The wind speed meter runs with the wind, faster when the wind blows harder. By counting the number of turns you can tell how the wind speed changes. It does not matter where the wind blows from, because the rotor is horizontal and the cups will cause it to turn when the wind blows from any direction.
Archive for February, 2011
All you need is a square piece of plywood any reasonable size, and a post that you can make from a broomstick, a piece of dowel wood, or any square piece of wood, we took a 2×2 centimeter piece of pine, about 5 inches or 12 centimeter long. Drill a hole in both ends to receive the nail, one to nail the post to the base and the other to act as the shaft for the rotor.
The medicine cups you can get at any drugstore, just ask for a few, three is enough, but you may want some spares. We melted a hole in the bottom for the screw instead of drilling a hole. I used a piece of steel wire from a coathanger and heated the end up with a gas flame, but a candle will work also, when the end is hot stick it through the bottom, don’t make the hole too large! You need some supervision by an adult with this!
The coloured sticks are from a craftstore, you can also use medical tongue depressors, they are the same size but not coloured. You should be able to get these parts easily. Drill a small hole in each stick for the screw that holds the cup onto the stick.
The hub is cut from a sun umbrella post, you can use any round or even square piece of wood, in this case cut or sand off the four corners to make it look better. You need to cut a slit in the hub at three locations divided around the circumference of the hub. Just use a small hand saw to make the cuts. You may need some help dividing the circumference by three, but most highschool students can help you, by dividing a circle by its radiius you get six divisions, pick every other division and you have the three you need. They should be 120 degrees apart. Nice geometry lesson …
Note the craft stick has been reinforced by a piece of electric tape, make sure you pull the tape hard around the stick, when you drill the small hole for the screw it does not split because of the plastic tape holds the wood together. The plastic medicine cup has been screwed with a number six self tapping round headed screw that you can buy at any hardware store. The screw is only one quarter inch, or about six millimeters long.
Note that we pulled some coloured tape around the rim of the medicine cups, that will make them stronger and it looks pretty!
Note that the post on the base has a hole in the top, put a nail through the rotor hub and put two small steel washers between the post and the hub, this will lessen the friction and makes the rotor turn more easily in the wind.
The harder the wind blows, the faster the rotor will spin. That way you can tell how the wind changes.
Show it to our teacher and friends and try other projects from this blog.
Oops, add a little light machine oil used for the sewing machine for example, to the centre of the hub and to the nail and washers, it will spin faster. Also leave space between the nail head and the hub, right?