I'm building a HAWT

[rcavictim]

As some of you are aware, about six years ago I began a very ambitious scratch built, DIY endeavor to build a VAWT to enable me to go off-grid.  That project has been an enormous challenge in many ways but is nearly completed.  If there were blades on it today, it would be making power today.  The four large blades, each the size of a small airplane wing, sit patiently awaiting my attention at the base of the large machine in my work yard.  Most of he work on the blades has been completed but they still need to be skinned.

As we all know, as far as going off-grid goes, you have to have back up systems in place in case your main source of power breaks down or for off-time to perform preventative maintenance, etc.  In my case if the big VAWT were to misfire in January here, it would be a long cold winter before it got warm enough outside for me to get to any repairs.  It is therefore essential that I have a second wind tuirbine here in operational status as a back-up.  The bonus is that although the main reason to build a second wind turbine is to have a back up machine, I would naturally be using it also as a source of energy, even with the larger VAWT operating.  The big VAWT won't make as much power as I can put to good use if one considers electrically generated heat for the house as an example of good use.

Last year I came up with a design for a HAWT which would be in the 2+ kW class to perform my backup requirement.  I did not want to clutter my field with unsightly guy wires so a totally free standing tower was needed. Complicating the issue is that the finished system can have no foundation.  It has to be stable merely sitting on the ground.  This is to avoid permits and taxation issues.  It needed to be tiltable to provide ground access to the turbine without climbing.  It had to be a motorized tilt system that I could operate working alone.  The tower had to be high enough to get the turbine into productive, non turbulent wind.  My design will place the turbine hub at approximately 66 feet.

It has been an enormous amount of welding, especially making the prefab 20 meter long tiltable 'stick'.  I made use of the inventory of 4-1/2" x 0.125" wall steel sprinkler pipe which I lucked across and also put to good use making the larger VAWT.  A single pipe 21 feet long is very stiff, but I found when I had welded three lengths end to end that the finished pole had the rigidity of a well cooked piece of spaghetti.  To fix this I welded a 12" x 12 " box frame around the entire length, tapering the frame the last 10 feet towards each end.  The box frame consists of twelve, 1/2" diameter solid cold rolled steel rods  running the length of the 63 foot  center pipe.  The surrounding box is welded to the central pipe every five feet through angle iron standoffs.

A substantial pyramidical shaped base frame was built with a solid steel pin at it's top where the tiltable tower will pivot 1/3rd up from the bottom of the tower height.  A gin pole and 3/8" steel aircraft cable is attached to the tilting section to prevent tower sag and to assist taking the weight of the nacelle and blades during the tilt up or down operations.  This drawing shows the basics of my tower design.

[rcavictim]

The second photo is an aerial shot of my work yard.  You can see my ambitious VAWT , the Big Green Thing aka BGT is on the left.  Look for the long white pipe that begins at the base of the BGT and ends part way along the barn building to the right.  This is the 20m tiltable tower section and is where I fabricated that large weldment.  This is the best photo I have which shows it's true length in some sort of perspective.

[rcavictim]

Last weekend with the help of a couple of friends I was able to relocate the tilt up tower section and the pyramidical base frame, now completed and painted, out to the field where this system will be set up shortly.  I welded a set of car ramps upside down under one side of the base unit and these acted like skiis, enabling me to pull this weldment quite easily with my wheeled loader.  My friend rode the beast like a large jet ski in my field, the wind in his hair and a wake left behind in the grass.  See picture.

[rcavictim]

Here are a few more pictures of the relocation drill last weekend.

[rcavictim]

Here is a close up picture of the hinge point which accepts the solid 2" steel pin at the top of the pyramidical base tower.

I have some more detailed construction photos which I will post later.  I need to re-size them first.

[Tom Reed]

Nice work! How do you find the time to post?

[deeiche]

I am always in awe when I see the things you do.

