Down wind faster than the wind

[ThinAirDesigns]

Yes, there appears to be little acceptance of qualitative descriptions along the lines of opposing forces. If only Einstein had not used the word "Relativity".

Yeah, "if only". LOL

In the context of this discussion Galileo and Newton beat Einstein to the punch by a large margin, but why quibble with details eh?

"13", I'm working on a response to your excellent "twin wind tunnel" question. Be with you in a bit.

Carry on.

JB

 

[spork]

humber says:
Your videos are evidence that something is happening. If I were to build one, I would fully expect to get the same result. What is being argued, is why that happens, and how it relates to support for a machine of this type that can actually travel faster than the wind.

You say you'd expect to get the same results, but you describe different results than we consistently get. This cart in a steady wind achieves a steady state speed faster than the wind. It will climb a hill steady state or it will push against a stop (at or above wind speed) steady state.

So, do you have links for a machine that does that in a controlled constant- wind environment?

Yes. I don't think I'm permitted to post links yet, but I've posted 6 videos we've made over the past several days. Look for spork33 on youtube and you'll see them all. Most of our tests are performed on the treadmill because this gives us exactly the controlled steady-state conditions you ask for. The treadmill represents a moving road immersed in a non-moving airmass. This of course is identical to a moving airmass over a non-moving road. The principle of equivalency of inertial frames tells us there is no way for any experment to distinguis between these two cases.

My_wan says:
Well, let's start at 0 craft speed. Propellers not turning and the wind blowing the craft itself is the only thing to move it. Once the wheels do turn then the prop turns at the same rate. We know the wheels have to be the power right now because if the wind in the prop was the power turning the wheels it would run the craft backward.

In our video #3 you can see the cart is started from a stand-still by a fairly abrupt gust. In this particular shot we did not have the rubber bands on the front wheels to act as treads. As such the wheels were forced to turn against the direction of motion of the cart for the first 3 seconds or so. This is NOT the norm. In that very same video you can see a start from a stand-still in which the prop turns in the normal direction from the very start. The reason for this is that, while the wind would *tend* to rotate the prop in the opposite direction, it also *tends* to push the prop (and therefore the cart) forward. The gearing and prop pitch is such that the latter tendency will always win out as long as the wheels don't slip.

Anyway.. there is a clear direction that the forces propagate through the craft and I'm not just picking the one that seems to make sense

That is correct, and in normal operation this direction is always the same - whether operating on the open road or on a treadmill. The two cases are dynamically identical.

humber
As far as I can see, the videos show a completely understandable and predictable trifle.

I think you'll see there is plenty of footage in our videos that don't even remotely support your oscillation assertion.

OK, it seems that you are proposing a rectifying mechanism. That would work, but not without storage. That is, energy is accepted one way, stored, 'turned around' and added to the motive force. Spronk's design has this built in, but he refuses to see it.

What I refuse to ACCEPT is a baseless theory of yours that involves the non-neccessary and non-observed oscillation that you seem to require to beat the wind. Our craft can and does exceed the wind speed steady state.

The propeller's precession, forces the rear wheels to engage with the road; the front will tend to lift, which probably accounts for its dragster-like design.

I don't think you know what precession means. It clearly has no bearing on any problem in which the cart's orientation is fixed. Perhaps you can elaborate on this.

What this means is that when the vehicle is being driven by the wind, a large amount of energy is absorbed. On the other hand, when the wind drops, it can coast on the stored energy while releasing less to the environment than it previously stored. It accumulates and stores as it goes along.

The oscillation theory is complete bunk. That is not what's observed, and that's not what my analysis shows. This is not an oscillating system.

If the propeller were also to be used to charge a battery and then drive a motor, would that qualify as a contender ?

NO! Steady-state operation is a requirement.

fsol
So, we can see your calculations where?

This vector analysis along with some verbal description can fully describe how the cart works and why it's possible to exceed the wind speed steady state. Look it over and let me know when you want to discuss what it means and how it applies to this cart.

.13. said:
Set up two wind tunnels. One has a solid floor and airflow the other has a treadmill with no airflow. Put a cart in each. Turn on the ariflow and the treadmill. Hold the carts above ground and make sure both of their wheels has zero angular velocity. Drop them on the ground. They will travel to opposite directions. Right?

