WIND REPORT FROM TORNADO ALLEY
1/19/2007
 
These recent storms were a major test for our Vertical Axis Drag Propulsion involute Spiral Wind Turbine”, or “VADPIS WiT” for short, which is still too formal for my tastes.  Can we give it a personal name like “Wendy”? Most of you have seen Wendy perched above the garden gate, (see attached pix in snow) surrounded by tall evergreen trees that absorb the wind in their graceful dance and buffet it around in swirling ever-changing gusts.  Even in these recent powerful storms, winds were mostly under 20mph by the time they reached Wendy, and frantically changing direction on a whim.  Wendy responded well to the fickle wind, without seeming to mind much except when there was momentary backwash suddenly stopping outgoing air.  A structural problem from a couple of previous accidents , however, limited Wendy’s top speed to about 80rpm.  Faster than that, and Wendy would start shaking from the buckled top leading edge of 2 vanes. (We need to install the lower brace cables and leading edge reinforcement)

I left the bicycle light generator engaged sometimes, and we would see the light go on and off intermittently (5 mph startup?). Several times I had to leave the big bicycle motor pressing on the bicycle wheel, which would spin in the bigger gusts (10mph startup?).  I tightened the lashings & cable tension, untangled the chain, checked wind speed in the driving rain and rescued the turbine from self flagellation on the stay cables …so far so good… then the last storm changed direction, now out of the West, straight from the water right up the draw between the high trees.  The bottom nut of one guy cable unscrewed and the turbine mast ripped from its bottom mounting and plummeted to the earth. Miraculously, relatively little damage was sustained, and this mishap may have saved Twister, in light of what happened later that night.

All of this I discovered the next morning. The big tent had collapsed from a gust so powerful that it first blew in one triangular tarp with such force that it ripped a dozen straps out of the truck-tarp material on one side, knocked loose the poles on the other side, ripped 5 more straps out of the tarp as it wrenched it off the remaining poles, accordioned the tarp into a bundle under the rest of the tent that fell on top of it.  None of the poles were damaged, and the tarp is repairable, but if that gust had hit the wind turbine, it would surely have ripped the top of the vanes off at the weakened crimps! So I feel fortunate that nothing more severe happened, and I think Wendy could easily sustain 50mph winds when it gets repaired and strengthened, perhaps much more when we get a variable-resistance alternator on the shaft.

So now we need to make these repairs and look to the next project, which is either to…

·      make a boat propelled by Wendy, so we can blow our way around the Sound, fastest into the wind. Could be a test prototype of 3 sailboards, steered and shifted through remote control (by Leonard Good)….or

·      suspend Wendy upside down from two stationary boats anchored in the current off Bush Point and see how much power we can generate.  This will give us valuable torque data with much greater power from a relatively slow-moving current. It can also show streamlines of fluid flow (with dye injection). Who has a simple accurate method of measuring current speed?

I’m inclined to try the second option first, since it could be done in a single day and would give us lots of valuable info.

Further thoughts & suggestions?  Who has a low-to-the-water boat?….two boats with good anchors?…….maybe even a floating dock with good strong current flowing by at high tide?

     _ITI_         
     { *|*}        
         V        
=+---<   >---+=        
         ( . )        
         I   I        
         I   I        
         I   I        
         I   I        
         I   I        
         I   I        
         L L

Fun & Magic in the New Year,

LAD
 

1/20/07

Steve,

 

Delighted to hear of your interest in this exciting development in VAWT technology.  I hope I can convince you to build one of this design.  2003 was the beginning of this stage of prototype development, but the latest one was finished last June, although not tested much. I recently updated the website report.  I’ll add recent discussions.  I should put you on the Wind Turbine list and I’ll send you further developments.  Did you see the video?

 

I have seen both those spiral wind turbines before, but am fascinated with the Mag-Wind. I would like to get mine and theirs connected to the same generator set-up and compare them.  The three-vaned involute has perhaps a third less material as the 8-vaned Mag-Wind for the same wind shadow, and the guy cable assembly is cheaper and simpler than their roller bearings, so it would be cheaper.  They don’t divulge much of their “product”, so I suspect it is really at a pre-commercial stage right now.

