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, 09:42 AM   #361
sol invictus
Philosopher
 
sol invictus's Avatar
 
Join Date: Oct 2007
Posts: 8,613
Originally Posted by humber View Post
Ignoring the observed tiny speed. we have two options:
The cart is at windspeed when in the hand or on the belt. ( no sensible wind over cart)
The cart is at zero velocity when in the hand or on the belt. ( no sensible wind over cart)
It's paradoxical, because it is nonsense.
This platform represents a cart that keeps itself at zero velocity regardless of windspeed.
It is understandable, but unbelievable that such a model would be proposed. That's the difficulty of understanding.
All this headbanging is astonishment at support of such a banal and absurd claim. It is not even wrong.
I really have no idea what you're trying to say. It's clear you've misunderstood something very basic, but I don't know what it is and I'm sick of trying to guess. So I give up.
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, 09:43 AM   #362
Thabiguy
Muse
 
Join Date: Feb 2007
Posts: 784
Originally Posted by humber View Post
Ignoring the observed tiny speed. we have two options:
The cart is at windspeed when in the hand or on the belt. ( no sensible wind over cart)
The cart is at zero velocity when in the hand or on the belt. ( no sensible wind over cart)
It's paradoxical, because it is nonsense.
You're right. Now, how about this?

Quote:
The cart is at windspeed when in the hand or on the belt. ( no sensible wind over cart)
The cart is at zero velocity with respect to the air when in the hand or on the belt. ( no sensible wind over cart)
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, 09:45 AM   #363
sol invictus
Philosopher
 
sol invictus's Avatar
 
Join Date: Oct 2007
Posts: 8,613
Originally Posted by technoextreme View Post
Which is wrong from a physics standpoint. You always need a torque greater than zero to turn a wheel.
Are you really an engineer? If so, I hope (for my own safety if I ever use something you've designed) that you're familiar with the concept of "inertia", or "moment of inertia"? Or maybe that you've heard of something called Newton's First Law?
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, 09:46 AM   #364
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by Ivor the Engineer View Post
Huh? Sol explicitly stated that by connecting the propeller to the wheels means a torque greater than zero is required to turn the wheels. With suitable gearing and propeller selection the net force from the treadmill on the cart and the prop can be adjusted (in theory and apparently in practice) to be in a direction which causes the cart to accelerate to above the speed of the treadmill.
Yes, huh.
The torque is the tiny difference between the drive from the wheels and the equal and opposite reaction from the propellor*. In an ideal world, these forces would be in balance, resulting in zero torque. It is fundamentally incapable of doing any work. Other ratios are possible, but that simply means that the propellor turns at a different speed in order to create the same result of standing still. It is not a model of anything other than it is. It is literal. There is no wind. The belt drives the wheels and the propellor.

*attributed to Newton or Zeus.
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, 09:52 AM   #365
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by ThinAirDesigns View Post
There's no need to wonder.

JB
I wonder how it is that you can speak for these men. They do an awful lot of your talking. Could it be that you have nothing to say that is not connected to an appeal to authority?
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, 09:52 AM   #366
ThinAirDesigns
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,058
techno:
Quote:
Right but it needs to be done in BOTH DIRECTIONS at the same time in order to travel faster than wind. You can't do it with just a belt drive.
Techno, I've seen you state the above and your "screw" analogy numerous times here on this thread. I know why you use the screw analogy and I understand why you think it's correct -- but it's just not. I know you don't believe me and you feel you have very good reasons for that, but it's just not.

I will make one small attempt at demonstrating your fallacy.

If the prop were not connected to the wheels, you would be using your "screw" analogy just perfectly -- a prop really is nothing more than a screw after all. Wind from the front ... screw turns one way. Wind from the back ... screw turns the other way. We get it, we really do. But the prop IS geared to the wheels and in spite of every bone in your body telling you this doesn't make a difference, IT DOES!.

