2" diameter rotor for norm

[rotornuts]

Well norm as soon as I read your comment regarding maple seeds on my single blade post I knew I had to do it. 20 minutes later I had a 2" diameter single blade wind turbine that shocked me into thinking my plan may actually work!

I went outside and under the old maple tree I found myself a couple dozen wings, singles that is, took 'em in and started launching them in the air till I could narrow down which one flew the best. Next I located the center of mass by balancing the maple wing on the side of a pin, interestingly it was located about where the wing ends and the seed pod begins,(must be a fluke) so I took a half a dozen more and balanced them as well and they to had their center of mass in about the same locations(just a bunch of flukes I guess). Next step - I took a straw and a pin, poked the pin through the straw, then poked a cut up piece of straw on the pin as a thrust washer, then you guessed it, on went the maple wing. I poked it at the center of mass location giving it  some pitch, took it back off, dabbed a tincy bit of hot glue on the wing over the hole and stuck it back on.

It took some fiddling with the pin to get it loose enough in the straw to spin freely but once it loosened up I could get what looked like several hundred rpm just by gently blowing on it. Of course I needed to test it in a more significant wind so I pulled out the fan cranked it to ludicrus speed and the maple wing turbine disappeared from sight, it must have been doing well over a thousand rpm. Cool, cool, cool.

Thanks Norm for an evenings entertainment. Any idea how many watts I might get?

Sorry no pics, my camera hasn't recovered from its fall to the floor yet.

I dare more people to try this out.

[Norm]

   You're welcome Rotornuts, believe it or not

this thought has been in the back of my mind for

years...if you hadn't posted about single blade

I might never have mentioned it...so thank you

for posting that in the first place.

   And trying it...Not too often anyone listens

to me...Made my day!

               Fun! Yes!

                    ( :>) Norm

[iFred]

I really like simply cheap experiments like that!

I am interested because it is unique, a single blade with counter balance. ummm...

My question is, what is the advantage of a single blade?

would this be more for rpm then of torque?  

Anyone got figures on TSR for a single blade of this nature?

Thanks!

Fred

[rotornuts]

IFred,

The big big big big big big big advantage is that one blade regardless of how wide you make it or whatever else you may do with it will never encounter the wake of another blade excepting its own at which point you may want to try and slow things down a bit(squinting eyes, grimacing mouth, upper body tilting back with shoulder manuvering in front of face type of stuff).

My whole logic train behind this, and bear with, me goes something like this. Achieving reasonable performance at low wind speeds is always a trade off because we attach more or fatter blades to the rotor which quickly brings the solidity factor up and reduces the amount of space between blades for the air stream to re-establish itself before the next blade comes along. To me this problem has become a real pain in the ---. Single blade rotors are known for their high tsr's exactly because they don't encounter these problems till they reach rudiculous speed. I never cared to have a rudiculous speed rotor but then I realized that it doesn't have to be that way. The determining factors in how much lift we can achieve are airfoil L/D ratios, windspeed, and wing area. Period. If you what to increase the lift of a wing you can change one of the above. L/D has been determined by a hopefully good blade design altitude etc, windspeed is fixed by mother nature so all that's left is wing area. Airplane designers moved away from bi and triplanes almost right away because they realized (after good wing design) the best way to increase lift at a given windspeed is to increase area. Sooo, what the heck am I doing trying to attach more blades to get more lift. I've seen data suggesting that a solidity factor of 10% is as high as you should go before you start to induce drag due to interference using a three blade rotor. More blades will only make the situation worse. And here it is, I reason that a much wider than usual blade adhearing to good rules of thumb with regards to the width/length ratio should give good low wind performance and good high wind performance as well because it has good area and is all alone.

You'd be hard pressed to build a single blade wide enough to achieve a 10% solidity without it being a gong show, but the reduced drag of only one blade should compensate leaps and bounds for this. remember we are dealing with low reynolds numbers and small just doesn't work very well.

I would never really suggest this confiquration for a larger machine such as a 30 footer at least not yet because you can fit a real blade on a machine that size.

This is just my latest goofy theory and Norms Idea has made me realize I may be right. The little maple wing rotor will spin by gently blowing on it and it will dissappear if you put it in front of a fan.

Fun fun

[rotornuts]

Actually, I just realized that if I mimicked the the tip to root cord width at station x kinda thing of the maple wing you may get around 10% in a nice design.

[nothing to lose]

As for the balance, I don't think that would be a fluke, thinking about it it makes sense to balance the wing at the seed pod. The wing needs to remain sideways as it floats down to the ground for it to work properly as an air foil wing (helicoptor) and the seed pod is not an air foil but only a weight to drag it downwards and balance the wing. I think you will find nearly all of them  (that fly  well) will be balanced close at the joint of wing/pod. May be varibles like how fresh or dry it is that would effect the ballance some.

