H'ethetheth
fishy rocket scientist
Down wind faster than the wind
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ThinAirDesigns
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Exactly why ice-boats don't have them
Ice-boats don't have them because a spinnaker would slow them down.
http://sports.groups.yahoo.com/group/2nalsa/message/161
JB
Correct. It would be not only unnecessary, it would be unusable.
Not correct. Ice boats do not have them because they indeed beat the wind going downwind and don't need them (see above where you were correct). It would be indeed impossible to set a spinnaker, since iceboats experience relative headwind even when they are sailing downwind. They are said to tack downwind. There is plenty of GPS data available to prove this. It doesn't even need to be any extreme iceboat or a great sailor.
I seriously suggest that you would try answering the question that has been three timesposed specifically on you: what is the definition of wind?
Unless you specify what you mean by wind it is pointless to continue. Whether you laugh or not.
The differences are more than an anemometer can disclose, but it could be that the readings be the same, and yet the two models still be different in significant ways.
If the requirements would be (my wording not sporks):
1) The cart has to move directly downwind
2) The cart has to move relative to ground faster than the air moves relative to ground
3) The cart has to be able to maintain its desired speed indefinately
4) The cart can utilize only the movement of air relative to ground as its power soure and nothing else
With these rules, is it "no problem" or "impossible" to achieve?
What requirement would you suggest in addition to the ones spork & co have claimed that would satisfy you?[/QUOTE]
If those are the rules then I think that only (3) would be a point of equivocation. I think that if the remainder are agreed, then such a cart is
not a big challenge.
As for the method, and one that may defeat me, is that there should be no means by which energy storage can occur. The energy consumed is important, otherwise the claim becomes trivial. The current evidence for such carts does not meet the standards that you have listed, so I think that matching what has actually been observed would not be difficult.
I would say that Goodman's cart is certainly disqualified undwe mt rules, and on appearance and design details, also Bauer's. Spork's is borderline, but then does it work?
User input is also a problem. If the cart exploits knowledge of the winds ahead fore example, it must pay for that. It cannot be pre-programmed.
The challenge is no one of technology, per se, but of the principles of thermodynamics. Perhaps it may be worth looking into the rules of the recent Ventomobile challenge.
tsig
a carbon based life-form
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Treadmills are not fans. They do not generate wind.
H'ethetheth
fishy rocket scientist
Porch anyone?
I was not thinking of those detail, but as to the last statement, that is definitely not correct. That is certainly wrong in significant ways.
"not even wrong", in Wolfgang Pauli's usage of those words.
ETA:
Sorry, but it is laughable. Greg London must be both bemused and amused.
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ThinAirDesigns
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From my previous post:
All you have to do to win the Nobel humber is to device a test that can tell you whether the wind is "real" (your term) or it's a calm day and the treadmill is turned on steady state.
Seize the day humber -- give us the test.
JB
Treadmills generate a situation where the ground is moving and the air is still. This is exactly the situation where a cart on the road is when it has reached windspeed and is supposed to be able to accelerate even furher. The ground is moving beneat it and there is no wind relative to the cart.
See why you have been asked about the definition of wind?
When wind is defined as speed difference between air and groud, the treadmill indeed generates wind.
Forget the wind. What do you think about the fact that the cart advances on the treadmill running in the opposite direction? Isn't that sort of strange?
tsig
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Why is there air?
I am sure that I have done, but I will do so again, I don' t have the time right at the moment.
The test of London's device is ludicrous. The disks are thin profile plastic.
The only means of energy transfer is limited by the rolling friction between those disks and a smooth and fast belt. The effects of slip-stick friction are all that you are seeing.
ETA:
I have made it pretty clear what I think of Spork. This does not extend to the rest of you, but I have difficulty in believing that you think a treadmill can just have 'wind' by virtue of its velocity.
A wind blown object is coupled to the wind by its viscosity, its momentum. I say that is a medium, you seem to say that it is a frame of reference. Either way, when you make a model ( frame of reference in your terms) you must model that too. Friction too. How things are coupled to the real world in each case?????
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Ok, for a while took you for an idiot but it seems I was mistaken. A troll it is.
tsig
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So you belief that that no wind is the equivalent of wind?
H'ethetheth
fishy rocket scientist
So you believe that that straw is the equivalent of man?
Somehow all this reminds me of when I complained that a fellow musician was playing a particular passage incorrectly. The director's response: "what if he doesn't know the difference."
I guess that's why a lot of people play B flat when they're supposed to play A sharp.
I guess that's why a lot of people play B flat when they're supposed to play A sharp.