If you're "screw" analogy was to suddenly become valid in this application, ever sailboat on the water would have suddenly come dead in the water and would have to toss up a spinnaker and head straight downwind only.

The keel on a sailboat allows the sail to "see" wind from a direction *other than* the direction you would think. The gearing between the wheels and the prop allow the prop to "see" wind from a direction *other than* you would think.

While you will likely remain rooted in your vision that when the cart chassis transitions from 'slower than the wind' to 'faster than the wind' the propellor sees the same change, it will never be true.

You can learn *why* it's not true, or you can continue believing your "screw" analogy while sailors the world over prove you wrong.

Your choice.
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, 09:53 AM   #367
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
And you, sir?
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, 09:54 AM   #368
my_wan
Graduate Poster
 
my_wan's Avatar
 
Join Date: Feb 2007
Posts: 1,074
Perfect. I take back my criticism of the substance of your argument.

Originally Posted by Thabiguy View Post
In fact, I explained with great detail why that is. You just didn't understand my explanation. Perhaps I didn't explain it clearly enough.
I'll let that slide sense the substance in this post is perfect. It even makes the source of our disagreement crystal clear and also makes your original claim very understandable. Nobody could ask for more.

Originally Posted by Thabiguy View Post
Let me try again. The craft is travelling right to left, wrt ground, at 4 mph. The wind is going right to left, wrt ground, at 8 mph (and also right to left, wrt craft, at 4 mph). The prop blows the air left to right wrt the craft, at 2 mph.
I do see how you got got your numbers now and why. I qualified my original claim you objected to with, "When the craft first takes off" for a reason. In the first video 4 mph is most of the ground wind speed and certainly can't be defined as "when the craft first takes off". By arbitrarily picking the prop wind speed at some arbitrary craft speed (such as 2 mph when the craft is at 4 mph) you can point the prop wind speed either direction you want wrt ground. Your chosen numbers would give a prop wind speed of 2 mph wrt the ground in the same direction as the craft.

If craft speed is 4 mph (far too fast to be when the craft first takes off) then:

From above wrt the ground (ground= 0mph wrt the ground).
Definitions:
Right to left is -mph wrt the ground.
Left to right is +mph wrt the ground.
A switch from + to - or - to + is a direction reversal wrt ground.
Sentence by sentence in the same order you stated above.
Craft = -4 mph wrt ground, right to left.
Wind = +8 mph wrt ground, left to right.
Prop air = +2 wrt craft but craft = -1 wrt ground therefore:
Prop air wrt ground = -4+2 = -2 mph wrt ground (same direction as as craft wrt ground).

What happens when we use these same numbers except with a craft speed much closer to "when the craft first takes off" as I specified, such as 1 mph wrt ground. Now the prop air speed wrt ground is 1 mph opposite the direction of the craft.

Craft = -1 mph wrt ground, right to left.
Wind = +8 mph wrt ground, left to right.
Prop air = +2 wrt craft but craft = -1 wrt ground therefore:
Prop air wrt ground = -1+2 = +1 mph wrt ground.

This is exactly why I specified "when the craft first takes off" in the quote of mine you chose to take issue with. To see it in context here is where you objected:
Originally Posted by Thabiguy View Post
Originally Posted by my_wan View Post
When the craft first takes off the prop is moving air in the opposite direction of the wind.
With respect to the device, yes. With respect to the ground, no. The air pushed back is moving in the opposite direction of the air wrt device, and in the same direction as the air wrt ground.

If you don't realize this, then you don't understand how the device works.
Originally Posted by Thabiguy View Post
What direction is the air blown by the propeller travelling, wrt ground? In the same direction as the air, or the opposite direction of the air?
When the craft first takes off it is in the opposite direction of the wind, as I originally stated and will show why. Now since gearing can be set so that either one of us can be right about the craft who is right concerning the craft given sporks specifications? We know that the gear ratio is 1 to 1 in rpm. So this same question becomes how does a propeller turning the same rpm as the wheels blow air faster than the wheels are moving the craft?

