Down wind faster than the wind

[Brian-M]

Yet you still don't seem to get the fact that the wheel and prop are directly tied to each other. If you turn it around the wheels turn the other way but that means so does the prop because they are tied together.

That's a very good reason why the device in the first video can't go faster downwind than wind-speed. If it started going faster than the wind, the headwind would be pushing the prop in the opposite direction, slowing the whole thing down.


I've a question for everyone, just to make sure I'm not jumping to false conclusions.

When a windmill/propeller is facing directly into the wind, can the force from the wind turning the blades ever exceed the force from the wind pushing the blades backward?

 

[.13.]

I'm agreeing with you. Im just pointing out you gave the same explanation as airplane on a treadmill.

I see. I just got confused by the frustrated tone of your post.

 

[Thabiguy]

But it is moving against both and useing that force to increase its speed against both.

That's correct. The boat sailing against the wind increases its speed against both the water and the wind. The car in my car-and-ball example increases its speed against all other cars. And the OP device increases its speed against both the air and the ground.

Such speed increase is perfectly valid. You should concentrate on the aforementioned examples and think about them really hard, until you're sure you completely understand what's going on in them.

This is not some issue of redefining coordinate systems.

Indeed, it is not some issue of redefining coordinate systems. The speed increase is real. Do the math. Check it for yourself.

The claim here is that if the you are on a treadmill going some speed and have wind blowing in the same dirrection of motion at a lower speed it will accelerate at the sources.

I don't know what "accelerate at the sources" means, but if you are on a treadmill going some speed and have wind blowing in the same direction at a lower speed, yes, you can use the wind to accelerate forward. If you stop for a while and think about it, you will realize that the boat sailing against the wind does exactly that.

Im going to scream if I hear one more person say that this has nothing to do with airplane on a treadmill I will scream.

This has nothing to do with airplane on a treadmill. Scream all you want; when you're done screaming, it will still be true.

 

[Modified]

The nature of vector addition might well kill this. The boats might be moving faster than the wind, but is the down wind component of their velocity faster than the wind?

Traveling upwind is possible, and that is effectively traveling downstream faster than the water (you can do that "for real" going downriver on a windless day). The air and the water are just two streams. So by symmetry it should be possible in a sailboat or something very much like it.

But you don't even need that. See my last iceboat example. If you can travel faster than the wind at some angle, then you can average faster than the wind in the downwind direction, by turning downwind and coasting with sails down, if you have low enough friction and drag. Now connect the sliding bar again and you have a system that can average faster than the wind in the downwind direction. Connect four boats with a more complex sliding system and you can maintain a steady downwind speed that is faster than the wind. Not practical in real life, but nothing wrong with it given semi-ideal components.

 

[Acleron]

The air is motionless with respect to the device as a whole, but not with respect to the blades of the propeller. (It's more obvious in the blower version.) The blades are moving backwards with respect to the air, which makes the air exert forward force on them.



The energy comes from the air being slowed, with respect to the ground, as it pushes the propeller forward.



No, because the air is still pushing forward on the propeller. It's easier to see in the blower version, but it's also true in the propeller version, when f < 1.

And I thought we had a really interesting discussion. Never mind. When somebody cannot see that enregy in cannot exceed energy out there is no argument.

 

[Thabiguy]

And I thought we had a really interesting discussion. Never mind. When somebody cannot see that enregy in cannot exceed energy out there is no argument.

*sigh*
Sometimes I wonder what is sadder - if it's woos who claim they invented machines that violate the law of conservation, or if it's people who miscomprehend a perfectly valid mechanism to the point of claiming it violates the law of conservation.

I think you have a little more chance of finding out that you're wrong than the woos. Good luck.

This should be a lesson to all skeptics, including myself: never be so full of yourself to think that you cannot be dead wrong about something.

 

[technoextreme]

*sigh*
Sometimes I wonder what is sadder - if it's woos who claim they invented machines that violate the law of conservation, or if it's people who miscomprehend a perfectly valid mechanism to the point of claiming it violates the law of conservation.

I don't think you correctly used the word drag once in this entire topic.

 

[Thabiguy]

People who have no clue what they are talking about is sadder. I don't think you correctly used the word drag once in this entire topic.

That's possible; I'm not a native English speaker. The irony is, even though you imagine I "have no clue what I'm talking about", it's you who weren't right once in this entire topic.

If you want to find out how the device operates, I can help to explain. If you think you can show that the device doesn't work, I can answer your arguments. And if you just want to hold on to your misconceptions, well, I hope you have a good time holding on to them.

 

[Thabiguy]

As this is an educational forum, I'll try and offer something useful to those who have a hard time wrapping their minds around the OP device, but are willing to give it a try.

Roadmap to comprehension:

1. This is a counter-intuitive gadget. There are many working mechanisms that are counter-intuitive, and may appear to violate the laws of physics, but don't. This is one of them.

