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Would be theoretically possible to build a device which travels upwind faster than the wind, and would this DUWFTTW cart be practically possible, or would inefficiencies prevent it from working?
How about a vehicle that rides the boundary of the treadmill belt, and could move up-belt faster than the belt or (equivalently) down-belt faster than twice belt speed? In this case the two flows have equivalent properties (assuming that we glue a piece of belt to the treadmill at the edge of the moving belt). I'm guessing that such a device is practical.
ETA: When someone offers you a bizarre alterative, and this is the basis of their faster than wind claims, you might just pay attention to the nature of this forum. Be skeptical.
You're damn straight I'm precious, but that's beside the point. It's not about me "keeping" my $100k - I want to take your $100K. And that's what will happen if you back up your claims with your cash.
Your vanity astonishes me. The next time that you are one of your cohorts sarcastically calls someone a "genius" , you might realise, that is perhaps the one thing that can be said to be relative.
Interesting point. If we search this thread we see that the ONLY one that ever uses "genius" sarcastically is YOU. In fact the only time JB refered to you sarcastically as a "genius" was at the end of the video we made and dedicated to you (#4 as I recall). And he did that only parroting your insult to him on another forum. Alrighty George?
humber said:
George Sychrovsky does not suggest cheating. The device runs on the inertial energy of the propeller. He means that...
I'm not trying to confuse you - the truth is that in all cases the device draws its power from the difference between the velocity of the wind and the velocity of the road.
Think about a sailboat sailing downwind faster than the wind by jibing back and forth really fast. Where is it getting its power from? The answer is that it's exploiting the difference between sea and wind.
My point is, and has been, that creating that difference in velocities requires that energy be introduced from outside the system. On the treadmill, it is the treadmill's motor introducing energy. In the sailboat, it is the sailor's jibing. And on the open road, it's a hellifiknow.
No, it's the wind. The jibing was just to illustrate it's possible to go nearly straight downwind faster than the wind. If you don't care about that you can sail on a straight line at an angle such that your progress downwind is faster than the wind's.
As I said it's the wind again, if you want to think of it that way.
Of course ultimately it's the sun that heats the atmosphere and sets it in motion with respect to the rotating globe underneath it. As I keep saying, all that matters is that there is relative motion between them.
I have no doubt Sol understands this subtlety, but for the purpose of this conversation I think there are a couple of points that are somewhat critical:
1) Whether we're talking about the cart on a treadmill, a sailboat, or the cart on the open road - it is *always* being powered by the differential between the wind and the opposite medium (water, road, tread). To say it's powered by the treadmill motor is basically like saying it's powered by the sun in the case it's on the open road. Yes, we can trace the origin of the wind back to its source in any case. But that isn't directly relevant. These vehicles are always directly powered by exploiting the energy at the interface of the two media.
2) This point is a bit more subtle, but has already been made once... kinetic energy, and therefore power, is not an intrinsic property, but rather a variable or parameter that can only be discussed relative to a given reference frame. If we carry out our equations from the inertial reference frame of the water, we conclude a sailboat is wind powered. But it's equally valid to base our equations on the inertial frame of the wind and conclude our sailboat is water powered. It doesn't seem right, but neither does a vehicle that can advance on a treadmill indefinitely - even uphill.
So Spork and ThinAirDesigns,
Lets get down to what really matters. Do you guys fly paragliders? What wing(s) do you fly? Is it time for me to get rid of my Apco Simba?
So Spork and ThinAirDesigns,
Lets get down to what really matters. Do you guys fly paragliders? What wing(s) do you fly? Is it time for me to get rid of my Apco Simba?
I'm not sure why that's what really matters - but yes. I fly hang gliders, paragliders, airplanes, sailplanes, ultralights, and have a little heli time. I also fly R/C planes, sailplanes, and helis.
I don't have a clue what an Apco Simba is. My para is an Arcus Swing. My most current HG is an Aeros Stealth III (the very one that JB used to turn in the fastest time in the world speedgliding championship in Greece). It has been tuned back to factory settings so mortals can fly it though.
Incidentally, JB probably wouldn't be caught dead on a paraglider (whereas I expect I probably will eventually).
I've flown HG for many years and never gave PG a second thought until last year. Don't know why. Just decided to give it a try, and now I really think it's a blast.
I'd like to try speedriding on skis or a snowboard. I think I figured it would help to learn the PG wing first.
But seriously... where's George? I think he was the last remaining guy on this thread that understood what's actually happening with our little cart.
In essence the prop and wheels are directly connected through a drive belt. I defended the idea on physicsforums but unfortunately spork (the OP poster) wouldn't refrain from rants about being attacked and the thread got locked twice. This guy spork made his own version. http://www.youtube.com/watch?v=1BRvYZd81AQ&fmt=18
Why I think it works:
It wasn't presented as perpetual motion and I agree that it's not. The source of energy is well define by the difference between wind speed and ground speed. This is regardless of the motion of the craft due to that difference being maintained by a direct belt connection between the prop and the wheels. With a constant power source at a given wind speed the velocity is limited only by the friction/wind resistance on the craft itself via Newton's first law.
