QUOTE (Precursor562+Feb 27 2007, 03:02 PM)
First off just because the cannon would blow up does not disprove orbit it just makes putting something into orbit by that means not possible using todays technology. Just like you couldn't get the belt moving fast enough using todays technology. If you could get it going fast enough the speed of the belt would have to be FASTER than the speed of the plane. In the original question the speed of the belt EQUALS the speed of the plane.
You seem to have a persistant problem understanding that I am relating the plane's speed to the surface of the belt, NOT to the IAS.
So, do you care to re-state, except this time, relate the speed of the plane to the surface of the treadbelt...I realize that this does not fit YOUR version of that you THINK the OP says....
Again, I think the question is asking 'Can a treadbelt prevent a plane from taking off"...I say YES....what do you say? (without blowing up tires and treadbelts or cannons)
QUOTE
QUOTE (mggb2001 @ Feb 26 2007, 05:54 PM)
Imagine this if you will.
A toy car sits on a treadmill and you use your finger to hold it in place. As the speed of the treadmill increases to a very high speed, the force your finger exerts on the car to hold it in place only slightly increases in comparison. The force with which you are pushing the car relative to the car's weight would seem to be perfectly acceptable to apply to the thrust of an engine and the weight of an airplane.
What I am trying to say is: No matter how fast the treadmill is going, you will always be able to overcome it.
The force to bring the car to zero mph relative to the surroundings must converge to a finite number. Tell me if this makes sense.]
What you basically said is this:
"As the speed of the treadmill increases to a ... high(er) speed, the force your finger exerts on the car to hold it in place... [irelevent information] ... increases in comparison.
So YES, there IS a treadbelt speed which will equal the plane's thrust.
Words like 'very fast' and 'slightly increases' are irelevent.
The facts is the essence of what you said....as the treadbelt speed increases, so does the force needed to hold it at 0 IAS. That's all you need to know to understand that a treadbelt CAN prevent a plane from taking off.
Now, what you are left with is the inturpretation of 'what is plane's SPEED'.
When it is related to the surface of the treadbelt (as you seem to like) then the plane no fly.
When it is related to the surrounding air...well, let's look at that for a second..."A plane moves though the air.....Does the plane move though the air...."....see Jane run...does jane run?....the answer to both of those questions is 'Yes' of course....go ask any second grader.
Imagine this if you will.
A toy car sits on a treadmill and you use your finger to hold it in place. As the speed of the treadmill increases to a very high speed, the force your finger exerts on the car to hold it in place only slightly increases in comparison. The force with which you are pushing the car relative to the car's weight would seem to be perfectly acceptable to apply to the thrust of an engine and the weight of an airplane.
What I am trying to say is: No matter how fast the treadmill is going, you will always be able to overcome it.
The force to bring the car to zero mph relative to the surroundings must converge to a finite number. Tell me if this makes sense.]
What you basically said is this:
"As the speed of the treadmill increases to a ... high(er) speed, the force your finger exerts on the car to hold it in place... [irelevent information] ... increases in comparison.
So YES, there IS a treadbelt speed which will equal the plane's thrust.
Words like 'very fast' and 'slightly increases' are irelevent.
The facts is the essence of what you said....as the treadbelt speed increases, so does the force needed to hold it at 0 IAS. That's all you need to know to understand that a treadbelt CAN prevent a plane from taking off.
Now, what you are left with is the inturpretation of 'what is plane's SPEED'.
When it is related to the surface of the treadbelt (as you seem to like) then the plane no fly.
When it is related to the surrounding air...well, let's look at that for a second..."A plane moves though the air.....Does the plane move though the air...."....see Jane run...does jane run?....the answer to both of those questions is 'Yes' of course....go ask any second grader.
Actually what I am saying is that the force stopping the plane from moving is the frictional forces acting on the wheels.
The way I see it (which may or may not be the correct way of thinking about it) is that as the speed at which the wheels rotate increases, the frictional forces acting on the wheels becomes more and more negligible. As the speed at which the tires are rotating approaches infinity, the frictional forces would seem to me to approach zero. Thus the plane would take off.
In addition, the point at which the plane would start moving forward (relative to the surroundings) would be when the thrust of the engines = the frictional forces in the wheels.
FRICTIONAL FORCES IN THE WHEELS ARE PRACTICALLY NEGLIGIBLE RELATIVE TO THE THRUST OF THE ENGINES.
THE PLANE WILL TAKE OFF, ALMOST EXACTLY THE SAME AS IF IT WERE ON GROUND.
What a pointless exercise.
Planes, birds, bats, etc., fly by aerodynamics lift from reaction forces on the wings due to relative velocity of air to wings. No relative velocity? No flying! in short:
1- plane wheels turns freely/frictionlessly (assumed) while conveyor belt is moving: relative motion between wheels and conveyor, plane stationary, no air velocity relative to wing=nonflying. Doesnt matter which way the plane's nose is pointed.
2 - plane wheels locked, conveyor moving, nose of plane in direction of conveyor belt moving: Plane will lift off the belt when belt linear velocity is equal to or greater than the plane's normal liftoff speed. which means plane's speed is equal to belt's speed relative to the stationary ground. Same idea used for donkey years as steam catapults on aircraft carriers.
3- plane's wheels turn freely, nose in direction of belt motion, engine at full blast: You will lift off in shorter distance when plane speed + belt speed > normal takeoff speed., saving some fuel (which will go in to machinery powering the belt, ha ha)
4- plane's wheels turn freely, nose in opposite direction of belt motion, engine at full blast: What a stupid idea. You will never lift off unless plane speed - belt speed > normal takeoff speed. Ever tried to run up a down-moving escalator??
Planes, birds, bats, etc., fly by aerodynamics lift from reaction forces on the wings due to relative velocity of air to wings. No relative velocity? No flying! in short:
1- plane wheels turns freely/frictionlessly (assumed) while conveyor belt is moving: relative motion between wheels and conveyor, plane stationary, no air velocity relative to wing=nonflying. Doesnt matter which way the plane's nose is pointed.
2 - plane wheels locked, conveyor moving, nose of plane in direction of conveyor belt moving: Plane will lift off the belt when belt linear velocity is equal to or greater than the plane's normal liftoff speed. which means plane's speed is equal to belt's speed relative to the stationary ground. Same idea used for donkey years as steam catapults on aircraft carriers.
