Cheap Chinese Blades

[veggieburner]

I had these 10ft Chinese blades up and running for about 6 months. Last week we had a 20 to 30+ mile an hour winds most of the night and the next day. When I woke up in the morning I found 1 blade left on the 30 ft tower and the 50 ft tower blades where still spinning. When I got home from work the 50 ft tower blades where gone except for one just like the 30 ft tower blades. Seems they could not handle the stress of flexing and they broke off by the root. I did email the company with no response on some kind of reimbursement. So now I am doing the wood blades with the chainsaw approach. They are 12 ft blades because the 10 ft blades stalled after a 15 + MPH wind.  Here are some pics.

Another episode of TGTBT turbine blades! (too good to be true)

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*veggieburner's second post & tragic too so he gets some slack, dinky file size but 800x600..  DanG

[imsmooth]

Go chainsaw blades!  If the weather is good I will be cutting Saturday.  The jigs are all done.

[bzrqmy]

What a sad sight.  Good luck with the new blades.  Please post your results!!!!

[deloiter]

Oh man, that's really a depressing sight.  I've had the "6.8 ft" chinese blades running for about a month and haven't had any issues yet but I don't think I've seen much over 20mph in my rather protected test location.  I hope your experience isn't what I have to look forward to.  Time will tell.

[hvirtane]

It looks quite bad.

Did they break at their fixing parts or where?

- hv

[tecker]

Root has to be part of the cord .That will fix those blades . Good test thanks for sharing .

[tecker]

I see you lost both sets ? Were those Axle machines?

[veggieburner]

Yes, they are Axle flux. They broke off just past the root, where the sharp angle starts. To be somewhat fair the blades were not furling to the side. So that would have helped. The problem is I would have felt better if the flew apart from the speed, that was not posible because they would stall past 15 + mph wind. This was because they could not take the flexing caused by the wind.

[tecker]

 They have to be stressed it does us all a favor to know these blade can't take the stresses to the root .I was about to get a set but I'll make a set instead .

[windstuffnow]

I've run the 6.8 blades for a couple years to see how they would hold up, they did fine.  Last fall I put up an 8.5 ft turbine and they are doing quite well also.   I just ordered a couple sets of the 10.6 blades and suspect they will work fine as well.  

I believe they have a recomended maximum rpm which shouldn't be exceeded.   As you said you didn't have a furling system on the turbines which could have easily exceeded the maximum rpm in high winds or gusts.  Even though the blades were stalling in 15 mph winds they could easily overcome the alternator load in higher winds especially not being furled.  In a 30 mph wind your pushing 3.5kw through the alternator and in a 40 mph gust your looking at 8.5kw with those blades.   My guess would be they experienced a few different forces that caused them to fail.  Firstly an overspeed condition, possibly trying to yaw while in the overspeed creating a massive flex and lastly their most likely, being fiberglass, a bit more brittle in the cold weather less likely to flex as well.   So the combination lead to the failure.

A furling system most likely would have saved the blades.   I'm just speculating by what you've said and there could very well have been some manufacturing defects that could have added to the situation.  

They aren't the best blades by any means, wood blades are much more durable.  They don't perform as well as my hand carved blades but the difference in cost ( price vs labor ) makes a quick inexpensive way to get a turbine in the air.  The do require a little work and definately need to be "re balanced" even though they say they are balanced.

I wouldn't recommend using them in an area where there are people or livestock in close proximity to the turbines.  

As with anything, do all you can to build a safe machine and the chances of failure is considerably reduced.

.

[birdhouse]

bummer about the blades.  

hopefully your wood replacements will give you more duration.  

did you top coat the blades with anything?  cheap epoxies have little to no uv resistance.  i'm wondering if the sun degraded them and made them weak which allowed the wind to destroy them.  

uv rays can be very damaging.  it only took one summer for the sun to kill my gore-tex teepee.  it started out powder blue, and by the end of the summer, the fabric was almost white and delaminating from the gore backing.  

good luck with the wood blades!

[hvirtane]

One question:

are those blades made with wooden parts at roots?

I've seen such Chinese blades.

I'm suspecting that it is one of the weak points. I don't think that you can ever fix well wood with fiberglass (resin). And where the wooden part ends, there is the weak point.

I think it would be better to use plastic with roots and continue it inside the blades, where they are filled with polyurethane.

- hv

[oztules]

Once you make the chainsaw jigs, you can bash out a set or two in no time. Imsmooth has the record at 3 odd minutes per side....Dang thats fast.

The bigger the blades, the more useful the chainsaw method becomes time wise. Multiple sets are even more worthwhile.

..........oztules

[imsmooth]

I lost my blades, too.  Use a chainsaw to save yourself the time.

For those interested, I am doing a lot of photos and will post video of the whole process this time.  I was going to cut Saturday, but it was raining.  I will be away for the week, but will hopefully cut on Sunday the 1st.  If anyone is interested in seeing this and duplicating oztules method you can follow it at http://www.mindchallenger.com/wind/bladecarving.html

The page will grow with the whole process.  I have the jig set up right now for the windward side.  I need one more picture to show the chainsaw lining up with the cross-sections.  I can bang out all three in no time.

[windjunkie]

Windstuff Ed,

I have been looking for some larger fiberglass blades, where are you getting your 10.6 blades from?

WindJunkie

[windstuffnow]

I actually believe their having problems with the 10.6 blades.   I had ordered a set a week or so ago and called them to see if they had been shipped.   They hadn't shipped them and it sounded like they really didn't want to sell them to me and suggested the 9.2 instead telling me they were of better quality.

So there may be a problem with the 10.6 blades they've been selling.  

Anyway, it's CMS ( China Magnet Source ) http://www.magnet4sale.com/home.php?cat=302

I noticed they removed the listing for the 10.6 blades as well.

[veggieburner]

I finished carving one set of 12' dia blades last weekend and it's up and running. I used the chainsaw method, seems to work well, I first drew out the lines on the blades so I would not cut to deep with the chainsaw. after that it did not take long. The bigest differance I noticed is with the power Iam getting out of the wood blades. 10 - 13 MPH winds I am seeing around 500 Watts. I was lucky to see that in a 20 MPH wind with the Chinese blades. Also they start up in no real wind at all. I was getting around 100 Watts in a 6 - 8 MPH wind. At least that is what the town I live by had for wind speed. I could noot really tell thre was much of a wind at all, so i am happy with the performance so far. The Chinese blades claim to start up in a 7 MPH wind, I never saw them start up in anything less than a 10 + MPH wind. And I spen time making sure they were balanced.

So on to the next set.

[Airstream]

Please know that's not a fly'n forget hub and blade now; allow a few weeks to weather and lower to check hardware, the Dans & crew and other folks here are forever finding the odd fastener working loose and such. Nice effort, that is a fine sight, an atta-boy to you!