If we drop each onto the surface, with no speed relative to that surface, and with no initial wheel rotation, they will behave identically with respect to the surface on which they're dropped. Galileo, Newton, and Einstein all tell us this has to be so.

humber said:
And the video of wind-powered craft operating in a controlled constant-wind environment ?

Youtube. Look at the videos under spork33. You'll find 6 (or more by the time you may happen to check it out). We continue to post videos to responsd to specific questions. If you have a question that can be resolved by an experiment we can conduct, we will try and do so, and post a video showing the result.

technoextreme said:
I know why. He thinks propellers work in only one direction.

I'm more familiar with the workings of propellers than you'll ever know.

The only reason why the cart doesn't go backwards is because the forces equalize and the cart stops accelerating.

The reason the cart doesn't go backwards is because it's exploiting the energy available at the road/wind interface which makes it go forwards - faster than the wind.

I'm not disputing the cart doesn't move but his mystical magical description ignores the fact that with the headwind the propeller starts acting like a generator in the wrong direction thus counteracting the force of the wheels.

Perhaps you should study the attached vector analysis and follow along as I describe how it pertains to the situation at hand. While it may seem mystical to you, I assure you it's just plain old physics and aero to anyone that understands the analysis.

 

[spork]

"13", I'm working on a response to your excellent "twin wind tunnel" question. Be with you in a bit.

JB, I address that question in the above tome. Unfortunately the answer could easily be missed amidst the shear quantity of verbiage. Unfortunately when I sleep the world continues to ask questions. That leads to LONG responses.

Perhaps you can add to my response to the wind-tunnel question.

 

[ThinAirDesigns]

Set up two wind tunnels. One has a solid floor and airflow the other has a treadmill with no airflow.

Hi 13. I like where you're going here, but to make sure we're on the same page I may have to ask a couple questions and add a few details before we can move forward. Hope you don't mind.

Tunnel "A" will be the one with a blower that moves the air.
Tunnel "B" will be the one with the motor moving the floor.

For ease of discussion, lets say both 'tunnels' are aligned in an east/west direction.

(I know there are two videos under discussion and while the dynamics of both carts are identical, the design is a bit different. These design differences make this discussion difficult so I'm going to arbitrarily pick one design to discuss -- and I pick the small version running on the treadmill. The cart I have chosen has two front wheels and a single rear and the prop is in the rear as the cart goes 'downwind'. Now we know the front of the cart from the rear and its direction of travel.)

To make is so the carts can face and 'travel' the same direction in both tests we setup our 'tunnels' in the following manner:

Tunnel "A" has the wind blowing from west to east.
Tunnel "B" has the floor moving from east to west.
The carts face east.

Put a cart in each. Turn on the airflow and the treadmill.

We'll do just that, and again for clarity let's set both controls to 10mph.

And one more thing before we proceed -- for sake of discussion I'm going to define the performance of our carts such that they have the performance to travel just 1mph faster than the wind that is propelling them.

Hold the carts above ground and make sure both of their wheels has zero angular velocity.

I'm with you ... the wheels and propellers are perfectly still in relation to the cart chassis. Of course this means that on cart "A" you have to lock the prop/wheels from free-spinning as they sit in the airflow but that's easy. Cart "B" has no such need as there is no air rushing by to spin the prop.

(Note #1: Please notice the difference in the above 'start environment between "A" and "B" ... I'll be referring to it later)

Drop them on the ground. They will travel to opposite directions. Right?

13, before I get to answering your question, would you mind confirming for me that my added details are OK with you and that I haven't twisted your scenario beyond recognition.

Thanks

JB

 

[mhaze]

How to make the machine go further and faster "against the wind"?

Make the prop heavier.

 

[my_wan]

OK, it seems that you are proposing a rectifying mechanism. That would work, but not without storage. That is, energy is accepted one way, stored, 'turned around' and added to the motive force. Spronk's design has this built in, but he refuses to see it.

In fact the only energy storage capacity of the device in sporks video is momentum. That is p=mv where p is the momentum and mv is mass times velocity. Given the extremely low mass of the device in sporks video this momentum would run that prop at any speed for more than several seconds even without expending it pushing the craft up that incline. Much less maintain full prop speed.

