ISF Logo   IS Forum
Forum Index Register Members List Events Mark Forums Read Help

Go Back   International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology
 


Welcome to the International Skeptics Forum, where we discuss skepticism, critical thinking, the paranormal and science in a friendly but lively way. You are currently viewing the forum as a guest, which means you are missing out on discussing matters that are of interest to you. Please consider registering so you can gain full use of the forum features and interact with other Members. Registration is simple, fast and free! Click here to register today.
Reply
Old 13th November 2008, 12:45 PM   #401
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
JB:
The offer was made to accept a model using Matlab, something that was well within the claimant's qualifications. They could be seen by all.
I see no reason to pay for an explanation that is not necessary, nor to keep it to myself.
Also, the offer required only the supply of what was many times promised, but not delivered, and restricted to the cart on belt problem.

I do not need to meet your demands. If you do not want to promote and support your ideas, then nobody is forcing you to do so. Placing claims on You Tube that you have something that defies conventional explanation, and then insulting those who would question you, is your choice.

If I take my car to be repaired, and it is placed upon a dynamometer, and the speedometer indicates 60mph, that does not mean that the car is going at that speed, nor that any of the aerodynamic properties of the car are being tested. For how long should I entertain such a notion?

I can add, that many cars have fans attached to the motors, this does not seem to give them any special properties. Simply setting up an artificial arrangement of these two ideas, does not make for anything that needs more than cursory examination. It has been heard, and its operation determined. Patents clerks see ideas like this by the bucket load. If that is not good enough for you, then return with something more substantive, or better supported.

Last edited by humber; 13th November 2008 at 01:58 PM.
humber is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 01:44 PM   #402
Rob Lister
Guest
 
Join Date: Apr 2004
Posts: 8,504
Originally Posted by humber View Post
JB:
The offer was made to accept a model using Matlab, something that was well within the claimant's qualifications. They could be seen by all.
Wouldn't the 'real thing' be more betterestly than a model?
Rob Lister is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 02:18 PM   #403
Michael C
Graduate Poster
 
Michael C's Avatar
 
Join Date: Apr 2007
Location: N 49° 52' 3" E 8° 40' 21"
Posts: 1,932
That's a neat toy. Thanks for all the good explanations as to why it works. I was stumped at first until I realised that the wheels were making the propeller turn against the wind.

This reminds me of Martin Gardner's spool that moves backwards. When you pull the string, the spool moves in the direction of the pull, moving faster than the hand that's doing the pulling.
Michael C is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 02:18 PM   #404
JWideman
Graduate Poster
 
JWideman's Avatar
 
Join Date: Dec 2007
Posts: 1,233
I may be a layman, but it has been stated that this is a basic principle of physics, therefore I should be able to understand it. I do understand intertial frames of reference, at least enough to understand why when I'm sitting in a parked car and a car next to me drives away it looks like my car is moving backwards. Condescengly offering me lessons on it isn't going to win you points, and I'm not about to accept physics lessons from someone who I think is trying to trick me anyway.
I don't dispute what happens with the treadmill. It works exactly as I'd expect, in fact. The belt provides energy, indirectly, to the prop, creating thrust. The thrust is sufficient to overcome the drag, which is the traction of the wheel on the belt, and thus the cart advances. And it works because there is still enough traction for the belt to turn the wheel.
What I dispute is your assertion that the treadmill is equivalent to the open road and tailwind. And the reason I dispute that is because the wind can only push against objects moving slower than it. Just like when you're in a car moving 20 mph in a 20 mph tailwind and you stick your hand out the window, your hand experiences 0 mph of wind. I ask again, what force is moving the cart faster than the wind speed? I don't believe at this point I'm going to get a satisfactory and non-condescending answer.
As for the iceboat you keep talking about, I'm only familiar with iceboats that have powerful motors and wide flat keels. They are used for breaking the ice.
JWideman is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 02:35 PM   #405
Myriad
Hyperthetical
Moderator
 
Myriad's Avatar
 
Join Date: Nov 2006
Location: Pennsylvania
Posts: 12,845
I'm convinced that the device can work.

