Author Topic: 8FT Windturbine Furling  (Read 4601 times)

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Yianie123.

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8FT Windturbine Furling
« on: September 15, 2014, 11:06:02 AM »
In my hopes of building a simple windturbine, I was wondering the importance of furling on an 8ft diameter windturbine.  Does anyone have any experience with not building furling capabilities?  I have noticed that some purchased units do not have furling with their windturbines.  Is it better to have other controls instead, like a load controller that if the voltage go's to high a load is added to slow the rpm's down?  Any and all input is welcomed.

gww

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Re: 8FT Windturbine Furling
« Reply #1 on: September 15, 2014, 01:14:17 PM »
Even with furling I had a 1 and1/2 inch pole bent double.  I would say schedule 40 water/gas pipe.  It was stood up against my garage.  I am no exspert but maby the motor type won't be hurt by overspeed.  Eight foot is a lot of force.

I know nothing compared to others on this site.
gww

Flux

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Re: 8FT Windturbine Furling
« Reply #2 on: September 15, 2014, 01:50:43 PM »
Some small machines are strong enough to survive, I doubt that any 8ft machine can survive if you get significant wind.

You have to keep blade speed safe and have a tower that can survive the thrust even if you can deal with the electrical issues.

Stall operation needs a massive alternator and suitable blades, if you loose load it fails to protect. Beyond about 40mph there is so much energy in the wind that you will struggle without furling or pitch control or other method of spilling power.

So much depends on the site and potential worst case wind speed, but even at 6ft I would never risk a machine without some form of power limiting. I  have seen a 6ft machine survive 70mph with no load, but from about a mile away, no way would I have gone up close to it, it was absolutely frightening.

I have seen some of the links to some sites you have posted, I don't want to comment except to say I wouldn't go there for anything bigger than about 4ft.

You can use a load controller but be prepared to build an alternator big enough for a normal 12 ft machine to be able to reliably hold down 8ft. What do you do if there is an electrical failure and you loose load, you just have to let the blade losses do what they can for survival, not my choice, tip brakes at least or some other manual shut down if you must go that way.

Flux

SparWeb

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Re: 8FT Windturbine Furling
« Reply #3 on: September 16, 2014, 10:49:49 PM »
With my 8 foot diameter turbine, the motor-conversion alternator is fairly self-limiting.  That means that over a certain speed, the resistance and reactance losses draw out most of the energy from the rotor, and the iron core can dissipate a lot of heat.  Some would take that as an invitation to skip the furling.  But I don't.  While it would be interesting to try it, the only proof that my turbine won't run away is by risking its destruction in a storm.  No thank you.
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kitestrings

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Re: 8FT Windturbine Furling
« Reply #4 on: September 17, 2014, 09:53:37 PM »
You probably have to see, or hear, a turbine run away to really appreciate this, but there is something to be said for the simplicity of furling.  I'm partial to this method as it doesn't rely on electronics to initiate something, or electrical loading for control.  It is not perfect, but it has proven to be very reliable over the years.  Personally, I don't think I'd run anything this size or larger without some means of protection.

Flyweight governors seem straight forward, but are harder to get right than most people assume.  The Winco "air-brake" approach I suppose could work on something this small, though I dislike 2-bladed rotors.

I like what Frans has done with variable pitch.  Pretty impressive really.  On an 8' turbine though, it would add considerable complexity, cost and weight I suspect.

I've had quite a bit of experience with tip brakes.  The simplest were aluminum, bent and preloaded against the end of the blade.  In an over-speed event they 'popped' and bent out to catch wind.  Kind of like a parachute behind a drag racer.  These were disposable/one shot and had to be replaced.  There were hinged designs - pivoting at the leading edge  - that relied on a spring latch.  The latch mechanisms, however, require regular maintenance to be reliable.

Electrical loading seems simple enough, but what if there's an open in the circuit - a pretty common state of failure in electro-mechanics.

