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Veritasium direct downwind video debunked

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Dacian:
Finally got around to setup my experiment to show how the direct downwind faster than wind cart actually works.
The Rigol 12bit oscilloscope was also very helpful for accurate force and current measurements.

I demonstrate that cart accelerates forward for 8 seconds and after that it decelerates as all the potential energy at the start was used up.
So direct downwind carts can only exceed wind speed for a limited amount of time proportional with the amount of stored energy in the form of pressure differential (below 2 Joule in my experimental setup) and after that energy is used up the cart decelerates (cart slows down).

Edit by gnif: Self promotion removed, this is the banned user `electrodacus`

Andy Chee:
Here's a build video of Veritasium's model cart on treadmill providing continuous thrust:


Dacian:

--- Quote from: Andy Chee on December 25, 2023, 06:54:43 am ---Here's a build video of Veritasium's model cart on treadmill providing continuous thrust:


--- End quote ---

It is not continuous thrust. They just did not measure that and made assumption of how and why it works.
That cart will work the same way as the one I build, meaning the cart speed after release increases as potential energy in the form of pressure differential is converted in to cart kinetic energy and heat  due to frictional losses.
When that energy is used up the cart will start to slow down as I demonstrated.

Gregg:
If I were to bet money on this, I’d bet on Veritasium.

Just because you haven’t duplicated the experiment, doesn’t mean you have debunked it.

The principle is the same as a sail on a sailboat. Many sailboats can go considerably faster than the wind when sailing a broad reach maximizing the thrust by trimming the sails. 

In the Veritasium experiment the propeller acts as a sail, but it isn’t directly propelling the model but it is using its rotary motion to impart additional forward thrust via the wheels.  It is far from a practical vehicle but it is possible.  Getting the exact propeller design and gear ratios to the wheels only works for a narrow set of circumstances.  Note in the Xyla Foxlin video how they had to try a large variety of propellers and wheel diameters in order to achieve any success. In addition Xyla did an exemplary job of keeping things simple, lightweight and efficient.  Making a more complicated model would probably add mass, friction and inefficiency to the point of negatively affecting the experiment.

Andy Chee:
In your video, you release your hand at steady state at ~17 seconds, then forward thrust, then fade to black cut the video at ~30 seconds.

If the potential energy is completely used up, then the treadmill should force the cart backwards.  Please show the cart moving backwards.

Also please note that Xyla's cart build is available for download (the bill of materials is in the video description):

https://www.thingiverse.com/thing:4897423

Please test her cart instead of your design.

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