Downwind Faster than the Wind #7

[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?

[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.

[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?

[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.

[sixmagpies]

Explanation: The force on the driven wheels has finite torque at a very finite speed. This force is transmitted to the prop via an (efficient) gear that acts also as a fixed ratio torque converter to turn the prop. The prop converts this torque into thrust with a NON FINITE speed which, in this case, the car being super streamlined and light, is just able to propel the car faster that the power wheels. Q.E.D. or twoddle?

It's that or the treadmill is sloped!

[spork33]

In some of our tests the treadmill is level. In others the treadmill is sloped so the cart has to CLIMB the incline. The thrust from the prop is definitely not infinite, but the prop is immersed in a moving fluid (the tailwind). This provides the necessary advantage.

[sixmagpies]

Sorry for my sloppy English... meant to say the thrust of the prop is 'not finite' ( ie. the speed range over which it applies power is wide.)

I sort of agree about your apparent wind theory too. I'm the guy who sailed the schooner for many years, so I KNOW we often used to sail downwind faster than the true wind, if light, just like a decently designed and well sailed catamaran or flying proa will will.

[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.

[Haricotsi]

I've seen that the treadmill is more or less leveled in other videos, but you do not show the same fact in this video.

Since I am pretty damn sure that the phenomenon is not caused by what you believe i would suspect something along the lines of the treadmill not been leveled in this particular experiment.

[spork33]

We're pretty sure the phenomenon is caused by very well known and well described aerodynamic principles. If you think the secret lies in having the treadmill not level, how do you account for all the other videos in which it IS level? This one is clearly going UP a small incline.

[TimpBizkit]

Oh ye of little faith....

Thou art a doubting Thomas

[brixbrix]

please stop wasting your energy on proving that it is not a hoax and concentrate on the actual work :-) As a future engineer I am very interested in the experiment, and would like to see the cart running on the thread mill in a much smaller and confined space e.g. a box surrounding the experiment. I am curios about how much turbulence the cart can handle before deceleration occurs. Make it transparent so we can see the outcome. Smoke is a good indicator and be included. Thanks

[candybubbles]

deceleration? Whens the last time you fly an airplane and it starts decelerating?? That's dangerous logic. Airplanes decelerating = crash

[jspade1019]

When airplanes experience great turbulence, they do in fact crash.

[EarDestroyer]

lol planes dont crash when they decelerate they crash (stall) when they reach a speed which is that is less than the amount of force required to stay in the air. just think of gliders they require no thrust once already in the air and can stay afloat for hours on just wind because there mass is much lesser then a boeing

[treborrelluf]

white carpeting...puhhlleeez!

[Josiah4jc]

If you guys want to prove that there is no wind, you should set up some ribbons. Though I suppose at some point you just have to accept that some people will not see reason.

[TheMistsOfFnordor]

HOAX! This is still obviously a hoax. You're not wearing red for example. In fact, in your next video, I'm gonna need you to wear Santa outfits and sing christmas carols. Yeah, with fake beards and everything. But you won't do that, because this is such a HOAX!

[ricglas]

You guys rock. Nice work ... again.