Mender, you say that when standing on the treadmill moving at 10kph, you feel a 10khp wind? Yes, I agree.
But there is a big difference between that wind, and a real wind.
To feel the treadmill wind, I must travel with the belt. My shoes must provide a reactive force to the belt. If I don't move relative to the belt, then the forces of the 'wind' and shoes are equal but opposite. That is also the maximum force that I will ever feel. To move back against the belt, the friction of my shoes must fall, but that will also reduce the force of the 'wind' against me.
The magnitude of the forces either way is a directly proportional to the friction to the belt. No friction = No Force = No 'wind'. That's what the cart does. It is due to its design. Another type of cart , may not do this. London's device is different. It simply does not stay on the belt.
What if the friction of his device, had been 'just so' as in the cart. Would that mean that his device does work? Couldn't I modify it so it does pass this friction test?
This is not the case with real wind, my friction can be zero to the ground, and yet I can be blown with it.
You know, I am not playing Devil's Advocate here, Mender. If you see no problem with the above, we occupy two different worlds.
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Dan O.
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Tsig, Are you just trolling for attention?
That you don't consider that a treadmill is an adequate simulation of a wind for testing the cart's ability to overcome friction and travel directly down wind at the speed of the wind shows that your view of reality is flawed.
State the testing conditions that you would accept. If you can't do that, Ill simply put you in my ignore file where trolls belong.
sol invictus
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Humber, if you truly want to find out where the disconnect is, I'll be more than willing to try as well. I get very tired of the evasive replies though.
1. "To feel the treadmill wind, I must travel with the belt." Agreed.
2. "But there is a big difference between that wind, and a real wind."
Why do you say there is a difference? I am discussing the air moving past as you stand on the belt. Let me try a guess based on what I've read so far: the real wind has momentum, the "fake wind" (from the treadmill movement) has none.
3. The direction of the belt of a conventional treadmill like the one in my basement, purchased for the sole purpose of being able to duplicate walking on a road without "moving". Front to back, or right to left as shown in the videos with the small cart. Belt direction as indicated, yes?
4. Standard level of friction between the belt and my shoes. If I stop walking, I move off the back of the treadmill. As that happens, I experience what I would feel if I now had a tailwind that was at the speed of the treadmill. Agreed?
5. Loss of friction: spray a miracle lube on the belt that would eliminate all friction between your shoes and the belt. Assuming the treadmill was level and that you temporarily held yourself in place as you once again put your feet on the belt, you could stand on the belt and the air around you would hold you in place. If the treadmill is tilted in either direction, you would slide off as gravity took its toll regardless of the speed or direction of the treadmill belt. Agreed?
Are we still in the same world at this point?
1. "To feel the treadmill wind, I must travel with the belt." Agreed.
2. "But there is a big difference between that wind, and a real wind."
Why do you say there is a difference? I am discussing the air moving past as you stand on the belt. Let me try a guess based on what I've read so far: the real wind has momentum, the "fake wind" (from the treadmill movement) has none.
3. The direction of the belt of a conventional treadmill like the one in my basement, purchased for the sole purpose of being able to duplicate walking on a road without "moving". Front to back, or right to left as shown in the videos with the small cart. Belt direction as indicated, yes?
4. Standard level of friction between the belt and my shoes. If I stop walking, I move off the back of the treadmill. As that happens, I experience what I would feel if I now had a tailwind that was at the speed of the treadmill. Agreed?
5. Loss of friction: spray a miracle lube on the belt that would eliminate all friction between your shoes and the belt. Assuming the treadmill was level and that you temporarily held yourself in place as you once again put your feet on the belt, you could stand on the belt and the air around you would hold you in place. If the treadmill is tilted in either direction, you would slide off as gravity took its toll regardless of the speed or direction of the treadmill belt. Agreed?
Are we still in the same world at this point?
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Humber,
Imagine that (with some supernatural being's help) we've arranged for the following idealised testing environment:
Earth has been essentially replaced with a giant billiard ball, thus having a perfectly flat surface (insofar as we use the term "flat" on earth), but it still has essentially the same size, mass, and gravity, as the earth, plus an atmosphere that is similar in terms of composition and so on. Let's say the rest of universe is completely empty. No sun, no stars. (But we'll allow ourselves torches or similar so we can see what we're doing!)
We've also arranged so the southern hemisphere can rotate independently of the northern hemisphere - as if the earth had been cleanly sliced in two through the equator and then the two halves put back together again with a frictionless interface between them. You can imagine a long shaft running through the north and south poles and thus joining the two halves if that helps but shouldn't really be necessary! We also have things set up so the southern hemisphere is rotating (from west to east) slightly faster than the northern half so that a person standing just south of the equator and looking north will see the northern hemisphere apparently moving right to left (east to west) at 10 mph, even though the northern hemisphere is still rotating at the usual earth rate - something close to 1000 mph at the equator if my quick calculation is correct.
