• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Wind generator no longer up or running.

Status
Not open for further replies.

tcmtech

Banned
Most Helpful Member
Light winds today but still I had a blade come apart. :mad:
The fiberglass in one blade had a major flaw. There was a large void in the fiberglass mesh that did not have any resin in it just above the root. :mad:
The blade tore out at that point and the massive imbalance crashed the generator.

It was not a generator design flaw on my part but just a simple blade manufacturing defect.:(

After falling 20 feet and landing on the blades the other two broke of at the root and bent the hub and shaft. :(
However to pat myself on the back for design robustness the whole frame and motor/gear box are still in solid usable shape! Only one slight ripple in the tail frame behind the pivot point. :)
Not bad for 150 pounds of metal crashing down from 20 feet while still spinning! ;)

It landed right as you see it, fully salvageable and reusable!

I am trying to contact the company I bought the blades from to see if there is any warranty coverage for showing proof of a manufacturing defect.
 

Attachments

Last edited:

JimB

Super Moderator
Most Helpful Member
What a bummer!

JimB
 

Andy1845c

Active Member
Man, that is a bummer. :(

Is there any salvation for the hub and the shaft?
 

duffy

Well-Known Member
Oh NOES! TEH WINDMILL!
 

microtexan

New Member
To echo the others.... bummer.:eek::( It sure looked good. Hope you can get a replacement from them and get it back up.
 

Leftyretro

New Member
There was a saying by old ham radio operators, "if your antenna didn't blow down last winter then it isn't big enough". Sorry about your bad luck, but large blades create large forces, some for the good and some for the bad ;) Good luck on getting the blade manufacture to make good.

Lefty
 

tcmtech

Banned
Most Helpful Member
As I finished moving the last of about 150 - 200 tons of manure, Anybody need unobtainium for over unity projects? I think I found its source! :D

I though about it and I am going to repair the one blade that ripped out, being its actually completely intact other than the tear spot, and make a plaster negative of it and cast a set out of aluminum.
I have experience with aluminum smelting and can build a smelter easily. Been wanting to justify building one for years too!;):)
All I need is the blade shape for the mold forming process.

So what do you guys think, should I go cast aluminum blades next? :)

The hub took me about an hour to make so no big loss there. The shaft is bent about a 1/4 inch off center so its done for.
I took the gear box apart this morning and the sudden stop apparently striped the gear teeth off the main drive gear right in one spot too.
If it had been the driven gear on the motor I would have suspected a catastrophic over spin did in the blades but when the drive gear losses teeth in one single area it shows it stopped so suddenly the driven gear had enough motor momentum going to over power it.

Well now I have a reason to rewind the big Getty's 5 kw servo to put out 200 volts at 1000 RPM instead of 50 volts per 1000 RPM.
That has a 1 7/16 inch shaft so I doubt it will bend during a 20 ft fall!
Actually I am going to put an anti lift off locking ring on the center pivot with the next design.
Never needed one in 20 years of home made generator experiments but now its going to be standard after this. ;)

Wind Max is the blade manufacture by the way.
I did some searching last night and found several others that gave them a bad review due to exactly the same manufacturing defect causing them to have a blade come apart at a speed and load well within its rated working range. :(
So my incident is not a random manufacturing flaw apparently. At least I did not pay several thousand dollars for my gen set that got knocked down after one week of run time! :)
 

bryan1

Well-Known Member
G'day Tcm,
When blades get to high speed they tend to bend backwards and cast ali would probably crack, besides that the weight of the blades would be a big stress to the bearings in the genny. Just make a new set out of wood and if your genny is coggless then you dont need high aspect blades. Go and checkout the backshed forum and search for Oztules story on using a chainsaw to make blades. That idea has really taken off and several other people around the world have done the same with top results.

Cheers Bryan

P.S. I'll also second the 'bummer' statement
 

tcmtech

Banned
Most Helpful Member
I thought for the price these blades are on the Internet and how high their efficiency ratio is I would try them. Money spent and something learned in return!;)

Me and a buddy of mine made several sets back about 7 -8 years ago and every one lasted for years! So I have done the homemade wood blades many times and with great results! We used a band saw and a belt sander to do the shaping. Now that I have a highly efficient air foil shape I will just copy it out of wood and do a fiberglass overlay.;)
Looks like I may be going back to treated 2 x 6's again!
The 2" x 6" never tore out at the roots even when our old 5 1/2 footers would push the the tip speed into the supersonic range! :eek:

being I have a good airfoil shape to copy now I may step up to 4" x 10" oak and try a 16 ft four blade design. I have the wood and a way to cut and shape it.:)
Plus I can easily make a 20 inch double plated 3/8" thick high strength steel hub in an evening. I didn't pay for the rotary indexer table for my mill for nothing! :p

I have a industrial duty gearbox already intended for that design. Its got a 2 7/16" chrome moly shaft with tapered roller bearings and is specifically designed to handle very high thrust loads. The down side is it weighs 250 pounds.
So when I do build the big system I will have to rent a high lift for the weekend to set it up. The whole generator, frame, gearbox and blades will weigh around 650 - 700 pounds!

As far as aluminum goes I know its used in airplane props and the run much more horse power through one of them and at far greater RPM than any wind generator blade would ever see.
Plus with doing my own casting I can build up the root thicker or more likely I will reinforce them with a length of heavier grade 8 all Thread down the center of the leading edge. At around 150,000 PSI tensile strength an pair of 3/4 inch all thread rods running down the first 1/3 of the blade and one running 2/3 of the length of the blade should solve any fatigue problems. ;)

Anyone have a reference source for calculation of centrifugal forces?
I am curious as to how much tension goes on a blade root at different combinations of length, mass, and speed.
 