This one is easy. 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. My statement therefore stands.

Originally Posted by Thabiguy View Post
Does this make statement number 2 true, or false?
Given the design specifications of the craft statement number 2 remains false. Of course you could change sporks specifications (gear ratio, wheel size, prop pitch, etc.) to make it true.

Originally Posted by Thabiguy View Post
Does this clarify what I mean? If not, what is still unclear to you?
Yes, perfectly. I even understand now how you did the vectors to reasonably lead you to that claim.

Originally Posted by Thabiguy View Post
ETA: I'm sorry, I mistyped one of the directions when I was typing this post. The error is now corrected. If you have read it before, please read the post again.
Not a problem. The above issue with gearing ratio changing the physics of the crafts operation is an excellent example of why "idealized" models are so often useless. I try real hard to qualify my statements for the specific characteristics of the real model under actual operational conditions. It is impossible to avoid all mistakes.
__________________
Peace to all people of the world. The evidence indicates that this is best accomplished through a skeptical approach.
my_wan 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, 09:55 AM   #369
ThinAirDesigns
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,058
Arguing over inertial frames of reference in this simple application is a silly as arguing over the basic laws of gravity.

I drop a brick on my foot -- it hurts. I switch frames of reference -- nothing changes.

If that's an appeal to authority -- I claim guilty.

JB

Originally Posted by humber View Post
I wonder how it is that you can speak for these men. They do an awful lot of your talking. Could it be that you have nothing to say that is not connected to an appeal to authority?
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, 09:56 AM   #370
mhaze
Banned
 
Join Date: Jan 2007
Posts: 15,718
Here's a simple test - Put machine on treadmill, use fish scale and measure stationary thrust. Do not allow machine to move in xy during test.

Might be easiest to suspend machine between two fish scales on a tight string.

Last edited by mhaze; 13th November 2008 at 09:58 AM.
mhaze 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, 09:59 AM   #371
ThinAirDesigns
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,058
Originally Posted by mhaze View Post
Here's a simple test - Put machine on treadmill, use fish scale and measure stationary thrust. Do not allow machine to move in xy during test.
EXCELLENT!! Someone has suggested a test. As it turns out, we do tests. We do tests on request.

We'll set it up and post it.

mhaze, any special concerns or requirements you wish to see us meet during the test?

Thank GOD someone wants to actually *do* something.

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, 10:00 AM   #372
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by Thabiguy View Post
You're right. Now, how about this?
What is the one thing that connects all together. No wind. There is no "equivalence" what you are seeing is a toy on a belt, doing what a toy would do if it were on a belt.

It is not a cart in wind, it is a cart on a belt in still air.
The monumental conceit, is that dead physicists are invoked to suggest that it otherwise. Why? Because no living physicist would support the idea, once he realised tghe difference between what is said to be presented, and what is presented.
I have challenged Spork to publish his calculations at on the Physics Forum. He doesn't seem at all keen.
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, 10:01 AM   #373
sol invictus
Philosopher
 
sol invictus's Avatar
 
Join Date: Oct 2007
Posts: 8,613
Originally Posted by humber View Post
The torque is the tiny difference between the drive from the wheels and the equal and opposite reaction from the propellor*. In an ideal world, these forces would be in balance, resulting in zero torque. It is fundamentally incapable of doing any work. Other ratios are possible, but that simply means that the propellor turns at a different speed in order to create the same result of standing still.
I see - they're always in balance. How odd... would they remain in balance if I aimed the propeller up? What if I applied a resistive brake to the wheels - will the cart remain stationary and its wheels spin at the same rate in that case too?

Rather than continue repeating yourself, why don't you show us why those forces are always in balance?
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, 10:05 AM   #374
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by ThinAirDesigns View Post
EXCELLENT!! Someone has suggested a test. As it turns out, we do tests. We do tests on request.

We'll set it up and post it.

mhaze, any special concerns or requirements you wish to see us meet during the test?

