Wind powered cart traveling directly down wind faster than the wind

[spork]

I would like to come out and witness the upwind version of Blackbird and play with the model downwind car. Please let me know (or know where to watch) for a schedule.

I have a list of emails that I send occasional updates to. If you'd like to PM me your email address, I'll add it to that list. You can also watch www.fasterthanthewind.org for updates.

As for whether the downwind is a hoax IMO FTTW is a hoax for sure.

It rather offends me that you insist on calling me a liar; and it rather surprises me that you won't even attempt to understand the very simple math that explains how this is possible.

Whether the cart can go downwind at all is something I need to witness.

How could you possibly doubt it could go downwind "at all". A brick on wheels will go downwind.

It seems to me that reverse direction torque from the prop would overpower or at least cancel out forward thrust from the wind.

Really!? What if I used very broad blades, at very nearly 0 pitch?

If it doesn't then I'll just admit I don't know WTF is going on.

But apparently you'll still claim that DDWFTTW is a hoax - even if demonstrated to you. I don't understand this.

 

[ebacon]

Spork,

When you say that the DDWFTTW cart is a brain teaser and wish that A. Bauer could be around for the "current round of silliness", then you must be ready to be called a hoaxster. It comes with the territory. I make no apologies for calling things as I see them -- and IMO I'm seeing a hoax.

As for the cart, or a brick, or anything being able to be blown downwind, that is certainly true. But the issue here isn't whether a hurricane can blow away the cart. Or a brick. Or a Bluebird Wanderlodge for that matter. The issue is whether the cart can travel faster than the wind. My position is no. No surprise there. Not even if the prop blades are very broad and very nearly 0 pitch at start and increase pitch thereafter.

What is the "very simple math" that you speak of? I've reviewed everything that I've seen, namely

* Four free-body diagrams
* Video of how a prop simulates a sail on a perpetual reach
* University research proposal analyzing the prop
* Graphic explanation of feedback power

Did I miss anything?

 

[spork]

I make no apologies for calling things as I see them -- and IMO I'm seeing a hoax.

Fair enough. You call my integrity into question and make no apologies, so I assume you would expect no apologies if I called your intelligence into question.

As for the cart, or a brick, or anything being able to be blown downwind, that is certainly true. But the issue here isn't whether a hurricane can blow away the cart. Or a brick. Or a Bluebird Wanderlodge for that matter.

Yes - apparently it is. You say that you only need to see it go downwind - not faster than the wind. I have no idea what the point of that is. See above.

The issue is whether the cart can travel faster than the wind.

Apparently that is NOT the issue. You've already decided you know it's a hoax, and don't even want to see it proved in real life or on paper.

My position is no. No surprise there. Not even if the prop blades are very broad and very nearly 0 pitch at start and increase pitch thereafter.

Who said anything about increasing pitch thereafter. You said you didn't think the cart would blow downwind at any speed. At some point as I decrease pitch, and increase surface area, I have little more than a spinnaker on a wheeled cart. I think most people would agree that can go downwind at SOME speed.

What is the "very simple math" that you speak of? I've reviewed everything that I've seen, namely

* Four free-body diagrams
* Video of how a prop simulates a sail on a perpetual reach
* University research proposal analyzing the prop
* Graphic explanation of feedback power

Did I miss anything?

So you're seen it all (you think), and you have no questions about ANY of it. It's all just wrong. Nothing specific - nowhere it went off the rails - just wrong. Which I take to mean you can't begin to understand it enough to even ask questions.

ETA: I wonder if you can find a single other person on this forum that thinks this is a hoax. Do you think we managed to trick our sponsors (Joby Energy and Google), NASA, NALSA, the Stanford Aero dept, and many many others? Only YOU have figured us out?

 

[EdFred]

You aren't thinking 3 dimensionally.

 

[ebacon]

Only YOU have figured us out?

It's not only me. You can challenge my intelligence all you want. It's been done before in this thread but it didn't persuade me that the cart works.

