Introduction: Contrarotating Non Power Generating Wind Turbine
This is a simple wind turbine using wood offcuts and some leftover kite-building spars and ferrules.
Planed wood offcuts up to 1 metre long
Kite spars or dowel or rods. Ferrules (optional)
Step 1: First Make the Blades
To make the blades, which are 280mm long x 40mm wide x 4mm thick, I ripped down some 2' x 4" planed softwood to make 16 sheets at the correct overall dimensions. Slats from fruit boxes or similar will do, as long as the blades aren't too thick. They need to be light in order to turn.
The easiest way to make the blades is to make one and then clamp a few blanks together and cut through them together with a jigsaw, then clean them up with glasspaper. They are so thin, this is easy work.
Then glue a piece of wood about twice the length and width of a matchstick to each blade as shown. This will go into the hole in the hub. Doing it this way gives it more strength than simply glueing the end of the blade into the hub.
Step 2: Now Make the Hubs
The hubs are made from 50mm cubes of softwood.
Cut the corners off to make an octagonal block and connect the diagonal corners to find the middle of each face. Drill holes in each face centre slightly smaller than the piece of wood you glued onto the blade.
Find the centre of the face of the hub and drill a hole in it to accept the shaft. The size of this will obviously depend upon the material you are going to use as a shaft. I used 6mm carbon fibre tube which was left over from kite building. For durability I glued an aluminium ferrule into the hubs. This is the perfect size to allow the hub to rotate freely about the shaft. If you don't have access to these, you can use a dowel, a pencil or any other similar thing you can find.
Whatever you use, the fit between the hubs and the shaft needs to be snug but not tight. Too tight and they won't turn; too loose and they will vibrate too much when turning and you will get a lot of wear.
Step 3: Now Mount the Blades Onto the Hubs
This version uses two sets of blades on 2 hubs and they rotate in opposite directions. This is achieved by turning the blades in different directions. The blade will turn in the direction of the windward leading edge. The peg on the end of the blade is positioned behind the blade when completed, so the blade in the example shown will go counterclockwise when viewed with the wind behind you. Do one hub with the blades angled at about 30 degrees one way and the other hub with the blades turned 30 degrees the other way. Sand the pegs down enough to get a tight fit in the holes in the hubs and glue them in place.
I ended up cable-tying the blades to the pegs that go into the hubs as I live in a very windy place and a couple of the blades did fly off! This may not be necessary with very strong glue, but it does give another feature to the turbine with the different spinning colours.
Step 4: Now Make the Boom
Take a piece of wood about 600mm long by about 30 or 40mm in section and drill the end to accept the shaft you have chosen. This needs to be secure and should be glued in.
Make a fin to keep the turbine facing into the wind. This I made in a similar way to the blades, but it needs to be about twice as wide. To do this, I joined 2 blade-sized pieces and mounted and glued them into a slot cut in the end of the boom.
Step 5: Now Mount the Hubs Onto the Prop Shaft
Pretty self-explanatory. I put washers between the hubs and the boom as well as between the hubs themselves.
Be sure to leave enough space between the two hubs that the blades don't hit each other. You may need to make a spacer out of a bit of wood with a hole drilled through it to go between the hubs.
You need something on the end of the shaft to stop the hubs creeping off the end. I used a small piece of wood (actually a dowel) and drilled it to fit over the end of the shaft.
Step 6: Make a Post and Mount the Boom on It.
The mounting post can be anything really. I used a bit of 2" x 2" softwood. I chamfered the top to make less resistance, drilled a hole to accept another piece of kite spar and drilled a slightly larger hole in the boom at the centre of gravity of the whole thing complete.
The post needs to be quite securely fixed as there is a lot of action going on when the wind blows and if the post moves around too much the blades don't turn as cleanly.
Step 7: Wait for the Wind and Spend Hours Being Mesmerised!
First Prize in the
Scraps Speed Challenge