What intrigues me is the problem of explaining it intuitively. Trying to craft intuitive explanations for complex or counterintuitive phenomena is something of a hobby of mine.

I'd like to try a different approach here, and I hope ThinAirDesigns spork, et. al. don't mind.

Imagine an inclined track, with a motorized chain running along it, like an old-fashioned roller coaster starting hill. The chain moves uphill, and let's also arbitrarily say that uphill is left to right (the top of the hill is toward the right).

The chain moves at some constant speed relative to the track. The chain is designed so that it can mesh with a sprocket wheel mounted in a vehicle that can travel along the track.

(We will assume that the return side of the chain, traveling in the opposite direction, is inaccessible below the track and will be completely disregarded. The only objects that our vehicle can come in contact with are the track and the forward-moving portion of the chain.)

The track has rough fixed high-friction surfaces (or, if you prefer, fixed racks in the rack-and-pinion sense) along its edges.

I will regard the following as obvious:

1. If the sprocket in the vehicle, that meshes with the chain, is fixed so that it cannot rotate, then the vehicle will travel along the track at the same speed as the chain. (Provided, which will go without saying henceforth, that the motor driving the chain can provide sufficient force.)

2. If the sprocket can rotate freely, without friction, then the vehicle will not travel forward along the track, except by its own momenum. From a standing start it would not move (if it's already at the bottom of the incline) or coast backward.

3. If the sprocket can rotate but its rotation is limited by a clutch, then the vehicle will either slip backward, remain stationary, or move forward along the track at less than or equal to the speed of the chain. It will only move at the speed of the chain if the clutch is sufficiently engaged to prevent the sprocket from rotating at all, which reduces to case 1.

4. If the vehicle has a motor in it that can drive the sprocket gear forward (clockwise, if the bottom of the sprocket is in contact with the chain and the forward direction of the track is left to right), then the vehicle can travel along the track faster than the chain.

The question for interested parties is, without modifying the track or chain, and without using a motor in the vehicle or making use of any stored energy (including stored kinetic energy) in any way, can a mechanism be installed in the vehicle that allows the vehicle to move along the track faster than the speed of the chain? What kind of mechanism might that be?

I believe, based on past experience, that for some the answer will be obvious but it might be elusive for others. Let's see what answers people have before proceeding further.

Respectfully,
Myriad

ETA: Dang, Michael C got there first, two posts ago. Please try to answer the question before clicking his link!
__________________
A zømbie once bit my sister...

Last edited by Myriad; 13th November 2008 at 02:42 PM.
Myriad is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 02:50 PM   #406
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by JWideman View Post
I may be a layman, but it has been stated that this is a basic principle of physics, therefore I should be able to understand it. I do understand intertial frames of reference, at least enough to understand why when I'm sitting in a parked car and a car next to me drives away it looks like my car is moving backwards. Condescengly offering me lessons on it isn't going to win you points, and I'm not about to accept physics lessons from someone who I think is trying to trick me anyway.
I don't dispute what happens with the treadmill. It works exactly as I'd expect, in fact. The belt provides energy, indirectly, to the prop, creating thrust. The thrust is sufficient to overcome the drag, which is the traction of the wheel on the belt, and thus the cart advances. And it works because there is still enough traction for the belt to turn the wheel.
What I dispute is your assertion that the treadmill is equivalent to the open road and tailwind. And the reason I dispute that is because the wind can only push against objects moving slower than it. Just like when you're in a car moving 20 mph in a 20 mph tailwind and you stick your hand out the window, your hand experiences 0 mph of wind. I ask again, what force is moving the cart faster than the wind speed? I don't believe at this point I'm going to get a satisfactory and non-condescending answer.
As for the iceboat you keep talking about, I'm only familiar with iceboats that have powerful motors and wide flat keels. They are used for breaking the ice.
Agreed. I simply got tired of having to accept preposterous notions like the wheels are the ground, for the sole purposes of being able to call it a different
frame of reference. It is not necessary to go beyond what has been determined; that it is working against its own drag.
The simple answer is not enough, when you aver that it is, then out come the canned references and of course, "you know nothing about physics".
Boring.
ETA: As I think you mentioned, I also toyed with things like this when I was a boy. Where do they get the idea that science should dance to their tune?