Thank GOD someone wants to actually *do* something.

JB
No need to bother. You can see from the video #5. It is quite clear that the cart can be moved very easily. There is no appreciable torque.
This has been mentioned several times, but we have yet to hear an explanation from Newton/Einstein/Galileo's clairvoyant.
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, 10:06 AM   #375
my_wan
Graduate Poster
 
my_wan's Avatar
 
Join Date: Feb 2007
Posts: 1,074
Originally Posted by spork View Post
Assuming a constant coefficient of drag, the resistance increases with the square of velocity. It's the power required that increases with the cube of velocity.
Yes but you have a set power available for the crafts use under a given wind speed and cross-section. Power is then the quantity you design for. Also, the coefficient of drag is not constant given the operational specs of this craft.
__________________
Peace to all people of the world. The evidence indicates that this is best accomplished through a skeptical approach.
my_wan 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, 10:07 AM   #376
spork
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,356
http://www.youtube.com/watch?v=Y15NnGZIBuM
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, 10:12 AM   #377
Thabiguy
Muse
 
Join Date: Feb 2007
Posts: 784
my_wan,

I'm genuinely pleased that we've been able to clear up some misunderstandings and move forward. Now, there's one significant thing to resolve.

Originally Posted by my_wan View Post
What happens when we use these same numbers except with a craft speed much closer to "when the craft first takes off" as I specified, such as 1 mph wrt ground. Now the prop air speed wrt ground is 1 mph opposite the direction of the craft.

Craft = -1 mph wrt ground, right to left.
Wind = +8 mph wrt ground, left to right.
Prop air = +2 wrt craft but craft = -1 wrt ground therefore:
Prop air wrt ground = -1+2 = +1 mph wrt ground.
I underlined the problem here. Correctly, the situation would be this:

Craft = -1 mph wrt ground, right to left.
Wind = +8 mph wrt ground, left to right.
Prop air = +0.5 wrt craft but craft = -1 wrt ground therefore:
Prop air wrt ground = -1+0.5 = -0.5 mph wrt ground.

The important thing to realize here that the prop air speed, wrt craft, is linearly dependent on the ground speed wrt craft (i.e. the propeller will slow down if the cart slows down wrt ground). It can't possibly stay constant, such as +2.

Are you with me so far?

(P.S.: I'll be AFK for a couple hours.)
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, 10:16 AM   #378
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Remember Mr Newton "for every action there is an equal and opposite reaction"
Changing the orientation of the propellor, will simply change the amount of drag, and therefore the amount of energy absorbed from the belt.
The two forces will always be in balance, not only because of that law, but that the sum of the two forces is that derived form the belt.
If I were to replace the propellor with a sail, it would do much the same. I can make the cart move forward or backwards according to how much drag I allow the sail to create.
It is held in placeon the belt by drag created by the propellor. The propellor is not a motive force, but a dissipator of energy. It is too busy keeping itelf on the belt that it does not have any time to do any other work.
A lame duck, backed by hubris and bravado.
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, 10:17 AM   #379
spork
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,356
Originally Posted by my_wan View Post
Yes but you have a set power available for the crafts use under a given wind speed and cross-section. Power is then the quantity you design for. Also, the coefficient of drag is not constant given the operational specs of this craft.
Nevertheless, I was commenting on your assertion that drag is proportional to the cube of speed. It's not.
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, 10:19 AM   #380
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by ThinAirDesigns View Post
Arguing over inertial frames of reference in this simple application is a silly as arguing over the basic laws of gravity.

I drop a brick on my foot -- it hurts. I switch frames of reference -- nothing changes.

If that's an appeal to authority -- I claim guilty.

JB
Yes, all bricks have the same mass to you. That last bit sums up your knowledge of inertial frames.
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, 10:19 AM   #381
Modified
Philosopher
 
Modified's Avatar
 
Join Date: Sep 2006
Posts: 6,145
Originally Posted by humber View Post
What is the one thing that connects all together. No wind. There is no "equivalence" what you are seeing is a toy on a belt, doing what a toy would do if it were on a belt.
"Wind" is the speed of the air relative to the surface. The speed of things other than the air and surface do not matter. Why would they?

