DDWFTTW Circular Wind Tunnel Test

[swerdna]

Even though I’ve experienced the evidence firsthand I’ve never quite been able to totally accept that the treadmill and turntable tests accurately represent a cart being powered solely by wind (like many others). So I’ve built a circular wind tunnel to test DDWFTTW in a “real” wind and the cart is only powered by moving air. It’s not high-tech but it works. Things move around quite quickly so you need to use slow motion or frame by frame to see what’s happening.

This video was taken during construction to show and explain the workings . . .

http://www.youtube.com/watch?v=simRdTslucs&feature=channel_page

This video is the wind tunnel and cart in action (the uploaded quality is very poor compared to the original) . . .



The cart not only beats the wind it also beats the vanes that create the wind! The series of images below show the flap each time it comes around and you can clearly see that the cart has advanced from vane 4 to vane 1. There is an image missing between the last two because the flap was in the reflection on the plastic and couldn’t be seen. The sequence represents eight revolutions of the cart. It wasn’t taken from the video posted but the same thing can be seen in that video as well.

http://www.accommodationz.co.nz/images/sequence.bmp

The vanes are turned by hand and it’s very easy to keep a constant speed. When the air is up to speed there is very little energy required to retain that speed so the vanes aren’t traveling much faster than the wind. The tunnel is totally enclosed and the air moves essentially as a single mass. The wind created would be at least as constant and stable as an outdoor wind.

 

[A.T.]

Even though I’ve experienced the evidence firsthand I’ve never quite been able to totally accept that the treadmill and turntable tests accurately represent a cart being powered solely by wind (like many others).

I think you just love to build experiments . Maybe you can upload the high quality version to http://www.megaupload.com/ or something similar.

 

[rcgldr]

I downloaded your video as a mp4 file from youtube and noticed it's 24.97 frames per second. What frame rate is your camcorder recording at? I'm guessing this is a PAL compatable camcorder (49.94 fps), as opposed to NTSC (59.94 fps)?

I converted this to a slow motion .WMV file

http://jeffareid.net/misc/ddwcirc.wmv

If you could upload a 50 (or 59.97?) frame per second video to filefront or other file sharing site, I could do a better job of this of making a slow motion version. If the camcorder is 4:3 aspect ratio, then 640x480 is a good video size, with a video bit rate of 2000kbps. If the camcorder is 16:9 ratio, then 854x480 is good, with a video bit rate of 2600kbps.

 

[Subductionzon]

Congratulations on thinking outside of the box to solve the problem of limited length of wind tunnels. You could tell that it works on the Youtube video, but just barely. I look forward to all sorts of denial on various other websites.

 

[swerdna]

Very sorry for the poor video quality. Will try to provide a better quality one as soon as I get time to do so.

 

[A.T.]

I look forward to all sorts of denial on various other websites.

I also don't think it will convince other people more than the turntable/treadmill, because it would be even easier to fake. And if you need such an experiment in the first place, because you don't get Galilean invariance, then you won't be convinced by anything. I think swerdna is doing it to convince himself, but mainly for the fun of constructing this stuff.

I like this new idea very much.

 

[swerdna]

I think swerdna is doing it to convince himself, but mainly for the fun of constructing this stuff.

Correct on both counts.

 

[ThinAirDesign]

Kudos to Swerdna, and ...

Where the heck is that Schroder dude? LOL Perhaps a heterodyne has stopped his heart?

JB

 

[rcgldr]

By the way, good job on the constuction of the new "turnmill".

 

[swerdna]

Thanks for all the positive feedback.

Haven’t found out how to increase the frame rate on my Sony Handycam yet (if it’s possible) or tracked down a high speed camera that can film in slow motion. In the meantime I thought I would make a close up video that may be a bit easier to view. Not that the overall quality will be any better. I did it in a darkened room to reduce glare on the plastic but unfortunately the internal light is inadequate and things are a bit dark. Thought I would post it anyway as I don’t have time to do it again right now. Have started the video with everything at rest to show the start up. Also removed the top inner cowling so you can see through the tunnel (wasn‘t required anyway). The knocking sound shortly after start up is the tether “tail” hitting the surface it travels over before it settles down. Most of the other noise is the chatter of the gears and wind.