That being said, I think a one blader just plain looks dumb! What the heck though, I have changed my blades out so often the screw holes in the plywood hub are all chewing out and I have little area for new holes. Change them ALOT sometimes 3 times a day on the test mill. Might as well try one of these myself

I have played with those seed pod wings for many many years, as a kid and even still today when I find them. Maybe that's where we really do need to look for great blade designs. At Nature!

If I can find a nice set of seed wings that ar4e working well maybe I will try to copy those for much larger blades with the next set of plastic barrel blades I build. Maybe make a 1 blade and a 2 blade set and try both.

Balancing a 1 blader should be much easier, another advantage.

[windstuffnow]

  Interesting subject...  I like norms "maple seed" turbine idea.   The one bladed turbines tend to spin much faster than their two or three bladed counterparts.  From what I understand they are a bit more efficient also.  They still suffer the same inherent problems that a 2 bladed unit does...

  I have one wing that I salvaged from a wrecked plane and the thought had passed through my mind to do something similar.   It's a short wing only spanning about 14ft.  After working out some calculations on the possibilities I soon lost interest in the idea because of the cost of the structure...  In any case small single bladed turbines might be fun to build and learn with but I don't see any extreem advantages to offset the extra engineering to make it work....

Lots of fun in the creation of different devices though...

Have Fun

Winstuff Ed

[Chiron]

Nice experiment, had to go out and dig through the leaf pile and find a few to play with.

Couldn't find any in very good shape so I may have to wait until the next time they fall to repeat your experiment. Center of balance was above the "root" at the seed pod and they were too brittle to survive having a pin put through them.

I had the further complications of a girlfriend who thought I was nuts and 3 kittens trying to intercept the wings in flight.

Maybe attach 2 very small Neos on either side of the pin and mount tiny coils on the straw to see how much it would put out, something like the hamster turbine

Any ideas on how to scale up the airfoil to a usable size? Material would be the biggest question IMHO..

[electrondady1]

thats very interesting.  it is in the interest of the tree to spread its seeds as far from the parent as possible. after perhaps one billion years of evolution i would think a very efficient design would be inherant in present day configurations. i'm not shure how the shape could be extrapolated into a more usefull size. NASA could do it.

[iFred]

So basically, this might be just the perfect type of blade for low wind speed at less then 50 watts or so, higher voltage type generator using some very small neos.. ummm. I have been thinking of this for awaile now, last couple months, wondering if there was a way to tap into ground level wind currents less then 10 ft air currents at high speeds, I could'nt come up with a blade to handle it, but this has potential!! if the generators where designed for high efficiency, high rpms and higher voltage units then it could work...

[wayne]

Hi

You caught my intrest and looks like fun. Here is a electric version of a maple seed, it at bottom of page.

http://www.tcrobots.org/members/rjesm.htm

Wayne

[Norm]

   I think they already have.....

http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/other/Maple_Seed.html

   So here's a good place to start...plenty of other places

on Google....

   Has anyone used a hobby motor like in those

little personal fans with the 2 AA

batteries...and put a couple of neos in place of

the ceramic ones even an actual maple seed might

power it?

                    ( :>) Norm

[Big All]

I'm surprised no one else brought these up yet.

Here's a link to one type, there are quite a few others out there

http://www.farreys.com/ceiling_fans/fanimation/enigma_fan.html

[Norm]

   First time I've ever heard of them...they would be a conversation piece.

                 ( :>) Norm

[rotornuts]

Ed, I never wanted to build a one or two blade rotor but then I saw an interesting example of a new single rotor turbine under development. They have taken a different approch to the vibration issue by placing instead of one, two counter balance weights  at 120 and 240 degrees off the blade creating a virtual three blade rotor as far as balance is concerned.

I'm hoping to have a blade with a large cross section that works well in low winds. The inherent high tsr's of the single blade rotor will hopefully begin to produce power sooner as well as perform well in high winds.

I'm actually going to model the maple seed but give it a stretch in length by something like 10 or 20% and I'll create an elongated section at 120 and 240 degrees from the blade on the scounter weight to give it the 3 blade effect for dynamic balance. I'll try a 48" rotor to put on my induction conversion so I can compare to jerry's stuff rather than build a comparison rotor myself.

Here's hoping it works.

[windstuffnow]

  If I didn't have so many projects going right now I would be tempted to put together a small one with some of the blades I have laying around.  Could be quite fun!   Can't wait to hear about yours... soon I hope ;o)

Have Fun and keep us informed!