So storing angular momentum in the spinning parts does occur by a very small amount. Let's assume it's enough to actually drive the craft off the treadmill as shown. This would mean that when he let loose of the craft it would take off very fast and slow down as the momentum was spent overcoming the treadmill going the other way. Now watch the video again.
http://www.youtube.com/watch?v=1BRvYZd81AQ&fmt=18
What you see is the craft taking off very slowly then gaining speed. This cannot by any stretch of the imagination be attributed to stored momentum. It would be like having your car gain speed when it lost power.

 

[ThinAirDesigns]

How to make the machine go further and faster "against the wind"?

Make the prop heavier.

Someone doesn't understand the term "steady state".

And just to put my above comment in context, here is my claim:

"We have built and can demonstrate upon demand a vehicle which can travel directly downwind, faster than the wind, powered only by the wind, steady state."

A heavier prop has no impact (other the added friction associated with the bearings, wheels, etc) on the results in a steady state scenario.

JB

PS: I don't think I've mentioned that I have been sporks partner in building mulitiple version of DDWFTTW devices seen on Youtube.

 

[Thabiguy]

The thing missing here is the fact that as the speed of the craft increases so does the speed of the propeller.

Yes, and so does the speed of the air that the propeller pushes back. But not by the same absolute difference as the increase of the speed of the craft.

Therefore the propeller will always push the air faster than the air is already moving by the same difference in speed as it was at lower speeds.

No, I'm afraid that's not the case.

As I said in my analysis, the wheels are connected to the propeller so that when the forward speed of the device (wrt ground) is v_dev, the propeller tries to move the air forward (wrt ground) at speed v_prop. v_prop / v_dev is a constant given by the transmission and the angle of the propeller blades, and I call it f, the leverage factor.

(This is from the ground's reference frame. If you wanted to look at it from the device's reference frame, which you seem to prefer, the ratio of the speed at which the propeller tries to move the air backward (wrt device) and the speed at which the ground moves backward (wrt device) is f₁. The following relationship applies: f = 1 - f₁. At this point, you should stop, do the math and check for yourself that this relationship is correct.)

What you need to realize is that in order for the device to move forward, f must be > 0 (and to move at higher than wind speed, it also must be < 1). This means that f₁ must be < 1 (and > 0). And this means that when the forward speed of the device (wrt ground) increases by x, the backward speed at which the propeller pushes air (wrt device) also increases, but by less than x. (Verify this. Be careful with signs and reference frames; I have not used them arbitrarily, I made very sure they are right.)

This means that the difference between backward air speed (wrt device) and the speed at which the propeller pushes air backward (wrt device) decreases as the device accelerates. When the device reaches forward speed (wrt ground) v_wind / f, the difference will be zero and the device will no longer accelerate. (Use math to verify this.)

If in doubt, ask Spork or JB. They seem to understand the theory behind their device and should be able to confirm this to you.

If the propeller had the same RPM at all speeds then you would be right, but it doesn't.

The propeller never has the same RPM at all speeds (unless f = 1, when the propeller always has zero RPM). This has nothing to do with whether I'm right or not. See above.

The wheels are geared directly to the propeller so that as the craft gains speed so does the propeller.

Yes, but not by the same amount (to be more accurate, the angular velocity of the propeller is irrelevant here; what's important is the speed at which the propeller pushes the air backward).

This gearing is such that the difference in propeller speed always exceeds the wind speed relative to the propeller by the same amount at all speeds.

Strictly taken, this doesn't make sense. If instead of "difference in propeller speed" you wrote "speed at which the propeller pushes the air backward wrt device", then it would make sense, but the answer is no.

This difference is the same amount as the air speed relative to the ground.

I'm afraid not. This would only be the case if f was 0, but in that case, the device would not work.

There are some practical engineering issues that makes this description less than mathematically perfect yet it remains qualitatively accurate. Hopefully you can see how the constant speed difference (power source) I kept talking about applies to the propeller vs wind speed relative to the propeller now.

Sorry, that's not the case.

Please try to remain as clear as you where in the post quoted above.

I tried.

 

[spork]

How to make the machine go further and faster "against the wind"?

Simply use a lower prop pitch and turn the cart into the wind.

Given the extremely low mass of the device in sporks video this momentum would run that prop at any speed for more than several seconds even without expending it pushing the craft up that incline. Much less maintain full prop speed.

