blade damage to galvinized blades

[hayfarmer]

 
 had a storm front for last 24 hours with forecasted wind gusts to 50 mph. 6 foot mill at home did fine , but at farm I get normally 25 % more wind than they forecast due to

nearby river and up slope winds from all directions,highest elevation in area. my amtek had issues with 75 mph winds throwing off blades in past years (forgot to put on stop

switch) operator error. This time I did however it slowed blades down but turned away from wind and bent the blades. I guess with metal blades you just have to take


mill down in 50 mph plus winds.)I don't know how fast it was blowing but stuff was thrown all around. 6 gallon water jug that was full was blown over most water leaked out ,


found it in the field with some water still in it. guess I will cut down the size of the blades that ripped off last time and try again.

[ghurd]

Be careful with high torque blades, high resistance generators, and stop switches.
Hate to have one of those Ameteks worth their weight in gold turn into this (not mine)
G-

[ChrisOlson]

This time I did however it slowed blades down but turned away from wind and bent the blades. I guess with metal blades you just have to take mill down in 50 mph plus winds.)

It can happen to any of them.  I just bought a used Jake 23-10 with the old 1-1/4" governor that has no blades on it because the blades hit the tower in high winds.  Bent one blade shaft and busted the pitch control spider, that blade split right thru the root and tossed it, and and the other two remaining blades are shortened up to about 4 feet long still dangling on the blade shafts by the ball joints on the spider.

You can only try to harness the wind.  You can never tame it.  And if you don't have busted wind turbines, then you live in a poor wind area.
--
Chris

[hayfarmer]

>   "And if you don't have busted wind turbines, then you live in a poor wind area." (Cris Olson)

love that saying cris, I think I will let her spin unless its way above 50 mph then tilt down the tower.only get real excessive speeds a few times a year 75 mph,was disappointed to

see bent blades with the brake on . 



hayfarmer

[gsw999]

Yeah this is what happened to mine when i didnt put the right bolts on one of the blades



SORRY STILL GETTING THE HANG OF ATTACHING , at least with Aluminium blades you can hammer them out and give them another go

[XXLRay]

Don't you have any mechanical storm securing system? Nothing like furling? I for myself don't trust just the electrical braking power of a generator.

[hayfarmer]

Ray, don't have a furling system yet.planed on taking tower down if forcast is over 75 mph , shorting mill just bent blades may have survived if I let it alone, so I changed them to

  6  composite fibre blades that are flexable and seem to turn much faster than either the alum or galv blades that were sacrificed to the wind gods. I posted a video on

  you tube of the new blades  link :  http://www.youtube.com/watch?v=vNLvTIdcME8

  hayfarmer

[ghurd]

"It's nothing pretty..."
Hint: Close the milk house door and it looks perfect.

Might want to consider tipping the PVs up a little steeper.
Gets more power when it is needed most (if it was only solar).
Mostly, keeps them cooler.  Cooler makes more power.
If they get too hot for too long, the cells burn and ruin the panel.  It does not take as much to ruin a panel as many people expect.
G-

[MattM]

The single bend in the blade is too weak.  What you want to do is use an 'ogee' concept, only instead of curves you are using opposing folds.  You can bend the first bend at say 60 degrees then use an opposing bend around 50 degrees.  Depends on the brake you do it on and the gap between bends.  I preferred a .125 inch gap and used 50 and 35 degree bends to end up with around 5 degrees of pitch.  You lose some pitch when you keep the gap small.  The opposing folds give you much better stiffness for the blade.

And if you use a hem and a pair of angles at the front to form a leading edge 'V' it will further stiffen your blade plus cut through the air more true.  I found not using the extra stiffening bends on the leading edge invited a flutter noise that became ominous at high speeds.  Fewer vibrations the better with metal blades.   

[bj]

   Hayfarmer--just for info, I ran a set of those composite blades for about 3 years, no furling.  They are tough.  They even survived eating a chunk of
vinyl siding that launched off of the house.  A couple of nicks, but sandable.  That was in 90 to 100 kph winds.

[MattM]

Just in case you didn't understand the design I was mentioning.  I finally had the time to draw it out in paint.  These blades work well and because they are reinforced where it helps they don't fail nearly as easily as the single-bend sheet metal blades.  I recommend 24 gauge for a three foot diameter, 20 gauge for a five foot diameter, and 18 gauge up to a six foot diameter. YMMV



I should also mention that it won't slice you up like the other style.

[SparWeb]

Wouldn't that still be pretty flexible Matt?
Mounted on the hub, and pushing on the tip, how much force does it take to bend the tip an inch?  Or twist the tip by 10 degrees?
Maybe if I had it in my hands, I'd be surprised; it's hard to picture it being stiff just from the drawing.

[WindriderNM]

I had a set of the galv. blades The first big wind they broke off at the hub it took me a few days to find them. I cut them off even and reinforced them with a steel strip from the framing dept at homedepot about 1.5 in x 8 in This lasted for several years then another big wind about 100 mph a few months ago one blade broke off. I still haven't found it. That same wind broke 3 blades (I think nylon) at the hub. I found 1 piece of 1 blade. I am making some blades from PVC pipe rapped with fiberglass. and filled with spray foam.

[MattM]

SparWeb-

The blades are very stiff from rotor to tip.  The failure point - like all metal blades - will eventually be at the attachment point.  They do flex a little from leading edge to trailing edge at the furthest point from the rotor, but the tiny bit of twist works in your favor because the leading edge is so rigid.  If you want blades that operate in low winds make them wider.  For best rotational speed keep the blade camber to a minimum and not as wide.

For best consistency between blades use a shear to consistently cut material and bend using an automated brake.