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cesiumfrog
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Can a simple craft (consisting of a fan geared up to a skateboard) go “directly down-wind faster than the wind” (without any additional power source, tricks nor wind fluctuation)?
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mender said:Can you add one more category to that list? I'd like to add "yes but not limited to a design with a propeller".
OmCheeto said:Get a bowling ball.
Then get a really, REALLY, powerful leaf blower.
Push the bowling ball down the street with the leaf blower.(might take half an hour or so...)
When the camera is off, run in front of the bowling ball, throw leaves in front of the camera, turn on the leaf blower showing the bowling ball rolling down the street AGAINST the wind.(as indicated by the direction of the leaves)
It is true. Trust me. Things can go faster than the wind.
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please don't ban me, please don't ban me, please don't ban me. ;)
Give me a break, I'm a physicist not an engineer.Jeff Reid said:If you change skateboard to cart on wheels [..] I'd agree
His "My Way" isn't really a "discussion", is it?schroder said:Russ has made it clear to me that he will only allow discussion in his thread only on this subject
I think that counts as "tricks or wind fluctuations", are you changing your vote?OmCheeto said:When the camera is off[.. suddenly move the leaf blower..] Things can go faster than the wind.
cesiumfrog said:His "My Way" isn't really a "discussion", is it?
I think that counts as "tricks or wind fluctuations", are you changing your vote?
Why is it, at the very end of the video, when the cart slows down and we can finally get a chance to see which way the fan is turning, the cart goes OFF CAMERA? The ONLY place in the entire video where this happens! Hell of an accident or coincidence? That video is a hoax and a very poor one at that.
Jeff Reid said:skateboard as the platform?
Sorry I misunderstood, I thought you meant modifying an actual skateboard.cesiumfrog said:Give me a break, I'm a physicist not an engineer.
schroder said:Mender, a cart on the treadmill with a properly pitched propeller will advance. I agree with that.
schroder said:I am saying the pitch is not the same in each instance.
mender said:As I already asked, what are you basing that on? If it is because your logic dictates that because you have convinced yourself that this is impossible (which you have), you are presenting your case based on circular logic, not observation. You can prove anything with circular logic and a blind eye to what you don't want to see, and nothing will be proof enough for you.
What would convince you that the cart is now doing the impossible and moving faster than the wind that is powering it? Seriously. How would you prove beyond a shadow of a doubt that the cart reached and exceeded the wind speed?
I really hope Russ is able to clear up your problem with equivalent frames of reference.
schroder said:Mender, a cart on the treadmill with a properly pitched propeller will advance. I agree with that.
schroder said:If the prop pitch changes for any reason between frames the frames are not equivalent!
And since the frames are not equivalent, ...
uart said:Guys the argument seems to have shifted. Does it really matter if the device needs to have a variable pitch in order to self start and also to achieve DWFTTW (I'm not saying that it does need this, just that even if it does then it doesn't in any way invalidate that fact that DWFTTW is possible does it?)
I think he was getting at the situation where the cart is well below wind speed, in which case the prop acts as a bluff body (sail). Assuming the cart is geared properly for DDWFTTW, then the prop never acts as a turbine unless the driving wheels are sliding forwards.ThinAirDesign said:The prop on the back of the cart acts as a propeller at all times the cart is approaching, at or above TWS.
Jeff Reid said:I think he was getting at the situation where the cart is well below wind speed, in which case the prop acts as a bluff body (sail).
Yes, it is possible for a craft to go faster than the wind. This phenomenon is known as DWFTTW (Downwind Faster Than The Wind) and has been proven through multiple experiments and demonstrations.
The key to DWFTTW is the difference in speed between the wind and the craft. By utilizing a propeller or sail that is angled in a specific way, the craft can generate more power and speed than the wind pushing against it.
Any type of craft that can harness wind power, such as sailboats, land yachts, and even cars, can potentially achieve DWFTTW. However, the design and efficiency of the craft play a crucial role in its ability to go faster than the wind.
While DWFTTW has been demonstrated in various experiments, there are certain limitations to consider. The craft must have a sufficient wind speed and direction to generate enough power, and the design and materials used in the craft can also impact its performance.
DWFTTW has potential applications in transportation, particularly for vehicles that rely on wind power. It could also be used in renewable energy production, as well as for recreational activities such as land yachting and sailing competitions.