Update on VAWT Model Project
By wind4Reg, Section Wind Posted on Fri Oct 28th, 2005 at 05:40:52 PM MST
Short Video

I thought I would submit an update on my progress with my VAWT straight bladed model. I have included a small video (small enough for dialup only 175KB) that shows the windmill in action. I did hook up a chain drive to a 108VDC motor and a auto lightbulb for fun. I was able to get some data on the performance and with a sloppy chain drive that really wasn't well aligned the windmill spun to a topspeed of 170 RPM open circuit and ran at an average speed of 116 RPM open circuit. I figured that I should be able to get at least 150 RPM under load with a properly designed transmission system. I do have another video of the windmill running with the chain drive connected to the motor and the lightbulb acting as the load. It actually lit the small lightbulb so that was at least a small feeling of achievement. I will post that video shortly. Well I knew it was bound to happen, since my windmill was just a model, it came crashing down. We had some extremely high winds 60km/h plus gusts reaching much higher. The bolt that went through the main bearing sheared off and the mill came tumbling down off the roof. It wasn't the soaring through the air killing everyone in it's path kind of story that you are warned about on here :-) but it did crash to the ground in front of my garage. The sad news is that the blades were too badly damaged to fix, so it looks like I will have to build another model, only bigger this time and stronger. It doesn't hurt too bad since the only thing I actually bought that is no longer usable is the pop rivots holding the trailing edge together, the rest of the mill was made from scraps. This one had 36" blades and a 60" cross arm length. I think I should triple that size on the next one... why not. Reg

Update on VAWT Model Project | 17 comments (17 topical, 0 editorial)

Re: Update on VAWT Model Project (3.00 / 0) (#1) by Norm (peppysue@suite224.net) on Fri Oct 28th, 2005 at 12:50:20 PM MST (User Info)

Looks good !  Love to watch 'em spin !  Your next one make arms a little shorter... but make 3 units stacked on top of each other and 45 degrees apart from each other will be smoother less vibration less likely to fly apart.    I guess it's time to build one myself.                    ( :>) Norm. ( :>) Norm

Re: Update on VAWT Model Project (3.00 / 0) (#2) by ghurd on Fri Oct 28th, 2005 at 01:14:29 PM MST (User Info)

"I will post that video shortly" I'll be waiting for it! G-

Re: Update on VAWT Model Project (3.00 / 0) (#3) by cr8zy1van (salsa117@hotmail.com) on Fri Oct 28th, 2005 at 03:30:13 PM MST (User Info)

Wind4Reg: Sweet job, I myself am building a VAWT of about the same size. My blades are about 34" long at this point but I also have thought about increasing that significantly. I am using a trailer axle, much like the HAWT guys. I mounted 2 pieces of square tubing on the bolts, and my blades are attached to those. I do have a couple questions for you. What angle are your blades set at? What airfoil are you using? I tried the airfoils pictures here: http://www.fieldlines.com/story/2005/10/7/63930/5558... Unfortunately the wind has died down completely and I have not had much luck testing.

Re: Update on VAWT Model Project (3.00 / 0) (#4) by windstuffnow (elenz(at)windstuffnow(dot)com) on Fri Oct 28th, 2005 at 04:45:49 PM MST (User Info) http://www.windstuffnow.com/main

Nice job Wind4 !      Let us know how it come out, love to hear some data on it! . Have Fun! Windstuff Ed

Re: Update on VAWT Model Project (3.00 / 0) (#5) by hobot on Fri Oct 28th, 2005 at 07:45:13 PM MST (User Info)

I'm mere lurker learner on list and never saw such a design before and certainly not one spining up but got a hit off your efforts. Watched and stopped, watched stopped video and have a question. Is it an optical illustion of carmera or are the blades skewing/pivoting vertically when turning fastest? hobot

Re: Update on VAWT Model Project (3.00 / 0) (#6) by sahlein (j.sahlein@att.net) on Fri Oct 28th, 2005 at 09:17:40 PM MST (User Info) http://att

Good eye! I thought I saw the same thing. Looks almost like they may be a bit heavier at the bottom. Joe [ Parent ]

Re: Update on VAWT Model Project (3.00 / 0) (#7) by Random Guy on Sat Oct 29th, 2005 at 09:43:01 AM MST (User Info)

The vertical wings are twisting around the horizontal support. I loaded the clip into Windows Movie Maker and single stepped through it. It's no wonder the mill did not survive. If I could figure out how to upload images I could post a couple of frames. I will try later.