Yuck! The uploaded video is crap - sorry about that

 

[rcgldr]

Haven’t found out how to increase the frame rate on my Sony Handycam yet.

Frame rate can be slowed down on some camcorders (24p or 30p), but few will go faster than 60i. Which Sony Handycam do you have?

The uploaded video is crap.

Instead of uploading the video to youtube, could you upload the videos to filefront or other file sharing web site? What format are you uploading to youtube? Note that youtube has a "hi-def" format if you upload at 1280x720, even if the upload image is expanded or letterboxed (padded with black) it usually looks better when played back via youtube.

The double images in your first post are probably due to a difference in the timebase frame rate of your video software and the actual frame rate from your imported video. It doesn't appear to be an interlace issue as I don't see a comb effect. What is the frame rate of your camcorder? Try to set your video software to the same frame rate (both PAL or both NTSC).

 

[uart]

Yes, nice effort Swerda. :)

I'm pretty sure that most people here already understood DWFTTW operation, or at least were convinced by previous videos. I think Shroder, Zoobyshoe and OMGcheeta were the main doubters. I'd like to see how thay explain this video. :)

 

[OmCheeto]

Thanks for all the positive feedback.

Haven’t found out how to increase the frame rate on my Sony Handycam yet (if it’s possible) or tracked down a high speed camera that can film in slow motion. In the meantime I thought I would make a close up video that may be a bit easier to view. Not that the overall quality will be any better. I did it in a darkened room to reduce glare on the plastic but unfortunately the internal light is inadequate and things are a bit dark. Thought I would post it anyway as I don’t have time to do it again right now. Have started the video with everything at rest to show the start up. Also removed the top inner cowling so you can see through the tunnel (wasn‘t required anyway). The knocking sound shortly after start up is the tether “tail” hitting the surface it travels over before it settles down. Most of the other noise is the chatter of the gears and wind.



Yuck! The uploaded video is crap - sorry about that

I thought it was pretty good.

I must say, you make some very interesting devices, and I cannot explain this one at all. But I'll keep watching.

I would like to make just one suggestion: find a way of mounting the camera to some part of the cart assembly. Perhaps just behind the wind flap.

OmgCheeta

 

[swerdna]

Frame rate can be slowed down on some camcorders (24p or 30p), but few will go faster than 60i. Which Sony Handycam do you have?

Instead of uploading the video to youtube, could you upload the videos to filefront or other file sharing web site? What format are you uploading to youtube? Note that youtube has a "hi-def" format if you upload at 1280x720, even if the upload image is expanded or letterboxed (padded with black) it usually looks better when played back via youtube.

The double images in your first post are probably due to a difference in the timebase frame rate of your video software and the actual frame rate from your imported video. It doesn't appear to be an interlace issue as I don't see a comb effect. What is the frame rate of your camcorder? Try to set your video software to the same frame rate (both PAL or both NTSC).

Thanks for the technical camera advice Jeff, and for making the slow motion video. My handycam is model DRC-SR42. I will wait until I have a good video before I upload it to a file sharing website. Hopefully I can borrow or rent a high-speed digital camera that will take slow motion (if they exist).

This is actually the third design of wind tunnel I’ve built. The first one had a smaller diameter and the cart traveled so fast I couldn’t video it successfully. Here are a couple of photos I took of it in action. As you can see from the angle of the piece of rag Pic1 is slower than the wind and Pic2 is faster (arrow indicates wind direction). The wind was created by a four bladed horizontal impeller about two feet directly below the cart and the wind traveled up to the cart as a vortex.

The second attempt also worked and used the same impeller as the first. I didn’t like it however as there were too many internal pieces disturbing the airflow and it was hard to create sufficient wind in such a large area with a the impeller. Also looked more like an alien spaceship. Here is a photo . . .

I may try using the impeller in the latest design to replace the vanes and see how it works as the tunnel has less internal restrictions.

 

[swerdna]

I thought it was pretty good.

I must say, you make some very interesting devices, and I cannot explain this one at all. But I'll keep watching.

I would like to make just one suggestion: find a way of mounting the camera to some part of the cart assembly. Perhaps just behind the wind flap.

OmgCheeta

I actually though of fixing the camera on the tether arm close to the centre and pointing at the flap, but don’t think it would be any better than filming from the outside.