If you want to show me that Blackbird and/or the model cart actually does DDWFTTW in real life then I'm willing to witness it. No treadmills. Earlier I said that I would let you off the hook for DDWFTTW for two simple reasons. First, my understanding was that Blackbird is reconfigured and no longer up to the task. Second, the model cart is a challenge to instrument.

My goal with witnessing the model is simple -- I would like to see whether the reverse torque from the prop swamps out the thrust of the tailwind during startup. I think it does and if I'm wrong I'll admit it. Of course if I show up at your place and the prop on the model cart is swapped out to some "very near zero" fixed pitch prop then I'll be disappointed. That would be an underhanded trick.

 

[ebacon]

You aren't thinking 3 dimensionally.

Who are you talking to?

 

[EdFred]

Who are you talking to?

You. Spork has it figured out.

 

[jesse]

Spork, if I were you, I wouldn't be wasting my time or energy educating one stubborn individual that you don't know whom is somewhere else on the internet. For all you know he is trolling you.

 

[ebacon]

You. Spork has it figured out.

I hope so. He built it.

Maybe you can explain it differently. What do you think I am missing?

 

[TripleZ]

D98 to GRR is a 1 hour flight. Make a day trip out of it, see the model in person. Make a new friend. Go flying.

Win-Win

 

[ebacon]

D98 to GRR is a 1 hour flight. Make a day trip out of it, see the model in person. Make a new friend. Go flying.

Win-Win

EdFred,

Do you have a cart?

 

[EdFred]

I hope so. He built it.

Maybe you can explain it differently. What do you think I am missing?

The blades move across the wind, not directly in line with it...

 

[ebacon]

The blades move across the wind, not directly in line with it...

I appreciate that theory. Here is why I don't buy it.

Recall that the apparent wind changes from directly behind to directly ahead as the cart supposedly accelerates through the condition of zero apparent wind. When the apparent wind reaches zero (I submit it never does but let's say it did) then the thrust provided by the prop is also zero.

When a blade is sitting in dead air (apparent zero wind) it creates no power regardless of its angle of attack. At that instant the vehicle will decelerate until the apparent wind picks up again. The vehicle will not, despite assertions to the contrary, magically accelerate upon the lack of power and punch through the zero relative wind boundary. Magic is against the rules. Spork said so.

 

[COFlyBoy]

I appreciate that theory. Here is why I don't buy it.

Recall that the apparent wind changes from directly behind to directly ahead as the cart supposedly accelerates through the condition of zero apparent wind. When the apparent wind reaches zero (I submit it never does but let's say it did) then the thrust provided by the prop is also zero.

When a blade is sitting in dead air (apparent zero wind) it creates no power regardless of its angle of attack. At that instant the vehicle will decelerate until the apparent wind picks up again. The vehicle will not, despite assertions to the contrary, magically accelerate upon the lack of power and punch through the zero relative wind boundary. Magic is against the rules. Spork said so.

The prop is rotating, so regardless of the relative speed of the cart to the air, the prop always produces thrust. Remember when you are sitting at the end of the runway on a calm day, there is zero wind, but your propellor manages to create thrust.

The only way for the prop to not generate any thrust would be if the wind became a swirling horizontal vortex of doom centered on the axis of the prop (I submit that this is unlikely).

 

[spork]

The vehicle will not, despite assertions to the contrary, magically accelerate upon the lack of power and punch through the zero relative wind boundary. Magic is against the rules. Spork said so.

Making bizarre claims about our assertions is against the rules as well. Speak for yourself or quote us.

 

[ziege]

Bounces...it really is a scam, just not the scam you think.

The whole thing is an exercise in verbal misdirection. Any sailboat (water, ice, or land) can do exactly what they are doing, and every cruising sailboat does it when covering long distances downwind. You hold a broad reach to port for awhile, then jibe across and hold a broad reach to starboard, then jibe back to port. At any instant it looks like the boat is going across the wind, but over hundreds of miles it obviously averages out to going directly downwind faster than the wind. Of course if you described it as downwind faster than the wind the way these cart drivers did people would laugh at you, but at a very high level that's what is happening..

