Building the Tower Stub

Well I finally have a tower stub put together. This is the part that the wind turbine (the yaw bearing actually) slides over at the very top of the tower. The wind turbine needs to pivot or yaw in order to point towards the wind. You may be surprised to find out that people don’t often use ball bearings for this moving part. I assumed at first that pillow block bearing or something like that would be best, but not so. They mostly use this kind of tube over tube design with lots of axle greese and sometimes a bronze or plastic bushing between the steel tubes. It turns out this design will keep the metal parts lasting plenty long, and it is actually prefered because the added friction keeps the turbine from nervously jittering back and fourth to face the changing winds. This way the turbine appearently stays pointed in the direction of the prevailing winds and produces more power. I like this keep it simple stupid approach since it is cheap and extremely easy to build…sometimes it is better not to over engineer something simple that just works.

I decided to build my tower stub a bit different from the design in the Homebrew Wind Power book. Instead of simply sliding the yaw bearing over a 2 inch pipe with some grease, I decided to use a slightly smaller diameter tube so I can slide a bronze or plastic bushing down the entire length of the tower stub and place a bronze washer at the top.

Below you can see the 2 inch piece of tube I started with. The outer diameter is exactly 2 inches. Look how crazy thick the walls are on this tube!!! This is expensive tube that I found in the scrap yard for only 40 cents a pound. The yaw bearing would never wear through this even if there were no bushings. It took 15 minutes to make one cut of this tube with my new steel cut-off saw!!!!


Anyway, I welded it to a 1/4 inch thick sqaure plate that can be bolted or welded to the top of the tower.

Below is the steel cap I welded that slides over the top of the tower stub. You put this on after sliding a section of 2 inch bronze or plastic down the length of the tower stub. This keeps there from being any steel on steel contact down the vertical legnth of the yaw being. I am going to order a bronze bushing tonight that should fit just right. I am also ordering a bronze thrust bushing that sits on top of the steel cap and keeps there from being any steel on steel at the top of the yaw bearing.

Above you can see the tower stub with a section of PVC and the steel cap. PVC was my first idea, but since I found a website you can order bronze from I have decided to use it.

When we are ready to set this thing up we will grease the entire tower stub, add the bushing, and finally slide the entire alternator assembly over the top. That is all there is to it. The grease and bushings will allow the wind turbine to spin around and face the wind.

I just ordered the bushing from the website below…

Vertical Bushing

Horizontal Bushing (Fluid Bearing)

Putting it all together

Take a look!!!! I put the first turbine together the other day in order to get a feel for how it will eventually look. It seems really big to me. I would not want to be in the way when it is spinning for sure. I definitely understand why this is not legal in the city…I would never put this up in my backyard. You could kill someone.
In these pictures it is assembled with the fiberglass blades that I ordered a while back, which actually put it at 9 1/2 feet in diameter. I have started carving a set of wooded blades according to the Homebrew Wind Power book design. These new blades will be 10 feet in diameter and will prabably perform much better. I was disappointed that the blades seemed very heavy and unbalanced. I am guessing that the extra weight and the smaller angle of attack will make it much harder to start up and get to cutin speed. I will give them a try but am not too hopeful.
Anyway, the wood parts still need to be coated with linseed oil and the metal parts still need to be protected. I am thinking about powder coating the steel since I found someone that will help me get a discount on this process. We will see if that actually makes it affordable. It is getting really close and I can’t wait to get her flying and tested.
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Shout out to my peeps!

So I realize that this blog has been just a bunch of dry boring technical wind turbine stuff. So far I have just been documenting the technical side of this experience? I have worked really hard to figure out how to build these turbines and to truly understand how they work. It has been much harder and taken much longer than I thought it would, but very rewarding too. I tend to get so obsseded with projects that I often just don’t even come up for air. I am a bit idealistic and detail oriented and sometimes just want to see it through at any cost. Anyway, the point is that I am embarassed because I have not given any “props” to a few people that have supported me on this project regardless of how silly it seems…

My investor, “Mommy 2.0” down in Texas, was kind enough to sponsor the building of 2 of these 10 foot wind turbines and I would like to thank her greatly for that. I can’t wait to have these turbines perfected and set one of them up on her land. Hopefully it will even be cost effective to set it up as a grid-tie system and watch her meter run backwards! I hope it will pay her back many times over in the long run. I thank her for being patient too since this is taking longer than I had hoped.

