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Forum Index : Windmills : Manual Furling

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fillm

Guru

Joined: 10/02/2007
Location: Australia
Posts: 729
Posted: 11:51am 10 May 2012
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Hi All,

As described in my recent post with the"VLLR" Variable Liquid Load Resistor" LINK " and what lead me to go down that path, then this would be the direct opposite in operation but with a similar out come. The event described there prompted me to put more effort and thought into how to control my wind gens in high wind conditions when all is going wrong and when a shut down is needed . The events I described there is the same for this thread and I considered my options.............

Mechanical braking... eg Disc or band/drum brake

Better Furling

Mechanical assist furling

Diversion Load resistor braking ..

Combinations of all the Above


At first I put lot of thought towards mechanical braking with either a disc, drum or band brake and was very much in one mind that this was the best solution and looked at sourcing a suitable brake caliper , even to the point where I bought one that I thought would be suitable as used on some go-kart brakes , it is a cable operated twin pull and a very nice unit.




My thoughts were to have the brake spring tension applied and cable to release as is done with air brake systems , because of quite a few reasons I decided not to go with the disc idea, and if I was to go down the path of mechanical braking would lean towards a band brake .
I moved my thoughts to one method that has been tried and proven over the years, and that is to be able to manually furl the mill as has been done with the old pumpers for over a century , so to have a go at incorperating that principal into the 500W mill I have flying, as well as making it furl better and earlier .

The easiest way to get it furling earlier is to increase the offset on the blades so that was increased another 20mm ~ 30mm.

The next was to get the control cable through the slip ring assy, a bullet swivel was crimped to the wire cable to stop twist .




The slip ring is held together with a 6mm bolt which allowed me to drill a 2.5mm hole through to allow 2mm multi strand cable to pass through.
A bullet swivel was crimped to the wire cable to stop twist up and to connect the pull rope too.

The cable then goes through to a 6mm Hyd steel tube guide that was bent with a small pipe bender.





Getting the cable pull point out far enough so it had enough leverage was a bit of a worry as was the friction through the tube. Cable operation is basicly the same principal as long as there is enough return force to pull the cable back .




I made a sliding clamp to connect the cable to the tail tube , this needed to align with the pull to the tube.



It has been up for quite a few months now and has been quite a surprise to how well it works , the mill starts to furl in about 30klm with the off-set and the cable just loops up on its self when it goes into furl.




Where it has surprised me, is by adding a 5kg weight to the pull rope the extra weight pulls the cable up each time the tail does a little furl but does not allow it to return to the stop . The furl moment is lowered a little( approx 20K ) but after a couple of gusts and at about 1/2 furl the weight has enough force to pull the tail into full furl and hold it there untill the weight is removed . With the blades in the full furl position and the power taken away from the blades it is now a whole lot safer to short the mill if required to do a full stop as well as reduces the loading on the tower. But if just left locked in furl with the GOE222 blades they will still give some power in high wind and so far not out of control.


5KG weight on pull rope, I used mower start cord but think it would be better to use quality no stretch rope next time as there is still some stretching .


Weight down and mill locked in furl

Because of my work and being away from home this system has made the other half a lot happier, if a storm is comming she just goes out and hangs the weight on the rope and does not have to worry about things going wrong .

The other options that could be done is instead of the weight it could be activated by other means , eg: linear actuator , winch , water weight .

Edited by fillm 2012-05-11
PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits
 
norcold

Guru

Joined: 06/02/2011
Location: Australia
Posts: 670
Posted: 06:25pm 10 May 2012
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Just a little tit bit, with our electric motorised RC gliders we use braking on the brushless motors to allow the folding propellors to fold back in against the fuselage, allowing the glider to thermal without the drag of a turning prop. We feed a little juice to the motors to induce the drag when one of those "heading for space" thermals are found This function is handled by the ESC(electronic speed control) and is activated when the throttle is closed. All it does is shorts the 3 phases as per in our mills.
Whilst I`m talking of a 12" dia prop that folds back, hardly of much to do with our mills, it is very effective. Perhaps with your skills and patience something similar could be applied to our mills. Have tested our little brushless motors(current one consumes 40A at 11v on full throttle) in the lathe and they are quite good little PMA`s for their size.
Of course folding back 3m props effectively would be no easy task, and is way above my very limited engineering capabilities(dumb arse plumber)
My two OEMs have put in 1055 a/hrs this year to date. 1055*50(volts)=50.75kWhrs, that is with them braked of a day let loose of a night and braked whenever a wind warning is out. Still have not got around to improving their furling as it seems the batteries will not let them speed up once the battery voltage gets around 59 volts.
We come from the land downunder.
Vic
 
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