[mobile_bob]

if i have said it once, i will say it again

your ambition is only surpassed by the quality of your build!

man dude, you are my hero!  i have no idea where you get the energy to design, much less
drag all that iron together and then fabricate stuff as large as it is, and do it in such an appealing manner.

artistry in iron in my opinion.

me?  i don't have that kind of energy or physical capability now, and quite frankly i am pretty sure i never did... wow.

that big machine, when you get it deployed makes me think i ought to put it on my bucket list as one thing to buy an airplane ticket to come and see.

i am not sure the average guy has any idea or is capable of fully appreciating the amount of work it takes to build such a machine..  holy crap it isn't like you can lay it all down on a bench and weld it all up in position.  just the thought of climbing up there to get in some over extended position to hang on by the hairs of my teeth, with 40 plus feet of welding cable draped over my forearm, and then have the strength to keep a steady arc?

even if that machine never makes a kwatt/hr, it is as far as i am concerned one of the 8 wonders of the DIY world!

great work, i so look forward to seeing that thing turning out power on a youtube clip some day soon.

bob g
ps. i am equally impressed with the smaller unit.

[Jens]

Holy crap batman, that is some very impressive metal construction!!!
I have to agree with Bob ..... where do you find the time and energy ?

BTW, what's with the antenna farm ?

[rcavictim]

Thanx for the compliments guys!  Bob, you are absolutely right about ordinary sheeple's inability to realize the level of detail and scope of this project.  Consider also that in the case of that large BGT, VAWT, at no time during building it have I EVER had a second pair of hands on site to help lift this or hold that.  Getting some of those pieces of steel wayyyy up there posed an enormous challenge.  In some cases purpose built jigs had to be engineered.  I'm close to completion of the four large airfoils which can be seen in that yard picture above.  One has a skin of sheet steel pop riveted to it but the wrinkling was so bad I have to drill out some 300 pop rivets and find another way to do this.     Like you I suffer some physical problems and I have to push myself really hard to do this stuff.  Getting old doesn't help either.  When I started the BGT I was able to handle those 21 foot lengths of pipe by myself.  This year I discovered that I am no longer able to carry them around the yard like I once could.  I am so thankful that I started these projects when I did.  Starting the BGT just a year or two ago would have been a total no-go.

Anyone who has tried to DIY a wind turbine knows how critical finding the right generator is to this task.  Preferred are high pole count, low RPM, neodemium magnet based alternators.  Some brushless AC servo motors used in CNC as machine controllers have been obtained by people like me, tilting at windmill types    and used to good effect.  Most of these servo motors are unfortunately high speed so gear boxes are necessary to increase the propeller shaft speed.  In searching for suitable gearboxes in scrap yards and surplus stores for the entire past decade, I can tell you that they practically do not exist.  Those that do are encased in very heavy cast iron gear cases, not optimized to hoist 60 feet in the air.  If one is fortunate to find a slow speed PM servo motor, one has the ideal generator for a wind turbine.  

I recently chanced across some 24 volt AC, 650 watt rated, 3-phase brushless wheelchair hub motors.  I discovered that they can put out enough voltage to deliver 15.5 VDC to a 12 volt lead acid battery at just 200 RPM.  At this speed they will charge that load at about 350 watts.  It turns out that if one removes the mechanical brake and electric brake activation solenoid coil assembly from the back of these a hex shaped short shaft, normally used to engage the brake, becomes exposed.  This stub is a perfect fit into a standard 6 point deep impact socket.  I purchased three deep socket impact sets to get three of the required 7/8" socket size and make couplers out of them so that I can put four of these wheelchair motors in series on the same propeller shaft.  My plan is to put a 3-phase bridge rectifier on the output of each individual motor and then wiring all four 15.5 VDC outputs in series to give me the charge voltage necessary for a 48 volt battery bank.  If my turbine blade can achieve ~300 RPM, I should be able to reach my 2 kW power production target.

I attach some pictures of these nifty little motors.  There are 44 NIB magnets inside an aluminum drum with a steel flux band on the ID of the drum and on the OD of the magnets.  There are something like 48 poles in this motor.  Cogging is very, very minor.  With all three output leads shorted together the braking action is smooth as silk and very strong.  With the brake components removed as I am using them they weigh in each at just 20 lbs.  