I also want to thank Heather for putting up with my S#*@. I have turned the entire garage into a workshop…the garage is no longer for cars and Heather has not been happy with this situation. I have spent a small fortune on tools and supplies and that just ain’t cool either. Heather has been more understanding than I could have imagined. I am glad that Heather is a knitter and not a wind turbine builder! Cloth is way cheaper than steel and copper.

Thanks to Kelly as well for helping me to put together a shop full of tools. The welder has worked great! You have also been helpful with some of the design issues.

Ok, so enough mushy stuff, I want to talk about metal, plastic, and things spinning really fast! I am starting to build the second 10′ turbine now and should have it done much more quickly than the first. I haven’t quite finished the first one yet, but it is getting very close. This way I can get some things done on the second one while I am waiting for parts for the first one in the mail and stuff like that. I think the second one will be of better quality since I am learning from my mistakes. There are a few little things I will do differently this time around that should speed up the process and simply make better, more efficient wind turbine.

I am really looking forward to getting these wind turbines up in the air and start testing them out. I will need to really start thinking about how best to measure and log the output from these things. This will be a whole new project in and of itself.

So What is Left?

It has been a little while since my last wind turbine post because we have been working on the house a bunch lately…mostly landscaping the front yard. I should be able to get back to work on the turbine here again soon. I ‘ve been thinking about what I have left to do though and it is not that much really.
I ‘ve been thinking about where I can set this turbine up in order to test it. We have been thinking it would be nice to fly it at a friends house in Toas but that is not looking like such a good option now. His off-grid system is a bit small and a different voltage from the 10’ turbine stator. I built this wind turbine for a 48 volt system, which has become kind of the standard for battery banks. My friends batteries are wired for 12 volts. Down the road, when I have the building of this type of turbine down, I would like to look for a small piece of land and use this turbine to power a small cabin on it. But, right now I just need a place, prefereably near by, to test it out and make sure that this design actually works well.
Anyway, here is my list of things I have left to do on the first turbine…
1. Finish the tower stub. The stub needs to be cut to size, reinforced at the bottom, and cleaned up since it is very rusty. I might as well go ahead and build the tower stub for the second wind turbine while I’m at it. I also need to order a few bronze or plastic bushings for the yaw bearing. I think the sides of the tower stub will be covered with a piece of 2 inch PVC to protect the steel along the sides of the tower stub. I’m not sure this is the best material for a side bushing, but will give it a try.
2. Put a couple of layers of boiled linseed oil on the wooden parts of the blade assembly and tail. I also need to quickly make sure the blade assembly actually fits on the alternator. I think the 1/2 inch stainless threaded rod is plenty long but need to double check. I used 3/4 inch disks instead of 1/2 inch so it might be tight.
3. Order flat plastic stock for building a new stator mold. I need another one for building the stator for the second 10′ turbine. I need 2 pieces of 18″ squares of plastic that are 1/2 inch thick.
4. Test alternator RPMs using the new laser tachometer. I quickly tested it out and it looks like the cutin is at 130 RPMs for 48 volts. This is already a bit under the RPMs that the Homebrew Wind Turbine book says it should be. The shorter blades will probably cause it to hit this RPM too quickly. Perhaps I will add washers to increase the air gap distance in the alternator. I think the air gap will need to be larger since the blades I am using are shorter. If the alternator over powers the blades then it will not spin up fast enough to avoid stalling in low winds.
5. Finally, I need to figure out the best way to protect the steel parts. I would like to powder coat the entire thing, but I hear that is very expensive. I will call around but it is probably cost prohibitive. So perhaps I will try to call some automotive body shops and see if they can paint it for cheap using the last bit of paint from a run. If I can’t find someone else to paint it I will just paint it myself with steel etching primer and acrylic enamel paint.
Also, here are a few posts on the discussion forum that I posted in the last couple of weeks or so…