Downwind Faster than the Wind #7

In this video we show that the DWFTTW cart is not being affected by any external fans or other devices. This video is in response to critics concerns.

Category:

Science & Technology

Tags:

• DWFTTW
• DDWFTTW

[aether222]

What about a water version of this? Replace the wheels with some a water wheel or turbine so that when the boat moves through the water the air prop is driven. That would be useful where I doubt wind driven cars are a plausibility.

[spork33]

@aether222

A water version could be made, but it would be much more difficult to achieve a significant multiple of wind speed. The cart was never intended to have a practical purpose. It's just the physical solution to a brain-teaser

[aether222]

@spork33 I have significant doubt as to if this could not be in some way Free Energy, however I can see one way this may go faster than the wind and not violate the conservation of energy (which I think can be beaten anyway), and that is it must blow the wind backwars to reduce the speed of the air OR on the treadmill it must somehow slow the treadmill down. If it doesn't have a breaking force on the belt it must be OU! I am interested in trying this, any tips on construction?

[spork33]

@aether222

This definitely doesn't represent free energy. I'm quite confident that law of conservation of mass and energy is alive and well. This DOES slow down the wind in its wake, and it does apply a braking force against the treadmill belt. Fortunately you can easily try it for yourself. I posted a set of 3 detailed build videos. Just look for them under spork33

[ArbitraryConstant]

@spork33

I love surprising, counter-intuitive results like this!

[spork33]

@ArbitraryConstant

Thanks. I'm the same way. That's why I love brain-teasers - and ultimately why we built this silly thing.

[StandardAI]

What would happen if you bent the frame slightly to the side so that it went around in a giant circle? would it just keep going?

[spork33]

Sorry, the prop is also turning at finite speed, and the treadmill is sloped UP hill. The reason the vehicle can go downwind faster than the wind is that the wheels are being worked on by the road at one speed, while the prop is working on air that's moving at a lower speed (due to the tailwind). Since power is force x speed, the road puts more power into the wheels than the prop needs to put into the air.

[spork33]

There is one critically important ratio - that's the speed the prop is trying to move through the air divided by the speed the wheels are trying to move over the ground. This number should be less than 1. Values of 0.7 or so are good for a reasonably efficient vehicle. I'll contact you via PM.

[sean6006]

My school's math and physics club is trying build one of these, but we've encountered some problems. Firstly, is the one-to-one gear ratio absolutely necessary? And is there any ideal ratio between the length of the prop and how far it is from the main wheels? And I know that if the weels had a smaller diameter the prop would turn faster, but have you found any ideal ratio between the wheel diameter and the gear size? We know that your design works, but how much leeway do we have to play around?