3- plane's wheels turn freely, nose in direction of belt motion, engine at full blast: You will lift off in shorter distance when plane speed + belt speed > normal takeoff speed., saving some fuel (which will go in to machinery powering the belt, ha ha)
4- plane's wheels turn freely, nose in opposite direction of belt motion, engine at full blast: What a stupid idea. You will never lift off unless plane speed - belt speed > normal takeoff speed. Ever tried to run up a down-moving escalator??
QUOTE (Vinnie lam+Feb 27 2007, 08:32 PM)
What a pointless exercise.
Planes, birds, bats, etc., fly by aerodynamics lift from reaction forces on the wings due to relative velocity of air to wings. No relative velocity? No flying! in short:
1- plane wheels turns freely/frictionlessly (assumed) while conveyor belt is moving: relative motion between wheels and conveyor, plane stationary, no air velocity relative to wing=nonflying. Doesnt matter which way the plane's nose is pointed.
2 - plane wheels locked, conveyor moving, nose of plane in direction of conveyor belt moving: Plane will lift off the belt when belt linear velocity is equal to or greater than the plane's normal liftoff speed. which means plane's speed is equal to belt's speed relative to the stationary ground. Same idea used for donkey years as steam catapults on aircraft carriers.
3- plane's wheels turn freely, nose in direction of belt motion, engine at full blast: You will lift off in shorter distance when plane speed + belt speed > normal takeoff speed., saving some fuel (which will go in to machinery powering the belt, ha ha)
4- plane's wheels turn freely, nose in opposite direction of belt motion, engine at full blast: What a stupid idea. You will never lift off unless plane speed - belt speed > normal takeoff speed. Ever tried to run up a down-moving escalator??
In response to number 4: The real question is; Have you ever tried running up a down moving escalator with rollerblades while wearing a jetpack?
Planes, birds, bats, etc., fly by aerodynamics lift from reaction forces on the wings due to relative velocity of air to wings. No relative velocity? No flying! in short:
1- plane wheels turns freely/frictionlessly (assumed) while conveyor belt is moving: relative motion between wheels and conveyor, plane stationary, no air velocity relative to wing=nonflying. Doesnt matter which way the plane's nose is pointed.
2 - plane wheels locked, conveyor moving, nose of plane in direction of conveyor belt moving: Plane will lift off the belt when belt linear velocity is equal to or greater than the plane's normal liftoff speed. which means plane's speed is equal to belt's speed relative to the stationary ground. Same idea used for donkey years as steam catapults on aircraft carriers.
3- plane's wheels turn freely, nose in direction of belt motion, engine at full blast: You will lift off in shorter distance when plane speed + belt speed > normal takeoff speed., saving some fuel (which will go in to machinery powering the belt, ha ha)
4- plane's wheels turn freely, nose in opposite direction of belt motion, engine at full blast: What a stupid idea. You will never lift off unless plane speed - belt speed > normal takeoff speed. Ever tried to run up a down-moving escalator??
In response to number 4: The real question is; Have you ever tried running up a down moving escalator with rollerblades while wearing a jetpack?
QUOTE (mggb2001+Feb 27 2007, 03:31 PM)
Actually what I am saying is that the force stopping the plane from moving is the frictional forces acting on the wheels.
The way I see it (which may or may not be the correct way of thinking about it) is that as the speed at which the wheels rotate increases, the frictional forces acting on the wheels becomes more and more negligible. As the speed at which the tires are rotating approaches infinity, the frictional forces would seem to me to approach zero. Thus the plane would take off.
In addition, the point at which the plane would start moving forward (relative to the surroundings) would be when the thrust of the engines = the frictional forces in the wheels.
FRICTIONAL FORCES IN THE WHEELS ARE PRACTICALLY NEGLIGIBLE RELATIVE TO THE THRUST OF THE ENGINES.
THE PLANE WILL TAKE OFF, ALMOST EXACTLY THE SAME AS IF IT WERE ON GROUND.
WOW!
So you're saying that you believe that the faster the belt spins, the LESS force is acting on the plane!?
That's weird...cause once I had a plane 'equalized' at 0 IAS with the belt spining at about 5mph....and when I increased the speed of the treadbelt, the plane then moved at (-) IAS....OR when I decreased the speed of the treadbelt, the plane then had + IAS.
So, your theory is contrary to my actual experiment....I believe you may be incorrect.
Doesn't it seem, from my findings, that an increase in treadbelt/wheelspeed will result in a GREATER force?
(BTW-Adding weight resulted in (-) IAS, and removing weight resulted in + IAS).
Alt5p
When the aircraft moves one inch as measured on the belt, the belt moves one inch backwards, but now...
the aircraft has moved two inches on the belt, the belt then moves two inches, but now...
the aircraft has moved four inches on the belt, the belt then moves four inches, but now...
the aircraft has moved eight inches on the belt, the belt then moves eight inches backward, but now...
the aircraft is now 16 inches from it's starting point, the belt moves 16 inches, but now...
the aircraft has moved 32 inches from it's starting point on the belt, the belt moves 32 inches backward, but now...
the plane has moved 64 inches on the belt, the belt moves 64 inches, but now...............
An infinite positive feedback loop. When the plane moves so much as one inch the belts speed INSTANTLY goes to infinity.
Grumpy
QUOTE
an infinate positive feedback loop will NOT occur when wheelspeed is used.
When the aircraft moves one inch as measured on the belt, the belt moves one inch backwards, but now...
the aircraft has moved two inches on the belt, the belt then moves two inches, but now...
the aircraft has moved four inches on the belt, the belt then moves four inches, but now...
the aircraft has moved eight inches on the belt, the belt then moves eight inches backward, but now...
the aircraft is now 16 inches from it's starting point, the belt moves 16 inches, but now...
the aircraft has moved 32 inches from it's starting point on the belt, the belt moves 32 inches backward, but now...
the plane has moved 64 inches on the belt, the belt moves 64 inches, but now...............
An infinite positive feedback loop. When the plane moves so much as one inch the belts speed INSTANTLY goes to infinity.