Last edited by humber; 13th November 2008 at 02:53 PM.
humber is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 03:14 PM   #407
Thabiguy
Muse
 
Join Date: Feb 2007
Posts: 784
Originally Posted by my_wan View Post
What you have done is changed the gear ratio to make yourself right again.
I did not change the gear ratio. In the first scenario, craft moving at 4 mph wrt ground results in the propeller moving air at 2 mph (wrt craft). This same, unmodified craft, when moving at 1 mph wrt ground, will result in the propeller moving air at 0.5 mph (wrt craft). This is because the gear ratio, and everything else, was not changed. The ratio of craft speed wrt ground and prop air speed wrt craft is constant.

Originally Posted by my_wan View Post
I admitted and fully explained that you can change sporks specifications to do this for real. I also explained in detail why sporks design as he specified is not geared this way, i.e., 1 to 1 rpm ratio and wheel diameter less that prop diameter. Read the rest of my response for more detail.
I did read it, but I'm afraid it's not true. This statement

Originally Posted by my_wan View Post
The prop has a much larger radius than the wheels. This means the tips of the prop has to have a higher angular velocity than the edges of the wheels on the road, even at the same rpm. Any part of the prop with a greater radius of the wheels must eject air faster than the wheels are moving the craft.
does not universally hold, because it doesn't consider the propeller pitch at all. If propeller pitch is sufficiently small, this will not be true.

But that's just a reason why it doesn't have to be true; it's not a reason why it's not true for Spork's device.

The reason why it's not true for Spork's device, as he specified and built it, is that it is not true, as a matter of fact. Let me demonstrate this.

HEY, SPORK!

Your device, as you specified and built it - does it eject air (wrt craft) faster than the wheels are moving the craft, or slower? Which is it?

Last edited by Thabiguy; 13th November 2008 at 03:32 PM. Reason: grammar
Thabiguy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 03:16 PM   #408
Brian-M
Daydreamer
 
Brian-M's Avatar
 
Join Date: Jul 2008
Posts: 8,044
Originally Posted by my_wan View Post
It's not the "propeller pushing the air backwards which supplies the forward momentum". At below wind speed it is the wind blowing the craft itself downwind with force.

But once the craft is moving at (or faster than) wind-speed, it is the propeller pushing the air backwards which pushes the craft forwards. Unless the craft is being pushed forwards by an external force, the only way it can accelerate is by pushing something backwards (in this case, the air). Equal and opposite reactions, etc.

I'm thinking of the propeller simply as a kinetic energy transfer device, providing forward momentum to the craft by transferring backwards momentum to the air, using kinetic energy extracted from the momentum of the ground (relative to the craft) via the wheels.

Am I misunderstanding this?

I'm also thinking of this device as exactly analogous to a wind-powered device pushing against the ground to move against the wind. (Only it's a ground powered device pushing against the wind to move against the ground.)

Are there any reasons why this wouldn't be exactly analogous?

In both cases, the devices would have to be geared-down in order to accelerate in the opposite direction against the source of it's motive force.

Originally Posted by Thabiguy View Post
Yes - if the transmission is right. If the propeller was just blowing air backwards at the same speed that the treadmill moves, then the thrust generated by the propeller would be cancelled by equal but opposite force exerted by the treadmill on the cart as it drives the propeller, and nothing would happen.

In order for the device to accelerate, the propeller must be geared to move the air slower (wrt device) than the ground moves (wrt device). Speed will be slower, but exerted force will be greater. This is what will generate the net forward force to accelerate the vehicle.

As it must be geared-down this means that a wind-powered device can't travel more than wind-speed against the direction the wind is blowing, and a ground-powered device can't move more that ground-speed against the direction the ground is moving (which means it can't travel more than twice wind-speed in the direction of the wind, once you change frames of reference).

(Of course, if you can change gear-ratios once you've sped up, this no longer applies. )

That's how I think it should be working.
Am I understanding it right?
__________________
"That is just what you feel, that isn't reality." - hamelekim
Brian-M is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 03:18 PM   #409
spork
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,356
Originally Posted by Thabiguy View Post
HEY, SPORK!

