Brian's Wind Turbine Rebuild

[Boss]

Crazy weather Spring 2011 combined with changes to the blade length caused a failure in the top of our wind turbine tower. When we brought it down we observed cracks in the vinyl-ester resin stator. It is time to make a new stator. Thanks to Mackenzie Thatcher we have more than enough copper to build new coils. The first stator mold was damaged primarily because the mold release was insufficient.



Stator mold I used 3/4 inch thick plywood for the top and bottom to help stabilize the mold,unfortunately the plywood had a warp I could not repair using heavy weights on top with the plywood spanning two saw horses. I then added the 2X4s to help straighten the wood. Reading the book again by Dan Bartman and Dan Fink from Other Power I realized the top was supposed to be round,no doubt to help keep the super sticky vinyl-ester resin from gluing the mold pieces together. 


Stator mold Above is the next idea I had:Still employing the 2X4s to help keep the warped plywood flat. I don't know if you can see the small space in the front where the warp in the plywood is raised.


Stator mold –This side as well as the opposite side are lying flat against the center piece which is cut out in a circle for the resin to be poured into.


Stator mold –I was thinking I would screw the plywood to the 2X4s,but then I would need to counter-sink the screws and fill them afterward,as this bottom of this top mold piece is against the resin and needs to be perfectly smooth.


Stator mold –Carpenters wood glue and clamps are what I decided upon. I hope it works.


Stator-coils-fiberglass –While I worked on the mold I also worked on the stator coils. They have been soldered already except for the output terminals. I'll do those after I get the coils in position. The fiberglass is glued with Super Glue and pressed in place using the magnet separators,which are made from polyurethane  which pretty much nothing sticks to.


Polyurethane is the material we prefer to use for the mold,but we could not find it at a reasonable price and we needed to get this project going.


Stator-coils-fiberglass –I used auto body working tools as weights. I still will need to shape the coils but first I need the coils to stay in place.
That plywood is from the first stator mold we built four years ago. See honey,it really does pay to keep seemingly worthless items around,hehe.

[SparWeb]

I see a bunch of cracks and splits in the old stator mold.  You're gonna need lotsa wax, man, lots.   

[Boss]

hehehe, yep, wax, grease, caulk, maybe some JB Weld too
Right now I have the fifty pound spool of copper and two 20 pound steel weights sitting on my coils hoping they squeeze down and fit in the 1/2 space of the new mold
Brian

 

[jlt]

  I put Some resin on my coils and then squeezed them between two pieces of metal with a couple of C clamps. It really helped to keep the stator thin.

[Boss]

Interesting, how thin is your stator?
How did you keep the metal from sticking to the coils?

[jlt]

I put a sheet of polyethylene under the coil and a second sheet on top. I used about two table spoons of resin per coil With a lot of catalyst. I removed the clamps after about 30 minutes.when they were set up and still a bit soft. My stator came out just under 1/2 inch .
        I used that oriented strand board for the outer    and inner part of the mold  .I painted the mold with featherfill. It is a polyester primer That is used In the auto body trade.

[Boss]

They certainly came out nice and neat.
I'm oscillating between plywood and OSB for the middle part of the mold. I have so much going on in my life now that I don't believe it really matters either way. We have plenty of copper, resin, and I really don't care if this mold survives. I do hope it comes off the stator, but I think the experiences from first time, around on my own, count for a lot. We did our first turbine in an OtherPower workshop, it was beautiful, the second one very ugly, but it did work and gave us two years of energy for our entertainment system, and that also counts for a lot in my book.

Like I said "oscillating," fitting I think. The OSB, as I sat and thought about the pros and cons isn't all that bad. I put a caliper on the OSB, it read 1/2 inch. Perhaps it was swollen, I don't know, the outer 3/4 inch plywood concerns me most as it still has a slight warp to it. I will really need to squish the mold with "C" clamps to straighten it, and then it still feels like a crap shoot.