You do realize that we are all on what is effectively a giant belt right? The earth is spinning.
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, 10:23 AM   #382
sol invictus
Philosopher
 
sol invictus's Avatar
 
Join Date: Oct 2007
Posts: 8,613
Originally Posted by humber View Post
Remember Mr Newton "for every action there is an equal and opposite reaction"
Yes, I remember. I also remember that the cart is not the only thing being acted on here - there is also the belt and the air, which you seem to have forgotten.

Quote:
Changing the orientation of the propellor, will simply change the amount of drag, and therefore the amount of energy absorbed from the belt.
The two forces will always be in balance, not only because of that law, but that the sum of the two forces is that derived form the belt.
So you think if I aim the propeller straight up the cart will remain motionless on the belt. I suggest you think again, and if you find that difficult, imagine the propeller is encased in a container full of thick viscous oil. If there is any resistance in the propeller - which there always will be in still air unless it's not rotating - there is a torque on the wheels. It's precisely like braking a car.

Quote:
The propellor is not a motive force, but a dissipator of energy.
That must make it difficult for propeller planes to fly, mustn't it?
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, 10:27 AM   #383
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by sol invictus View Post

That must make it difficult for propeller planes to fly, mustn't it?
That's how planes convert the engine's power to motive force. So, there you go, you now understand a little bit more.
Go play now.
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, 10:34 AM   #384
sol invictus
Philosopher
 
sol invictus's Avatar
 
Join Date: Oct 2007
Posts: 8,613
Originally Posted by humber View Post
That's how planes convert the engine's power to motive force. So, there you go, you now understand a little bit more.
Go play now.
So you're going to ignore all the substantive question I asked you? Evidently that means you believe cars can't brake?
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, 10:40 AM   #385
my_wan
Graduate Poster
 
my_wan's Avatar
 
Join Date: Feb 2007
Posts: 1,074
Originally Posted by spork View Post
Nevertheless, I was commenting on your assertion that drag is proportional to the cube of speed. It's not.
Oops. My bad.
__________________
Peace to all people of the world. The evidence indicates that this is best accomplished through a skeptical approach.
my_wan 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, 10:47 AM   #386
my_wan
Graduate Poster
 
my_wan's Avatar
 
Join Date: Feb 2007
Posts: 1,074
Originally Posted by Thabiguy View Post
my_wan,

I'm genuinely pleased that we've been able to clear up some misunderstandings and move forward. Now, there's one significant thing to resolve.

I underlined the problem here. Correctly, the situation would be this:

Craft = -1 mph wrt ground, right to left.
Wind = +8 mph wrt ground, left to right.
Prop air = +0.5 wrt craft but craft = -1 wrt ground therefore:
Prop air wrt ground = -1+0.5 = -0.5 mph wrt ground.

The important thing to realize here that the prop air speed, wrt craft, is linearly dependent on the ground speed wrt craft (i.e. the propeller will slow down if the cart slows down wrt ground). It can't possibly stay constant, such as +2.

Are you with me so far?

(P.S.: I'll be AFK for a couple hours.)
What you have done is changed the gear ratio to make yourself right again. 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.
__________________
Peace to all people of the world. The evidence indicates that this is best accomplished through a skeptical approach.
my_wan 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, 11:15 AM   #387
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by sol invictus View Post
So you're going to ignore all the substantive question I asked you? Evidently that means you believe cars can't brake?
Now you're getting there. The propellor is a brake. It impedes the cart's motion. Why? Because it would otherwise move with the belt, so it impedes its motion to stop that happening.

You're keen on experiment. Take the propeller drive shaft and move so that it is now vertical, rather than at the rear. The cart will perform the same.