I am now in the process of building the nacelle which holds the four of these in an inline stack.  Before someone mentions it, I have arranged rubber compliance for every motor in it's three mounting bolts so that slight imperfections in the shaft alignment geometry does not end up wiping out the nice ball bearings in these very nicely manufactured motors.

The propeller shaft size is 1-1/8".  I picked up a rather unusual find at the recycling place where I got these wheel chair motors a while back.  It is a WW-2 fighter trainer propeller, 8 feet long.  Just for fun I have manufactured a keyed hub so that I will be able to try this prop on this wind turbine.  It is way too small however to make the power I am designing for. At 100 lbs it might be too heavy for my tower. For the 2kW+ power target I am shooting for I need to manufacture a 3 bladed propeller some 13 feet in diameter.  The last photo here shows my airplane prop hanging off the front of the nacelle under construction.  This is the closest sort of thing that I do nowadaze for actual fun.  

This entire project is very much being designed as a R&D test bed.  Tilt up tower, etc.  Even the furling system is research oriented.  I decided against using one of those tail fin driven furling systems that rely on a balance between the system size and weight, and the propeller characteristics.  To implement one of those you need to have the actual blade you plan to use in hand.  I do not yet know what my blade weight will be.  Furthermore, those mechanical jerk and flip furling systems are extremely hard on the turbine shaft and roots of the blades.  I made the executive decision to power the azimuth axis of the turbine, pointing in or out of the wind, by smooth, precise electric motor control.

This involves a clever system I came up with that will employ a remote 3-cup anemometer tachometer generator to give me a wind speed related rising voltage.  That voltage will drive a small 28 volt gearhead motor to rotate a plate with two micro switches on it against a spring.  This switch assembly will in this way be rotated from 0-90 degrees around the bottom of the shaft of a small wind direction sensing vane located on the back of the generator nacelle.  This free wheeling tail fin will always head towards the direction the wind is blowing.  The closure of the microswitches on the rotating plate will command the DC gearmotor that turns the nacelle in azimuth.  One switch closure makes the system turn CW until it lines up with the null point of the vane switches.  The other switch closure makes the nacelle turn CCW until the same null point is reached. As wind direction changes, this will cause the nacelle, and thus the turbine propeller to follow it.  If there is low wind, the position of the rotating plate upon which the microswiches are mounted is aligned so that this null is directly in line with the nacelle pointing direction.  If the wind is at a high level which adjustments have determined is where the blade must be fully furled, then the tachometer generator will make a voltage sufficient to rotate the switch plate against it's balance spring to place the null of the microswitches at 90 degrees to the nacelle pointing direction.  In this instance the nacelle will do an azimuth move and stop moving when it finds the new null spot where the tail fin is pointing 90 degrees off the pointing of the nacelle.  The beauty of this system is that it can be calibrated to do smooth partial furling automatically so as to keep the blade at max power point despite winds that would normally be the cause of full furling.  I hope I was able to describe this concept clearly enough.  I plan to use mosfets between the microswitches and the DC azimuth drive motor.  In this way, due to the high Z of the Mosfet gate, I can add some integration capacitance to smoothen the response of the azimuth drive to ignore short turbulent gusts and only concentrate on the actual trend.  This and the electric drive ought to go a long way towards relieving my (likely DIY) blades of destructive stress and overspeed.

In answer to a question from Jens.  The antenna farm is my astronomical radio observatory which I have been building here as a back burner project.  I hoped to end up with a community teaching resource for high school and university students in physics, astronomy, computer programming and electrical engineering.  I've brought it a long way by myself but require actual grant funding or help from a philanthropist to get it over the hump to fruition. The dish antenna in my avatar is on site here now awaiting my attention.  It will make a very nice radio telescope.  This project is looking less likely to happen as the world implodes financially. This project represents a lifetime of struggle.  It is Big Picture stuff.  The wind turbines are just pieces of the infrastructure part of that bigger picture.  I have always believed that lack of funding was not a good enough excuse not to proceed with the really important pursuits of intellectual mankind.  Astronomy is arguably one of those really important pursuits.  With the wind making electricity here, having to come up with money for electricity is one less funding requirement standing in the way of tuning in on the cosmos.  One less barrier to DISCOVERY!  