 

[rcgldr]

Slow motion version of windtunnel3:

http://jeffareid.net/misc/ddwcirc3.wmv

 

[OmCheeto]

Slow motion version of windtunnel3:

http://jeffareid.net/misc/ddwcirc3.wmv

how come my mac won't play a .wmv file?

 

[swerdna]

how come my mac won't play a .wmv file?

Will upload it to Youtube for you shortly. Am uploading another new video first

 

[swerdna]

I’ve been very surprised (almost disappointed) that there hasn’t been any sceptical critsism of the circular wind tunnel. Not that I want to provide a bone to chew on but one of the concerns I had before testing was that the design of the vanes with a circular hole for the cart to pass through might have had some sort of venturi effect that would speed the cart up. The tests disproved this concern but just to confirm I’ve made a video using an impeller instead of the vanes. It’s very hard to get enough overall wind flow using the impeller but you should be able to see that the cart beats the wind even if only by a small amount. The immediate wind coming off the impeller would also be creating a faster wind in the top of the tunnel than the bottom. I may create vanes with just oblong surfaces at the very top and bottom. Would also make the flap and cart easier to see as they travel around.



Slow motion version of windtunnel3 (thanks Jeff)

 

[ThinAirDesign]

one of the concerns I had before testing was that the design of the vanes with a circular hole for the cart to pass through might have had some sort of venturi effect that would speed the cart up.

Swernda, I admire your sticktuitivness -- I really do. But said in good humor, you can test this six ways to Sunday and these devices goes DDWFTTW every freakin' time. It's just what they do.

The math proves it. The street proves it. The treadmill proves it. The turntable proves it. The impeller proves it. The vanes prove it.

As jjcote alluded to on another forum, swerdna gets his own little bullheaded (in a good way) wing in the ddwfttw hall of fame.

JB

 

[A.T.]

I’ve been very surprised (almost disappointed) that there hasn’t been any sceptical critsism of the circular wind tunnel.

Well, I guess everyone is amazed with the machinery. But rationally, the treadmill/turntable test are far more conclusive, as they provide a stable wind. The airflow in the circular wind tunnels is probably highly turbulent.

 

[ThinAirDesign]

Well, I guess everyone is amazed with the machinery. But rationally, the treadmill/turntable test are far more conclusive, as they provide a stable wind. The airflow in the circular wind tunnels is probably highly turbulent.

Yep -- the simplest, most accurate, and absolute conclusive proof is a plain old treadmill in a still air room. Perfectly steady and smooth airflow -- millions are spent on wind tunnels attempting to get flow nowhere near the quality of the wind over the treadmill in our living room.

JB

 

[OmCheeto]

I’ve been very surprised (almost disappointed) that there hasn’t been any sceptical critsism of the circular wind tunnel.

Ok. I'll bite.

It can't work! Something is going on that I can't see!

Otherwise I'd have figured out how it works.

One last thing. I've noticed that a lot of the DD'ers are computer programmers.
How come no one has written a simulation program that mimics the dynamics of at least one of the carts?

Surely at least one of them knows Java, and could throw something together in a few minutes.

 

[swerdna]

Ok. I'll bite.

It can't work! Something is going on that I can't see!

Otherwise I'd have figured out how it works.

One last thing. I've noticed that a lot of the DD'ers are computer programmers.
How come no one has written a simulation program that mimics the dynamics of at least one of the carts?

Surely at least one of them knows Java, and could throw something together in a few minutes.

Not sure if your “bite” was meant to be taken seriously or not. However - In this video I removed the top cowling so you can see all the moving parts. I give you my word that what you see is all there is. You don’t have to accept my word of course and I can‘t prove I‘m not cheating without showing you the equipment in person. You’re welcome to visit me any time you like.

When I first saw this claim demonstrated with the Jack Goodman outdoor video I though - “Yeah right, what a crock” and suggested he could be cheating (which he could have been). I then flip-flopped several times between believing it was possible and not. I realized that the only way that I could find out the truth for sure (for me) would be to build my own equipment and test it. I expected that my first test would disprove the claim but it didn‘t. Every test I’ve done has supported the claim and the final wind tunnel test proves the claim (to me) beyond any reasonable doubt. As the Mythbusters would say - “CONFIRMED”. The considerable time, effort and money I’ve spent on my equipment and tests has never been to prove or disprove anything to anyone other than myself.