The cart fools people into thinking it is different than the sailboat because it is able to "jibe" very quickly without flipping the sail from one side to the other. That's it. The eye is drawn to the wrong place... drawn to the cart instead of the sails... and you perceive it as different than the sailboat. They are counting on that to pull of their scam.

If what they are doing is "directly downwind" then any iceboat has them beat over a mile...and if they start quibbling about the cart not moving side to side, well, tell 'em you'll listen when their sail stops turning.

 

[ebacon]

The prop is rotating, so regardless of the relative speed of the cart to the air, the prop always produces thrust. Remember when you are sitting at the end of the runway on a calm day, there is zero wind, but your propellor manages to create thrust.

The only way for the prop to not generate any thrust would be if the wind became a swirling horizontal vortex of doom centered on the axis of the prop (I submit that this is unlikely).

Simply not the case. If the prop is modeled as a rolled up plane (such as a flat lakebed) then undo the model and go back to reality.

On a flat lakebed the relative windspeed actually goes to zero. When that happens thrust also goes to zero regardless of the sail's angle of attack.

There is no magic in a propeller. If it generates 150 MPH wind in still air then when a 150 MPH wind is blown at its back its thrust will be zero. The wind does not need to be a swirling horizontal vortex of doom.

 

[ebacon]

Making bizarre claims about our assertions is against the rules as well. Speak for yourself or quote us.

Here it is. Using magic is cheating, aka against teh rulezorrx.

I was very careful not to employ any magic at all in designing this vehicle. I think that would be considered cheating.

 

[Skylane81E]

Honestly if you look at it like this the physics are sound

The air has kenetic energy in the form of wind

The cart needs energy to counteract drag

So long as the car manages to slow the wind it has extracted some engergy

The prop blows backwards into the wind slowing the wind, that energy has to go somewhere...

Now as to the self start ability of it if the pitch is fine enough the push forward against the cart would be greater than the push sideways on the prop trying to rotate it.

 

[Skylane81E]

There is no magic in a propeller. If it generates 150 MPH wind in still air then when a 150 MPH wind is blown at its back its thrust will be zero. The wind does not need to be a swirling horizontal vortex of doom.

The windspeed may drop to zero but it takes a force to slow the tailwind to zero and the reaction to that force would push against the prop

 

[ebacon]

Honestly if you look at it like this the physics are sound

The wind has kenetic energy in the form of wind

The cart needs energy to counteract drag

So long as the car manages to slow the wind it has extracted some engergy

The prop blows backwards into the wind slowing the wind, that energy has to go somewhere...

Now as to the self start ability of it if the pitch is fine enough the push forward against the cart would be greater than the push sideways on the prop trying to rotate it.

I agree with all of that. But there is one more vital element that is missing.

When the wheels turn the prop they are acting like brakes. Unless the prop makes more thrust than the braking action produces the cart won't move.

But if the prop makes more thrust than the wheels generate braking action then energy came out of thin air. Magic.

Since magic is against the rules then it must be thin air, aka a hoax.

What's the name of the outfit that designed the car? Thin Air Designs. They design brain teasers. Hoaxes. That's what they do and they are damn good at it.

That's my story and I'm sticking to it.

EdFred!!

Do you have a model cart? Someone suggested you might. I fly out of KPTK and could be there in a jiffy.

 

[Skylane81E]

then energy came out of thin air.

Exactly, it DID come out of thin (moving) air, by extracting some of the energy from the wind, any delta V involves an exchange of energy

 

[ebacon]

Exactly, it DID come out of thin (moving) air, by extracting some of the energy from the wind, any delta V involves an exchange of energy

I agree with that, too. Where are we disconnecting?

Do you agree that the wheels will provide braking action whenever they are powering the prop?

 

[spork]

Bounces...it really is a scam, just not the scam you think.

