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Mess with your minds: A wind powered craft going faster than a tail wind speed.

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gnuarm:

--- Quote from: bdunham7 on December 30, 2021, 11:31:03 pm ---
--- Quote from: gnuarm on December 30, 2021, 11:04:48 pm ---The wind resistance is low compared to the force generated by the propeller driving the wheels because the angle of the blades is nearly parallel with the wind.  The lift of the airfoil is what provides the force that rotates the propeller and therefore the wheels. 

It is a very simple process once it is properly understood. 

--- End quote ---

It is fairly simple, but you have it backwards.  The propeller is driven by the wheels.  If you posit the wind driving the propeller somehow, ED's theories would be right since the interaction between the propeller and the wind is dependent on the windspeed relative to the vehicle.  The way it works when the vehicle speed is the same as the windspeed is the propeller reacts with apparently still air, neglecting a bit of turbulence, and that allows it to continue to push the vehicle even when it already at or above windspeed.

--- End quote ---

Maybe we are talking past each other.  In the downwind case the wheels drive the propeller.  In the upwind case the propeller drives the wheels.  That's why I had trouble understanding the upwind case, because if the wind pushes on the propeller very hard it will run downwind, with the propeller turning backwards by the wheels.  But because the propeller is nearly feathered there is very little resistance to the wind.  However the airfoil gives enough lift to spin the propeller in the correct direction which pushes the vehicle upwind. 

I didn't understand this until I looked at the angle of the blades in the videos.  Look at the two videos and you will see the downwind car starts with the blades full on to the wind while the upwind car starts with the blades feathered (parallel to the wind).

gnuarm:

--- Quote from: fourfathom on December 30, 2021, 11:32:16 pm ---Stored pressure-difference energy?  I was looking up explosive shock-wave overpressure propagation, and even at only 1 PSI, the pressure-wave is moving about 70 MPH (about 700 MPH at much higher pressures).  The idea that wind-pressure builds up behind a surface (and a surface that is slowly accelerating towards windspeed), and somehow this accumulated open-space pressure will persist for minutes, or even seconds, is pretty ridiculous.

--- End quote ---

Yes, as soon as the force from the propeller stops, the pressure behind the propeller dissipates.  The idea that the blackbird ran for minutes or even just seconds from the energy in this pressure is absurd.  There is just not that much of it.  Then he takes close up photos of gears nearly slipping and talking as if the micro level of energy involved in that is providing the necessary energy for faster travel.  It's pure BS.

Every car with a clutch has springs in the clutch plate to absorb some of the shock of a sudden engagement.  What ED is saying is that the energy stored in these springs would somehow provide extra power to the car to go faster.

gnuarm:

--- Quote from: Labrat101 on December 31, 2021, 08:20:41 am ---@ gnuarm
You haven't seen his website or his personal forum.
 It's worth looking at ..   :phew:

--- End quote ---

Yeah, I just took a look.  I don't see anything terrible.  The website is pretty amateurish, but it doesn't show the lack of understanding of physics this conversation does.  I think he started on page 4 or 5 and we are on page 56 now.

fourfathom:

--- Quote from: gnuarm on December 31, 2021, 04:27:21 pm ---Then he takes close up photos of gears nearly slipping and talking as if the micro level of energy involved in that is providing the necessary energy for faster travel.  It's pure BS.
--- End quote ---

The whole stick-slip hysteresis energy storage explanation is silly.  If there is a stick-slip cycle then energy is stored and released during the cycle.  If ED's explanation were true, the vehicle would be varying above and below windspeed at the cycle rate.  But the downwind speed of the vehicle through many of these nonexistent "cycles" remains faster than windspeed.

Labrat101:

--- Quote from: gnuarm on December 31, 2021, 04:21:23 pm ---Maybe we are talking past each other.  In the downwind case the wheels drive the propeller.  In the upwind case the propeller drives the wheels.  That's why I had trouble understanding the upwind case, because if the wind pushes on the propeller very hard it will run downwind, with the propeller turning backwards by the wheels.  But because the propeller is nearly feathered there is very little resistance to the wind.  However the airfoil gives enough lift to spin the propeller in the correct direction which pushes the vehicle upwind. 

--- End quote ---
I did mention this about the feathering of this type of propeller a good many pages back . and also the vortex affect
 that are created which is an important factor . as the vortex is like entering a slip stream  .
 This is also better explained in the PDF that IanB  showed a link to .
Also I did mention a few examples of this being used in torpedoes as a similar thing happens in water.
The torpedo will accelerate though the vortex  with almost Zero friction .
Also mentioned is that the Blackbird front wheels will also start to lift off the ground when the aerofoils are moved into
thrust so the drag from the front will drop and will allow the extra acceleration .
 The Maths are 3 Dimensional  . ED is working in only 2 Dimensional this is why the numbers will never be correlated.
 This I tried explaining but as usual just ignored or not understood .
 So if every one was to read and understand This very nice working PDF . Snoopy will be able to travel again faster than tail wind .. without all the BS etc .

  Happy new Year to every one ..  And may the force be with you .. :popcorn:

With complements from IanB
This was first done as long ago as 1969. Reference here: https://projects.m-qp-m.us/donkeypuss/wp-content/uploads/2009/06/Bauer-Faster-Than-The-Wind-The-Ancient-Interface.pdf


 

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