Step 1: What you need.
1 sheet of 6mm thick acrylic 250mm x 500mm
Aluminium rod 500mm length x 8mm diameter
500mm x 500mm x 10mm MDF
4 x Bearings
Set of Bevel Gears
Step 2: Create a Mould
Then cut it in half to provide space for the axle.
Step 3: Produce Casts From the Mould
Repeat this for the other half of the acrylic also.
Once you have your casts cut them out around the edges to produce your fins.
Step 4: Creating the Main Axle
At one end make it 10mm deep and the other 40mm to accommodate the gears and bearings to be attached at a later date.
Step 5: Create the stand
Produce this with MDF and counter sink a space for the two bearings.
Then create a stand to mount the motor make the motor sit at a 45 degree angle from you base board like the one below.
Step 6: Adding it all together.
Attach the bearing
Then using hot glue attach the first wing of the wind mill at least 5mm from the bearing
Then attach the second wing at a 90 degree angle from the first.
Using one of the two stands created earlier insert the bearing and attach the stand the the base board using two screws careful not to split the wood.
Now back to the axle and attach the other bearing and stand and attach to the board.
Step 7: Adding it Together Part 2
Now line up your motors gear with the gear on the axle and give it a go at turning if it doesn't do this frictionlessly have another go if it works perfectly glue it down quickly with hot glue. (it can take many attempts to get it good so when you get it you don't want to lose it!)
After this screw the motor down and just double check it works.