Your device, as you specified and built it - does it eject air (wrt craft) faster than the wheels are moving the craft, or slower? Which is it?

Slower. For this thing to work the advance ratio (prop vs. wheels) must be below 1.0
spork is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 03:25 PM   #410
spork
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,356
Originally Posted by technoextreme View Post
I've never said it's impossible. You just can't do it with the plans for this cart because of the propeller.
And yet WE did.
spork is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 03:26 PM   #411
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
This is the basis of their claim that the treadmill represents a real wind test.
It can be found at #306

A:
Windspeed 10mph
Vehicle speed 10mph
Difference 0mph

B:
Windspeed 10mph
Vehicle speed 0 mph
Difference 10mph (sign ignored)

Their conclusion: When the difference is 0, the car is at windspeed.

The treadmill is said to have a property that allows case A to be assumed.

They forgot C:
Windspeed 0mph
Vehicle speed 0mph
Difference 0mph

So which is it?
in case A: Kinetic energy = 1/2mV^2
in case C: Kinetic energy = 0

Despite visible evidence for C, marginal speed, no kinetic energy, no wind.
They insist that it must be A: the vehicle is at windspeed and not essentially stopped.

LOL, genius
humber is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 03:29 PM   #412
ThinAirDesigns
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,058
Originally Posted by JWideman View Post
I do understand intertial frames of reference, at least enough to understand why when I'm sitting in a parked car and a car next to me drives away it looks like my car is moving backwards.
-
When it comes to understanding inertial frames of reference, we'll call the level you have described above, "Level X"

Quote:
What I dispute is your assertion that the treadmill is equivalent to the open road and tailwind.
-
No offense, but what's clear is that a "Level X" understanding of inertial frames of reference apparently isn't enough because the treadmill IS the physics equivalent of the open road.

Quote:
Condescengly offering me lessons on it isn't going to win you points, and I'm not about to accept physics lessons from someone who I think is trying to trick me anyway.
-
I now understand why you will not engage on the subject. Fair enough. For the record, I don't find anything "condescending" in my attempts to engage you. I believe you simply consider the statement "you don't understand the basics of inertial frames of reference" to be condescending -- but I can't change the facts to make them seem more palatable to you. Randi wouldn't approve.

IF you wish to understand the DDWFTTW concept of this device, you should find someone qualified who you *don't* think is trying to trick you and accept physics lessons from them. Your understanding of basic inertial frames of reference is lacking and could be proven to be so quite easily if you would engage.

JB
ThinAirDesigns is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 03:51 PM   #413
Modified
Philosopher
 
Modified's Avatar
 
Join Date: Sep 2006
Posts: 6,265
Originally Posted by humber View Post
This is the basis of their claim that the treadmill represents a real wind test.
It can be found at #306

A:
Windspeed 10mph
Vehicle speed 10mph
Difference 0mph

B:
Windspeed 10mph
Vehicle speed 0 mph
Difference 10mph (sign ignored)

Their conclusion: When the difference is 0, the car is at windspeed.

The treadmill is said to have a property that allows case A to be assumed.

They forgot C:
Windspeed 0mph
Vehicle speed 0mph
Difference 0mph

So which is it?
in case A: Kinetic energy = 1/2mV^2
in case C: Kinetic energy = 0

Despite visible evidence for C, marginal speed, no kinetic energy, no wind.
They insist that it must be A: the vehicle is at windspeed and not essentially stopped.

LOL, genius
Kinetic energy is relative to some reference frame. The vehicle maintaining speed on the treadmill has kinetic energy in the reference frame of the tread surface, but not in the frame of the room (apart from the inertia of the prop).
Modified is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 04:11 PM   #414
spork
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,356
Originally Posted by Modified View Post
Kinetic energy is relative to some reference frame.

THANK YOU for that. I don't know why, but this is a point that's completely lost on most people. They think that a bullet shot through the air HAS some specific kinetic energy. They don't realize that its kinetic energy can be anywhere between 0 and astronomical depending on your reference frame.

