Blades Run From The Wind

[oak leaf]

Hi Y'all,

I have been watching my blades spin on my test stand while I build my coils and rotor. I have noticed that when the wind picks up speed about 7 - 10 mph the blades move out of the wind, then will move back and pick up speed again, over and over. When the wind gets higher it happens more rapid. Will this problem solve its self when I install the stator and rotors? Do I have a problem with the tail setup?

Thanks,

Harlon

[wpowokal]

Harlon, to me it seems the blades may be following the turbulance at what I assume is low level, more than in full service. I can't quite see how you carved your blades but they can quite effectivly seek the wind under certain conditions and overpower the tail.

Your tail set up may be ineffective it's a bit hard to make out the fine detail.

If you don't have access to a camera then a good description will help, like test tower height, blade diamiter,tail area, boom lenght, material, offset, angle?

allan down under

[Flux]

I agree with Allan.

Firstly I would never do what you have done, running blades with no load is simply crazy and I strongly suspect you are in a turbulent area with little real wind. You may not have sufficient wind for the final thing to be much use.

On a good wind site unloaded blades you will reach crazy speeds very easily and you will have rather frightening helicopter noises as the things drop efficiency in an attempt to hold the speed down.

You give no real information about your set up, we don't know how long or how big the tail is or whether the prop axis is offset. If the tail is totally inadequate and there is an offset then it might turn from the wind. The AirX is a bit this way inclined even without an offset. My guess is that you are down amongst the trees or you are in an urban environment and you have no useful wind.

Flux

[oak leaf]

Thank You for your input,

How do you test your blades for ballance if you do not run them before you hoist them 40',50',60' or higher in the air? I have seen ceiling fans that have made me not want to be under them, and they are farly low rpm.

I will get the tail info for you after work. I have built this from the plans posted on otherpower.com for the homebrew 10' turbine. It has the offset shown in the plans. Yes It is neer the ground on a "test stand" to ballance the blades.  

Thanks,

Harlon

[Flux]

If it is on a test stand close to the ground you are almost certainly seeing turbulence so it should be ok when you get it up into clean air.

Normally there is some lack of balance in the alternator itself and the final balancing would take care of that. It may be adequate to balance the blades alone if the alternator is very well made.

Adding weights to give a static balance is usually all that is required, when you can no longer determine a heavy spot it should be ok. It would be fine to check on a test stand before raising it to great heights, but unless you are pretty sure the wind is very modest it would still be wise to have the alternator operating and connected to a rectifier and temporary battery. At the very least have the alternator connected to a brake switch, then you can stop it if the wind picks up.

Now that you have explained what you are doing it seems a bit less frightening and turbulence is almost certainly causing your turning out of the wind. Bear in mind that things can run rough in turbulent conditions so don't confuse this with lack of balance.

If it is out of balance it will always be rough, but with turbulence it will only shake when the wind is swinging about.

Flux

[wpowokal]

And don't forget to track the blades, that is the tip of all blades should pass some marker in the same place.

allan down under