, it would be an idea to drive down a road in one direction using, say, a blue pencil. Then drive the other way, making all the marks in red. Permanent marks could then be made mid-way between the colored ones, thus averaging out errors caused by wind. Doing all this during a dead calm would be ideal, but how often does that happen!
One of the simplest and evidently quite practical ideas for a wind speed meter is the floating flap. A simple box is constructed, open at 2 ends so the wind can blow right through. In the middle, inside the box, hangs a flap connected to an axle. On the outside of the box, the axle is connected to a pointer which rotates around a scale drawn on the outside of the box. Simple! The stronger the wind, the higher the flap sits before the torque force balances out the wind's force on the flap.
A little hand-held windsock could also be constructed with a long spar down the middle to hold it out straight. The spar could be pointed at one end so it indicates angle on a scale, much like the floating flap idea. The windsock and scale would need to rotate on a bearing to remain in line with the wind direction. Otherwise, it would under-read.
In theory, a venturi could be constructed from a couple of funnels connected together by a very short pipe between the narrow ends of the funnels. A length of plastic tubing could then be joined to a hole in the short pipe. Air-tight of course! The tubing would then be attached to a board which would need to be vertical like a wall. With a long 'U' shape held into the tubing, it could be partially filled with a colored liquid.
With no air flowing through the venturi, the fluid level would sit at the same height on both sides of the 'U'. However, as air starts to flow through the venturi, the air pressure in the short pipe would drop markedly. This in turn would suck the colored fluid through the tube causing the 2 fluid levels to differ. Hence you've got something to calibrate! In fact, despite this apparatus being very impractical to carry around and transport, it would actually deliver a very accurate wind speed reading! I'm sure of it, since the principle is still used in aircraft.
Now for a real flight of fancy! The MBK Pie Chart Wind Speed Meter (MBKPCWSM). ;-) In theory, once again, this should work to a degree. OK, the idea is that you draw a series of colored pie-sections on a solid flat wheel. Ever seen a pie-chart illustrating financial or other data? Something like that, except there would be many, narrow slices of pie. Also, the wheel would be hitched up to, or part of, a windmill in order to spin the colors around.
Now for the tricky bit. Trial and error would be required, and lots of it! At 5 kph, the blue pieces of pie would merge into a solid image, since they are rather close together! At 10kph, the red pieces would merge, changing the color of the disk once again. Some purple kind of color probably. At 15 kph, the green pie sections would merge, resulting in a combined color that would make anyone looking at it puke! Get the idea? Getting the angular width and spacing right for all those colored pie sections would be a nightmare, but it should work :-) Lastly, of course, the whole wind speed meter would need to be mounted on a swivel-mount like a real wind-mill so it always faces into the breeze.
The uhhm MBKPCWSM (pronounced 'mah-book-pok-wizzum') could actually be made in quite small sizes if the engineering and manufacturing technology was clever enough. Remember, you saw this wind speed meter idea here first!