Merged DDWFTTW in a “Real” Wind

[Llyricist]

It came from Steve Smith. Up until that point, Drela and Bauer where the references, and neither of those two make that distance claim, and neither did Spork.

But, I have the NASA approved motor test, from one of their engineers who wrote to me with the very claim you are making. Steve Smith. He suggested it as a test of the idea.

But, acceleration tells all. Both the cart and the prop must accelerate at the same rate. So for linear acceleration, each will travel S= 1/2at^2.
That distance that is independent of initial velocity. Hence S = ut +1/2at^2, where u is the initial velocity.

LOL, you can't tell from having typed it that if u is different, S will be different?

 

[humber]

LOL, you can't tell from having typed it that if u is different, S will be different?

Fail. Superposition.
http://en.wikipedia.org/wiki/Superposition_principle

 

[Llyricist]

Fail. Superposition.
http://en.wikipedia.org/wiki/Superposition_principle

Double fail, Non sequitor

 

[humber]

Double fail, Non sequitor

Sure pal.

But I don't need to bother with your innumeracy.

I have the electrical model. There are all sorts of generators and motors, from the pick-up on your axe, to the loudspeaker in your Fender 90, dude.

All you need is Faraday. So off you go, to prove your claim.

 

[Llyricist]

My claim is that you believe the distance through the air will always be the same as the distance over the ground. Do you dispute that?

 

[humber]

My claim is that you believe the distance through the air will always be the same as the distance over the ground. Do you dispute that?

The shoe is on the other foot, so there is no room for your nescience.
Answer to the electrical model. That has support other than your opinion.
Or are you now going to turn on your own expert, and add him to Spork's lengthy roll call of idiots?

You are going to swallow that upwind farce, whole, aren't you?

 

[A.T.]

The American Journal of Physics is intended as a pedagogical resource for physics students. Apparently that paper was badly written.

Actually Ruina's paper was fine. He considers the general problem of extracting energy for propulsion from the velocity difference between two media, and concludes correctly that the achievable velocity is unbounded in both directions, and limited only by efficiency.

Ruina was responding to a paper by Blackford who considered only the case where the air rotor turns the water rotor, but ignored the opposite case, so he failed to see that DDWFTTW is possible. Blackford himself was one of the reviewers and suggested Ruina's paper for publication.

The other reviewer lacked the abstraction skill to understand the mechanical analogies offered by Ruina, and started bitching around (There are humbers everywhere I guess)

If you google for "The Push-Me Pull-You Boat is Better Still" you will find both papers and both reviews in one PDF.

 

[humber]

Actually Ruina's paper was fine. He considers the general problem of extracting energy for propulsion from the velocity difference between two media, and concludes correctly that the achievable velocity is unbounded in both directions, and limited only by efficiency.

Ruina was responding to a paper by Blackford who considered only the case where the air rotor turns the water rotor, but ignored the opposite case, so he failed to see that DDWFTTW is possible. Blackford himself was one of the reviewers and suggested Ruina's paper for publication.

The other reviewer lacked the abstraction skill to understand the mechanical analogies offered by Ruina, and started bitching around (There are humbers everywhere I guess)

If you google for "The Push-Me Pull-You Boat is Better Still" you will find both papers and both reviews in one PDF.

It was rejected. It's funny to here Mr Nobody say a peer-reviewer lacked what he thinks he has.
Guanna has taken up that same argument about the parameters. Despite that incredible insight, the real carts don't exceed 65% WS.

One has to ask what Spork knows, that Stuttgart University and Delft TU don't know. It's you. He knows you will swallow the lure.
Sporky has power generation ambitions, don't you Sporky?

This time, let's take a look at the con before it starts.
It's true that all the professional carts use a small rotor, but that does no preclude them using the same ideas. Why are they not refining Spork's ideas, but doing something else?
What can the difference be? The size of the prop. One that is so big, it can dip into the high speed air that is several meters above the ground.
If Spork know so much, why not take the easier and much quicker course of building a cart the same size as the professional carts, and then wowing Stuttgart and Delft?
That would surely attract a lot of attention from academia, and he would then not have to keep knocking on their doors.
No need to go to Europe! Videos are proof, right? Wake up.