Can you provide any proof of your claim that “it can’t work”? Why can’t it work?

If you’re not going to believe practicle, physical demonstrations of it working why should anyone waste their time creating an abstract computer program to demonstate it working? If you trust abstract computer programs more than reality you really should get out more.

ETA - You could always build and test your own equipment of course. If you did you would find out it actually does work regardless that you still might think it can’t or shouldn‘t.

 

[OmCheeto]

If you trust abstract computer programs more than reality you really should get out more

Ha ha! My very first computer program was very much in line with this topic.

Let me tell you the story...

I was 14. I loved cars. I loved physics.

But alas, I had only derived one equation, and cars were a whole year away...

Given the mass of various vehicles, drag coefficients, gear ratio's, frontal area's, differential ratio's, I could determine which car would win in a drag race.

Uh oh. The equation was wrong! ahhhhhhhh! My entire life has been a lie!

poop.

 

[A.T.]

I don't know if this has been posted already, but I just recently discovered Bauer's original DDWFTTW-paper on the net:

http://projects.m-qp-m.us/donkeypus...aster-Than-The-Wind-The-Ancient-Interface.pdf

 

[Cyrus]

One last thing. I've noticed that a lot of the DD'ers are computer programmers.
How come no one has written a simulation program that mimics the dynamics of at least one of the carts?

You are confusing being a dynamicist with being a computer programmer/video gammer. I am a flight dynamicist, and will ask you to refrain from confusing the two in the future. One makes video games, the other makes simulators people train to fly actual aircraft on. The two are not synonymous.

 

[A.T.]

I made some animations explaining DDWFTTW in terms of simple mechanical analogies:

The stick-lever analogy:
- http://www.youtube.com/watch?v=g8bxXRQtcMY"
- http://www.youtube.com/watch?v=Ufk6HVWdSzE"

The squeezed wedge analogy:
- http://www.youtube.com/watch?v=H_OKNr120t4"
- http://www.youtube.com/watch?v=zPFzHoubQzg"A project to build a cart with passenger and reproduce / improve Bauer's results:
http://www.fasterthanthewind.org/

 

[rcgldr]

The squeezed wedge analogy

A wedge effect isn't needed. How the aerodynamic force is generated doesn't matter as long as it's efficient. You could simply have a sail attached to a wheel driven conveyor belt, that moves the sail backwards at some fraction of the carts forward speed.

Using some imaginary numbers, assume a 10 mph wind, the cart moving downwind at 12 mph, with the sail moving backwards at 4 mph relative to the cart, a reduction ratio of 3 : 1 (-12 mph ground speed : -4 mph sail speed). The sail moves at -2 mph relative to the wind, slowing the affected wind from +10 mph to +8 mph, and is large enough to generate enough force to equal the rolling resistance related 12 mph downwind speed and the aerodynamic drag related to 2 mph apparent headwind speed.

The power input is the force at at the driven wheels times 12 mph. The power output is the sail force applied to the air times 4 mph. Even if the sail force is double that of the wheel related force, the difference in speed is 3:1, so the power output is less than 67% of the power input.

To make this continuous, a pair of collapable sails could be at opposing ends of the conveyor belt, with the upwind sail on top of the belt opened, and the downwind sail on the bottom of the belt and collapsed. Sort of a crude enlongaged paddle wheel, with no wedge effect.

Propellers are used because they are more efficient than paddle wheel type devices, not because of the wedge effect.

 

[OmCheeto]

I made some animations explaining DDWFTTW in terms of simple mechanical analogies:

The stick-lever analogy:
- http://www.youtube.com/watch?v=g8bxXRQtcMY"
- http://www.youtube.com/watch?v=Ufk6HVWdSzE"

The squeezed wedge analogy:
- http://www.youtube.com/watch?v=H_OKNr120t4"
- http://www.youtube.com/watch?v=zPFzHoubQzg"


A project to build a cart with passenger and reproduce / improve Bauer's results:
http://www.fasterthanthewind.org/

I see I didn't comment on the SJSU project, although I remember seeing it. What an awesome engineering project. Those kids are going to learn so much.

btw, your "Continous" video is exactly what was going through my head one day in an effort to comprehend what was going on with this D&D stuff. Thank you for putting that together for me.