In addition we have a perfectly smooth and constant speed air flow moving around the globe from "west to east", at exactly the same speed as the southern hemisphere at the equator but also sufficiently far to the north and south of this also for the purposes of any cart testing we may want to do in that area. So this air flow is like a belt around the earth's equator and it's speed matches the speed of the ground in the southern hemisphere in the equatorial regions.
I'm presuming that you're happy to accept that the slight curvature of the earth's surface, and similar very small effects that come from that (plus missing stars and sun, etc) are not significant enough to make a difference in terms of testing a cart like spork's on this version of earth. But please tell me if this presumption is incorrect, and if so what the problem is. I agree there could be extremely minor effects, or difficulties with getting the "perfect test environment" from some of this, but I haven't seen you raise this earlier so it seems likely that you agree we can ignore these issues unless unless perhaps we ended up looking at a cart where the difference between possible success and failure of some test was extremely small. Spork claims his cart can comfortably beat the wind, so that doesn't appear to be a likely scenario. We're not using General Relativity either are we?
Finally, let's say you are standing right in the northern hemisphere, close to the equator, and I am standing near to you (for now) but on the southern side of the equator. We will be moving relative to each other though because the two hemispheres are moving relative to each other. We both also have a spork type cart, exactly the same in every important respect.
Before we move onto testing the carts, can you please confirm that this description is clear. Please tell me if you would feel any "real wind" where you are standing in this idealised world (just north of the equator), and in which direction and speed it might be blowing. And what would I be feeling at my position just across the boundary in the southern hemisphere? Is that "real" also or not? Does any of this set-up suffer from the problems that you see with the treadmill tests?
Imagine that (with some supernatural being's help) we've arranged for the following idealised testing environment:
Earth has been essentially replaced with a giant billiard ball, thus having a perfectly flat surface (insofar as we use the term "flat" on earth), but it still has essentially the same size, mass, and gravity, as the earth, plus an atmosphere that is similar in terms of composition and so on. Let's say the rest of universe is completely empty. No sun, no stars. (But we'll allow ourselves torches or similar so we can see what we're doing!)
We've also arranged so the southern hemisphere can rotate independently of the northern hemisphere - as if the earth had been cleanly sliced in two through the equator and then the two halves put back together again with a frictionless interface between them. You can imagine a long shaft running through the north and south poles and thus joining the two halves if that helps but shouldn't really be necessary! We also have things set up so the southern hemisphere is rotating (from west to east) slightly faster than the northern half so that a person standing just south of the equator and looking north will see the northern hemisphere apparently moving right to left (east to west) at 10 mph, even though the northern hemisphere is still rotating at the usual earth rate - something close to 1000 mph at the equator if my quick calculation is correct.
In addition we have a perfectly smooth and constant speed air flow moving around the globe from "west to east", at exactly the same speed as the southern hemisphere at the equator but also sufficiently far to the north and south of this also for the purposes of any cart testing we may want to do in that area. So this air flow is like a belt around the earth's equator and it's speed matches the speed of the ground in the southern hemisphere in the equatorial regions.
I'm presuming that you're happy to accept that the slight curvature of the earth's surface, and similar very small effects that come from that (plus missing stars and sun, etc) are not significant enough to make a difference in terms of testing a cart like spork's on this version of earth. But please tell me if this presumption is incorrect, and if so what the problem is. I agree there could be extremely minor effects, or difficulties with getting the "perfect test environment" from some of this, but I haven't seen you raise this earlier so it seems likely that you agree we can ignore these issues unless unless perhaps we ended up looking at a cart where the difference between possible success and failure of some test was extremely small. Spork claims his cart can comfortably beat the wind, so that doesn't appear to be a likely scenario. We're not using General Relativity either are we?
Finally, let's say you are standing right in the northern hemisphere, close to the equator, and I am standing near to you (for now) but on the southern side of the equator. We will be moving relative to each other though because the two hemispheres are moving relative to each other. We both also have a spork type cart, exactly the same in every important respect.
Before we move onto testing the carts, can you please confirm that this description is clear. Please tell me if you would feel any "real wind" where you are standing in this idealised world (just north of the equator), and in which direction and speed it might be blowing. And what would I be feeling at my position just across the boundary in the southern hemisphere? Is that "real" also or not? Does any of this set-up suffer from the problems that you see with the treadmill tests?