 

[humber]

I am tired of Sporky ripping off my ideas. This cart is my latest creation. There is a wind gradient between the ground and the air above. Galilean Transform says that gradient will be there, no matter what the speed of the cart. There will always be a difference.
I use that to travel 3.2 times WS, upwind. Now tell me it won't work.

http://www.internationalskeptics.com/forums/attachment.php?attachmentid=21442&stc=1&d=1300529735

 

[Jack by the hedge]

The claim is that the cart is not PM, because it extracts energy from the wind. But, the wheel drives the prop. What drives the cart, to get that headwind that is said to drive the prop?

It's the wheel, apparently.

No. You're still not paying attention.

The wind pushes the prop.

The prop pushes the cart.

The cart moves over the ground.

The ground turns the wheels.

The wheels turn the prop.

The power does not come from the wheels turning the prop. The turning is only required for the prop blade faces to present a bearing surface to the wind which is always travelling slower than the wind.

 

[Jack by the hedge]

Recall that the is supposedly a ratchet, so there is not chance of the prop influencing the wheel, but if it's not there, it still won't work. The small cart has no ratchet, yet the the BB and that cart are said to be the same.

The ratchet does not operate while the cart is running. It is as if the ratchet was not present. So functionally the two are the same, just as bicycles with or without a freewheeling hub are functionally indestinguishable while pedalling.

In other words, forget about the ratchet. It's irrelevant to the normal operation of the cart.

 

[Jack by the hedge]

...Which means the wheel must turn faster. Which turns the prop faster, which turns the wheel faster. Why does that not work in still air?
Push the cart, and it sees a headwind, which you say is tailwind to the spinning prop, so off it goes?


As long as....
What wind pushing from the rear? There is no tailwind. That is why dwfttw is considered to be impossible. You have the cart generating it's own headwind and tailwind! Good grief.

It would not work in still air for the same reason a land yacht would not work.
It is not generating its own tailwind; the wind is the tailwind. It is generating a "sail" surface which is travelling below windspeed.

Imagine a more conventional land yacht, for a moment: No problem with something like that being pushed directly downwind, is there?

Now imagine it had a moveable mast which could slide to any position along the full length of the yacht. Silly, but it would still work just like a yacht.

Now imagine a mechanism to drive the mast along its slide, geared to the yacht's wheels.

You might want to imagine a clutch too, so that the mechanism is initially disengaged.

With the mast in its forward position, run the yacht DDW to its top speed.

Now engage the clutch.

The mast moves backwards.

As it moves, the windspeed from the sail's point of view has increased.

The yacht begins to speed up a little.

Unfortunately, it quickly runs out of travel and the yacht will resume its former top speed, now with the sail at the back.

(Take a breather there and please indicate if you have any objection in principle to the mechanics of the above)

Next, if you don't object, we can start on how a propeller blade presents the equivalent of a constantly-retreating face to the air behind it.

 

[humber]

No. You're still not paying attention.

The wind pushes the prop.

The wind does what? That same headwind which strikes the chassis is drag. Spork has that as an opposing force. It is taken away from the net. That is calculated that way. You want me to believe that if it strikes the prop, it drives the cart.

The prop pushes the cart.

If there is power input to the drive shaft.

The cart moves over the ground.
The ground turns the wheels.

Ground power. Medieval. Waiting for Spork to rediscover. Everyone else has missed it. Einstein missed it.

The wheels turn the prop.

True.

The power does not come from the wheels turning the prop. The turning is only required for the prop blade faces to present a bearing surface to the wind which is always travelling slower than the wind.

Won't work electrical model says so.
But the basic problem that "most" people see is that there is no tailwind above WS. A sail could never exceed WS, even hypothetically.

So the solution is to move the prop so that there is a difference, is that it?

Drag drives the prop, which drives the cart, which makes the drag which drives the prop...but the ground drives the wheel. Errr...

 

[humber]

The ratchet does not operate while the cart is running. It is as if the ratchet was not present. So functionally the two are the same, just as bicycles with or without a freewheeling hub are functionally indestinguishable while pedalling.

In other words, forget about the ratchet. It's irrelevant to the normal operation of the cart.

Nice try. You can't drive the wheel while pedaling backwards. The ratchet disengages. Throw away the chain and gears.
As I said, if the prop can drive the cart without driving the wheel, you never needed the chain in the first place.
That leaves you with the ground driving the wheel and then the prop. The ratchet makes it a one way street.