We specifically address this question in video #5. When we lift the cart off the treadmill the prop coasts to a stop in under 7 seconds. In video #6 we manage to balance the cart and treadmill (with positive incline) well enough to keep the cart in operation unassisted for 1:48 before it falls off the treadmill. Clearly the cart didn't store enough energy to make this possible.

 

[humber]

In fact the only energy storage capacity of the device in sporks video is momentum. That is p=mv where p is the momentum and mv is mass times velocity. Given the extremely low mass of the device in sporks video this momentum would run that prop at any speed for more than several seconds even without expending it pushing the craft up that incline. Much less maintain full prop speed.

So storing angular momentum in the spinning parts does occur by a very small amount. Let's assume it's enough to actually drive the craft off the treadmill as shown. This would mean that when he let loose of the craft it would take off very fast and slow down as the momentum was spent overcoming the treadmill going the other way. Now watch the video again.
http://www.youtube.com/watch?v=1BRvYZd81AQ&fmt=18
What you see is the craft taking off very slowly then gaining speed. This cannot by any stretch of the imagination be attributed to stored momentum. It would be like having your car gain speed when it lost power.

Perhaps you have not read my posts, but this is largely what I have been saying, though we are not fully in agreement.

1.Yes, he shows that.
2. It's not so small, but that is not that important.
3. If that assumption is made, then there would be even less to show.

When the device is first placed on treadmill and held, (spinning) the opposing forces of drag, and that from the belt, are almost in equilibrium. So, when released it could go either way, but it goes forward. It won't take off fast, because as you say, the momentum is relatively small. In principle, it could be spent, and the device reverse direction, but in practice, simple natural mechanisms serve to maintain that momentum.

You accept the the momentum can drive it forward, so what in general, stops it from doing that? The force from the belt.
This is the crux of the matter, the drive and drag are not separate forces, but opposing forces derived from the same source, but split in direction.
It could be either; increase in one, reduction of the other.

However, the presence of the momentum, will probably, (though by no means certainly) drive the device forward. It won't "run out" because it is constantly replenished.
There are many opportunities for simple and natural phenomenon to achieve this, apart from the necessary but convenient finger.

I think you will agree that the belt "should" carry the device backwards. But what if the friction between the wheels were to be momentarily reduced?
Now the drive is gone, but the propeller is spinning, so forward it goes. When friction returns, the lost momentum can be regained. It need not necessarily be a complete loss of friction, so some mechanism, such as non-linear or slip-stick friction, could do the same. It happens over short time scales, perhaps at the frequency of the fan or treadmill motor.
It is an example of natural forced feedback with a storage element.
A fully detailed explanation would cover perturbation theory etc.

As far as the incline goes, it makes no real difference. In principle, if the forces were to be completely and always in balance, then the device would stay in position regardless of how fast the drive belt were to be going. Changing the angle simply changes the horizontal component of the forces.

So, properly designed, I would think such device could show much more assured progress than you see in the videos.

 

[humber]

Yeah, "if only". LOL

In the context of this discussion Galileo and Newton beat Einstein to the punch by a large margin, but why quibble with details eh?

"13", I'm working on a response to your excellent "twin wind tunnel" question. Be with you in a bit.

Carry on.

JB

Yes, if only people read Einstein's papers, those that he won the Nobel prize for, perhaps the would learn something about momentum.

 

[.13.]

13, before I get to answering your question, would you mind confirming for me that my added details are OK with you and that I haven't twisted your scenario beyond recognition.

Thanks

JB

Looks good.

JB, I address that question in the above tome. Unfortunately the answer could easily be missed amidst the shear quantity of verbiage. Unfortunately when I sleep the world continues to ask questions. That leads to LONG responses.

Perhaps you can add to my response to the wind-tunnel question.

I noticed. I'll let JB answer it with more detail.

 

[casebro]

So if the cart is placed on an incline, in still air, it will go uphill spontaneously?

Scalability? How big of a prop is needed to actually make man-sized one?

 

[.13.]

The emphasized statement was:
"if the wind in the prop was the power turning the wheels it would run the craft backward".
Now look at the diagram I drew:
[qimg]http://www.internationalskeptics.com/forums/imagehosting/15393491aaeb9be526.gif[/qimg]Direction of travel is to the left <----.