My debate with spork concerned how the power was distributed through craft and the effects that had on efficiency. I could well have been wrong on some points of the wind powered version. However, the specifics in that regard are likely determined by prop to wheel ratio and prop efficiency. There is a difference in the treadmill case and wind powered case irrespective of the validity of the Galilean relativity argument.
Without going into physics and reading past the first page, there is something wrong with the camera. It never gets ahead of the vehicle to show nothing is pulling it.
Second, how did the vehicle move so straight for so long?
Thanks for stopping by with that in-depth analysis.
my_wan said:
I defended the idea on physicsforums but unfortunately spork (the OP poster) wouldn't refrain from rants about being attacked and the thread got locked twice.
Wow - is that ever a mischaracterization! In point of fact, the posters on the physics forum were the most hard-of-thinking group I've ever come across, and they DID insist on attacking me as a scammer, and a fool who didn't know the first thing about physics or aero. Do you really want to drag that pissing match over here my_wan? I guess new and unfamiliar concepts are really scary to some people. And by the way, WHY would I be scamming anyone? I've got nothing to sell.
While I can understand how the device works in still air on a treadmill, I'm still trying to see how it works on the ground with a tailwind. My thinking so far is along the lines of:
The wind pushes on the air from the prop, applying a torque to the prop, which through the transmission applies a torque to the wheels to drive the cart along the ground in the direction of the wind.
No, the wheels are not driving the cart. I thought of it this way at first and couldn't understand what was going on. Here's my stab at an "intuitive" explanation:
1. Imagine that the propeller is uncoupled from the wheels, and fixed so that it cannot rotate. What happens when we place the vehicle in a downwind?
- Answer: the vehicle moves, but not as fast as the wind. The propeller acts like a sail, exerting a backwards force causing the vehicle to move forwards.
2. Still with the propeller uncoupled from the wheels, we attach a motor to it so that it rotates against the wind direction. What happens now?
- Answer: the vehicle can now easily move faster than the wind. It is powered by the sum of two forces, one created by the wind blowing on the propeller, and the other created by the rotation of the propeller itself.
3. The vehicle seen in the video combines these two scenarios. The vehicle is pushed forward by the wind. This cases the wheels to turn. The turning wheels take the place of a motor, driving the propeller. The motion of the propeller creates an additional backwards force. This force, added to the force created by the wind already pushing the vehicle, can cause it to move faster than the wind.
The important point is that the movement of the wheels is driving the propeller, not the other way round.
I realise the two frames of reference are equivalent, but I was trying to construct a description of what's going on from the point of view from an observer in the ground reference frame, or in the case of the treadmill scenario, an observer moving on the treadmill.
No, it's the wind. The jibing was just to illustrate it's possible to go nearly straight downwind faster than the wind. If you don't care about that you can sail on a straight line at an angle such that your progress downwind is faster than the wind's.
JB, Spork
OK I will take your bet. I have thought of a plan.
You say, that nobody can claim to have "the correct" view, so it follows that there can be no single judge
I will offer $100 to each judge in order to take part. I choose 10 judges. You claim to have a Masters in Aero, but my minimum requirements for qualification will be high school physics. I win if there is a majority.
The money is not dependent upon supporting my view. I will post my calculations, and you yours, to be judged in open view, on the Physics Forum.
Get working.
Yes, but dishonest again. From your commentary, you have indicated that you have had previous discussion. The deception, is that you are using simple momentum to claim something else. You also allowed him no right of reply. He is right, and I am paying him back. Incidentally, I do not know who he is, nor have I even read the posts at Physics Forum.
ETA:
I note that your only response related to these remarks. Still no physics, then
Interesting point. If we search this thread we see that the ONLY one that ever uses "genius" sarcastically is YOU. In fact the only time JB refered to you sarcastically as a "genius" was at the end of the video we made and dedicated to you (#4 as I recall). And he did that only parroting your insult to him on another forum. Alrighty George?
O.K. George
Here's the video JB made in response to your post George Sychrovsky:
2. Still with the propeller uncoupled from the wheels, we attach a motor to it so that it rotates against the wind direction. What happens now?
- Answer: the vehicle can now easily move faster than the wind. It is powered by the sum of two forces, one created by the wind blowing on the propeller, and the other created by the rotation of the propeller itself.
Michael, it's fine to look at it this way to the extent that it helps to make a difficult aspect of the problem more intuitive. But the reality is a little different. We can't look at this as the summing of two forces. The reality is that the propeller is operating in a medium (the air) that's moving at a different speed than the ground. We have to look at the force the prop produces working in this medium. It may be a subtle difference, but I think it's an important one to understand the physics of how this thing works.
I think your understanding is essentially correct. The subtlety I mention has more to do with aerodynamics, than the workings of the cart itself.
Ivor said:
I didn't phrase my question particularly well.
I realise the two frames of reference are equivalent, but I was trying to construct a description of what's going on from the point of view from an observer in the ground reference frame, or in the case of the treadmill scenario, an observer moving on the treadmill.
So this is getting into an even more subtle area. In this case you are both right. There's no question that JB is right to say the two scenarios (open road or treadmill) are physically identical. However, as I pointed out above, energy is not an experimental result or an intrinsic property of the vehicle. If the calculations are done from the inertial frame of the steady wind the result will be that the energy (force x distance) comes from the belt. But it's important to understand that this is a bookkeeping distinction - not a physical one.
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