How to proceed: do not trust your instinct. Your gut judgement can be misleading. Instead, go the rigorous way. Use math. Apply the laws of physics. Check your assumptions, check your results. Do not try to come up with proofs supporting your beliefs - instead, be inquisitive and try to find out what is actually going on. If it works, how exactly does it work? If it doesn't work, how exactly does it fail?

2. Realize that downwind travel faster than the wind is not violating the law of conversation.

How to proceed: realize that there already are existing machines that do just that. There are many examples in this thread. Concentrate on understanding how these existing machines work. Concentrate on understanding why these existing machines do not violate the law of conversation.

3. Verify that the OP device happens to be one of those devices that can travel faster than the wind.

How to proceed: try to understand how it works. It's not easy, but if you go through this thread, you may find posts that will help you. Ask questions; people will explain. You might even try to build the device yourself.

 

[my_wan]

That's a very good reason why the device in the first video can't go faster downwind than wind-speed. If it started going faster than the wind, the headwind would be pushing the prop in the opposite direction, slowing the whole thing down.

It doesn't slow it down, it only slows down how fast it accelerates until the wind is resistance gets so high it can't accelerate anymore.

I've a question for everyone, just to make sure I'm not jumping to false conclusions.

When a windmill/propeller is facing directly into the wind, can the force from the wind turning the blades ever exceed the force from the wind pushing the blades backward?

No, but force and speed are two entirely different things. When the forward force of the craft matches the winds resistive force the craft stops accelerating and simply stays at that velocity. When the craft is very near wind speed the resistive forces are very small but the force is quiet large because even though the wind speed is low relative to the craft the wheels must forcefully turn which then forcefully turns the prop. If the resistive force didn't keep increasing with speed the craft would eventually accelerate ever nearer light speed. In fact in space you can accelerate an elephant with the constant force output of a house fly to near light speed given enough time. That is the principle of how ion drives work. It is also true that the craft can't exceed the ground air speed + the average air speed of air coming out of the prop. Ground air speed + prop air speed is faster than wind speed alone though.

ETA: Reason why force and velocity is not the same: f=ma or force equals mass times acceleration, not velocity. Without friction zero force is required to maintain a relative velocity. Force is only needed to increase or decrease velocity relative to something.

 

[technoextreme]

If you want to find out how the device operates, I can help to explain.

No you can't because you don't even know the definition of drag, what it is, and why it's important to this discussion.

How to proceed: do not trust your instinct. Your gut judgement can be misleading. Instead, go the rigorous way. Use math. Apply the laws of physics. Check your assumptions, check your results. Do not try to come up with proofs supporting your beliefs - instead, be inquisitive and try to find out what is actually going on. If it works, how exactly does it work? If it doesn't work, how exactly does it fail?

I told you how it fails. DRAG DRAG DRAG DRAG DRAG DRAG DRAG. Look up the definition of DRAG. Read it. Embrace it. Hug it. Kiss it. Because you make the assumption that it doesn't stop the propeller.

How to proceed: realize that there already are existing machines that do just that. There are many examples in this thread. Concentrate on understanding how these existing machines work. Concentrate on understanding why these existing machines do not violate the law of conversation.

No. The only examples given really utilize tacking which isn't related to this discussion.

No, but force and speed are two entirely different things. When the forward force of the craft matches the winds resistive force the craft stops accelerating and simply stays at that velocity.

You forgot about DRAG. DRAG DRAG DRAG DRAG DRAG DRAG DRAG DRAG. And more drag.

 

[Thabiguy]

No you can't because you don't even know the definition of drag, what it is, and why it's important to this discussion.

Drag is the aerodynamic analogue of friction. It is a force resisting movement through a fluid.

I have explained that drag is essential to the operation of the device, and how. If you think you have some additional knowledge that I don't have about the importance of drag to this discussion, then please, do not just state that I don't know it, but tell us what it is.

 

[Thabiguy]

I told you how it fails. DRAG DRAG DRAG DRAG DRAG DRAG DRAG. Look up the definition of DRAG. Read it. Embrace it. Hug it. Kiss it.

You are not making any sense. That's like saying that a bicycle cannot work, because of FRICTION. And instead of explaining how friction prevents a bicycle from working, just shouting "FRICTION, FRICTION, FRICTION."

In order to show how drag prevents the device from working, you have to show how drag prevents the device from working. Not just shout "DRAG, DRAG".

 

[Thabiguy]

You forgot about DRAG. DRAG DRAG DRAG DRAG DRAG DRAG DRAG DRAG. And more drag.

 

[technoextreme]

Drag is the aerodynamic analogue of friction. It is a force resisting movement through a fluid.