Grumpy
QUOTE (Grumpy+Feb 27 2007, 04:01 PM)
Alt5p
When the aircraft moves one inch as measured on the belt, the belt moves one inch backwards, but now...
the aircraft has moved two inches on the belt, the belt then moves two inches, but now...
the aircraft has moved four inches on the belt, the belt then moves four inches, but now...
the aircraft has moved eight inches on the belt, the belt then moves eight inches backward, but now...
the aircraft is now 16 inches from it's starting point, the belt moves 16 inches, but now...
the aircraft has moved 32 inches from it's starting point on the belt, the belt moves 32 inches backward, but now...
the plane has moved 64 inches on the belt, the belt moves 64 inches, but now...............
An infinite positive feedback loop. When the plane moves so much as one inch the belts speed INSTANTLY goes to infinity.
Grumpy
I realize that it may SEEM that way Grump...but it is NOT.
Let's take a airpowered vehicle that will do 5mph MAX on static ground, calm air....the plane has 5mph IAS, and the prop sees a 5mph 'headwind'.
On the treadbelt, when the airpowered vehicle is at MAX power and 0 IAS, the treadbelt will be spinning GREATER than 5mph. It will take MORE TREADBELT SPEED than mere 'plane's top speed on static ground'.
Every time you increase the speed of the treadbelt, you are also increasing the backwards force applied to the plane....it may not seem like much...that's why we continue to increase the speed of the treadbelt, until that point is found.
I'll give you an example:
Actually, it goes like this:
When the aircraft moves one inch as measured on the belt, the belt moves one inch backwards, but now...
the aircraft has moved 1.9 inches on the belt, the belt then moves 1.9, but now...
the aircraft has moved 3.8 inches on the belt, the belt then moves 3.8, but now...
see how that goes?
Eventually, you'll see:
the aircraft has moved 1000 inches on the belt, the belt then moves 1000 inches, but now...the net forward IAS force of the plane is now 0 due to the counter force of the treadbelt....
When the aircraft moves one inch as measured on the belt, the belt moves one inch backwards, but now...
the aircraft has moved two inches on the belt, the belt then moves two inches, but now...
the aircraft has moved four inches on the belt, the belt then moves four inches, but now...
the aircraft has moved eight inches on the belt, the belt then moves eight inches backward, but now...
the aircraft is now 16 inches from it's starting point, the belt moves 16 inches, but now...
the aircraft has moved 32 inches from it's starting point on the belt, the belt moves 32 inches backward, but now...
the plane has moved 64 inches on the belt, the belt moves 64 inches, but now...............
An infinite positive feedback loop. When the plane moves so much as one inch the belts speed INSTANTLY goes to infinity.
Grumpy
I realize that it may SEEM that way Grump...but it is NOT.
Let's take a airpowered vehicle that will do 5mph MAX on static ground, calm air....the plane has 5mph IAS, and the prop sees a 5mph 'headwind'.
On the treadbelt, when the airpowered vehicle is at MAX power and 0 IAS, the treadbelt will be spinning GREATER than 5mph. It will take MORE TREADBELT SPEED than mere 'plane's top speed on static ground'.
Every time you increase the speed of the treadbelt, you are also increasing the backwards force applied to the plane....it may not seem like much...that's why we continue to increase the speed of the treadbelt, until that point is found.
I'll give you an example:
QUOTE
When the aircraft moves one inch as measured on the belt, the belt moves one inch backwards, but now...
the aircraft has moved two inches on the belt, the belt then moves two inches, but now...
the aircraft has moved two inches on the belt, the belt then moves two inches, but now...
Actually, it goes like this:
When the aircraft moves one inch as measured on the belt, the belt moves one inch backwards, but now...
the aircraft has moved 1.9 inches on the belt, the belt then moves 1.9, but now...
the aircraft has moved 3.8 inches on the belt, the belt then moves 3.8, but now...
see how that goes?
Eventually, you'll see:
the aircraft has moved 1000 inches on the belt, the belt then moves 1000 inches, but now...the net forward IAS force of the plane is now 0 due to the counter force of the treadbelt....
QUOTE (Johan_K+Feb 26 2007, 06:12 PM)
Hello again 
I shall try it.. with baby steps for my own good
Now I'm no physicist (or physician for that matter either), so I'm feeling an incremental approach is sensible here.
I think we all agree on the basic formula
Power=Force*velocity
(With all the add-ons that the forces has to be parallel to the tangent of travel etc. etc.)
If we solve P=F*v for F, we get F=P/v, and indeed, putting the numbers from HowStuffWorks in there we see that in both cases (55 and 75 mph), we get the same result for the force, namely:
F = 12(hp) * 746(W) / 33.53(m/s) = 8.8(hp)hp*746(W) / 24.59(m/s) = 267.2 N.
So the statement:
Isn't actually correct since the increase in power and velocity cancel each other out in calculating how large the force applied is.
So I think we can both agree on the fact that the actual Force that is needed to hold the plane stationary on the conveyor is constant no matter how fast the conveyor is spinning?
I noticed Atl5p didn't touch this.
I would RESTATE that last line though.
So I think we can both agree on the fact that the actual Force that is AVAILABLE to hold the plane stationary on the conveyor is constant no matter how fast the conveyor is spinning?
Arthur
PS, Atl5p when are we going to SEE that YOU TUBE video of your MODEL on the TREADBELT???
I shall try it.. with baby steps for my own good
Now I'm no physicist (or physician for that matter either), so I'm feeling an incremental approach is sensible here.I think we all agree on the basic formula
Power=Force*velocity
(With all the add-ons that the forces has to be parallel to the tangent of travel etc. etc.)
If we solve P=F*v for F, we get F=P/v, and indeed, putting the numbers from HowStuffWorks in there we see that in both cases (55 and 75 mph), we get the same result for the force, namely:
F = 12(hp) * 746(W) / 33.53(m/s) = 8.8(hp)hp*746(W) / 24.59(m/s) = 267.2 N.
So the statement:
QUOTE
(http://auto.howstuffworks.com/tire4.htm)
From these calculations you can see that the three things that affect how much force it takes to push the tire down the road (and therefore how much heat builds up in the tires) are the weight on the tires, the speed you drive and the CRF
From these calculations you can see that the three things that affect how much force it takes to push the tire down the road (and therefore how much heat builds up in the tires) are the weight on the tires, the speed you drive and the CRF
Isn't actually correct since the increase in power and velocity cancel each other out in calculating how large the force applied is.