What wind speeds do you have there, which is where?  Unless you have steady 20 mph winds there you would need to build a larger one.

After I did the phonograph disk size prototypes, I built a small crude triangular sailed one, which spun like mad and got me all excited to build a larger one, which was two mirror ones with the disk in the middle removed.  This, I thought, would give twice the surface area and twice the height, with the greatest surface area higher.  It was a dud, a big disappointment, which is one reason I dropped the project for 30 years!  So we built this single one with the disk.  It would certainly be something to experiment with further, but not by me at this stage.  There are many other variations to test, as mentioned on my webpage, including 180° involutes, which might be better in high winds, or even 360°.  Remember, in drag propulsion, increasing the surface area of the vanes impacted by the wind increases the momentum of the turbine, and I expect there are optimum configurations for different wind speeds and conditions.

I would like to build a 12 foot diameter version of the present 4ft dia. one.  That would give nine times the sail-vane area and get power from light breezes. Scaling up to that size should not be difficult with the triangular vane/guy cable approach.  Look at the much heavier and taller crystal swing with 3/16” cable holding it up, loaded with spinning adults, for 33 years.  The top bearing is from an old model-A front wheel and has only been repacked once. You can’t beat this arrangement for lightness of construction and least stress on bearings, which is the main reason why I didn’t use a cylindrical profile with bottom bearings on a super strong mast, and why sail boats generally have triangular sails with rigging holding the top of the mast rigid.

No I don’t have a satisfactory generator – a low-speed direct drive electronic-controlled one would be so much better.  Any recommendations for a 200 - 500 watt alternator?

I could draw you up some enlarged plans to cut out of 4’ x 12’ aluminum sheets.  In fact, I will eventually have the aluminum sheets laser-cut with tabs and slots to join the bottom of the vanes to the disk.

Let me know how I may help and what other ideas you have.

Warm regards,

Larry

-----Original Message-----
From: sredmond [mailto:sredmond@snolab.ca]
Sent: Saturday, January 20, 2007 9:50 AM
To: dancer@stiltman.com
Subject: (Rescued) VERTICAL AXIS INVOLUTE SPIRAL DRAG PROPULSION WIND TURBINE

 

Larry Dobson:

 I came across your web site and this article on your wind turbine design and experiments recently while looking for novel VAWT (http://www.stiltman.com/html/wind_power.html ).  Since this particular result looks to be dated about 2003, I was wondering if you or anyone you know of has taken this further, to improve performance or understanding of the design. 

Although I have yet to build my first decent wind generator, that is my goal, up to a house-sized system in the order of 10+ kW capacity. Of course I’ll start small if it is experimental.  I am an electrical engineer, and have more in the way of electronics than gears in my junk box. I will undertake some simple mechanical construction to move forward.  I have been attracted to Savonius and Darrieus designs, and VAWT in general. 

I came across some very elegant looking and functional VAWT designs recently, and yours caught my eye as having some of the same qualities.  Have a look, e.g., http://www.windside.com/design.html ,  http://mag-wind.com/ .

I am also interested in variations which you may have tried, and generally what tends to make this circle involute design work better or worse.  For instance, why did you use a circle involute of 240 degrees and not something less, more like 180 deg? Did you have some considerations for preferring a conical over a cylindrical shape? If you used cylindrical shapes, was the torque and power essentially doubled compared to the conical shape, in proportion to the projected area, or is there more to it?  Although it’s purely intuitive on my part, the ‘flat’ bottom seems to be a potential problem if the wind isn’t strictly parallel to it, and I wonder if you tried something like a ‘double-ender’. Did you resolve a generator system that was satisfactory, and do you have some power output data?  Would the 53” high x 48” diameter vanes be able to deliver in the order of 1+ kW?

Regardless of what you can add to what you already posted, I’d just like to say this looks a little bit special, and I’m going to give it a whirl and whip up something similar.

Thanks for publishing your work.

Steve Redmond
tel: (705) 523-0029
email: steveredmond@sympatico.ca