In meteorology, an anemometer (from Ancient Greek άνεμος (ánemos) ‘wind’ and μέτρον (métron) ‘measure’) is a device that measures wind speed and direction. It is a common instrument used in weather stations. The earliest known description of an anemometer was by Italian architect and author Leon Battista Alberti (1404–1472) in 1450. (wikipedia) This post is about my DIY anemometer’s rotors.
In my mind anemometer rotor (or what ever is the proper name) has four arms and some kind of cups. First version followed that recipe. Four arms and sauce cups. In the photo there are not cups, I purposed them for other use. The arms are made from some bamboo sticks (9mmX3mm, I bought them years ago from ali, I can find the order any more) I had in my stock. Arm length in all versions is around 10cm. The center hole is 6mm to match the aluminum extrusion I found for axle. The disappointment with that extrusion is that is not 6.0mm, but 6.1mm and it does not fit to the ball bearings (696ZZ) I got for Station 2, I filed it a bit to make it fit.
Later I read that more efficient are with three arms and hemisphere cups. Ping pong balls for example. So I made version 2.
When I build Station 2, I made enhanced version 2 rotor, with longer arms and double cups (version 2.1).
Yesterday we had a little wind and I was watching the behavior or rotor 2.1, and some times was rotating in reverse. That shouldn’t happen! I it is supposed that the round side of the ball was much less friction/drag compared to the haul side. After few minutes of deep thinking, I came up with version 3. The arms are made of souvlaki sticks (3.2mm diameter, sourced years ago from local S/M) not those bulky flat bamboo sticks. Also I added some bases to glue the cups at the end of the stick.
Immediately after installing version 3, the improvement was obvious! Do not add the bases for the balls to reduce more the friction. Hot glue only joint. Version 3.1 is more slick, the center piece was not in very good condition. And didn’t not coated them yet with primer for rain protection. Not expecting any rain in the next days, so I have time for that.