So I think we can both agree on the fact that the actual Force that is needed to hold the plane stationary on the conveyor is constant no matter how fast the conveyor is spinning?
I noticed Atl5p didn't touch this.
I would RESTATE that last line though.
So I think we can both agree on the fact that the actual Force that is AVAILABLE to hold the plane stationary on the conveyor is constant no matter how fast the conveyor is spinning?
Arthur
PS, Atl5p when are we going to SEE that YOU TUBE video of your MODEL on the TREADBELT???
QUOTE (Johan_K+Feb 26 2007, 06:12 PM)
Hello again
I shall try it.. with baby steps for my own good Now I'm no physicist (or physician for that matter either), so I'm feeling an incremental approach is sensible here.
I think we all agree on the basic formula
Power=Force*velocity
(With all the add-ons that the forces has to be parallel to the tangent of travel etc. etc.)
If we solve P=F*v for F, we get F=P/v, and indeed, putting the numbers from HowStuffWorks in there we see that in both cases (55 and 75 mph), we get the same result for the force, namely:
F = 12(hp) * 746(W) / 33.53(m/s) = 8.8(hp)hp*746(W) / 24.59(m/s) = 267.2 N.
So the statement:
Isn't actually correct since the increase in power and velocity cancel each other out in calculating how large the force applied is.
So I think we can both agree on the fact that the actual Force that is needed to hold the plane stationary on the conveyor is constant no matter how fast the conveyor is spinning?
Coulda sworn I replied to this:
It looks like you disagree with my web source.
But are you sure you aren't coming up with a calculation describing how much force is needed to get the wheel moving from a dead stop?
Also, please note my findings:
And I no longer have access to the treadbelt...maybe one day I will again...will try for a video at that time.
I shall try it.. with baby steps for my own good
Now I'm no physicist (or physician for that matter either), so I'm feeling an incremental approach is sensible here.I think we all agree on the basic formula
Power=Force*velocity
(With all the add-ons that the forces has to be parallel to the tangent of travel etc. etc.)
If we solve P=F*v for F, we get F=P/v, and indeed, putting the numbers from HowStuffWorks in there we see that in both cases (55 and 75 mph), we get the same result for the force, namely:
F = 12(hp) * 746(W) / 33.53(m/s) = 8.8(hp)hp*746(W) / 24.59(m/s) = 267.2 N.
So the statement:
Isn't actually correct since the increase in power and velocity cancel each other out in calculating how large the force applied is.
So I think we can both agree on the fact that the actual Force that is needed to hold the plane stationary on the conveyor is constant no matter how fast the conveyor is spinning?
Coulda sworn I replied to this:
It looks like you disagree with my web source.
But are you sure you aren't coming up with a calculation describing how much force is needed to get the wheel moving from a dead stop?
Also, please note my findings:
QUOTE
That's weird...cause once I had a plane 'equalized' at 0 IAS with the belt spining at about 5mph....and when I increased the speed of the treadbelt, the plane then moved at (-) IAS....OR when I decreased the speed of the treadbelt, the plane then had + IAS.
So, your theory is contrary to my actual experiment....I believe you may be incorrect.
Doesn't it seem, from my findings, that an increase in treadbelt/wheelspeed will result in a GREATER force?
(BTW-Adding weight resulted in (-) IAS, and removing weight resulted in + IAS).
So, your theory is contrary to my actual experiment....I believe you may be incorrect.
Doesn't it seem, from my findings, that an increase in treadbelt/wheelspeed will result in a GREATER force?
(BTW-Adding weight resulted in (-) IAS, and removing weight resulted in + IAS).
And I no longer have access to the treadbelt...maybe one day I will again...will try for a video at that time.
Nope.
Force = Power / Velocity
Which is the same as
Force = Power * Time / Displacement
Which means spin that treadbelt all you want, the force remains the same.
Once the Airplane designers know how much extra force they have to deal with they simply insure the power supply is up to the task.
The Airplane designers ALWAYS win.
Arthur
PS, real shame how you lost the ONLY THING that would be considered PROOF of your untenable position.
Force = Power / Velocity
Which is the same as
Force = Power * Time / Displacement
Which means spin that treadbelt all you want, the force remains the same.
Once the Airplane designers know how much extra force they have to deal with they simply insure the power supply is up to the task.
The Airplane designers ALWAYS win.
Arthur
PS, real shame how you lost the ONLY THING that would be considered PROOF of your untenable position.
QUOTE (Atl5p+Feb 27 2007, 08:51 PM)
WOW!
So you're saying that you believe that the faster the belt spins, the LESS force is acting on the plane!?
That's weird...cause once I had a plane 'equalized' at 0 IAS with the belt spining at about 5mph....and when I increased the speed of the treadbelt, the plane then moved at (-) IAS....OR when I decreased the speed of the treadbelt, the plane then had + IAS.
So, your theory is contrary to my actual experiment....I believe you may be incorrect.
Doesn't it seem, from my findings, that an increase in treadbelt/wheelspeed will result in a GREATER force?
(BTW-Adding weight resulted in (-) IAS, and removing weight resulted in + IAS).
Sorry, what I should have said is that the MARGINAL FRICTIONAL FORCE should approach zero.
In other words, as the speed increases to infinity, the frictional force should approach a finite number that is much less than the force of the thrust given by the plane's engine. Thus, the plane takes off.
So you're saying that you believe that the faster the belt spins, the LESS force is acting on the plane!?
That's weird...cause once I had a plane 'equalized' at 0 IAS with the belt spining at about 5mph....and when I increased the speed of the treadbelt, the plane then moved at (-) IAS....OR when I decreased the speed of the treadbelt, the plane then had + IAS.
So, your theory is contrary to my actual experiment....I believe you may be incorrect.
Doesn't it seem, from my findings, that an increase in treadbelt/wheelspeed will result in a GREATER force?
(BTW-Adding weight resulted in (-) IAS, and removing weight resulted in + IAS).
Sorry, what I should have said is that the MARGINAL FRICTIONAL FORCE should approach zero.