The wheels take energy from the belt, to drive the fan in air, so that it can impede the cart's motion. Orientation makes no significant difference.

You see, I know you can't cheat this, because without it, there is nothing to see. You must balance the forces to avoid the embarrassment of it going backwards. Go ahead. You can do MHazes experiment at the same time.

ETA:
Just to make it crystal clear. Balance will be achieved, because what ever the drag the propellor
causes, is taken from the belt. The balance does not involve any 'thrust'. Therefore the smaller the fan, the less torque will be measured, but it will still hover about much as it does. You can also demonstrate the effect of changing the belt speed, much the same will occur.

Last edited by humber; 13th November 2008 at 11:33 AM.
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, 11:26 AM   #388
spork
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,356
Originally Posted by humber View Post
That's how planes convert the engine's power to motive force. So, there you go, you now understand a little bit more.
Go play now.
To see you addressing the likes of Sol in a condescending manner is literally painful for me to watch.
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, 11:30 AM   #389
Ivor the Engineer
Philosopher
 
Ivor the Engineer's Avatar
 
Join Date: Feb 2006
Posts: 9,425
Originally Posted by humber View Post
Now you're getting there. The propellor is a brake. It impedes the cart's motion. Why? Because it would otherwise move with the belt, so it impedes its motion to stop that happening.

You're keen on experiment. Take the propeller drive shaft and move so that it is now vertical, rather than at the rear. The cart will perform the same.

The wheels take energy from the belt, to drive the fan in air, so that it can impede the cart's motion. Orientation makes no significant difference.

<snip>
Holding the cart stationary and orienting the fan upwards will create a force orthogonal to the force from the treadmill. The cart will move in the direction of the treadmill once it is released.

That is a significant difference.
__________________
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, 11:32 AM   #390
sol invictus
Philosopher
 
sol invictus's Avatar
 
Join Date: Oct 2007
Posts: 8,613
Originally Posted by humber View Post
Now you're getting there. The propellor is a brake. It impedes the cart's motion.
Good - so you admit you were wrong before when you claimed the forces always balance. We're making progress.

Next question: when the propeller is spinning in still air (as opposed to inside a can of oil attached to the car, for example), is the only force on the car due to the torque from its wheels, or is there another force?

Remember - we're working in a frame where the car is stationary, the air is stationary, the ground is moving, and the wheels are spinning.
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, 11:37 AM   #391
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by Modified View Post
"Wind" is the speed of the air relative to the surface. The speed of things other than the air and surface do not matter. Why would they?

You do realize that we are all on what is effectively a giant belt right? The earth is spinning.
Do you think then, that if you put a fan in closed box, the box will move?
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, 11:38 AM   #392
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by spork View Post
To see you addressing the likes of Sol in a condescending manner is literally painful for me to watch.
How pleased I am to hear that.
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, 11:47 AM   #393
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by sol invictus View Post
Good - so you admit you were wrong before when you claimed the forces always balance. We're making progress.

Next question: when the propeller is spinning in still air (as opposed to inside a can of oil attached to the car, for example), is the only force on the car due to the torque from its wheels, or is there another force?

Remember - we're working in a frame where the car is stationary, the air is stationary, the ground is moving, and the wheels are spinning.
See the top line? That's called tautology. Saying to me what I said, but in a different manner.

I do not accept that you are qualified to judge my answer. Do the experiment. The previous posts, indicate what you must do.
You have yet to supply any supporting calculations, because you can't do them, so we must resort to seeing is believing.
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, 11:52 AM   #394
sol invictus
Philosopher
 
sol invictus's Avatar
 
Join Date: Oct 2007
Posts: 8,613
Originally Posted by humber View Post
See the top line? That's called tautology. Saying to me what I said, but in a different manner.