Re: Update on VAWT Model Project (3.00 / 0) (#8) by cr8zy1van (salsa117@hotmail.com) on Sun Oct 30th, 2005 at 09:06:32 AM MST (User Info)

I slowed the clip down 8x. You can download a clip from the original clearly showing the twisted wings... HERE, 173 KB Its in Windows Media Format...

Re: Update on VAWT Model Project (3.00 / 0) (#9) by wind4Reg (reg_manzer at hotmail dot com) on Wed Nov 2nd, 2005 at 05:51:58 AM MST (User Info) http://users.xplornet.com/~rmanzer/windmill/

Hi, you guys that noticed the twisting are very perceptive. After it ran for about 2 weeks it started twisting more and more, to the point I thought one of the blades was going to twist off due to metal fatigue. There are three main reasons it was twisting, first the crossarm was very light angle iron and not box or round tubing and under the stress it would allow some twisting action, then the second thing was the brackets that attached to the blades were too light gauge metal and were bending. The third thing was the internal skeleton, the backbone ;-) was 1 1/2 " ABS plastic pipe that also allowed too much flex. I considered this a test model and never really intended to get any power from it, its sole purpose was to see if it would fly and how the design worked, plus I really wanted to know if all the negativity about the H-rotors not self starting was really fact. Interestingly enough though even when the blades got twisted really badly and were not even twisted at the same angle it still flew reasonably well, but not as good as when the blades were straight of course, but I was surprised to see it still self start and fly with the twisted blades. It actually survived all the twisting and I eventually took it down and fitted it with a chain drive. To see a video of it flying with the blades really twisted  follow this link (467KB): Mr. Twisty I had also mentioned posting a video of it running a DC motor with a chain drive. I have that video now to post. In this version of the windmill, I did change the brackets to the same angle iron as the cross arm so this stiffened up the unit quite a bit and really helped with the twisting but it did not completely eliminate it for the other two reasons mentioned above, plus the main bearing is not a precision bearing and definitely not what I would use in a production model plus it was a bit sloppy for this job. The bearing is basically a belt drive idler pulley from a snow blower welded to the top of my steel pole. Yep, I built this puppy cheap. Here is the link to the video of it running under load (auto lightbulb) with the chain drive setup (503KB): Chaindrive Note: if you look real close you can see the bulb lit, it is taped on the pole with red tape, its hard to make out. Someone had asked what angle I set the blades to, I used a symetrical airfoil shape and I drew a line dividing this airfoil shape into two equal halves, then I set this line at 90 degrees to the cross arm. Send in more comments, I enjoy reading them. I just found out that there is a machine shop within a 1/2 hour drive that might have the capabilities needed to make some of the parts I need for a larger unit, so I am going to be checking that out, then it will have to pass by the approval committee member {the wife :-) } to get approved for adequate funding. Reg

Re: Update on VAWT Model Project (3.00 / 0) (#10) by wind4Reg (reg_manzer at hotmail dot com) on Wed Nov 2nd, 2005 at 09:48:03 AM MST (User Info) http://users.xplornet.com/~rmanzer/windmill/

Hey cr8zy1van, I just noticed that you asked about the airfoil I used, it is NACA0018. Reg.

Re: Update on VAWT Model Project (3.00 / 0) (#11) by sahlein (j.sahlein@att.net) on Thu Nov 3rd, 2005 at 04:19:47 AM MST (User Info) http://att

Hi Reg, I understand the modifications to beef up the machine to overcome the twisting. The question in my mind is: What is CAUSING the twisting?? Seems like for some reason there is more centrifugal force at work on the bottom of the "wings".  OR Something like that! See my point??  If you have to beef it up, there has to be a reason WHY. Just a nit-pickers point of curiosity....  I'm not trying to slam your machine. This comes from many years of trying to find out why various types of machines tend to fly apart. Joe

Re: Update on VAWT Model Project (3.00 / 0) (#12) by ghurd on Thu Nov 3rd, 2005 at 06:27:54 AM MST (User Info)

I wondered about that too. Is the structure causing uneven flow? Is the top or bottom half 1% better efficiency, or stronger built than the other? Are the materials placed such that it is easier to twist one way than the other? Maybe the wind was crooked? hehe. I also thought that some kind of controlled, even twisting and untwisting could be used as a "furling" mechanism. G- [ Parent ]