Notice that when the wheels rotate as shown the prop ejects air to the right while the wind travels to the left. Now if this wind is what turned the propeller the ejected air would necessarily be in the same direction as the air turning it, but it's not. If the air output is reversed from that shown the wheels must also turn in the opposite direction, because they are directly connected, making the craft go right instead of left as shown. Since the craft does go left the prop must be driven by the wheels and not visa versa. So there's you "why" on the emphasized statement.

You say: "Now if this wind is what turned the propeller the ejected air would necessarily be in the same direction as the air turning it, but it's not."

I agree that the air is not ejected backwards. But: That doesn't mean the wind isn't turning the propeller. The propeller slows down the wind flowing through it and that gives the cart energy to move forward. Right?

If you were right and the wind would drive the cart to opposite direction: Wouldn't the cart initially accelerate backwards instead of forward?

 

[humber]

You say you'd expect to get the same results, but you describe different results than we consistently get. This cart in a steady wind achieves a steady state speed faster than the wind. It will climb a hill steady state or it will push against a stop (at or above wind speed) steady state.

Referring to the item on the belt, I have never expressed otherwise. The wind experiment could be anything. I have already covered that. Against a stop is even easier. However, you do claim that the treadmill experiments support the wind versions. You do disagree with my version of how it operates. Also the claim that these demonstrations violate any of the known laws of physics. I heard that.

Yes. I don't think I'm permitted to post links yet, but I've posted 6 videos we've made over the past several days. Look for spork33 on youtube and you'll see them all. Most of our tests are performed on the treadmill because this gives us exactly the controlled steady-state conditions you ask for. The treadmill represents a moving road immersed in a non-moving airmass. This of course is identical to a moving airmass over a non-moving road. The principle of equivalency of inertial frames tells us there is no way for any experment to distinguis between these two cases.

OK, but please stop making such claims for wind performance until demonstrated.

In our video #3 you can see the cart is started from a stand-still by a fairly abrupt gust. In this particular shot we did not have the rubber bands on the front wheels to act as treads. As such the wheels were forced to turn against the direction of motion of the cart for the first 3 seconds or so. This is NOT the norm. In that very same video you can see a start from a stand-still in which the prop turns in the normal direction from the very start. The reason for this is that, while the wind would *tend* to rotate the prop in the opposite direction, it also *tends* to push the prop (and therefore the cart) forward. The gearing and prop pitch is such that the latter tendency will always win out as long as the wheels don't slip.

That is correct, and in normal operation this direction is always the same - whether operating on the open road or on a treadmill. The two cases are dynamically identical.
I think you'll see there is plenty of footage in our videos that don't even remotely support your oscillation assertion.

I think you are assuming that I connect the treadmill and real-world wind performance. They show superficial similarities, but I have already mentioned that I don't seriously connect the two. My "oscillation assertion" applies to the the video posted by the OP. The big trolley with the wooden propeller. I didf suggest that as a putative mechanism for how the trolley moves up the treadmill. They are not strongly related ,though

What I refuse to ACCEPT is a baseless theory of yours that involves the non-neccessary and non-observed oscillation that you seem to require to beat the wind. Our craft can and does exceed the wind speed steady state.

I have not seen any evidence that it beats the wind. Yours or any other. Once again, most this applies to the other video. Your wind demonstrations are in another category again.

I don't think you know what precession means. It clearly has no bearing on any problem in which the cart's orientation is fixed. Perhaps you can elaborate on this.

In the only video showing any real claim to recorded performance is the one that I just mentioned. The precession of that propeller, will indeed do as I claim. However, it could be something that concerns the other model in terms of stability. I used it to demonstrate that the cart in that video is nothing more than a flywheel on wheels, which it is.

The oscillation theory is complete bunk. That is not what's observed, and that's not what my analysis shows. This is not an oscillating system.

Must be some misunderstanding.

NO! Steady-state operation is a requirement.

Irony

This vector analysis along with some verbal description can fully describe how the cart works and why it's possible to exceed the wind speed steady state. Look it over and let me know when you want to discuss what it means and how it applies to this cart.

Sorry, but I really don't know what you are on about here. The device in video #3, in the carpark? Well, that's another matter. Looks to me like it is a response to the gust that initiates its launch. Could be anything.
I am surprised that you think there is anything to claim.

Perhaps you should study the attached vector analysis and follow along as I describe how it pertains to the situation at hand. While it may seem mystical to you, I assure you it's just plain old physics and aero to anyone that understands the analysis.