Kinetic energy is NOT an intrinsic property.
spork is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 04:12 PM   #415
Thabiguy
Muse
 
Join Date: Feb 2007
Posts: 784
Originally Posted by Brian-M View Post
As it must be geared-down this means that a wind-powered device can't travel more than wind-speed against the direction the wind is blowing, and a ground-powered device can't move more that ground-speed against the direction the ground is moving (which means it can't travel more than twice wind-speed in the direction of the wind, once you change frames of reference).
Well, not necessarily. The gearing works both ways. I'll give you a specific example: if the propeller is geared to move the air backwards (wrt craft) at 2/3 of the wheel speed, the propeller-moved air is moving forward (wrt ground) at 1/3 of the craft speed. The wind will accelerate the craft until the propeller-moved air is moving forward (wrt ground) at the same speed as the wind. But because propeller-moved air is moving at 1/3 craft speed, this means that by this time the craft is moving at 3 times the wind speed.

Originally Posted by Brian-M View Post
Am I understanding it right?
You care whether you understand, and that means you're on the best way to understanding!
Thabiguy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 04:14 PM   #416
spork
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,356
Originally Posted by humber View Post
LOL, genius
JB probably wouldn't want me divulging this, but he is in fact - literally a genius. As such your sarcastic rant may not have the effect desired.

What's more interesting is a story JB told me recently that's too long to recount here, but the spoiler is this... there is no way for stupid people to tell they're stupid. Of course this is a pretty pedestrian way of summarizing the results of a carefully controlled study.
spork is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 04:16 PM   #417
spork
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,356
Originally Posted by Thabiguy View Post
You care whether you understand, and that means you're on the best way to understanding!
I second that. And my hat's off to you for opening yourself up to the possibility of something that just doesn't seem right intuitively.
spork is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 04:28 PM   #418
Ivor the Engineer
Philosopher
 
Ivor the Engineer's Avatar
 
Join Date: Feb 2006
Posts: 9,425
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.

Is this correct?
__________________
My Blog.
Ivor the Engineer is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 04:33 PM   #419
sol invictus
Philosopher
 
sol invictus's Avatar
 
Join Date: Oct 2007
Posts: 8,613
Originally Posted by JWideman View Post
What I dispute is your assertion that the treadmill is equivalent to the open road and tailwind. And the reason I dispute that is because the wind can only push against objects moving slower than it. Just like when you're in a car moving 20 mph in a 20 mph tailwind and you stick your hand out the window, your hand experiences 0 mph of wind.
That's more like it - a polite and reasonable question.

Here's the deal. All of the equations of physics depend only on differences in velocities, not on velocity itself. There is no absolute rest frame, no special velocity at which the laws of physics are different than at other ones. This is pretty obvious if you remember that the earth is hurtling through space at a gigantic velocity relative to every other thing in the universe.

A consequence of this fact is that one can add or subtract any velocity from all the velocities in a given problem without affecting the equations (since that addition or subtraction cancels out of all velocity differences). That's called transforming to a different reference frame. OK?

So - imagine a cart in a steady wind on flat ground. The cart is rolling at exactly the speed of the wind (say 20mph), and in the same direction. Someone riding the car feels no breeze at all, just as you said. But the ground is moving past them at 20 mph, and the wheels of the car are spinning at the appropriate rate (which depends on their radius).

Now, transform from the reference frame in which the ground is at rest and the cart is moving (the "ground" frame) to the one where the cart is at rest and the ground is moving (the "wind" frame). Wind speed in the first frame is 20 mph, in the new frame it's 20mph-20mph = 0 (that's why I called it the wind frame). But ground speed is 0-20mph = -20 mph (the minus means it's going the opposite way the wind was).

So in the new frame the cart and wind are at rest, but the ground is moving. That's precisely the cart at fixed position (relative to the treadmill, not the belt) on the treadmill. Its wheels are spinning, but it's in still air (apart from the breeze that's created when the propeller is attached to the wheels).

Quote:
I ask again, what force is moving the cart faster than the wind speed?
The propeller, which is driven by the moving belt.

Last edited by sol invictus; 13th November 2008 at 04:40 PM.
sol invictus is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 04:35 PM   #420
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Don't forget to include the greast big hand that will magically take the cart from 0mph to 10mph, instantaneously and without any apparent energy exchange.

