Hi Adrian and others,
I can give you some photo`s of various stages of the construction of my new Turbine and some details on the sequence of event`s.
I did not want to mention earlier that i use PVC pipe blades, as i would imagine many people would think it stupid to state these high output figures when using these blades.
Before i go on, i have been shaping these blades now for 4 years and have got a good air foil shape worked out, mainly with trial and error and had no problems with fatigue.
Another point i would like to mention is that I have noticed a distinct increase in efficiency/output when i mount the blades on any of my turbines, so that the leading edge is aimed at the centre shaft and the trailing edge away.
I have noticed other people mounting these blades the opposite way, and in most cases i have noticed that general blade/hub design`s are arranged so that the blade is mounted with it aiming to the centre shaft.
Construction: I started with a 40Amp 24V truck alt, I expected with strong magnets, that it would reach 15V at a good cut in speed.
I then machine the standard field coil rotor down, in a way that the fingers are machined off and you are left with two 80mm/10mm steel discs.
Then i make up 12 flat steel plates from a length of 20mm/4mm steel, cut into 50mm long length`s which i then clamp down onto the discs with a large hose clamp and weld in place.
You then arraldite the magnets in place before resining with a strap in place so they don`t go flying.
Important: You must arrange the 12 steel pieces and Magnets so that there is a bigger gap between two, this reduces cogging a lot, also the magnets must be arranged so that they are angled slightly, this also reduces cogging.
All this helps when making a blade for high speed performance.
The magnets are about 1.5mm from stator.
Blades: I use three blades, the root is 95mm wide, the tip is 40mm wide, the thickest part of the blade is 7mm, tapering of to the trailing edge at around .5mm.
The pitch at the root is about 18 degrees, half-way point is 9 and the tip is about 4 degrees.
I sandwich the blades between two triangle cut pieces of 4mm alum plate.
Finally, I think another boost to the efficiency, is the use of thick Neo rare Earth Magnets, i use 25mm/30mm/11.5mm Neo mag`s.
I am very excited about this new turbine and want to get it tested properly to get an honest output figure, so far it looks very good compared to my Dual motor 2.2M F&P Turbine which is only just ahead in performance, and other car alt conversions i have done and had to rewire the stator have put out 10Amps/140Watt at 10m/s with a 1.2M blade rotor.
This one is putting out around 28Amps/380Watts at 10m/s with a 1.5M blade rotor.
And not bad at lower winds eg: 10amps at 6m/s, and a cut in speed of about 3-4m/s.
I will be setting up a Web site soon detailing many projects, My F&P turbine pics and an article on it can be found at www.thebackshed.com and Thank`s to Glenn at thebackshed for publishng the info.
Matt Au.