Are we going sailing ? The drive belt demonstrations are said to support your ideas.
I agree, it's just plain old aero. Air is quite viscous you know. The performance of objects of the size and mass shown in #3, are not subject to such simple analysis.

 

[mhaze]

You say: "Now if this wind is what turned the propeller the ejected air would necessarily be in the same direction as the air turning it, but it's not."

I agree that the air is not ejected backwards. But: That doesn't mean the wind isn't turning the propeller. The propeller slows down the wind flowing through it and that gives the cart energy to move forward. Right?

If you were right and the wind would drive the cart to opposite direction: Wouldn't the cart initially accelerate backwards instead of forward?

If the machine does not operate by way of a transient stored momentum (this being partly in the machine, and partly in the local airstream) then it should be possible to put on it, RC controls and get it to remain stationary on the moving belt for an arbitrary length of time.

Glue a small diameter tube to the machine, and place it on the treadmill with a piano wire parallel to the track, said wire sliding through the tube. Use one RC servo to vary friction against the wire with a felt pad - this is to keep the machine from sliding off the forward end of the treadmill.

 

[humber]

Too much like evidence.

 

[my_wan]

Yes, and so does the speed of the air that the propeller pushes back. But not by the same absolute difference as the increase of the speed of the craft.

Which is exactly why the wind speed difference wrt craft remains a constant at all speeds. It may not be exactly the "same absolute difference" but close enough and it can be designed so that it does making it even more efficient.

No, I'm afraid that's not the case.

So just because the difference is not exact due to design issues that a difference is not maintained at all. Isn't that like admitting that a properly designed craft would work but since this one isn't perfect it can't work?

As I said in my analysis, the wheels are connected to the propeller so that when the forward speed of the device (wrt ground) is v_dev, the propeller tries to move the air forward (wrt ground) at speed v_prop. v_prop / v_dev is a constant given by the transmission and the angle of the propeller blades, and I call it f, the leverage factor.

Quote one says: "propeller pushes back". Here you say: "the wheels are connected to the propeller so that when the forward speed of the device (wrt ground) is v_dev, the propeller tries to move the air forward". The propeller cannot possibly change direction and start moving the air forward without reversing direction of the prop which also reverses direction of the wheels.

When the craft first takes off the prop is moving air in the opposite direction of the wind. If the wind was powering it it would go the same direction, not opposite. You only need to watch carefully the video below to see that. Once the craft gets faster than the ground wind speed then the prop wind is going the same direction as the wind. Therefore the wind can't reverse it because the wind is helping it go that direction, which is the same direction it was going when below wind speed and blowing against the wind.

Watch this video again and pay careful attention to the prop blade angles and the direction of wind.
http://www.youtube.com/watch?v=aJpdWHFqHm0
Below ground wind speed the prop is working against the wind. So if the prop was going to reverse its direction due to wind it would be before the craft exceeded ground wind speed, not after.

 

[humber]

The sock is scarcely evidence of anything. Not far out enough to definitely say it is the breeze, yet close enough to the obfuscating propeller. This is an extraordinarily lax way of demonstrating a supposedly extraordinary device. Smoke and mirrors.
There is sufficient momentum to cover transient wind drops.
Propeller's are simply not a case of driving one way or the other, but you already know that.
Real wind is not an homogeneous entity. It has general and local turbulence, and very locally, around objects such as trees, road surfaces and dodgy wind carts. Weeps.

 

[ThinAirDesigns]

If the machine does not operate by way of a transient stored momentum (this being partly in the machine, and partly in the local airstream) then it should be possible to put on it, RC controls and get it to remain stationary on the moving belt for an arbitrary length of time.

Glue a small diameter tube to the machine, and place it on the treadmill with a piano wire parallel to the track, said wire sliding through the tube. Use one RC servo to vary friction against the wire with a felt pad - this is to keep the machine from sliding off the forward end of the treadmill.

Humber:

Too much like evidence.

Perhaps I'm confused here. Are the two of you claiming that our video, posted on youtube and titled "downwind faster than the wind #6", showing the cart running on the treadmill *untouched* by human hands for almost TWO MINUTES, doesn't cover all the points in mhaze's post?

OK, I'll asked the question directly -- If close to two minutes isn't enough time to convince you, within the 10 minute limit of YouTube, how long must we leave it run before you will drop the "stored momentum" argument?

JB