I thought I would go to Wallyworld (the only store in town) and look for a thin sheet of polyurethane for the top and bottom, but then I thought, it is the sides that will undoubtedly stick, and there is no way that I can think of to secure a strip of polyurethane to the inside edge of the mold. If I can, today I will dope up the mold with the Silicone II caulk I bought, and let it dry for a few days.
I have time, I'll wait and see how it looks

[Boss]

June 21st 2011 adding new pics and stuff to the new stator project

 This is a dry run to see what the stator looks like in relation to the magnet rotor. First thing was centering the stator on the hub


stator-1-magnet-rotor –I had to figure out a way to adjust the stator laterally. First I tried to file out the holes but there really isn't room on the stator because the coils and the mounting holes are very close. Then it occured to me that I could bend an offset in the mounting bolts which are made of All-thread. I did a rough bend in the vise hitting first one side then the other,leaving four nuts in place to protect the threads. As usual the first off-set bend wasn't enough,so I went too far on the next two,one of which you can see in the above photo. I'll need to straighten that one a bit.


stator-1-magnet-rotor-front –Above you can see that centering the stator with the off-set all-thread worked well enough. There isn't but about a 1/16th of an inch clearance so it had to be pretty close to not rub.


stator-1-magnet-rotor-side - the next adjustment was getting the stator back against the magnet rotor evenly. I'm pretty happy with this gap. The magnet rotor isn't real true so I can only get it so close before it wobbles into the stator.


stator-1-magnet-rotor-close –the gap on this one side I have the magnet rotor on is around a millimeter- with play of half that all the way around


stator-1-magnet-rotor-top –looking down –A multimeter showed exactly the same readings from each terminal to the next:20 VAC spinning the hub by hand fast as I could.

Now that I know the stator sits well I'll try to get a coat of polyester resin to fill in around the coils. I was thinking about making a jiggler table out of an orbital sander and a motor speed controller

[SparWeb]

For someone who says he's busy you've made a lot of progress now.

A "peanut gallery" comment:

Did you give a thought to "drifting" the holes in the mounting arms on the mount?  I think that if I had the choice between bending the studs or making the holes oval, I'd choose bending the studs, like you did.  HOWEVER  All-thread will not withstand much bending.  The thread groove at the bottom is sharp like the thread points.  When you flex the rod those sharp grooves really want to open up like cracks.  For the ones you showed trying to adjust by bending too far and a bit back...  I'd throw those away and start again.

[Volvo farmer]

How are you going to adjust the air gap with bent studs like that?  Couldn't you rotate the stator some 30 degrees and drill another set of holes more accurately?

[David HK]

Stop for a moment.

You have worked very hard to get this far and I would hate to see your efforts fail.

The arms holding the stator studs will flex in high winds and you can assume that metal takes on the characteristics of rubber.

On many occasions members of this forum have seen the results of stator stud bolt arms bending with the usual result.

You will need to strengthen them so they do not twist or flex, otherwise the stator will grind on the magnet rotors.

Its difficult to see from the photograph, but the studs holding the stator will eventually work loose. You will need to weld up the bolts or use 'pinned' nuts or something equivalent..

I am sure other readers will endorse my observations and you have the time to take remedial action.

You might be able to strengthen the stator stud bolt arms and lengthen or shorten them at the same time to get rid of the offset studs.

Good luck and read everything that other forumites can offer in the way of advice.

David in HK

[Boss]

Thanks everyone, I do love it when I get feedback. 

Did you give a thought to "drifting" the holes in the mounting arms on the mount?

Yes I did, and I also went as far as sticking a file in one of the steel holes, unfortunately, there wasn't enough roon to work on the one which is off by the greatest error. Perhaps I could get my pneumatic die grinder in there, but I haven't any small carbide bits for it. That's when I thought about filing the polyester resin. I only need a 1/16th inch.  I guess I may have patted myself on the back too soon for my quick workaround

The arms holding the stator studs will flex in high winds and you can assume that metal takes on the characteristics of rubber.

  Sorry I never heard of this before. Regardless of steel's stiffness, I don't see it moving, for what ever my pseudo-engineering is worth. Although the point you make about the off-set All-thread possibly twisting, does give me pause, I'll have to think about that for a while, thanks

For someone who says he's busy you've made a lot of progress now.

Thanks I really need to hear this more often. We've missed one hell of a windy Spring with the turbine down, perhaps it is a blessing. Anyway it doesn't look like the wind is going to quit any time soon It is so friggin dry here, I just don't know what will happen next, no doubt nothing good will come of it.