All things are relative. How literal can you be?
humber is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 04:37 PM   #421
sol invictus
Philosopher
 
sol invictus's Avatar
 
Join Date: Oct 2007
Posts: 8,613
Originally Posted by humber View Post
Despite visible evidence for C, marginal speed, no kinetic energy, no wind.
They insist that it must be A: the vehicle is at windspeed and not essentially stopped.

LOL, genius
You're really making yourself look like a fool. Energy is not invariant under these transformations.

If you had taken even a first year college course in physics you'd know that energy is the first component of a 4-vector, not a Lorentz invariant. Not that one even needs that - Galilean transformations are enough.
sol invictus is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 04:40 PM   #422
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Keep the $100K, because you're precious. The only winds in this experiment come from you, and the ideas flying over your head.
humber is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 04:44 PM   #423
technoextreme
Illuminator
 
technoextreme's Avatar
 
Join Date: Jun 2007
Posts: 3,785
Originally Posted by spork View Post
And yet WE did.
No you didn't. You in fact rediscovered an 100 year old perpetual motion machine that just happens to ironically be tied to boats. This is the reason why I'm so stubborn because I've seen this before and if it did anything useful we would have found out 100 years ago.
__________________
It's amazing how many of these "paranormal" icons seem to merge together. There always seem to be theories about how they link together in some way. I'm sure someone has a very good explanation as to how Bigfoot killed JFK to help cover Roswell.-Mark Mekes
This isn't rocket surgery.-Bill Nye

Last edited by technoextreme; 13th November 2008 at 04:47 PM.
technoextreme is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 04:47 PM   #424
Brian-M
Daydreamer
 
Brian-M's Avatar
 
Join Date: Jul 2008
Posts: 8,044
Originally Posted by Thabiguy View Post
Well, not necessarily. The gearing works both ways. I'll give you a specific example: if the propeller is geared to move the air backwards (wrt craft) at 2/3 of the wheel speed, the propeller-moved air is moving forward (wrt ground) at 1/3 of the craft speed. The wind will accelerate the craft until the propeller-moved air is moving forward (wrt ground) at the same speed as the wind. But because propeller-moved air is moving at 1/3 craft speed, this means that by this time the craft is moving at 3 times the wind speed.

D'oh!

I worked it out using 1/2 as a convenient ratio. I forgot different ratios would have different limits.

Originally Posted by Thabiguy View Post
You care whether you understand, and that means you're on the best way to understanding!

I've found the best way to understand a new idea is to work out exactly why your existing ideas are completely, utterly wrong.
__________________
"That is just what you feel, that isn't reality." - hamelekim
Brian-M is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 04:51 PM   #425
ThinAirDesigns
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,058
Originally Posted by humber View Post
This is the basis of their claim that the treadmill represents a real wind test.
It can be found at #306

A:
Windspeed 10mph
Vehicle speed 10mph
Difference 0mph

B:
Windspeed 10mph
Vehicle speed 0 mph
Difference 10mph (sign ignored)

Their conclusion: When the difference is 0, the car is at windspeed.
-

Humber, I sure hope folks will go to Post #306 as you referenced it, because it will show that your case "A" and "B" above are NOT the cases that were presented. I have no idea if you simply made a typo error, or if you are intent on twisting the cases, but either way unless you can accurately read words on a page it's garbage in, garbage out.

Here is the ACTUAL representation of case "A" and "B" as copied directly from Post #306:

Quote:
We are going to mount a wheel driven speedometer and a *chassis mounted* air speed indicator on the device.

Let's just take the case of "as fast as the wind" and compare:

Case "A": cart is going down the street at 10mph in a 10mph tailwind.

Speedometer: 10mph
Air speed indicator: 0mph

Case "B": cart is on the treadmill(TR) which is set at 10mph and is neither moving towards the front of the TR nor to the rear of the TR.

Speedometer: 10mph
Air speed indicator: 0mph
-
Now, if you wish to comment on the above scenario, be my guest. If you wish to disagree with the scenario, that's perfectly OK. BUT if you wish to keep misrepresenting the data in #306 I will continue pasting it in directly so everyone can see the mispresentation first hand.