The whole thing is an exercise in verbal misdirection.

Wrong. It's a brain-teaser and billed as such. There is no scam, nor any verbal misdirection.

Any sailboat (water, ice, or land) can do exactly what they are doing

Wrong again. No traditional sailing vessel can go directly downwind, faster than the wind, steady state.

Of course if you described it as downwind faster than the wind the way these cart drivers did people would laugh at you, but at a very high level that's what is happening..

Wrong yet again. We describe directly downwind faster than the wind as going "directly downwind faster than the wind". It's what we claim and it's what we do. No traditional sailing craft can do that.

The cart fools people into thinking it is different than the sailboat because it is able to "jibe" very quickly without flipping the sail from one side to the other.

Wrong yet again. Each blade of the prop is on a continuous helical broad reach. The craft, the pilot, and even the center of gravity go directly downwind - no tacking.

That's it. The eye is drawn to the wrong place... drawn to the cart instead of the sails... and you perceive it as different than the sailboat. They are counting on that to pull of their scam.

I thought there was a rule about keeping things civil on this forum, but you guys seem to be fine with calling me a liar and a scam artist.

If what they are doing is "directly downwind" then any iceboat has them beat over a mile...and if they start quibbling about the cart not moving side to side, well, tell 'em you'll listen when their sail stops turning.

Interesting theory. Must EVERY single particle go directly downwind? Can we have wheels? Essentially the entire wheel is going some direction other than directly downwind.

On a flat lakebed the relative windspeed actually goes to zero. When that happens thrust also goes to zero regardless of the sail's angle of attack.

Is your plane able to produce thrust by spinning the prop during run-up in no wind?

As to the words you're putting in my mouth, they were quoted in that same post. You said:
"The vehicle will not, despite assertions to the contrary, magically accelerate upon the lack of power and punch through the zero relative wind boundary"

That's why I say you should speak for yourself and quote me. I don't need you getting things completely wrong and attributing them to me.

Honestly if you look at it like this the physics are sound

The air has kenetic energy in the form of wind

The cart needs energy to counteract drag

So long as the car manages to slow the wind it has extracted some engergy

The prop blows backwards into the wind slowing the wind, that energy has to go somewhere...

Now as to the self start ability of it if the pitch is fine enough the push forward against the cart would be greater than the push sideways on the prop trying to rotate it.

Bingo.

 

[spork]

When the wheels turn the prop they are acting like brakes.

Correct.

Unless the prop makes more thrust than the braking action produces the cart won't move.

Correct

But if the prop makes more thrust than the wheels generate braking action then energy came out of thin air. Magic.

Wrong. See my post where I explain the energy balance in astonishingly simple terms.

Since magic is against the rules then it must be thin air, aka a hoax.

It's clearly time for me to start reporting posts. I'm tired of these accusations.

What's the name of the outfit that designed the car? Thin Air Designs. They design brain teasers. Hoaxes. That's what they do and they are damn good at it.

Is this the part where we just make up random things and state them as fact!?

 

[ebacon]

Is your plane able to produce thrust by spinning the prop during run-up in no wind?

It is, but in that case the energy for thrust comes from avgas.

If there is no apparent wind at the prop then its thrust is zero.

 

[ebacon]

It's clearly time for me to start reporting posts. I'm tired of these accusations.

My buddies kid does that. When his sister touches him he falls to the floor in feigned pain, screaming for his mother. Between screams he winks at his audience as he lays in wait for his sister to get in trouble.

 

[EdFred]

I don't have a model, but could easily make one. two rods, a couple pieces of balsa, a couple gears, three wheels, one prop, done.

 

[COFlyBoy]

Simply not the case. If the prop is modeled as a rolled up plane (such as a flat lakebed) then undo the model and go back to reality.

Huh?

On a flat lakebed the relative windspeed actually goes to zero. When that happens thrust also goes to zero regardless of the sail's angle of attack.