BTW, there is a discussion about high pole count pancake generators along the lines of the wheelchair motors I discuss here at this link.   http://www.microcogen.info/index.php?topic=2800.0

In this other thread I first learned the term "wound in hand", referring to the number of paralleled conductors would in a motor slot to facilitate the mechanics of winding in tight spaces and tight radius turns that are impossible to accomplish with really large magnet wire sizes.  For anyone interested, the wheelchair motors I have described are wound with '6 conductors in hand'.  You may be able to see this in the photo I provided.

[Frank S]

First off I like the tower base solution to a non guyed free standing tower the pyramid looks to have a nice height to ground coverage ratio plus you have the capability to position several heavy blocks of concrete or other weight on the base structure to add additional stability if needed. The tower? well its a tower that looks like an artwork befitting to the rest of the structure, and should be quite suitable for your turbine. If latter you find you need taller or stronger you can always change it out.
your Assembly for your generator is so far first rate as far as I can see with one exception that I see. and this could be due to the incomplete status of your assembly. I will not try to second guess that.
But the one thing I noticed (and again bare in mind I don't know where your thoughts are.) it has to do with the shaft for the  Turbine. From what I can see you have 1 bearing on the shaft and it looks like you will be using the generator hub itself as the 2nd bearing That worries me unless you have plans to place a second support bearing further out to nullify any loading in the generator. or the coupling
Another thing I was thinking was if you were to relocate the turbine shaft above the nacelle then use a cog belt drive you could put a large sprocket on the turbine shaft and a smaller one on the generator shaft . You could then also use a hollow turbine shaft as well and add in an active and even a passive pitch control This would also allow you the possibility of using a much larger diameter turbine blade setup if need be, and you might even see that your generators could produce 3 or even 3.5 KW or more if you additionally added in  forced fan cooling

[rcavictim]

First off I like the tower base solution to a non guyed free standing tower the pyramid looks to have a nice height to ground coverage ratio plus you have the capability to position several heavy blocks of concrete or other weight on the base structure to add additional stability if needed. The tower? well its a tower that looks like an artwork befitting to the rest of the structure, and should be quite suitable for your turbine. If latter you find you need taller or stronger you can always change it out.
your Assembly for your generator is so far first rate as far as I can see with one exception that I see. and this could be due to the incomplete status of your assembly. I will not try to second guess that.
But the one thing I noticed (and again bare in mind I don't know where your thoughts are.) it has to do with the shaft for the  Turbine. From what I can see you have 1 bearing on the shaft and it looks like you will be using the generator hub itself as the 2nd bearing That worries me unless you have plans to place a second support bearing further out to nullify any loading in the generator. or the coupling
Another thing I was thinking was if you were to relocate the turbine shaft above the nacelle then use a cog belt drive you could put a large sprocket on the turbine shaft and a smaller one on the generator shaft . You could then also use a hollow turbine shaft as well and add in an active and even a passive pitch control This would also allow you the possibility of using a much larger diameter turbine blade setup if need be, and you might even see that your generators could produce 3 or even 3.5 KW or more if you additionally added in  forced fan cooling

Frank,

Thank you for your valuable comments.  It sounds like you have a fair bit of experience with these machines.  That drawing is impressive.  Did you make that?

