New 11 feet Blades.

[seanchan00]

Till the new set is done I extended the old 8 feet 6 inches diameter blades like this. It has more torque and starts easier but a bit on the slow side as it was for TSR 5.5 designed for diameter 7 feet 6 inches now extended to 10 feet 6 inches.

Dated 28th May 2006.

Here's Tan Boon Hwa the carpenter friend who carved the blades for me. We just finished balancing the blades. Because of two different kinds of lumber used 2 blades weighed 3 kilograms and one of them is 700 gms lighter. See the bottom blade loaded with lead strips, 420 gms all in to balance. Dynamic balance was also carefully done. When we spun the blades by hand it just didn't seem to stop.

Here it is up on the tower and waiting for the wind to be strong enough to turn towards it.

There it goes facing the wind and starting to spin slowly. Watching the new blades for a while it didn't seem responsive to low winds. Well have to wait and see what happens next. This new blades is designed using Alton's Blade calculator with the following specifications. 3.4 meter prop with TSR of 7.5, angle of attack of 4 degrees, 3 blades and a coefficient of lift of 0.8

I have also closed the air gap to minimum clearance from the stator to harvest what little power the winds provide.

Somehow I suspect this won't be the end of my quest for enough power. I am sure this wind project has more problems and fun in store for me.

Dated - 30th May 2006 - I was at the farm from 2pm to 7pm yesterday and the blades didn't budge even though I could feel the wind blow. I am wondering if 3+ Kg each blade has loaded up the starting torque?

SeanChan (:>)

To Editor - I have posted this 3 times and it didn't show on the board so I am posting again. If this is superfluous please delete and I tender my apologies for adding load to your good work.

SeanChan.

SeanChan;


The lost story thing must have been something other than an editorial removal. I checked the log and this is the only copy showing as being posted. It is fairly easy to miss an error while posting such as intro text problems "spellcheck", etc. This is a nice story, exactly the kind we need here so it would not be removed, at least by me.

Editor.

[willib]

sean,i seem to remember Danb opened his air gap and got more power because the blades were able to  spin faster .

if your alt is trying to extract more power than the blades can give ,then it will have a startup problem

since you used altons blade calculator , did you happen to notice the large root required by such blades?

that is not a mistake .

it is there to give you better low wind startup, and more overall torque.

i could fabricate you a set of root sections if you are any good at epoxy- glassing.

[harrie]

Hi SeanChan. I think some of the problems we have in low wind areas, is the yaw bearings. I consider the bearings that I have made on my machines, to be well built, using brass bearings and grease zerks. they are machined close tolarance. But at this time, I have found that they should be roller, or ball bearings so the turbine will yaw in very light winds. I think it is different in some mountian areas where there is high winds, and turbulant winds, that would maybe make it better if the yaw was a little stiff. Ya gotta get it into the wind before it will turn the props. With light winds, and just pipe inside of pipe will not do it.

Hope this helps, Harrie

[seanchan00]

Hi Harrie,

My yaw has a 3 piece bearing sitting on the top of the end pipe as shown below.

http://www.otherpower.com/images/scimages/3841/WindGenerator.gif

Both you and Willib don't consider 3 kg per blade total almost 10 kg for the blades as too heavy? Esp if well balaced? When I spun by hand on the ground they seemed to spin non stop.

My previous set of blades total just 3 kg all in.

SeanChan.

[seanchan00]

Hi Harrie,

My yaw has a 3 piece bearing sitting on the top of the end pipe as shown below.

http://www.otherpower.com/images/scimages/3841/WindGenerator.gif

Both you and Willib don't consider 3 kg per blade total almost 10 kg for the blades as too heavy? Esp if well balaced? When I spun by hand on the ground they seemed to spin non stop.

My previous set of blades total just 3 kg all in.

SeanChan.

[seanchan00]

Thanks WILLIB,

I can do that and it will mean even more weight on the blades. No problem there?

SeanChan.

[willib]

Have you gat any wood like cedar , in your country?

lightweight yet strong.

[Flux]

I wouldn't worry about the weight of the blades.

From the pictures the front face of the prop looks fine, but although the pictures are not taken from the right direction I suspect the back surface is far from ideal.

It looks as though the leading edge is square at the centre part and even out towards the business area the profile is lumpy and casting shadows.

With that size of prop you should be starting in very low winds and I certainly wouldn't worry about large chords at the centre, it should start in winds where the power is too low to produce anything.

Also remember you can feel winds so low that they carry no extractable power so don't panic until you have seen a reasonable wind.

Also it should get up to running speed without problem with any air gap, so don't open that at the moment, it is unlikely that you will have to anyway for those blades.

Flux

[Ungrounded Lightning Rod]

If your blades are static balanced, your bearings are good, and your generator isn't cogging, the weight doesn't matter.  If you touch the tip with a finger and it starts moving, and if you give it a gentle shove during a calm and it makes a complete revolution, then slows down and stops rather than ending up rocking back-and-forth, you should be OK on static balance.  (Dynamic imbalance just means vibration while it spins fast so it doesn't affect startup.)

More weight (mass and angular inertia) means it takes longer to approach a spin rate proportional to the wind speed (either to speed up or slow down), but it doesn't change THAT your blades start, or that they approach the equilibrium speed.

If it spins nicely with a touch, checking harri's theory that the mill may not be tracking low winds.  Yaw it by hand to see if it starts.

If it's a tracking problem and your yaw bearing seems OK you can extend and/or enlarge the tail to increase the tracking force.  (Be sure to recheck your furling point when changing the tail.)  Check that the yaw axis is vertical, too, so it doesn't try to "point downhill" in low winds.

[seanchan00]

Thanks Flux,

I too was not happy with the leading edge and the profile at the back of the blades when I was setting them up. This is the problem where the theory is in my brain and the maker is anotner brain who knows nothing about the lift forces contributed by the back profile. I will have to do this myself later. You are also right that this is the middle of the intermonsoon period here. Changing from Northeast to Southwest. Now it is mainly southerly and very weak with short gusts when the blade will start to move slowly. I wil observe more before I take action.

SeanChan.

[Ungrounded Lightning Rod]

Remember that your blades don't need to start unless the wind is high enough to spin them up to cutin speed.  If they start reliably in wind even slightly below that you're fine.

[tecker]

You could cut the load and look for a current base that works for your combination that's up there now : ie> blade specs , air gap etc. If it turns in low wind with no load taking into affect  you doubled you blade weight you might need a kick start for low wind . I find a smaller unit works in my case .Put the smaller blades on a amtek or a tread mill motor .These will have a higher voltage than the axial and you just have to do some impedance matching with the two gen sets.