Mini DIY 12" Wind turbine
This was a very successful project, I used an off the shelf 3 bladed propeller, beautifully balanced and extremely strong, made from glass filled nylon, they are designed as 'pusher' props and can spin at up to an amazing 13 000 rpm when driven by a radio control plane engine. I suspect just 2000 rpm will be my max as a wind generator.
I am using this propeller mounted backwards, so the flat side is facing forwards and the true aerofoil is on the back.
Having the blades pre made allowed me to focus my attention on matching the alternator to the blades characteristics, having seen Ed Lenz's work over on Windstuff now using radial air core alternators, I decided to work along similar lines. The benefit being, no iron in the design therefore no cogging effect that would kill a tiny wind turbine (mechanical resistance making it barely start up).
I sourced a very powerful N42 Neodymium cylinder magnet here that differs from most magnets in that it is diametrically magnetised i.e. the 2 poles are on the edge of the cylinder and not the face, as with most. This would give me a 2 pole single phase alternator.
Using adobe illustrator I drew to scale my alternator idea, and this helped me to realise the design and the layout.
I decided to use 6mm (1/4") polycarbonate sheet for the end mounts, and a printed template was glued onto the polycarbonate sheet and I carefully cut out the profile. All fastenings were made from non magnetic A2 stainless steel studding and nuts.
Once the 2 end mounts were assembled I wound 300 turns of 0.38mm enamelled copper wire per side of the magnet both in a clock-wise direction.
A quick spin with my fingers would light an LED, and using my cordless drill I was seeing 2.4 DC volts at the drills max speed of 700 rpm, so roughly 1 volt generated per 300 rpm (open circuit).
The current into a near dead 3.6v NiMh battery pack was around 500 mA, therefore approx 1.8 watts of power can be generated maybe more with increased windspeed.
As the images above show, I used more polycarbonate sheet to fabricate a turbine chassis and tail fin. Polycarbonate is extremely tough and won't split or crack like acrylic sheet might.
In a good wind, approx 16 m.p.h I charged the 3 AAA batteries in under an hour and then tested a cluster of 60 LEDs directly powered, which were lit without a problem in a good wind (16 mph)
Here is a video of the Gotwind mini turbine in action powering 60 LEDs
This design worked beautifully, I have since fitted non magnetic 6mm diameter sintered bronze bushes, available here
I can see this being a valuable educational project for schools and the like.
If you have managed to make this alternator, please email me an image, I would love to see them along with any improvements made.