Windstuff Ed

[rotornuts]

I started to plot the maple seed tonight and discovered some interesting things. Seems nature adores the golden rule(the rule of thirds). Here's some neat results with fudge factors of only a few percent!

center of mass lenghtwise - 1/3 pod side, 2/3 blade side

center of mass widthwise  - 1/3 leading edge, 2/3 trailing edge

max cord width location   - 2/3 total length

max cord width            - 1/3 total length

And the seed pod which acts as the counter weight has a slight twist in the opposite direction of the blade.

I measure a few seeds that were the best flyers of the lot and thats what I got.

Creepy!!!

[Norm]

   Nice going...well, guess I really got you

going on something, have you figured out the TSR

yet? probably rate of descent to number of turns?

                  ( :>) Norm.

  What's so creepy about it?

  You probably got up this

  Morning and didn't think

  anything about it ??

   LOL

[Norm]

   Nice going...well, guess I really got you

going on something, have you figured out the TSR

yet? probably rate of descent to number of turns?

                  ( :>) Norm.

   

[windstuffnow]

  Can you get an angle of attack of the "good fliers" ?  What about rotational speed at that angle.   It may work good to "fly" itself but you may have to alter it a bit to actually perform work efficiently.

Sounds fun...

Windstuff Ed

[whatsnext]

I'm pretty sure that if you watched a maple seed progress towards the ground that the center of mass is not the center of rotation. The reason for this is that the dynamic forces are all off center while in flight and this would induce quite large torques while the seed is in motion. If you go to the American Modelers Assoc site you should be able to find pictures of indoor free flight planes that use single blade props. These planes vibrate like crazy while in flight. I know that balance and vibration are rarely issues on these forums but it would be a huge issue with a single bladed turbine because you would likely need good static balance to allow easy starting.

John.....

[whatsnext]

I got the name of that group wrong. It's actually The Acadamy of Model Aeronautics. Their site is:

http://www.modelaircraft.org/

John......

[rotornuts]

Ok Ed and Norm, it took some time but I measured the approximate angle and the approximate rate of descent. Using that info I calculated approx. rpm. I measured 5 "best flyers"(seeds that descended at the slowest rate with the highest rpm). Here it is.

15. " descent in 1 second
    
3. -6 degree pitch angle(this assumes the seed pod or counterbalance area is zero)
   
1. 375" blade length
   
   

To calculate actual pitch - 75%(twist average)radius * 2 * 3.14 = circ. at 75% = 6.47"

                            6.47" * TAN 6 degrees(.10510) = .68" pitch

To get rpm - 15".68 = 22rev. per. second * 60 = 132 rpm at 6 degrees

Circ. 100% radius = 8.64 * 132 rpm = 1140" per. min. (or 1.08 mph).85mph = TSR 1.27

So in a perfect world our little 2.75" diameter seed was falling .85 mph at 132 rpm at a pitch angle of 6 degrees or 264 rpm at a pitch angle of 3 degrees which yielded a TSR of 1.27 at 6 degrees in a .85mph wind or a TSR of 2.54 at 3 degrees in the same wind.

Whew!

Note to whatsnext - I've concluded firmly that the center of mass is indeed the axis or extreamly close to it.

Well there you have it, any questions?

                           

[windstuffnow]

  Wow, thats pretty intense!  Nice work.  I wonder if the wing could be enhanced... Such as creating a more aerodynamic shape to the existing structure of the wing while leaving the dimensions similar but scaled up.   Hey lets redesign the maple seed!  

  Some other ideas just came to mind!!!  Email me!  Norm should be in on this idea also...!

Windstuff Ed

[rotornuts]

Ed, I hope you see this. I realized I made an error with regards to the rpm by a factor of 10. What should have been 22 revolution per second * 60 turned out to be 22 * 6.

So corrected the rpm and TSR looks like at 6 degrees 1320 rpm, TSR - 12.7 and at 3 degrees it's 2640 rpm, TSR - 25.4. WOW, I think it's time to correct for the real world.

If we assign an efficiency of 50% we correct to 660 rpm, TSR - 6.35 at 6 deg. and 1320 rpm, TSR - 12.7 at 3.

that's even nicer isn't it?

[Norm]

   Rotor...you're getting closer and closer to

the ideal match for one of my blower motors if I

ever get the wire ready so I can rewind one.

   You might not believe this but all of this

stuff I've been posting is related just like this

counter on my website ....

http://www2.suite224.net/~peppysue/Projects.html

is so I can put some wire on two reels with equal

lengths on each reel so that I can rewind this

armature with 2 coils at a time....so that with a high speed little prop it'll charge a battery.

   Why is it with some of these people as soon as

you mention something ...they start telling you

why it won't work on a 12,14 or 18 footer.

                    Well back to my old rerun

   movie for tonight on the 32" tv. Didn't get any better on a larger screen. Yep...I just gotta

get off the grid! Electricity is costing me too much! LOL!

                   ( :>) Norm.