In other words, as the speed increases to infinity, the frictional force should approach a finite number that is much less than the force of the thrust given by the plane's engine. Thus, the plane takes off.
QUOTE (Atl5p+Feb 27 2007, 11:19 AM)
OK, I'm not sure exactly what you're talking about, could you please be more specific. 1st, try spelling out exactly what (if any) thing you disagree with the quote you have of mine.
Then you could try explaining what you think would happen, or be more specific as to what you want me to explain.
I see you seem to want me to 'compensate' for the 'movement'(over treadbelt or static ground, I dont' know), by using a variable pitch prop.(?)
The purpose of my post was to show that a plane that can produce a maximum IAS on static ground may go 50mph....that same plane would need a treadbelt spinning at much faster than 50mph in order for the treadbelt to hold the plane at 0 IAS. That is due to the 'static thrust' being higher than thrust with an artificial/self generated headwind a plane has when it is + IAS.
Now you seem to want to put a Variable Pitch Prop (your idea BTW) on the plane....in order to do WHAT?! On Which plane? And WHEN? For what REASON? I don't know.
You SEEM to want to make the plane on static ground go faster than 50mph, by using a variable pitch prop....that's all I can make of it.....WHY you want to do that, and WHAT you're trying to prove, I really wish you'd explain.
Making the plane go faster than 50mph on static ground was not my point.
My point was this: If you have a plane that goes MAX 50mph on static ground, do not expect a 50mph treadbelt to hold it at 0 IAS...it will need to be much faster.
Now you want me to:
And I don't know what the heck you're talking about....please speak english.
Maybe you want to use the variable pitch prop while the plane is on the treadbelt? Not sure why you'd want to do that though...Say you are using turbo-prop setup, the engine computer keeps the prop's RPMs constant, no matter what the pitch is set at? So increasing pitch is basically the same as increasing the power on a 'regular' plane.(?) SO spinning the treadbelt faster will still lead do a speed where the plane's speed over treadbelt = treadbelt speed....plane still at 0 IAS....so I don't understand your point...either way, you're burning more gas to make more power, which is countered by the treadbelt...what's you're point?
Aducate said
Wondering if you missed this one....
Then you could try explaining what you think would happen, or be more specific as to what you want me to explain.
I see you seem to want me to 'compensate' for the 'movement'(over treadbelt or static ground, I dont' know), by using a variable pitch prop.(?)
The purpose of my post was to show that a plane that can produce a maximum IAS on static ground may go 50mph....that same plane would need a treadbelt spinning at much faster than 50mph in order for the treadbelt to hold the plane at 0 IAS. That is due to the 'static thrust' being higher than thrust with an artificial/self generated headwind a plane has when it is + IAS.
Now you seem to want to put a Variable Pitch Prop (your idea BTW) on the plane....in order to do WHAT?! On Which plane? And WHEN? For what REASON? I don't know.
You SEEM to want to make the plane on static ground go faster than 50mph, by using a variable pitch prop....that's all I can make of it.....WHY you want to do that, and WHAT you're trying to prove, I really wish you'd explain.
Making the plane go faster than 50mph on static ground was not my point.
My point was this: If you have a plane that goes MAX 50mph on static ground, do not expect a 50mph treadbelt to hold it at 0 IAS...it will need to be much faster.
Now you want me to:
And I don't know what the heck you're talking about....please speak english.
Maybe you want to use the variable pitch prop while the plane is on the treadbelt? Not sure why you'd want to do that though...Say you are using turbo-prop setup, the engine computer keeps the prop's RPMs constant, no matter what the pitch is set at? So increasing pitch is basically the same as increasing the power on a 'regular' plane.(?) SO spinning the treadbelt faster will still lead do a speed where the plane's speed over treadbelt = treadbelt speed....plane still at 0 IAS....so I don't understand your point...either way, you're burning more gas to make more power, which is countered by the treadbelt...what's you're point?
Aducate said
QUOTE
Too bad Atl5p can't remember what he posted:
So now all you have to do is show you can't compensate for the movement of the plane (up to takeoff speed) by employing a Constant Speed (Variable Pitch) prop.
Arthur
So now all you have to do is show you can't compensate for the movement of the plane (up to takeoff speed) by employing a Constant Speed (Variable Pitch) prop.
Arthur
Wondering if you missed this one....
Okay, I am now willing to admit that my theory of decreasing marginal friction force is wrong, but by reading this post in another forum I think this should prove the FACT that the plane WILL take off.
Yes, the plane can take off. The key is that the plane's wheels
*freewheel*, they are not driven. the conveyor belt therefore provides
NO force to the plane (OK, there's a little friction in the bearings
which could provide a couple of pounds force to a nomal GA category
airplane, but that's insignificant compared to the thrust. For an RC
plane, the situation should be similar). The prop pushes the plane
through the air until it reaches takeoff AIRspeed, which is the same no
matter how fast the wheels are going. So if you were inside watching
the instruments, you would observe that the wheels are spinning at a
GROUNDspeed different than the indicated AIRspeed, but that does not
matter, since it is AIRspeed you need in order to take off. (Caps
added for emphasis).
Your friction calculation basically assumes you have skids instead of
wheels, and would be basically correct for that case, but notice that
velocity does not appear anywhere in the equation. If you had a plane
with skids, it would take off if it had the power to get sliding with
or without a conveyor runway. It would not matter how fast the
skid-to-runway surface were moving. The friction force F = u * N is
the same at either groundspeed.
Hope this helps!
David Brandt, P.E.
QUOTE
Yes, the plane can take off. The key is that the plane's wheels
*freewheel*, they are not driven. the conveyor belt therefore provides
NO force to the plane (OK, there's a little friction in the bearings
which could provide a couple of pounds force to a nomal GA category
airplane, but that's insignificant compared to the thrust. For an RC
plane, the situation should be similar). The prop pushes the plane
through the air until it reaches takeoff AIRspeed, which is the same no
matter how fast the wheels are going. So if you were inside watching
the instruments, you would observe that the wheels are spinning at a
GROUNDspeed different than the indicated AIRspeed, but that does not
matter, since it is AIRspeed you need in order to take off. (Caps
added for emphasis).