First off, The pyramid base has five base bolt down plates at the OD.  See picture.  The plan is to have a cement plant custom pour me five, 2' x2' x 4 ' cement blocks with a weldment inserted which I will provide which has significant rebar welded up inside and a substantial steel plate to end up being centered on the top of the block once cured.  I will weld a 1-1/8" bolt to each block and the turbine base frame will bolt down to these five blocks which themselves sit on hard clay layer exposed just 10" below my excavated topsoil.  I have been welding up the rebar assemblies for the past three days. I hope to have these foundation weights delivered and in place late this week.  Since delivery will coast me $300 and the truck can carry more than the five blocks I need for this job, I am also making four extra weights to be used as extra ballast for the BGT.  So... the pyramid frame seen in these pictures will actually be sitting over a foot above the grass level perched on what will look like rectangular concrete foundations, but could be relocated with my loader and a fair bit of work down the road if necessary.  It still qualifies as just 'sitting on the ground, no foundation and is movable'.  With each block weighing over 2000 lbs, and the generous footprint, I will sleep well enough comforted that the tower will be resistant enough from blow over.

Your concern about the first generator being used as the rear bearing for the propeller shaft troubles me.  I figured I was going to be OK with this plan.  The wheelchair motor has two fairly substantial bearings in it close to each other.  This would be seen for practical purposes as a single, beefier bearing to the rear of the prop shaft.  I attach a close up photo of the back of one of the generators with the brake section removed.  It shows one of the bearings and the six sided shaft I use to couple to the following unit.  I could add an additional front nacelle bearing, just like the beefy single flange block bearing now employed ,but this would set my propeller farther forward than I had counted on from a nacelle balance point perspective.  I'm going to give this some serious thought. If I am going to make a modification like this, now is the perfect time.  The front bulkhead of the nacelle is all 1/4" steel so it is heavy enough to handle such an add-on.

I like the idea of a speed up with toothed belt but do not want the extra weight and the extra complications building weather covers.  I am also not funded for purchasing such components. That pair of pulleys and a belt could set me back $500.  I just cried hard because I had to purchase a new 80 tooth, #50 roller chain sprocket (16" diameter) for my azimuth drive system because the one I had tried to use from a scrapard was too worn out and the chain kept binding. This was $135 not planned for.  We in Canada sure have to bend over hard to buy hardware up here.  I am going to fly it initially direct drive as planned. 

The higher speed would be attractive as it would produce increased voltage.  At the same amperage the I2R losses of the windings would make no more heat than normal so a speed increase would be a legitimate way to get more wattage out of these units without overheating.  I have the opportunity of rewiring the outputs of the four bridges to say series parallel to accomodate a doubling of produced voltage if I need to.  Increased voltage would not be bad anyhow because it would possibly lower the wind regeime that the wind turbine could charge a 48 volt bank in without having a step up capable charge controller.  I will have to address a charge controller once the turbine is up and running.

[Frank S]

The thing that caused my concern is having the coupling between your 2 most important bearings on the whole project. That coupling even if it were a pressed fit is a potential flex joint. if there is any way to place 2 bearings on the same shaft even if they are back to back one being inside and the other outside then the moment would be canceled out instead of being transmitted through the coupling.
you 14 or 14 ft diameter turbine will create a huge gyroscopic force this in turn is translated into the shaft which becomes a moment of inertia perpendicular to the shaft. Even if a shaft has a slight amount of flex as long as it is not an accumulative fatigue stress that builds up in the shaft is would not be a worry. but transmitting the moment through a single bearing into the coupling will eventually cause the coupling to become loose and fail.
If you have a Dial indicator and a way to clamp it to you framework set the indicator point against the shaft next to the red coupling then try to move the end of the shaft up and down take note of the movement.then use your air plane prop install it on the shaft and try to move the tip of one of the prop blades  at rt angles to the shaft and the indicator take the readings again note how much different it is. and know that the prop has no way near as much leverage as the tip of the turbine blades will be.
As far as the drawing I posted that is just a part of a 5 to 30 KW generator that I am designing I have the stater the cooling fan the rotor and a lots of other stuff suppressed out of the picture for clarity to show the principle of the pitch control concept. The design that i have been working on could have either internal or external stater direct driven epicyclic gear driven or as shown belt or chain drive but I am dealing with the prospect that the turbine blades might be upwards of 20 meters in diameter or larger. depending on what wind zone it might be mounted in.
And no I do not have any RE power at this time my last wind machine was a Chrysler 105 amp Alt re wired and modified for 9 ph mounted on a sail fan like a water windmill. as an experiment over 30 years ago