 

[humber]

What about my gradient cart? I have been told I am a super-troll.
If I were to have launched that on the internet, and told you that you "just didn't get it" and recruited others to tell you the same, do you think I couldn't sell it to you?
I can make a TM, and cart too. And more, believe me.

I have been thinking about this. I make a prop cart which uses Spork's generator/motor combo. I say it would fail.
But, when the belt is off, it climbs the belt. No batteries, no wires, no stored energy, fans....nothing. Level.
How does it work?

 

[humber]

It would not work in still air for the same reason a land yacht would not work.
It is not generating its own tailwind; the wind is the tailwind. It is generating a "sail" surface which is travelling below windspeed.

At windspeed Vwind - Vcart = 0 +/- whatever the prop does
In still air Vwind- Vcart = 0 +/- whatever the prop does.
Should work

Imagine a more conventional land yacht, for a moment: No problem with something like that being pushed directly downwind, is there?

Not sure what the top speed is, but less then WS.

Now imagine it had a moveable mast which could slide to any position along the full length of the yacht. Silly, but it would still work just like a yacht.

Now imagine a mechanism to drive the mast along its slide, geared to the yacht's wheels.

Yes. That is a sort of fan. The problem is there is nothing to power the mechanism or do the work against the air. PM talk.

You might want to imagine a clutch too, so that the mechanism is initially disengaged.
With the mast in its forward position, run the yacht DDW to its top speed.
Now engage the clutch.
The mast moves backwards.
As it moves, the windspeed from the sail's point of view has increased.

That too should work in still air.

The yacht begins to speed up a little.

Unfortunately, it quickly runs out of travel and the yacht will resume its former top speed, now with the sail at the back.
(Take a breather there and please indicate if you have any objection in principle to the mechanics of the above)
Next, if you don't object, we can start on how a propeller blade presents the equivalent of a constantly-retreating face to the air behind it.

But you have not solved anything. The reason that a sail could never exceed WS, is that it would have to move away from the tailwind. Retreat from the tailwind.
Now you have the prop face moving away from the tailwind.

 

[D'rok]

The wind does what? That same headwind which strikes the chassis is drag. Spork has that as an opposing force. It is taken away from the net. That is calculated that way. You want me to believe that if it strikes the prop, it drives the cart.

In today's lesson from the Humberverse, I learned that it is impossible for a sailboat to tack downwind because the headwind generated creates drag.

Back in the realityverse, I remember seeing a youtube computer animation with a sailboat tacking downwind that morphs into a sailboat tacking downwind on a cylinder. Does anyone have a link to that? It is a very helpful visualization tool.

ETA: Found it

 

[humber]

In today's lesson from the Humberverse, I learned that it is impossible for a sailboat to tack downwind because the headwind generated creates drag.

Tacking allows lift too. DDW doesn't.
AND your GURU HIMSELF has that headwind as drag and subtracts it from the net force. But when that wind hits the prop instead of the chassis...hey presto, it drives the cart!

Back in the realityverse, I remember seeing a youtube computer animation with a sailboat tacking downwind that morphs into a sailboat tacking downwind on a cylinder. Does anyone have a link to that? It is a very helpful visualization tool.

Made by a tool.

ETA:
Here's a "reality check" A headwind. Remember that there is still the virtual wind, so there must be a headwind coming from the left foward of the cart, faster than the cart
That should disengage the ratchet.
Do you want to buy some shares in my gold mine? Get in on the ground floor, before the shares rocket. Act now. (or accept the upwind cart)

 

[D'rok]

Tacking allow lift too. DDW doesn't.
AND your GURU HIMSELF has that headwind as drag an subtracts it from the net force. But when that wind hits the prop instead of the chassis...hey presto, it drives the cart!

You are conflating the tailwind and the headwind. There is still an apparent tailwind past wind speed. The headwind is generated by exceeding wind speed. The two winds act on the cart simultaneously.

 

[humber]

You are conflating the tailwind and the headwind. There is still an apparent tailwind past wind speed. The headwind is generated by exceeding wind speed. The two winds act on the cart simultaneously.

No the apparent wind is turning the tail towards the rear, as in the picture above (>WS), but just a few seconds later the true wind is coming form the left towards the cart. A real headwind, not a tailwind.
That is why Richard Jenkins says, rather uneasily, "significant headwind".

ETA:
And get this into your head. There is NO TAILWIND above WS. Hence FASTER THAN THE WIND.