wooden blades

[alexl]

hi, i am new here and to the wind-power community.  A friend and i are building a wind turbine for a science fair project and plan to use it to charge batteries and use inverters afterwards. I ordered a treadmill motor from the surplus center that we plan to use as the generator.  We would like to build our own axial-flux alternator eventually, but the ease of buying a generator for our first build seamed logical. We are going to try several different types of pvc blades but we weould also like to try a set of wooden blades. Could anybody tell me how, or direct me with a link or page on how to cut out blades from a simple 2x4 or 2x6?  WE would really like the design of the blade to be simple because it will be our first project. I appologize if this topic has been gone over many times, but i searched the board and used the FAQ section but i couldnt quite find what i was looking for.  Thanks alot, Alex

[Tritium]

http://otherpower.com/blades.html

http://otherpower.com/bladecarving.html

Take a look at these links

Thurmond

[brokengun]

Are you sure the treadmill motor is an induction motor? Also, there is some good info on PVC blades around, just google it. They might be a little easier than making them out of wood.

[hiker]

i built a few blades --2by4 2by6- just a simple angle that looked good to me..

used no numbers-just eye balled the blade-balneced the blades..those were just

2 bladers-airfoil on back side-flat on the front -angle going flat towards

the tips..then i built a few 4 bladers -with a wooden hub[made from 3 plywood disks]-with the angles cut in the hub-then insert blades-screws and epoxy to hold.

blades were made fron 1by4 ceader fence boards-airfoil back side-tappered flat

towards the ends..easy blades

[hiker]

bolts to hold the blades--not screws............

[scoraigwind]

Your first step is to find out the best speed for the motor to run as a generator and then to match this speed with suitable blades.  What speed does the treadmill motor cut in at for charging (say) a 12-volt battery?

There are plenty of recipes for wooden blades.  I have a couple of pages describing how to carve them on my site (pretty old pages but clear enough I hope).

http://www.scoraigwind.com/liselotte/

http://www.scoraigwind.com/selfblade/

 But your blades really needs to be sized right or it will not work even if the blades are fantastically wellmade.

Pay attention to the tip speed ratio of the blades you are making (usually designed to run at about 6 times the windspeed) and calculate the rpm that the blades will run at in a 7 mph wind or so.  Try to match this roughly to your cut in speed.  Also look at the speed it does full power and try to match this to a windspeed where your blades will make a similar power output.

The key to a satisfying wind turbine is to have parts that work well together.  PVC pipe blades are good at starting, but slow in operation, so they will have to be pretty small to match the motor well and run fast enough.  That small size means a meagre capture of energy.  You will be able to use a much larger diameter wooden rotor and get a lot  more power.  That's because they will have a higher tip speed ratio.

[alexl]

i can get about 4 volts out of the motor if i spin it by hand on a bench