[rcavictim]

The thing that caused my concern is having the coupling between your 2 most important bearings on the whole project. That coupling even if it were a pressed fit is a potential flex joint. if there is any way to place 2 bearings on the same shaft even if they are back to back one being inside and the other outside then the moment would be canceled out instead of being transmitted through the coupling.
you 14 or 14 ft diameter turbine will create a huge gyroscopic force this in turn is translated into the shaft which becomes a moment of inertia perpendicular to the shaft. Even if a shaft has a slight amount of flex as long as it is not an accumulative fatigue stress that builds up in the shaft is would not be a worry. but transmitting the moment through a single bearing into the coupling will eventually cause the coupling to become loose and fail.
If you have a Dial indicator and a way to clamp it to you framework set the indicator point against the shaft next to the red coupling then try to move the end of the shaft up and down take note of the movement.then use your air plane prop install it on the shaft and try to move the tip of one of the prop blades  at rt angles to the shaft and the indicator take the readings again note how much different it is. and know that the prop has no way near as much leverage as the tip of the turbine blades will be.
As far as the drawing I posted that is just a part of a 5 to 30 KW generator that I am designing I have the stater the cooling fan the rotor and a lots of other stuff suppressed out of the picture for clarity to show the principle of the pitch control concept. The design that i have been working on could have either internal or external stater direct driven epicyclic gear driven or as shown belt or chain drive but I am dealing with the prospect that the turbine blades might be upwards of 20 meters in diameter or larger. depending on what wind zone it might be mounted in.
And no I do not have any RE power at this time my last wind machine was a Chrysler 105 amp Alt re wired and modified for 9 ph mounted on a sail fan like a water windmill. as an experiment over 30 years ago

Frank,

Yes I have a dial indicator or two.  You have convinced me on the need for a second front shaft bearing.  I'll see what I can come up with and post back here about my plan.  Thanx for your valuable input!

That design you are working on is very precisely documented.  When I toss parts together I seldom have anything more detailed than the rough sketch of the tower I posted above to work with and what is in my head.  My hands usually know what to do.  Obviously that approach doesn't work when others are involved in the manufacture of components for the system as appears to be your case.

I was thinking about the balance issue introduced by moving the propeller forward.  It turns out I have a fifth wheelchair motor which wouldn't be a lot of work to add at the rear of the nacelle frame since the back section is not completed yet.  This is attractive from  the 20% cross-the-board gain I'd get in system output voltage.  I worry about the weight I'm putting up there though.

Regarding my tilt portion of the tower.  I don't see ever needing to make it taller. As for  strength, it will have to do as is.  I have so many other projects on the go presently and then planned that I just need to get this system up and running as quickly as practical.  If the tower is happy with the weight and looks like it could handle say 100 lbs more then maybe later an upgrade to a belt speed increase as you suggest could be performed.  This would enable a slightly larger prop to be used to good advantage.  Perhaps a 14-15 footer.  After this one is running I have to direct my full attention back to completing the main BGT VAWT system.  FYI, that system has a swept volume of about 45 square meters (rectangle seen by the oncoming wind).

[Frank S]

Back in the days when I was a one man show and anything I did in my factory was pretty much up to me as long as I could put food on the table and keep the bills paid. Now I am part of a much larger corporation I still do as a darn well please but every square foot of floor space is valuable so I don't have my off the wall project space like I used to have. plus with 50 to 60 workers on the floor if I were to start building something all of them would want to try and stand around to see what I was doing. Neither I nor the company can afford for that to happen. Most of my time is tied up in designing products and ongoing projects, so I do 90% of my prototyping now on my computer.
Not like the old days when I sat down with a customer and sketched out a design for a 16 ton cap freight elevator with a 4 story rise on a couple of table napkins and managed to convince him to hand over half the price of it in cash with the contract being one of the napkins.