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mel n rob

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Joined: 02/01/2010
Location: Australia
Posts: 4

Posted: 02:23pm 07 Jan 2010

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can someone point me at calculations to determine blade pitch ( variable pitch )

blade diameter up to 6 meter

material would be a composite that allows variable pitch

i dont have concrete numbers yet for design wind speed , other than the govt data supplied for the area of typical 4 - 9 m/s and gusts of 26 ms

design would have governed blades and furling tail.

assuming blades may be governed at around 25 m/s wind speed

still playing with AXFX design , but could use 6 phases / 18 coils / 20 - 24 magnets using one stator , or two stators of a smaller diameter in parrallel , undecided yet.

assuming the inverter will be capable of the voltage range from the range of wind speeds produced by 4 - 26 m/s wind speeds

what other factors would you look at guys ?

KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178

Posted: 02:18am 11 Jan 2010

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I'd seriously consider the chainsaw blades, cheap and effective. Variable pitch DIY is going to be very difficult and ultimately probably not necessary.

at 6m diameter I'd be thinking you are looking at a power one 4-6KW inverter approved inverters.

This is going to be an expensive piece of kit $5K+, perhaps at this size a gearbox and an induction or squirrel cage motor is appropriate seeBreezy 5.5

Luck favours the well prepared

Perry

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Joined: 19/11/2009
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Posts: 190

Posted: 11:57am 11 Jan 2010

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Hey Karl,
Do you have any idea how the Breezy's hold up. Interesting design.

Perry

oztules

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Joined: 26/07/2007
Location: Australia
Posts: 1686

Posted: 07:31pm 11 Jan 2010

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A decent blade calculator can be found here

For that size mill I see no reason to not use timber. Clear pine will do in a pinch, but there are plenty of other types suitable. It does not need to be sitka or anything exotic to work well. For that size blade 5-6 hours should see them done and painted.

For axial flux, you need only a simple blade. You can ignore the inner 1/3 of silly pitch you will find in the calculators. You don't need any help to startup. If you use a gearbox and ACIM you will need a better root shape perhaps.

Single disk units are less efficient with your magnets, then dual disk. Your magnetic fields are very non-linear in this configuration. Two disks gives you a very predictable field to work with, of uniform density.

A unit this size is probably up in the 30" disk range, with big magnets. 3 phase is fine.

2 smaller stators (stacked stator design) is very much a step backwards, and a waste of resource.

If you have variable pitch, you won't want the furling tail. The parameters that are used to tune the tail, will be thrown into disarray as the pitch changes.... better to leave it straight.

..........oztules

Village idiot...or... just another hack out of his depth

KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178

Posted: 01:05am 12 Jan 2010

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I have no idea how the breezy stacks up but you can buy the plans for peanuts, looks good to me

OZtules might be able to advise how the power companies feel about connecting this type of motor to the grid, I'm thinking that would be the only headache.

phillm does both a 300mm and a 400mm AXFX and given the boys on fieldlines were completely blown away by the output I consider it to be a triumph of these lads (Gordon and Phill) mechanical skill and intellect in this "field" (pardon the pun).

In addition to this I visited Phill's place last week to witness the miracle and indeed "miracle" is an accurate term, Phill's site is not what I'd call fantastic, even with the wind in the right direction to avoid the trees, there are trees behind which doesn't help performance one iota.

Here are the big questions.
1) Budget
2)Application assuming grid feed
3)how much power you want
6m is good for 8KW (again guessing based on 3m good for 2KW+ in reasonable winds using AXFX)

Here's my tip, I'm alot like you and everyone else that started here a while back, read a few dozen posts, decide that solution (A) suits me down to the ground then go for it.

Unfortunately most of these projects get stalled in one way or another and never end up in the wind.

So.....

IF the budget is $6k which is a fair chunk of change for most of us here is what you would end up with.

1KW turbine ($1500)
1.2KW inverter ($2000)
Wiring from mill to house ($3-600)and batteries $400 and up/ charge controller $300/ dump load $50 call it $1500.
Tower $1000.

now you're thinking "wow my money didn't go far"
But -what you have is a working reliable setup that is a great start, a tower capable of supporting a bigger mill down the track and an inverter that will do 100% of the time and 95% of the time with a 2KW mill.

Phill's dual stator or AXFX is a great start, and due to the design of the mill head is flexible enough for a variety of solutions, eg do what I did start with a dual F&P which is available for varying prices depending on how complete you want it, eg do you need Phill to build the tail?, do you need him to assemble and balance the blades? or use your own blades and just get a flat disk to mount them on.
then step up to the oZAXFX, it bolts on to the same mill head and will run the same blades, thus saving you building things twice and keeping costs down.

Here is the thing that I note -Gordon is traveling the countryside fixing skystream 3.7's among other things....

This surprises me to no end, they are best part of $30K worth of kit + installation (for a miserable 1.8KW grid feed turbine) and if they dont work out of the box from a major turbine manufacturer then what hope do we have?

compare this to say the OZAXFX 400 with 4m blades on a 14m tower with two PVE1200's, cap doubler and tripler and the thing will pump out (guessing) 4KW+ and given the construction of mine (dual F&P), I'd say bulletproof. I'm also guessing that this is a $15K solution.

To me the tower is the toughest bit, to get as high as you can be very strong and yet still manageable for DIY.
for most of us 8m is going to be about it. above this things are getting tricky and potentially deadly.

Wind turbines aren't light, the dual F&P with blades weighs in at a hefty 45KG -climbing up the mast with one of these on your shoulder is not an option!

Again my tip is spend $$ here, this may well end up the most expensive and troublesome part but done right will be good for anything you care to throw at it.

EG 20m tall monopole, top 8m section tilting, big winch
3mx3mx3m foundation is going to cost probably $10K

Luck favours the well prepared

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