I do not accept that you are qualified to judge my answer. Do the experiment. The previous posts, indicate what you must do.
You have yet to supply any supporting calculations, because you can't do them, so we must resort to seeing is believing.
OK, humber, I guess that's that then. I've demonstrated what the forces are, that they don't always sum to zero, and that there are no physical principles that forbid the cart from outrunning the wind. Others have done the experiment and very thoroughly documented it. All of us have shown considerable patience in trying to help you through your basic confusions about physics.

Given your attitude I'm not interested in continuing any further.
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, 12:07 PM   #395
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by Ivor the Engineer View Post
Holding the cart stationary and orienting the fan upwards will create a force orthogonal to the force from the treadmill. The cart will move in the direction of the treadmill once it is released.

That is a significant difference.
Scarcely. It is rather a matter of balancing the torques. If there is an imbalance, of what you see as thrust, then the nature of the trick will be exposed. A weak push or pull one way or the other.
It could be rigged to show it going backwards, but then I would simply ask them to show that it could be otherwise. The obvious facility of such changes, and the lack of torque, would make the banality of the idea, obvious. It's only useable output, is the torque imbalance. It really is parlour trick dressed up in a lot of talk of inertial frames.

I have no fear of saying this, because it is so easily demonstrated to be guff.
There are no "calculations" and if there were, they would confirm my and other critic's assertions. It wastes energy from the belt so it can stay were it is. The slight progress is due to simple imbalances. The small momentum of the propeller, serves to keep it in the one direction, but that is happenstance rather than anything else.

Last edited by humber; 13th November 2008 at 12:09 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, 12:09 PM   #396
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
Originally Posted by sol invictus View Post
OK, humber, I guess that's that then. I've demonstrated what the forces are, that they don't always sum to zero, and that there are no physical principles that forbid the cart from outrunning the wind. Others have done the experiment and very thoroughly documented it. All of us have shown considerable patience in trying to help you through your basic confusions about physics.

Given your attitude I'm not interested in continuing any further.
Mission accomplished. Yes, yes, yes. No documentation from you, though.

Last edited by humber; 13th November 2008 at 12:12 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, 12:10 PM   #397
GreyICE
Guest
 
Join Date: Mar 2008
Posts: 7,149
Look, there's a reason that this topic earns you a ban on the XKCD forums. And its because it degenerates into a flamewar.

http://blag.xkcd.com/2008/09/09/the-...amn-treadmill/
GreyICE 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, 12:23 PM   #398
humber
Philosopher
 
Join Date: Dec 2007
Posts: 5,928
You are right of course, but this is not about the plane thing, but a direct claim concerning this rather silly cart, so the burden of proof was upon them, but apart form a lot of the usual, there was no acceptance of what were blinding flaws in the whole concept. There is nothing to explain. It is what it is.
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, 12:24 PM   #399
ThinAirDesigns
Graduate Poster
 
Join Date: Nov 2008
Posts: 1,058
humber:
Quote:
Do the experiment.
I *have* done the experiment and have succeeded.

"I have built, and will demonstrate on demand, a vehicle which travels directly downwind, faster than the wind, powered only by the wind, steady state."


Those who "know" we are wrong and actually have the committment that humbers *states* he has should get the escrow paperwork started and send a note to spork -- he's just dyin' for some little fishy to dart at the shiny hook.

Unfortunately, humber only *states* the committment -- he doesn't actually have it or escrow would have already been executed.

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, 12:41 PM   #400
technoextreme
Illuminator
 
technoextreme's Avatar
 
Join Date: Jun 2007
Posts: 3,785
Originally Posted by sol invictus View Post
Good - so you admit you were wrong before when you claimed the forces always balance. We're making progress.

Next question: when the propeller is spinning in still air (as opposed to inside a can of oil attached to the car, for example), is the only force on the car due to the torque from its wheels, or is there another force?

Remember - we're working in a frame where the car is stationary, the air is stationary, the ground is moving, and the wheels are spinning.
There is another force. Just as a side note I've never said it's impossible. You just can't do it with the plans for this cart because of the propeller.
__________________
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 12:56 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
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 09:23 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.