Your friction calculation basically assumes you have skids instead of
wheels, and would be basically correct for that case, but notice that
velocity does not appear anywhere in the equation. If you had a plane
with skids, it would take off if it had the power to get sliding with
or without a conveyor runway. It would not matter how fast the
skid-to-runway surface were moving. The friction force F = u * N is
the same at either groundspeed.
Hope this helps!
David Brandt, P.E.
QUOTE (Atl5p+Feb 27 2007, 05:36 PM)
Aducate said
Wondering if you missed this one....
Nope, the constant speed prop changes the pitch to compensate for the headwind, (it doesn't move your power lever). Thus it maintains a constant thrust even as the plane accelerates.
Arthur
Wondering if you missed this one....
Nope, the constant speed prop changes the pitch to compensate for the headwind, (it doesn't move your power lever). Thus it maintains a constant thrust even as the plane accelerates.
Arthur
QUOTE
That can only mean 'speed over the ground'...NOT airspeed...if he meant 'airspeed' then he would have said 'knots'.
He was relating the speed of the plane to US standing on the ground
He was relating the speed of the plane to US standing on the ground
Um not exactly. They were talking about air speed. Such air speed is the speed of the plane passing through STILL air above a MOTIONLESS ground. Provided that you were a MOTIONLESS audience then that would be the same as relating the speed of the plane to you on the ground but only because you were still. If you (the audience) were to move in any direction at any speed the speed of the plane would not change. If the ground were to move the speed of the plane would be unchanged. If the ground, air, crowd were to all move (independently or otherwise) the speed of the plane would not change.
QUOTE (->
| QUOTE |
| That can only mean 'speed over the ground'...NOT airspeed...if he meant 'airspeed' then he would have said 'knots'. He was relating the speed of the plane to US standing on the ground |
Um not exactly. They were talking about air speed. Such air speed is the speed of the plane passing through STILL air above a MOTIONLESS ground. Provided that you were a MOTIONLESS audience then that would be the same as relating the speed of the plane to you on the ground but only because you were still. If you (the audience) were to move in any direction at any speed the speed of the plane would not change. If the ground were to move the speed of the plane would be unchanged. If the ground, air, crowd were to all move (independently or otherwise) the speed of the plane would not change.
1) There are many reference points by which you can determine speed…you can determine speed via a stationary object (like a tower), or a moving object (like reading IAS while flying in a 20mph wind)
Yes there are many but they merely allow you to 'see' the movement. Also when using a moving object as the point of reference to see such movement you must subtract that motion from the 'equation'. You end up with a stationary point of reference. For example. we'll use what your going with in determining speed.
A plane flies over a movable runway (conveyor belt) and in relation to the belt is passing over it at 500 mph. The surface of the belt however is moving in the opposite direction at a speed of 200 mph. What is the actual speed of the plane?
The actual speed of the plane is 300 mph. The speed of the plane is 500 mph in relation to the belt but the belt speed incorporates 200 mph of that 500 mph and so you must subtract it from the equation leaving you with a fixed point of reference to 'see' the true speed of the plane which is 300 mph.
Once again you absolutely can not use the belt in this question as a point of reference since the speed value of the belt is a dependent variable whose value depends on the speed of the plane.
QUOTE
You seem to have a persistant problem understanding that I am relating the plane's speed to the surface of the belt,
No, I know that is what you are doing. You just seem to have the persistent problem understanding why you can not use the belt to 'see' the plane's speed.
QUOTE (->
| QUOTE |
| You seem to have a persistant problem understanding that I am relating the plane's speed to the surface of the belt, |
No, I know that is what you are doing. You just seem to have the persistent problem understanding why you can not use the belt to 'see' the plane's speed.
So, do you care to re-state, except this time, relate the speed of the plane to the surface of the treadbelt...I realize that this does not fit YOUR version of that you THINK the OP says....
Already did above.
QUOTE
That's weird...cause once I had a plane 'equalized' at 0 IAS with the belt spining at about 5mph....and when I increased the speed of the treadbelt, the plane then moved at (-) IAS....OR when I decreased the speed of the treadbelt, the plane then had + IAS.
So, your theory is contrary to my actual experiment....I believe you may be incorrect.
So, your theory is contrary to my actual experiment....I believe you may be incorrect.
Now I know your full of it.
I have done it and no matter how fast I set the treadmill, the plane sped up forward the same as if it were on still ground.
QUOTE
I am asking "Can a treadbelt prevent a plane from flying"....the answer is YES.
No. Sorry. The answer is NO.
The treadbelt can't impart force through free spinning wheels to counter the thrust of the engines. The plane takes off.
WOW 482 pages.
I'll say it again, cant resist.
forward speed of aircraft + rearward speed of belt = increased speed of wheels.
belt cannot impart any significant force to plane, only to the wheels.
belt cannot match any speed greater than zero of the wheels or airframe at any time, because the speed of the wheels is a RESULT of the belt and airframe motion. The belt just speeds up infinatly, with the wheels spinning infinatly + forward speed of the airframe. Plane flys off into the sunset, with smoked wheel bearings.
Belt cannot perform as specified, logic is flawed.
***, i got sucked in again.
I'll say it again, cant resist.
forward speed of aircraft + rearward speed of belt = increased speed of wheels.
belt cannot impart any significant force to plane, only to the wheels.
belt cannot match any speed greater than zero of the wheels or airframe at any time, because the speed of the wheels is a RESULT of the belt and airframe motion. The belt just speeds up infinatly, with the wheels spinning infinatly + forward speed of the airframe. Plane flys off into the sunset, with smoked wheel bearings.
Belt cannot perform as specified, logic is flawed.
***, i got sucked in again.
QUOTE (Atl5p+Feb 27 2007, 08:06 PM)
I was at an airshow recently where the announcer said that the F18 was going to fly past us at 600mph. That can only mean 'speed over the ground'...NOT airspeed...if he meant 'airspeed' then he would have said 'knots'.
He was relating the speed of the plane to US standing on the ground...NOT related to the air around us.
So, you might want to let the NAVY know that they are incorrect.
The anouncer states MPH because they want the crowd to understand what they mean. If you say 521 knots, most of the general public doesn't know what a knot is, or if that is faster or slower than mph.
Had it been a show somewhere where the metric system is used he would have said 965 km/h! Because they want people to relate to the speed, not be puzzled by it.