Not sure why it has to be a lakebed, but on any flat surface when the relative speed between the cart and the wind drops to zero, the prop will still produce thrust because it is turning. A turning prop (assuming positive pitch) will produce thrust, doesn't matter if there is wind or not.

There is no magic in a propeller. If it generates 150 MPH wind in still air then when a 150 MPH wind is blown at its back its thrust will be zero. The wind does not need to be a swirling horizontal vortex of doom.

No, The thrust will still be whatever it was at 0 windspeed. You are correct that if the prop can accelerate still air to150 mph, and you hit it from the back with a 150mph wind, then the wind will stop. But, the prop did work to stop the air, and that work took force (ie. thrust). So, the prop had to produce thrust to stop the air.

 

[ebacon]

Huh?



Not sure why it has to be a lakebed, but on any flat surface when the relative speed between the cart and the wind drops to zero, the prop will still produce thrust because it is turning. A turning prop (assuming positive pitch) will produce thrust, doesn't matter if there is wind or not.



No, The thrust will still be whatever it was at 0 windspeed. You are correct that if the prop can accelerate still air to150 mph, and you hit it from the back with a 150mph wind, then the wind will stop. But, the prop did work to stop the air, and that work took force (ie. thrust). So, the prop had to produce thrust to stop the air.

I'm curious, do you race sail boats?

A lot of the BS supporting this cart looks good on paper. Also airplane pilots might not have a grasp of how zero a zero apparent wind really is.

Zero apparent wind is frickin zero. It is so zero that smoke hangs in the air even if the real wind is blowing fifteen. There is no power. None. Zilch. Bupkis. It's the end of the line for free power. If you want to go faster than that you need to get additional energy from somewhere else, such as an engine.

 

[spork]

It is, but in that case the energy for thrust comes from avgas.

If there is no apparent wind at the prop then its thrust is zero.

Wrong again. You're making a career of this. I'm beginning to believe those that warned me about you being a troll.

My buddies kid does that. When his sister touches him he falls to the floor in feigned pain, screaming for his mother. Between screams he winks at his audience as he lays in wait for his sister to get in trouble.

The policy says "be civil". It's a rule or it ain't. I'll be happy to take the gloves off it that's the policy here.

A lot of the BS supporting this cart looks good on paper.

How can you say that!? You clearly don't understand the first thing about what's been explained - including our claims.

airplane pilots might not have a grasp of how zero a zero apparent wind really is.

Yes, I'll grant you that you might not understand anything about this.

Zero apparent wind is frickin zero. It is so zero that smoke hangs in the air even if the real wind is blowing fifteen. There is no power. None. Zilch. Bupkis.

Do you understand the difference between apparent wind and true wind? Never mind - that was a rhetorical question. Of course you don't.

It's the end of the line for free power. If you want to go faster than that you need to get additional energy from somewhere else, such as an engine.

Or how about getting it from the true wind?

 

[ebacon]

Wrong again. You're making a career of this. I'm beginning to believe those that warned me about you being a troll.




The policy says "be civil". It's a rule or it ain't. I'll be happy to take the gloves off it that's the policy here.



How can you say that!? You clearly don't understand the first thing about what's been explained - including our claims.



Yes, I'll grant you that you might not understand anything about this.



Do you understand the difference between apparent wind and true wind? Never mind - that was a rhetorical question. Of course you don't.



Or how about getting it from the true wind?

I give up. You beat me with experience.

Hope to see you later this year.

 

[ziege]

Wrong. It's a brain-teaser and billed as such. There is no scam, nor any verbal misdirection.

That's all there is. You say it's going directly downwind when it's actually on a broad reach. That's a verbal misdirection.

Wrong again. No traditional sailing vessel can go directly downwind, faster than the wind, steady state.

Steady state means "unchanging in time" ... your cart changes constantly. You are not doing what you claim to do.

When we allow that it is not steady state but average, then ANY sailboat can do exactly what you do, maintain a broad reach over a long distance and average the changes so that the vehicle maintains an average course directly downwind.