Bob Scott

New Member
Anyone have a reference source for calculation of centrifugal forces?
I am curious as to how much tension goes on a blade root at different combinations of length, mass, and speed.
I think you should try some way to govern the blade angle with all blades somehow mechanically connected in unison to the same but variable angle, similar to the speed governor of an old Victorola record player. Use spinning weights or a spring mechanism to limit the forces on and rotational speed of the blades.

Or blades that bend, like the cheap springy variable rate sheet metal replacement fans you can use in cars with A/C instead of using a clutch fan.

C.F. = (M * V^2) / R

C.F. is force in Newtons
M is Mass in kilograms
V is velocity in meters per second
R is distance of weight from center (radius)
 
Last edited:

tcmtech

Banned
Most Helpful Member
I have not seen it until now! thanks!

I have a design for a variable pitch hub system but so far I have never needed it.
I have always built my units with over sized generator capacity, very stout blade structures and redundant load dump systems.
However I will be incorporating it into the big 16 foot unit when I do get it up. Loosing a 60 - 80 pound blade 8 feet long would do much damage to my house or shop if it came down the hill!

Mine was not a over speed failure though. I have not actually ever had one so far.
I just got a bad blade. Thats life, some days things like this just happen.

I was talking with my brother and we are going to try and fabricate a new wood set some time soon. And possibly do up a fiberglass set as well. I do plan to put high strength steel rods in the fiber glass blades if we make them though.
If I can incorporate them into the wood set I will do that too!
 

tcmtech

Banned
Most Helpful Member
I finally got at reply form the dealer that sold me the blades.
The original manufacture went out of business. Windmax is apparently owned by a different company now that is selling their product under the original name.

Quality was an issue with the original manufacture but the dealer claims the new blades are far better.

Thats all I got.
 

Sceadwian

Banned
Same ****, different day...
 

Boncuk

New Member
Hi tcmtech,

I kept track with danish wind generator design for a long time. The first generation had variable pitch blades which requires strong mechanical construction, hence a lot of weight in the hub.

The last 10 years the design changed to fixed pitch blades with a small flap at each blade's tip.

Winds at the North Sea Coast might gust to 250km/h in spring and autumn and will rotate a 40m dia wind mill fast enough to exceed sonic speed at the blade tips unable to control those masses timely.

Small flaps (spoilers) have huge influence of the aerodynamic behaviour of the blade and braking action is almost instantaneous.

A well known manufacturer of wind generators is "VESTAS" and you might be able to have a look at their design to alter yours accordingly.

Boncuk
 
Last edited:

Nigel Goodwin

Super Moderator
Most Helpful Member
I finally got at reply form the dealer that sold me the blades.
The original manufacture went out of business. Windmax is apparently owned by a different company now that is selling their product under the original name.
Don't know about the USA, but in the UK it's the RETAILER who is responsible, and NOT the manufacturer. You would have a claim against the retailer, as he supplied you the incorrectly manufactured blades.
 

duffy

Well-Known Member
Cast aluminum sounds like a fair amount of weight, and I'm not sure a casting would be stronger after it vibrates in the wind for a few years. Might get conked in the head with a heavy chunk of aluminum one day.

What about carbon fiber instead of fiberglass? What about wood?
 

tcmtech

Banned
Most Helpful Member
I have often wondered about those flaps. I have seen the big multi megawatt units around here have them too.

I have a solid design for a variable pitch hub but its estimated weight is going to be 20% of the whole generator system!
And thats factoring in that I over build the generator frames and over size the gearbox and generator itself!

I will have to look into Vestas and see if they sell smaller size blades in the 10 -20 ft rotor diameter sizes.

Thanks!
 

tcmtech

Banned
Most Helpful Member
I dont have any problem with trying to make a set of aluminum blades.
But carbon fiber is still expensive as is and to make individual blades 8 feet long are way out of my price range!
Unless someone knows where to get the fiber and resin cheap!

My brother and I are thinking about doing up several sets of smaller wood blades. A good friend and I have made them in the past with great results. I just thought I would try the fiberglass ones due to the cheap cost and far better aerodynamics.
My 8.5 foot set that this thread is about only set me back about $130 with shipping.
Ive wasted more than that for far less educational stuff!
 

tcmtech

Banned
Most Helpful Member
Around here dealers often get shafted when a manufacture goes out of business and then gets bought up by a different company.

If the original company was making bad product the new owner likely bought the name and nothing else. It saves them the hassle of having to deal with warranty claims from the previous owner.
The dealers then often get left hanging. They typically bought sales rights to the original companies product but once the company that supplies it goes under they have no one to back them up. And then is left with the choice of going under trying to make good on bad product they may very well had no honest idea about as to how well or bad it was made or just shaft the customer like the original company shafted them.

Around here buying into a franchise is not any better than buying the product as a customer themselves. They pay fair money just to be a middle man.

We have had several manufacturing companies in our region just lock up the doors one day and disappear. The employees showed up for work, including management personnel, the doors are locked, delivery trucks and river are sitting in the parking lot wondering whats going on and nobody ever got their last paycheck.
Some time later a different company buys the name and manufacturing facilities and simply tells the former employees you have first hire back rights but we do not have any responsibility for your lost pay.
The dealers get the exact same treatment too. If they want seller rights they have first opportunity to get back in but thats all! All losses are not the new owners problem. They bought the name and the physical property but none of the legal or financial hassle.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top