I have explained that drag is essential to the operation of the device, and how. If you think you have some additional knowledge that I don't have about the importance of drag to this discussion, then please, do not just state that I don't know it, but tell us what it is.

Thats not drag. Every single time you've said drag you mean thrust. Every single time. How am I supposed to take anyone seriously that can't understand the difference between thrust and drag?

 

[spork]

The nature of vector addition might well kill this. The boats might be moving faster than the wind, but is the down wind component of their velocity faster than the wind?

Yes, the downwind component can be 3X or more the wind speed. There is plenty of GPS data to back this up. This is not in contention. It's an every day thing for ice-boat racers.

I don't think this will be resolved until you've posted the plans as promised, spork.

Fair enough. I can't imagine that will resolve it, but at least it will make it possible for anyone to try it.

I don't have it all laid out, but it's pretty darn straightforward. Hopefully this will be enough for anyone that wants to try it:

Get:
- A set of GWS 4" wheels (LXHHZ7) from any R/C hobby shop
- The 90 degree gear drive from a T-Rex 600 R/C heli and the torque tube that drives it.
- A 14" x 10" GWS plastic slow-flyer prop (same hobby shop)
- A 5 mm carbon tube for the axle
- A relatively soft aluminum tube from the hardware store (Orchard Supply Hardware in our case)
- A little bitty tail wheel.

- Remove the tail rotor drive shaft from the T-Rex 600 tail rotor gearbox and replace it with the 5mm carbon axle.
- Carefully drill out the hubs of the GWS wheels to fit the 5mm axle, and stick them on.
- Mount your aluminum tube to the bottom of the gear box (get creative) and bend it to form an arc like you see on JB's model (Make sure you have the gear box oriented such that pushing the cart forward causes the prop to spin clockwise when viewed from behind).
- Mount the tailwheel on the bottom of the arc'd aluminum tube
- Make a bearing support on the top of the arc'd aluminum tube to support the aft end of the torque tube.
- Drill the hub out on the GWS prop in order to fit it on the torque tube, and stick it in place (curved surface forward).
- Make sure everything spins VERY freely - spray the gears with silicone lubricant if necessary. You can even clean the lube out of the bearings to reduce the drag.

Place it on your treadmill at 10 mph. If it doesn't go straight ahead (and it won't) adjust the steering by bending the soft aluminum tube very slightly. Make sure this doesn't mess up the alignment and cause any drag.

Take a video and post it on youtube.

Don your flamesuit.

 

[my_wan]

No. The only examples given really utilize tacking which isn't related to this discussion.

Why is it not related? That's somewhat like saying a motorboat and a car is unrelated. Yet they both depend on an internal combustion engine for power. In sailing "tacking" works because wind speed + boat speed make the effect wind relative to the boat faster than the ground wind speed. This craft works because the ground wind speed + the propeller wind speed is faster relative to the craft than the ground wind speed alone.

The sailboat is still moving against the wind even if at an angle. Why wouldn't drag stop that from working?

 

[technoextreme]

Uggg... I right the first time. It's the problem with the drive ratio. You need to flip direction sometimes and you can't do that with a single belt drive.

 

[ThinAirDesigns]

Thabiguy:
>Drag is the aerodynamic analogue of friction. It is a force
>resisting movement through a fluid.

techno:
>Thats not drag. Every single time you've said drag
>you mean thrust. Every single time.

Someone needs to break it to techno that Thabi has presented a perfectly good definition of "drag" and it is he/she not Thabi who is confused in this regard. Ok, I'll do it.

techno, "thrust" is not the aerodynamic analogue of friction -- drag is.

techno, "thrust is not a force resisting movement through a fluid -- drag is.

techno, just to cover it better, apples are not oranges, green is not red, light is not dark and "thrust" is not the aerodynamic analogue of friction.

Just sort of wanted to throw the thrust thing in there with some other obvious tid-bits.

JB

 

[my_wan]

Thats not drag. Every single time you've said drag you mean thrust. Every single time. How am I supposed to take anyone seriously that can't understand the difference between thrust and drag?

Is the air resistance around your car thrust or drag?

Let's compare. Thabiguy said:

Drag is the aerodynamic analogue of friction. It is a force resisting movement through a fluid.

You responded:

Thats not drag. Every single time you've said drag you mean thrust. Every single time.

Here is what wiki says:

In fluid dynamics, drag (sometimes called fluid resistance) is the force that resists the movement of a solid object through a fluid (a liquid or gas). The most familiar form of drag is made up of friction forces<snip>

Ok maybe wiki is off so let's check NASA.

Drag is the aerodynamic force that opposes an aircraft's motion through the air. <snip> Drag is a mechanical force. It is generated by the interaction and contact of a solid body with a fluid (liquid or gas). <snip> We can think of drag as aerodynamic friction

So how is Thabiguy wrong? He used exactly the same definition as wiki and NASA.