NEW MILL IN THE AIR

[ubud]

I DID NOT USE THE STRESSED SKIN BLADES .... STARTED TO COME LOOSE WITH BOUT

1 HOUR OF WAGGLE TIME ON THE GROUND.

SOOOOOOOO I carved a set of wood blades, and here is i think a novel way to balance

I think.



With paint!

The light blade only took 1 extra coat.

Next shot IT's IN THE AIR.....NOW IF THE WIND WOULD ONLY BLOW! 2 DAYS AND WAITING.

[Waterfront]

Don't you know? After putting up a new genny, the wind will stay dead for at least a week, hehehe

[TomW]

ubud;

and here is i think a novel way to balance I think.

I don't want to bust yer bubble here, but that method has been in use for a long long time. It is the first way I saw to do it going back at least 4 or 5 years. The mill looks very nice, by the way!

Cheers.

TomW

[willib]

looks beautiful !

very impressive

[JohnC]

Looks good UBUD.

Your shop is getting to look like my bedroom.

Hope the winds blow soon for you.

[hiker]

i use a 3ft long level-hang it from the ceiling-check to make sure its level-

then hang a blade from each end--find your lightest blade -then carve off a little from the heavy ones-rehang the blades from each end untill the level  reads level on all blades...simple and accurate..

[Gagster]

Do minor imballances in the hub become a factor when doing the blades one at a time?  Is there a significant advantage to ballancing the completed assembly or is the difference minor enough to be ignored.  One obvious advantage to doing individual blades is that it requires less footprint in a crowded shop.

[Flux]

This raises a couple of interesting things.

It is not that easy to balance blades individually as you don't normally know where the centre of gravity is.

If you stand the root end on a pivot and weigh the tip end it should get you near. If you weigh the whole blade it may not.

The other issue is a more serious one, not so much the hub, but the complete alternator should be dynamically balanced. Static balance with something with 2 separated discs is not good enough and you can't correct it with balance weights on the prop.

Make sure the 2 discs are as balanced as possible individually. If they are machined or laser cut and you space the magnets carefully there is no problem. If they are rough discs or your magnet spacing is rough you should balance each disc and not try to balance the complete alternator with random weights it will give a static balance but you will be left with a couple.

This may not be a big issue with a large slow machine but can be a problem with a fast one with a small prop.

A small residual unbalance in the hub or alternator can be corrected as an assembly with the prop on.

[dinges]

It's the idea was having too, glad to see it confirmed here.

I try to balance everything individually: each rotor plate, the bearing assembly (in my design this rotated too). Then assembling the rotors to the bearing assembly and rechecking the balance. Then when making blades, weighing each individually, making sure they're same weight. Mounting them on the prop-plate, balancing. Finally, assembling the genny + prop together and rechecking balance.

Judging from this, one might mistakenly conclude that I have a balanced personality

BTW, Would you believe that I once tried explaining the difference between static & dynamic balance to a teacher (master's in Physics (nuclear), teacher of system dynamics in our school) and he didn't have a clue what I was going on about. Besides, I still have difficulty grasping the difference myself, but do know that static balance does NOT guarantee dynamic balance.

Peter,

The Netherlands.