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Whistling blades on wind direction weather vane

I have a propeller with four blades that acts as a wind direction weather vane. What I would like is for the propeller to make a whistling noise when it is rotated by the wind. Someone told me if I put a small hole or a slit in each of the blades it will make a whistling noisy which should change with wind speed. Can anyone tell me what size hole/slit I would need? Also at what angle would the slit have to be? Or can you tell me any other way to get a whistle from the blades when the wind is blowing? The blades are metal and about 200mm long (400mm overall diameter).

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StuartP32 years ago

. . . I HATE QUITTERS! WHEN THEY DON'T BOTHER TO WRITE FOR THOSE FOLLOWING A THREAD, WHAT'S BEEN CONCLUDED; POSITIVE, NEGATIVE, OR NEUTRAL/QUIT.. AN AUDIBLE WINDSPEED VANE SHOULD BE EASILY ACHIEVED; WITH DELIGENCE.. I'M THINKING THAT WINDVANE WHISTLES WILL NEED LARGE FUNNEL SHAPED COMPONENTS.. WHILE, MUCH FASTER SPINING ELECTRIC FAN BLADES, SHOULD BE EASIER TO MAKE "WHISTLE".. BUT I DON'T SEE ANY SIGNIFICANT CONSUMER DESIRE. . . IF I TRY THE NERF COMPONENTS, I'LL POST RESULTS.. I MAY ALSO TRY WHOOPIE CUSHION COMPONENTS.. ALL THESE ARE ONLY TANGENTAL TO INVENTIONS I THINK MAY BECOME POPULAR. . . THANKS . . . WALTER

LouL (author) 9 years ago
Thanks guys for all your suggestions. I have already thought of sticking a whistle to the blades and that would be an easy way out. But what I want to do is neatly modify the blades to create a whistling sound. There must be a way to put a slit, a hole or a louvre in the blades themselves so that a whistling noise is created when spun by the wind. I was hoping someone who knows a bit more than me about air physics could tell me what to do. LOL, is I had a spare fan I'd start hacking into it until it made a noise!
gyromild LouL9 years ago
You will need to make a slit, and add a closed chamber on one side of the slit, like in the image below. That should give you a whistling sound.
blade.gif
LouL (author)  gyromild9 years ago
Thanks gyromild, that's getting closer to what I'm looking for. I'm sure your suggestion would work if the fan blades were spun by a motor but since the blades are spun by the wind acting on them I fear that this might cancel out the whistling. I don't know, what do you think? R Lou
gyromild LouL9 years ago
I'm sure there will be whistling sound, similar to putting your lips and blowing into a bottle..but in terms of the loudness and pitch, they depend on a whole lot of other factors, ie, slit opening, chamber size, wind speed etc. You will have to tweak around. No doubt the slit and chamber will create extra drag. But if you currently manage to get the blade to spin in the wind, then adding short 5cm slit and chamber would only make it spin somewhat slower than it used to, thats it. Perhaps this illustration will help you better. You may need to try both setup to find which works best for you. All the best, and do let us know the outcome.
blade2.gif
LouL (author)  gyromild9 years ago
Looks like this may a bigger problem than I thought! I might have to bite the bullet and make up a set of blades to experiment on unless someone comes up with a positive idea. I'll see what I can do over the next couple of weeks and let you know. Thanks for your input. R Lou
Kiteman LouL9 years ago
Have a look at the whistles we suggested, and copy their shape.
rimar20009 years ago
I suggest you to hit provisionally with adhesive or tape, a small plastic or aluminum pipe with an extreme blocked, in the leading edge of a blade. The axis of the pipe should be approximately parallel to the axis of the mill.
dchall89 years ago
There is a toy called a Nerf football. It is shaped like an American football and has a tail. Located at three different positions on the side of the football are whistlers. You might visit a toy store and check out how the Nerf people did it. It is very effective even at low Nerf speeds.
Kiteman dchall89 years ago
Just what I was going to suggest. You can also get cheap plastic frisbees and boomerangs with whistling attachments that are sort of an added plastic capsule. Buy a cheap toy, cut off the capsules and glue them to your blades. Use tacky stuff (poster-fix, blue-tac) to fix them temporarily so make sure you get the position / angle correct.