Wrong yet again. We describe directly downwind faster than the wind as going "directly downwind faster than the wind". It's what we claim and it's what we do. No traditional sailing craft can do that.

You are just on a run with these false accusations. You do not go directly downwind. Parts of your vehicle go directly downwind while others go across the wind.

Wrong yet again. Each blade of the prop is on a continuous helical broad reach. The craft, the pilot, and even the center of gravity go directly downwind - no tacking.

That's not wrong, that's another way of saying what I said.

I thought there was a rule about keeping things civil on this forum, but you guys seem to be fine with calling me a liar and a scam artist.

You could just take it as a compliment. I'm not saying your cart doesn't move. I'm just pointing out that you've chosen a deliberately obscure way of describing a simple device in order to foster argument. Maybe scammer should be replaced with "troll"....

Interesting theory. Must EVERY single particle go directly downwind? Can we have wheels? Essentially the entire wheel is going some direction other than directly downwind.

If it is "steady state" then yes, at normal scale every part must remain fixed relative to every other.

 

[Skylane81E]

I agree with that, too. Where are we disconnecting?

Do you agree that the wheels will provide braking action whenever they are powering the prop?

Yes I agree, this is where it becomes an engineering problem rather than a physics one:wink2:

 

[ebacon]

Yes I agree, this is where it becomes an engineering problem rather than a physics one:wink2:

That's fine. Explain how the power provided by the prop exceeds the power consumed by the wheels.

Recall that there is no external source of power here. No treadmill motor. No gas engine. No battery power. Just the wind, and that was used up getting the car up to the speed of the wind. At lest according to the free body diagrams.

Where is the additional power coming from? A winky smiley doesn't help me undertand.

 

[Skylane81E]

That's fine. Explain how the power provided by the prop exceeds the power consumed by the wheels.

Recall that there is no external source of power here. No treadmill motor. No gas engine. No battery power. Just the wind, and that was used up getting the car up to the speed of the wind. At lest according to the free body diagrams.

Where is the additional power coming from? A winky smiley doesn't help me undertand.

The wind didn't stop blowing, it's still there, the rearward push of the prop is causing the wind to slow and for that reason the wind is continuing to do work on the cart. Now that you have something to do work you just need to keep the efficencies high enough to keep the amount of work done > mechanical drag of the system and the cart will accelerate

 

[ebacon]

The wind didn't stop blowing, it's still there, the rearward push of the prop is causing the wind to slow and for that reason the wind is continuing to do work on the cart. Now that you have something to do work you just need to keep the efficencies high enough to keep the amount of work done > mechanical drag of the system and the cart will accelerate

I agree with all of that, too.

But if the efficiency of the wheel/prop system is <=1 then the cart can't punch through the zero wind barrier.

And if their efficiency is > 1 then it's a perpetual motion machine.

Are saying that if 1 HP is applied to the wheels then > 1 HP will come from the prop? If not then the prop/wheel system must be a net brake, not a net power source.

 

[Skylane81E]

I agree with all of that, too.

But if the efficiency of the wheel/prop system is <=1 then the cart can't punch through the zero wind barrier.

And if their efficiency is > 1 then it's a perpetual motion machine.

Are saying that if 1 HP is applied to the wheels then > 1 HP will come from the prop? If not then the prop/wheel system must be a net brake, not a net power source.

Conservation of energy, if the tail wind has slowed where did the energy go?

 

[Skylane81E]

Or to put it another way:

The wind is doing work on the cart,

the cart isn't doing work on the wind

 

[ebacon]

Conservation of energy, if the tail wind has slowed where did the energy go?

When the cart is sitting still and the wind is blowing across it then the cart has zero kinetic energy. After the cart gets moving it has kinetic energy that came from the wind.

The maximum kinetic energy is 1/2mv^2 where v is the wind speed if the cart is 100% efficient at capturing the wind energy. But it isn't 100% efficient. It's less than that and if it's more then it's magic.