Re: Update on VAWT Model Project (3.00 / 0) (#14) by wind4Reg (reg_manzer at hotmail dot com) on Thu Nov 3rd, 2005 at 07:09:31 AM MST (User Info) http://users.xplornet.com/~rmanzer/windmill/

You should never need a furling mechanism on an H-rotor VAWT, see the following excerpt from http://www.eurowind-uk.net : From the research carried out in the UK during the 1970's - 1980's, it was established that the elaborate mechanisms used to feather the blades were unnecessary. The drag/stall effect created by a blade leaving the wind flow would limit the speed that the opposing blade (in the wind flow)could propel the whole blade configuration forward. The fixed straight bladed VAWT (H-Rotor) was therefore self regulating in all wind speeds reaching its optimal rotational speed, early after its cut-in wind speed. This makes sense too and is another feather in the cap of the H-rotor VAWT. Reg. [ Parent ]

Re: Update on VAWT Model Project (3.00 / 0) (#13) by wind4Reg (reg_manzer at hotmail dot com) on Thu Nov 3rd, 2005 at 06:51:41 AM MST (User Info) http://users.xplornet.com/~rmanzer/windmill/

Hi sahlein, this was anything but a precision designed machine, more like a proof of concept that worked well enough that I let it fly longer than what was originally intended. I did not do any blade balancing and I suspect that the blades were not perfectly perpendicular with the crossarm or 100% aligned with each other. One blade twisted more than the other one so there were definitely alignment differences. I guess I personally would not read too much into the twisting given these details and the scrap materials this windmill was built out of, definitely not ideal, but super cheap and a heck of a lot of fun! Reg [ Parent ]

Re: Update on VAWT Model Project (3.00 / 0) (#15) by EWL (info@enterpriseworks.co.uk) on Sat May 13th, 2006 at 05:51:20 AM MST (User Info)

How did you decide on your blade profile(aerofoil)? You have two blades on your model...what would be the implication of having three? I look forward to hearing from you. Hugh...EWL

Re: Update on VAWT Model Project (3.00 / 0) (#16) by wind4Reg (reg_manzer at hotmail dot com) on Mon May 15th, 2006 at 07:00:32 AM MST (User Info) http://users.xplornet.com/~rmanzer/windmill/

Hi Hugh, I read the research done by Sandia, looked at what commercial companies had done and made my decision based on that information. What I found was that the NACA 0018 was a popular choice with companies who were actually building VAWT H-Rotors. One company was even using a fatter profile, the NACA 0021. From the research by Sandia, it looked to me like the NACA 0018 was probably the best all around choice, it seemed to combine the best possibilities for likelihood of being able to self-start and run at a decent speed. So I figured that companies and research facilities had much deeper pockets than I and if they were choosing a NACA 0018 profile, then they had done the necessary research to pick the best choice. I guess you could say that I just piggybacked on their hard work. I recently viewed a Universities Mech Eng website ( I actually got input on that project ) where they tested a NACA 4415 VS a NACA 0018 and various chord lengths for a self starting VAWT project they were working on. All their research was pointing them to the NACA 4415. They saw my windmill on here and contacted me and asked me what profile I was using. I convinced them to give the NACA 0018 a try when they built their VAWT. They did and it outperformed the NACA 4415 quite nicely. That was a good confirmation to me that I had made the right choice. What would be the implication of having three? I am going to find that out within the next 6 months. I expect that it will be slightly slower RPM, however with three blades that means higher solidity and most likely better startup in lower winds, and also the unit should be better balanced with 3 blades VS 2 blades, so hopefully this will reduce some of the extreme forces this type of turbine produces. I am in the process of building a larger unit right now and I am initially putting 3 blades on it. I plan on building the hub assembly so it can be fitted with two blades if the 3 blade configuration doesn't perform well. I am currently working on the blades and just glued together my first two pieces last night. These are huge blades 12 feet long each with a 19 inch chord. It will take me some time just to complete the blades, since I have 78 strips of 2"x3"x12' to laminate to make the blades. I'll have to post some info on this project as it progresses. wind4Reg [ Parent ]

Re: Update on VAWT Model Project (3.00 / 0) (#17) by skipinder on Thu Mar 27th, 2008 at 04:27:51 PM MST (User Info)

He he 'It doesn't hurt too bad since the only thing I actually bought that is no longer usable is the pop rivots holding the trailing edge together, the rest of the mill was made from scraps.' I'm in the same boat, those darn pop rivets are the only thing I've paid for yet... Scrap's great :-)

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