[Boss]

I just had to throw that out there
This morning before work I mounted the stator again

New-Stator-Second-Coat Resin _ I added a pint of polyester resin with a disposable paint brush. Pressing the resin and jiggling the area over the coils so the resin would penetrate and soak in as best it would. The idea is to get a even coating of resin everywhere,for strength as well as heat dispersement.

Rebuilt-Tower-Stub-in place –I needed more room in the shop,so I moved the tower top piece out,and placed it back in position in the tower.

Exciting

[David HK]

To continue on stator bolts, these photographs may be worth many words.

I only work in stainless steel and the turbine shown below was made  several years ago and has not yet flown in earnest.

The turbine is my upgraded version of the Hugh Piggot 8 foot diameter swept area machine with a 12  volt stator and in a good wind is capable of 500 watts according to the designer.

The stator bolts are tapped through the stainless steel angle and then tack welded to the angle. They should never come loose. The remaining bolts are Inesita pending a flying test and adjustment of the air gap. Once this is done the bots which contain pre-drilled holes through the flats can be finally drilled through the thread and pinned. That is one option, but I have others in mind.







Hope this helps.

David in Hong Kong

[David HK]

Apologies for the mispelling in the above text. The obvious should read in-situ and bolts.

Here is a U-Tube URL regarding Nord Locks. Watch this and you will understand a great deal about nuts and bolts coming loose.

http://www.youtube.com/watch?v=mgwmuZuJ02I


Regards,


Dave Weaver in Hong Kong

[zap]

I watched that Nord Lock video a while back, it is a good one.  The ebike folks seem to like those washers.

[Boss]

Smart concept that Nord-Lock system. I would love to try them out. Our budget bottomed out with the usually expensive (for our lifestyle)  purchase of the 2005 Jeep Liberty CRD (biodiesel compatible) utility vehicle.

I am practicing projects on zero budget at least for the Summer, or until we pay it off
   

[Boss]

Wow, you must work with a lot of vibration wracked equipment. That is a lot of serious connection security

[David HK]

What you and other readers cannot see is the thrust bearing inside the cylindrical stainless steel block.

All my wind turbines use a standard design pole mounting and the entire machine is designed to sit on it.

Mounting a wind turbine on a hollow steel pipe produces the result seen quite often in this forum.

Hence the use of a thrust bearing and the necessity of wiring up the cap mounting bolts for obvious reasons.

I do not design and build for failure of mechanical parts.

Regards,

David in Hong Kong

[Boss]

What you and other readers cannot see is the thrust bearing inside the cylindrical stainless steel block.

Hmmm, wish I could see that thrust washer setup. I am thinking of upgrading that system on mine while it is down. I was thinking bronze, or perhaps just a steel washer, would help keep the friction on the stub to a minimum
 

[Boss]

This morning I'm trying to get a little done on the turbine, while I'm washing a batch of biodiesel

Stator back on after adding a pint of resin to fill in the voids from pouring too-hot last time.

Gap looks much better than the first stator

I thought I better check the grease on the bearing, good thing too. It was ready



Next on my hit list is figure out how to work around the Blacksmith shop's misreading blueprints and making the jacking holes larger instead of smaller than the all-thread holes

[RP]

Go to your hardware store and get some steel threaded inserts (made for wood) that'll fit in those oversized holes and tack them in.  Otherwise maybe weld some plain nuts on the underside?

[Boss]

Alrighty then
Kevin helped me jack down the outer magnet rotor by hand. We were able to do cutin tests for the new stator.

Kevin rigged a bicycle speedometer up and with the help of a safety disk of wood we set a more powerful magnet than came with it to overcome the effects of the magnet rotor fields. Using an online metronome to help us calibrate the speed readout for our diameter rotor and a little bit of research into the program of the bike speedometer we got consistent readings for RPMs

After discussing whether the energy derived from two terminals was the same as all three if we used a rectifier, we decided it was close enough.

The bottom line is at 150 RPM the multimeter read 24.5

Even though the camera couldn't catch it, the scope showed a very clean sine-wave

Being that this stator is more properly formed I believe I can remove the thin washers from between the nuts on the hub and the outer magnet rotor. We're trying t decide if the combined air gap might cause a stall in the blades. Kevin has a crazy new blade design which he has been working on. He said I can't show you yet though.
Well maybe a little peek wouldn't hurt:

[SparWeb]

That's an albatross wing isn't it?   

[Boss]

Another coat of resin

Self portrait