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DDWFTTW Circular Wind Tunnel Test

  1. Mar 24, 2009 #1
    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 travelling 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.
     
    Last edited by a moderator: Apr 24, 2017
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  3. Mar 24, 2009 #2

    A.T.

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    I think you just love to build experiments :smile:. Maybe you can upload the high quality version to http://www.megaupload.com/ [Broken] or something similar.
     
    Last edited by a moderator: May 4, 2017
  4. Mar 24, 2009 #3

    rcgldr

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    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.
     
    Last edited: Mar 24, 2009
  5. Mar 24, 2009 #4
    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.
     
  6. Mar 24, 2009 #5
    Very sorry for the poor video quality. Will try to provide a better quality one as soon as I get time to do so.
     
  7. Mar 24, 2009 #6

    A.T.

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    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.

    wallace+sawing.jpg

    I like this new idea very much.
     
  8. Mar 24, 2009 #7
    Correct on both counts.
     
  9. Mar 24, 2009 #8
    Kudos to Swerdna, and ...

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

    JB
     
  10. Mar 24, 2009 #9

    rcgldr

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    By the way, good job on the constuction of the new "turnmill".
     
  11. Mar 24, 2009 #10
    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
     
    Last edited by a moderator: Sep 25, 2014
  12. Mar 25, 2009 #11

    rcgldr

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    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).
     
    Last edited: Mar 25, 2009
  13. Mar 25, 2009 #12

    uart

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    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. :)
     
    Last edited: Mar 25, 2009
  14. Mar 25, 2009 #13

    OmCheeto

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    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. :wink:

    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
     
    Last edited by a moderator: Sep 25, 2014
  15. Mar 25, 2009 #14
    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 travelled 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 travelled up to the cart as a vortex.

    slower.jpg

    faster.jpg

    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 . . .

    windtunnel.jpg

    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.
     
    Last edited: Mar 25, 2009
  16. Mar 25, 2009 #15
    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.
     
  17. Mar 25, 2009 #16

    rcgldr

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  18. Mar 25, 2009 #17

    OmCheeto

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  19. Mar 25, 2009 #18
    Will upload it to Youtube for you shortly. Am uploading another new video first
     
  20. Mar 25, 2009 #19
    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)

     
    Last edited by a moderator: Sep 25, 2014
  21. Mar 25, 2009 #20
    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
     
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