(as a quick reference for those seeking humbers "mistake", notice that in the #306 case, "A" and "B" always return the same result from the instruments. In humbers "A" and "B" they don't. Now if humbert disagrees with our instrument returns, that's OK --- but humbert should NOT post different data and represent it as "the basis of *our* claim")

JB
ThinAirDesigns is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 05:08 PM   #426
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by Ivor the Engineer View Post
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.

Is this correct?
But there's no wind. The correct interpretation, is that the cart takes ALL of it's energy from the belt. Hold the cart on the belt, but with the prop de-coupled.
How do you get the prop to turn? Connect it to the wheels. And so it turns.
Due to Newton's law of opposite and equal reaction, the torque on the prop shaft will be the opposite of the wheel drive shaft. These cancel to produce zero torque. That means, the cart will not move, because, there is no torque!
The SOLE purpose of the prop, is to achieve that very condition.
The small travel that you see, is the result of small differences between the two torques, being integrated by the mass of the propeller. Small details, aside, that is all this wonder does.
For yet another time, everybody, the belt drives the cart so that it will stay in place. There is no wind!

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.

Last edited by humber; 13th November 2008 at 05:13 PM.
humber is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 05:14 PM   #427
ThinAirDesigns
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,058
Originally Posted by humber View Post
But there's no wind. The correct interpretation, is that the cart takes ALL of it's energy from the belt.
<snip>
For yet another time, everybody, the belt drives the cart so that it will stay in place. There is no wind!
-
Ivor:
Quote:
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.
-
Ivor, it works *exactly the same in both cases because both "cases" are exactly the same.

There literally isn't a single scientific test (no matter how sensitive the instrument) which can be performed to determine if the air is moving and the ground is still or if the air is still and the ground is moving.

Answer the question "Is a sailboat wind powered or water powered?" and it becomes clear -- "both" or "either" are each correct depending on your frame of reference and neither answer changes how the boat works.

Squeeze a watermellon seed between your fingers and pop it to the other side of the room -- "which finger 'powered' the seed?" Same answer as the sail boat.

Place your two open hands on opposing sides of a empty drinking glass and move your hands in a way that makes the glass spin between them -- "which hand is spinning the glass?". Same answer.

"Which powers the DDWFTTW cart, the road or the wind?" Same answer.

Motion is relative and as long as the rolling surface and the air are moving relative to each other, the DDWFTTW cart will happily zip along.

JB

Last edited by ThinAirDesigns; 13th November 2008 at 05:46 PM.
ThinAirDesigns is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 05:19 PM   #428
sol invictus
Philosopher
 
sol invictus's Avatar
 
Join Date: Oct 2007
Posts: 8,613
Originally Posted by humber View Post
How do you get the prop to turn? Connect it to the wheels. And so it turns.
Due to Newton's law of opposite and equal reaction, the torque on the prop shaft will be the opposite of the wheel drive shaft. These cancel to produce zero torque. That means, the cart will not move, because, there is no torque!
So now we're back to the forces always cancel? You already admitted that was wrong, just a few posts back.
sol invictus is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 05:31 PM   #429
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
That is precisely, what I said, hence my tautology remark.
You do not read what is posted, but scan it for ammunition or flattery

Quite. We can resort to post-modernist ideas on the nature of reality, or we can look for what we all call EVIDENCE.

The cart has no velocity, no kinetic energy. There is no wind at all.

Which do you think is the most plausible? A call to a Pantheon of deceased physicists, or your own logic and senses, and the highly unlikely prospect that the laws of physics have been overturned by You Tube.
humber is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 05:41 PM   #430
ThinAirDesigns
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,058
Originally Posted by humber View Post
The cart has no velocity, no kinetic energy. There is no wind at all.
Relative to where you (or the camera in the video) are standing you are correct -- "the cart has no velocity, no kinetic energy and there is no wind at all"

humbers, I hate to break it to you, but in physics, everything isn't about you.

Relative to the rolling surface -- be it the street or the belt, in both cases the cart HAS velocity, kinetic energy and wind in spades -- exactly the same in both cases as it turns out.

