DDWFTTW - Demonstration of Flawed Design

[planetofthescums]

What happens if you blow air against the direction of the treadmill, as you would have in the real world before reaching wind speed?

[nickrupert]

if you had a cover on the bottom front that blocked the scoops from the headwind it would work woudln't it

[itsandbits1]

the thing all these other suggestions do is get away from the fact that the propeller is a propeller, not a turbine which is what these other sav and lenz ideas are. Of course they won't work. you need something annalagous to the wheel to propeller drive for it to work; perhaps a large helix inside a tube driven by the wheels but why not just accept the simple beauty of the unit as it is???

[UTJhn]

This tries to use the principal of an anemometer which turns directional wind into rotation. But its rotation cannot create directed wind. So it can replace a windmill but not a propeller. So it cannot go DWFTTW.

A windmill is needed for upwind, but this has the wrong ratio.

However, an anemometer attached to much smaller coaxial wheels riding on elevated rails could go upwind.

[macrumpton]

The big problem I see is this rotor does not have any particular direction that it blows air when it is spun. It blows the same amount towards the front and the back and the top and the bottom, so of course there will be no thrust. Also, Savonius type rotors use drag to create rotation from wind which is far less efficient than using an airfoil rotor. It would be interesting to see if a lenz turbine would do better, although that would not work on a treadmill, it would need to have actual wind.

[spork33]

@macrumpton - Any design that works with actual wind will work on a treadmill. There's no way to distinguish between air moving over a surface vs. the surface moving beneath the air.

[macrumpton]

@spork33 Now that I think about it more I see you are correct.

Perhaps a gyromill type VAWT that has blades that change angle according to the wind direction would work, but then you get right back to the mechanical complexity of your design, although it would have the advantage of being able to accept wind from any direction.

[spork33]

@macrumpton

Everything you say about this design is correct. It is flawed in its very conception. That's what we set out to prove to the guy that proposed it. However, you did get one part not quite right...

>> although that would not work on a treadmill, it would need to have actual wind.

There's no such thing. The treadmill and "actual wind" are the same thing.

[UTJhn]

@macrumpton

A "lenz turbine" and all other VAWT that don't require anything to turn them into the wind have the same problem. None of them can create a directed wind. So, they can all replace a windmill (but not always as efficiently), but none can replace a propeller. And, none can be used to go DWFTTW.

But your lenz turbine might do better at going upwind than a comperable anemometer.

[mylexusis]

no wind powered craft will ever travel at a constant speed greater than the wind directly down wind , any one trying to develop such a craft is wasting there time

[spork33]

@mylexusis

Your theory has the one problem that it can't explain the fact that we did build such a vehicle. We expect to establish the first world record in that category in the next few days.

[macrumpton]

@mylexusis Imagine an iceboat (which easily exceed 4x wind speed going across the wind) attached to a string going through a pulley fixed to the ground. It is easy to see that the the string will be pulled through the pulley at the speed of the iceboat in any direction you lay out the string. It is not self contained, but the principle is easily adapted.

[planetofthescums]

@macrumpton This principle is easily adapted... really? You can throw a rock off a building, tie a rope around a pulley and have it lift a person off into the sky. Can this be easily "adapted" to shooting people up into the with gravity?

[pallidinyou]

That whole test scenario is in reverse!

The applied force is NOT supposed to be on the wheels as in this demo, rather on the vanes!

With a 2:1 ratio, air blowing 10 mph against the vanes will rotate the outer surface of the wheels at 20mph.

[spork33]

The test only looks like it's reversed. Whether the device sits on a moving surface in still air, or on a stationary surface with moving air (wind) makes absolutely no difference. In neither case will it do as you predicted.

[sixmagpies]

Savonius would be COMPLETELY useless as the trailing blade is stopped and the leading blade is actually going twice the road speed against the oncoming airflow.

Stupid.

[Wesnex1]

Centrifugal force will also be stronger than with human powered flight because the prop acts like a wind turbine moving with the wind. Wind turbines use very strong blades but the props on these carts must turn faster to collect the same energy since the forward motion of the cart increases the prop's necessary spin speed relative to the motion of the air.

[spork33]

In both the case of human powered flight and this cart the propeller acts as a prop at all times, never as a turbine. Both cases could use a prop of similar diameter and rotational rate.

[Wesnex1]

Converting to upwind would be problematic but there should be a way. If the propeller still wins, I suggest using two oppositely rotating props for manned vehicles to prevent prop torque from causing rollovers. As size is scaled up, weight increases exponentially, and going from a small cart with no payload to a large cart with human, prop surface must be very large to still break the downwind speed barrier. Large props get high torque and can rip apart from centrifugal force at high rpm.

[spork33]

I assume you're refering to the prop-cart from our other videos. In that case converting to upwind operation simply requires using smaller wheels. As to larger propellers, the sort of propellers that have been used for human powered flight should do just fine.

[Wesnex1]

I think Greg London's document with illustrations is one of the most complete explanations of how DDWFTTW is physically possible for people who don't know much about aerodynamics, compression, centrifugal force, etc. It should help people who have mechanical minds. Too bad some are so smart that he offends them. Maybe I'm out of the loop but I never saw where he claimed the device in the video would work. It seems it was just a step in his reasoning to eventually explain the prop cart.

[spork33]

Wesnex1, You really should look at his original version of the document here:

filesavr . com / tumbleweed

He says things that are COMPLETELY wrong and condescending. His new document has been toned down quite a bit when he was taken down a few notches. But he continues to insult us, and even the new document is simply riddled with things that are just plain wrong.

[Wesnex1]

For this to work it has to have a non-rotating part. Also the air catching surfaces need not be kept near the center to get the right speed ratio since air compresses. A flow of air through the turbine and directed only back against the wind with enough thrust is necessary to achieve DDWFTTW. Maybe a squirrel cage fan in a housing aiming wind to the rear with the shaft connected to rollers just bigger than the housing with extra wheel to keep the housing from rolling. Must be very light weight!

[VideoJunkie666]

I would like to thank the Greg Londons of the world for making me feel like a total genius.

[mamalala72]

It's absolutely astonishing how greglondon spouts out that people don't have a clue, but that he has. And in the end he comes up with an idea whose principle had been demonstrated long ago, claims it is his explanation, and then totally screws it up by applying it completely the wrong way.

I'm just too lazy to register at boingboing. However, any discussion with that guy is as useful as talking to a wall.

[spork33]

Greg is a pretty special guy.  You can read his "rigid engineering" treatment of this device at filesavr . com / tumbleweed

[mamalala72]

Yes, i have read that document. Thats what i meant with "...and then totally screws it up by applying it completely the wrong way."

[spork33]

Understood. I just wanted to post the document for anyone that might be interested.

[mamalala72]

What i found especially entertaining: While he said that people don't know how a certain works and that you failed to explain, when he was asked for a explanation and how it works for his thing, he just said like "it's all in there, if you don't understand, i cant help you".

He complained about evidence, videos, etc, but when asked to present proof for his contraption, a video of it, etc, he refused it.

Hypocrisy anyone? ;-D

[CousinoMacul]

PWNT!!!