I think they all come down to compromise and trade-offs.  Simple is easy.  Robust is harder.  Combining the two, now that's a true challenge.

~kitestrings

Mary B

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Re: 8FT Windturbine Furling
« Reply #5 on: September 18, 2014, 04:24:22 PM »
There is a 20 foot turbine on the route I take to buy groceries that uses tip braking. The tips rotate 90 degrees to the rotation acting as air brakes. It sits there with the tips tripped most of the time because it doesn't reset right.

kenobrock

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Re: 8FT Windturbine Furling
« Reply #6 on: September 19, 2014, 07:18:46 AM »
With 47 years in the water pumping windmill business, selling, installing and designing systems, I know that a windmill without an automatic furling or governor system is headed for disaster. Water pumping windmills use a very simple and fail poof system to keep from over speeding. The windmill wheel is mounted to one side of the gearbox and the tail is in the center of the back of the gearbox. A spring holds the tail at right angles to the wheel to keep the wheel facing into the wind. In a high wind, the wheel gets a side pressure from the wind that overcomes the tension on the spring and the wheel and gearbox turn out of the wind slightly or all the way depending on the wind speed. When the wind dies down, the spring brings the wheel fully into the wind again. If that spring should get old and break, the windmill just turns out of the wind.

Smithson

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Re: 8FT Windturbine Furling
« Reply #7 on: September 21, 2014, 07:33:17 PM »
If you routed a channel down the backs of your three blades then installed an aircraft wire cable with epoxy and staples in each channel hooked to the steel hub would this be a substitute for furling?

The description of a runaway turbines scares me.

What kind of damage would this do to the tower?   Just wondering.  Arch

kenobrock

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Re: 8FT Windturbine Furling
« Reply #8 on: September 22, 2014, 08:50:16 AM »
I don't understand your idea of a furling system. However, if one of the blades came off or was damaged, it could shake your whole tower down. Or at least do some serious damage. It depends on what kind of tower you have. A free standing water pumping windmill tower probably would not be damaged too much. It would still be a dangerous situation.

frackers

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Re: 8FT Windturbine Furling
« Reply #9 on: September 22, 2014, 10:44:37 PM »
The description of a runaway turbines scares me.

What kind of damage would this do to the tower?   Just wondering.  Arch

What sort of damage?
This...


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gww

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Re: 8FT Windturbine Furling
« Reply #10 on: September 23, 2014, 08:18:54 AM »
Been there and done that,  If I had taken pictures, mine would have been even more dramatic.  We have both gotten back on the horse that threw us.  Furling is good and it is better if we can keep a good load on the turbine at all times.  The op wants to build a simple turbine.  I find they are pretty simple to build but not.  We have it made, that others before us have made some of the mistakes and come up with ways of handling them, took pictures of the prosess and failures and then let us copy their successes.
Cheers
gww

PS  I only have experiance with hugh piggotts "wind turbine hand book"  I believe it gives a person new to wind turbines some of the basics and theory and after reading helps understand the post on this site where you get further knowladge and help.  If you are new like me I believe it helps.  There may be other books but I have only read this one and know it helps.
« Last Edit: September 23, 2014, 08:27:52 AM by gww »

clockmanFRA

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Re: 8FT Windturbine Furling
« Reply #11 on: September 23, 2014, 12:28:19 PM »
My No2 12footer.

Reason for failure....... water got into the root of the blades, and was out of balance. Along came a big storm, tail furled but vibration made the tail stop ride up its stub, and off came the tail and hit the blade on the way down.

1.    Ensure the tail geometry is correct and the stop does not try to force the tail assembly up.
2.     Just in case, I have now installed a bronze line that will not allow the tail to jump off again.
3.      Make sure that water can not get into the blade roots, lots of silicone on bolt holes etc.
4.     Keep your blades balanced,  dddeeerrr. I had been doing it once a year, but now every 6 months. 
Everything is possible, just give me time.

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