JB

Last edited by ThinAirDesigns; 13th November 2008 at 05:47 PM.
ThinAirDesigns is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 05:45 PM   #431
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Edited by Gaspode:  Removed for breach of Rule 12.


Mod WarningAttack the argument, not the arguer
Posted By:Gaspode

Last edited by Gaspode; 13th November 2008 at 06:11 PM.
humber is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 05:48 PM   #432
JWideman
Graduate Poster
 
JWideman's Avatar
 
Join Date: Dec 2007
Posts: 1,233
Originally Posted by sol invictus View Post
Originally Posted by JWideman
what force is moving the cart faster than the wind speed?
The propeller, which is driven by the moving belt.
That's the treadmill. What about the open road?
JWideman is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 05:54 PM   #433
Brian-M
Daydreamer
 
Brian-M's Avatar
 
Join Date: Jul 2008
Posts: 8,044
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?
__________________
"That is just what you feel, that isn't reality." - hamelekim
Brian-M is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 05:57 PM   #434
Brian-M
Daydreamer
 
Brian-M's Avatar
 
Join Date: Jul 2008
Posts: 8,044
Originally Posted by JWideman View Post
That's the treadmill. What about the open road?
The open road does the same job as the treadmill. Relative to the wind, the open road is moving in the opposite direction, so you end up with the same situation as you have with a treadmill and no wind.

ETA: If the cart is moving at wind speed, then relative to the cart there is no wind, and the road is moving.
__________________
"That is just what you feel, that isn't reality." - hamelekim

Last edited by Brian-M; 13th November 2008 at 05:59 PM.
Brian-M is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 05:58 PM   #435
ThinAirDesigns
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,058
Me:
Quote:
Relative to the rolling surface -- be it the street or the belt, in both cases the cart HAS velocity, kinetic energy and wind in spades -- exactly the same in both cases as it turns out.
humbert:
Quote:
You are an idiot. stop wasting our time.

It's very entertaining to see those two statements adjacent to each other considering that my statement precisely matches tried and true both the physical laws of the universe and their scientific explanations.

JB
ThinAirDesigns is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 06:03 PM   #436
ThinAirDesigns
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,058
Originally Posted by Brian-M View Post
The open road does the same job as the treadmill. Relative to the wind, the open road is moving in the opposite direction, so you end up with the same situation as you have with a treadmill and no wind.
-

Perfectly put Brian. The evidence to the contrary is not rationally debatable.

Humbert, soon you will be the only one on the forum waving his arms and screaming "they're not the same, they're not the same".


JB
ThinAirDesigns is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 06:09 PM   #437
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
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.
humber is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 06:10 PM   #438
Thabiguy
Muse
 
Join Date: Feb 2007
Posts: 784
Originally Posted by Brian-M View Post
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?
Sure; just make the propeller blow air backwards wrt cart at, say, 1.5x cart speed (=0.5x cart speed backwards wrt ground). But practically it would be more difficult to build, because unwanted drag will work against you harder when it moves upwind. You would have to put more effort into minimizing losses.

Last edited by Thabiguy; 13th November 2008 at 06:20 PM. Reason: clarification
Thabiguy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 06:14 PM   #439
ThinAirDesigns
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,058
Originally Posted by humber View Post
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.
Unfortunately for you, there are many things that are relative -- and the three that are key to this discussion are:

1. Velocity
2. Kinetic energy
3. Wind

There is no absolute (or "real world" as you call it) with any of those three.

JB

Last edited by ThinAirDesigns; 13th November 2008 at 06:15 PM.
ThinAirDesigns is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 13th November 2008, 06:14 PM   #440
sol invictus
Philosopher
 
sol invictus's Avatar
 
Join Date: Oct 2007
Posts: 8,613
Originally Posted by JWideman View Post
That's the treadmill. What about the open road?
The wind .

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.
sol invictus is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Reply

International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -7. The time now is 03:38 PM.
Powered by vBulletin. Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
© 2014, TribeTech AB. All Rights Reserved.
This forum began as part of the James Randi Education Foundation (JREF). However, the forum now exists as
an independent entity with no affiliation with or endorsement by the JREF, including the section in reference to "JREF" topics.

Disclaimer: Messages posted in the Forum are solely the opinion of their authors.