"Ladies and gentlemen, if you look now, low and to the left, you'll see Lieutenant Commander John Allison in the lead solo aircraft, approaching show center at a speed of 600 MPH!"
"Ladies and gentlemen, if you look now, low and to the left, you'll see Lieutenant Commander John Allison in the lead solo aircraft, approaching show center at a speed of 521 knots!"
Which one do you think will get a US crowd's attention more?
Was it ground speed or airspeed, could have been either, but that has nothing to do with the unit of speed he used.
Now think hard what did he really say.
"approaching show center at 600mph" "flying past show center at 600mph" " passing in front at 600mph" "reaching 600mph as he passes in front"
A subtle change could mean the difference between the speed the plane is flying, or the speed the plane will pass show center.
Oh by the way, I fly my hang glider with MPH, not knots. Actually my speed indicator will show km/h or mph, doesn't even have an option for knots.
He was relating the speed of the plane to US standing on the ground...NOT related to the air around us.
So, you might want to let the NAVY know that they are incorrect.
The anouncer states MPH because they want the crowd to understand what they mean. If you say 521 knots, most of the general public doesn't know what a knot is, or if that is faster or slower than mph.Had it been a show somewhere where the metric system is used he would have said 965 km/h! Because they want people to relate to the speed, not be puzzled by it.
"Ladies and gentlemen, if you look now, low and to the left, you'll see Lieutenant Commander John Allison in the lead solo aircraft, approaching show center at a speed of 600 MPH!"
"Ladies and gentlemen, if you look now, low and to the left, you'll see Lieutenant Commander John Allison in the lead solo aircraft, approaching show center at a speed of 521 knots!"
Which one do you think will get a US crowd's attention more?
Was it ground speed or airspeed, could have been either, but that has nothing to do with the unit of speed he used.
Now think hard what did he really say.
"approaching show center at 600mph" "flying past show center at 600mph" " passing in front at 600mph" "reaching 600mph as he passes in front"
A subtle change could mean the difference between the speed the plane is flying, or the speed the plane will pass show center.
Oh by the way, I fly my hang glider with MPH, not knots. Actually my speed indicator will show km/h or mph, doesn't even have an option for knots.
Ahh, but as you neither have wheels or a tread belt?
So whatever speed you might be referring to, has nothing to do with this serious scientific pursuit!
Please allow us that take this question seriously to follow it to its inevitable end ;)
So whatever speed you might be referring to, has nothing to do with this serious scientific pursuit!
Please allow us that take this question seriously to follow it to its inevitable end ;)
QUOTE (Precursor562+Feb 27 2007, 06:47 PM)
Now I know your full of it.
I have done it and no matter how fast I set the treadmill, the plane sped up forward the same as if it were on still ground.
Ah, you must've used an airplane that's capable of flight.
ATL5P used a lego truck that he attached a "weak" airplane engine to. (The amazing part is that he thinks that actually proved something.
)
Hello again
QUOTE (Atl5p+)
It looks like you disagree with my web source.
Well partly. I agree with them that it takes more force to push the wheel down the road when you increase speed if you account for the air-resistance, otherwise I think that the author probably just made an error writing the article and typed "force" when he actually meant "power". I have written to "HowStuffWorks" and asked them about that but I'm still waiting on the reply. I'll post if should I ever receive it
But are you sure you aren't coming up with a calculation describing how much force is needed to get the wheel moving from a dead stop?
Yes quite sure, but it's a good point since for other objects that slides, like say a box, the initial friction coefficient you have to overcome to "get it moving" is a little higher than the friction coefficient for when the box is already sliding along, though once you've gotten it going the friction is indeed constant.*
I would RESTATE that last line though.
So I think we can both agree on the fact that the actual Force that is AVAILABLE to hold the plane stationary on the conveyor is constant no matter how fast the conveyor is spinning?
I'm not quite following you there on the "available" modification of the statement? I mean that if you anchor the plane with a newton-measure-springy-thingamajig, it won't show an increase in the force needed to hold the plane.
Of course, the laws of friction is a model for how things work in general in "the big picture". In the small picture however, when the wheels and/or the underlying surface deforms ever so slightly the mathematics gets a bit more complicated and the dependencies more numerous. Now, I don't pretend to actually know this stuff, but I dug a few papers up and skimmed through them the best I could and in the case of the deformable underlying surface, the frictional coefficient did indeed increase a little for increasing speeds but then went back down again when the speed increased even more, it had something to do with how fast you were rolling vs. the speed at which the material bounced back after being deformed as far as I could tell. All this was for pretty small speeds though (a few m/s) - I'm guessing this might be something like that "increased friction coefficient for getting the box sliding" or something? Harder wheels rolling on harder surfaces deviates less from the model. Anyhow, if the law for rolling friction was more complicated, and especially if the effects of velocity specifically were not negligible (often when you roll stuff you get it up to speed after all), I'm pretty sure that That's what would be taught and used - so for all practical purposes the force is constant.
As for the model plane on the treadmill: that's a pretty cool experiment and I got a bunch of own ideas with skateboards and stuff I'm thickening about trying at the gym! (Now that would be a fun sight and I'm sure people would wonder about what the heck I was doing and what kind of insane I was.) I'm thinking the treadmill/model-plane setup isn't exactly accurate or rather directly comparable to the big picture though (I'm sure it's accurate! It's a frikken live Test). I theorize that, for instance, when you make the treadmill spin faster, the belt "coming up" in the front of the loop gets "thrown up" more than when it goes slower since it's elastic. (I know it's a crappy explanation but it's the best I can do*heh*) That would create sort of a "hill" that the plane (or skateboard or wheeled cart) had to fight against. Also, the normal treadmill speeds I think are probably around in that area where the frictional force Is velocity dependent and before it starts going back down.. so that's a b***h 
Also, I'm thinking that the small wheels of the model is more sensitive to unevenness of the surface (perhaps deforms it more) etc. that might affect the experiment more. It's a pretty cool experiment though and should get things pointing in the right direction. If you get a hold of that mill again you should try and see if you can make the treadmill prevent the plane from taking off, that's what I would have done. I'm gonna give some more thought about doing that skateboard/treadmill experiment and film it. I just have to get my hands on/build the equipment for measuring the forces and what not though.
Well partly. I agree with them that it takes more force to push the wheel down the road when you increase speed if you account for the air-resistance, otherwise I think that the author probably just made an error writing the article and typed "force" when he actually meant "power". I have written to "HowStuffWorks" and asked them about that but I'm still waiting on the reply. I'll post if should I ever receive it
QUOTE (Atl5p+)
But are you sure you aren't coming up with a calculation describing how much force is needed to get the wheel moving from a dead stop?
Yes quite sure, but it's a good point since for other objects that slides, like say a box, the initial friction coefficient you have to overcome to "get it moving" is a little higher than the friction coefficient for when the box is already sliding along, though once you've gotten it going the friction is indeed constant.*
QUOTE (adoucette+)
I would RESTATE that last line though.
So I think we can both agree on the fact that the actual Force that is AVAILABLE to hold the plane stationary on the conveyor is constant no matter how fast the conveyor is spinning?
I'm not quite following you there on the "available" modification of the statement? I mean that if you anchor the plane with a newton-measure-springy-thingamajig, it won't show an increase in the force needed to hold the plane.
Of course, the laws of friction is a model for how things work in general in "the big picture". In the small picture however, when the wheels and/or the underlying surface deforms ever so slightly the mathematics gets a bit more complicated and the dependencies more numerous. Now, I don't pretend to actually know this stuff, but I dug a few papers up and skimmed through them the best I could and in the case of the deformable underlying surface, the frictional coefficient did indeed increase a little for increasing speeds but then went back down again when the speed increased even more, it had something to do with how fast you were rolling vs. the speed at which the material bounced back after being deformed as far as I could tell. All this was for pretty small speeds though (a few m/s) - I'm guessing this might be something like that "increased friction coefficient for getting the box sliding" or something? Harder wheels rolling on harder surfaces deviates less from the model. Anyhow, if the law for rolling friction was more complicated, and especially if the effects of velocity specifically were not negligible (often when you roll stuff you get it up to speed after all), I'm pretty sure that That's what would be taught and used - so for all practical purposes the force is constant.
As for the model plane on the treadmill: that's a pretty cool experiment and I got a bunch of own ideas with skateboards and stuff I'm thickening about trying at the gym!
(Now that would be a fun sight and I'm sure people would wonder about what the heck I was doing and what kind of insane I was.) I'm thinking the treadmill/model-plane setup isn't exactly accurate or rather directly comparable to the big picture though (I'm sure it's accurate! It's a frikken live Test). I theorize that, for instance, when you make the treadmill spin faster, the belt "coming up" in the front of the loop gets "thrown up" more than when it goes slower since it's elastic. (I know it's a crappy explanation but it's the best I can do*heh*) That would create sort of a "hill" that the plane (or skateboard or wheeled cart) had to fight against. Also, the normal treadmill speeds I think are probably around in that area where the frictional force Is velocity dependent and before it starts going back down.. so that's a b***h Also, I'm thinking that the small wheels of the model is more sensitive to unevenness of the surface (perhaps deforms it more) etc. that might affect the experiment more. It's a pretty cool experiment though and should get things pointing in the right direction. If you get a hold of that mill again you should try and see if you can make the treadmill prevent the plane from taking off, that's what I would have done. I'm gonna give some more thought about doing that skateboard/treadmill experiment and film it. I just have to get my hands on/build the equipment for measuring the forces and what not though.QUOTE (Johan_K+Feb 28 2007, 10:26 AM)
Hello again
Yes quite sure, but it's a good point since for other objects that slides, like say a box, the initial friction coefficient you have to overcome to "get it moving" is a little higher than the friction coefficient for when the box is already sliding along, though once you've gotten it going the friction is indeed constant.*
I would RESTATE that last line though.
So I think we can both agree on the fact that the actual Force that is AVAILABLE to hold the plane stationary on the conveyor is constant no matter how fast the conveyor is spinning?
I'm not quite following you there on the "available" modification of the statement? I mean that if you anchor the plane with a newton-measure-springy-thingamajig, it won't show an increase in the force needed to hold the plane.
Of course, the laws of friction is a model for how things work in general in "the big picture". In the small picture however, when the wheels and/or the underlying surface deforms ever so slightly the mathematics gets a bit more complicated and the dependencies more numerous. Now, I don't pretend to actually know this stuff, but I dug a few papers up and skimmed through them the best I could and in the case of the deformable underlying surface, the frictional coefficient did indeed increase a little for increasing speeds but then went back down again when the speed increased even more, it had something to do with how fast you were rolling vs. the speed at which the material bounced back after being deformed as far as I could tell. All this was for pretty small speeds though (a few m/s) - I'm guessing this might be something like that "increased friction coefficient for getting the box sliding" or something? Harder wheels rolling on harder surfaces deviates less from the model. Anyhow, if the law for rolling friction was more complicated, and especially if the effects of velocity specifically were not negligible (often when you roll stuff you get it up to speed after all), I'm pretty sure that That's what would be taught and used - so for all practical purposes the force is constant.
As for the model plane on the treadmill: that's a pretty cool experiment and I got a bunch of own ideas with skateboards and stuff I'm thickening about trying at the gym! (Now that would be a fun sight and I'm sure people would wonder about what the heck I was doing and what kind of insane I was.) I'm thinking the treadmill/model-plane setup isn't exactly accurate or rather directly comparable to the big picture though (I'm sure it's accurate! It's a frikken live Test). I theorize that, for instance, when you make the treadmill spin faster, the belt "coming up" in the front of the loop gets "thrown up" more than when it goes slower since it's elastic. (I know it's a crappy explanation but it's the best I can do*heh*) That would create sort of a "hill" that the plane (or skateboard or wheeled cart) had to fight against. Also, the normal treadmill speeds I think are probably around in that area where the frictional force Is velocity dependent and before it starts going back down.. so that's a b***h Also, I'm thinking that the small wheels of the model is more sensitive to unevenness of the surface (perhaps deforms it more) etc. that might affect the experiment more. It's a pretty cool experiment though and should get things pointing in the right direction. If you get a hold of that mill again you should try and see if you can make the treadmill prevent the plane from taking off, that's what I would have done. I'm gonna give some more thought about doing that skateboard/treadmill experiment and film it. I just have to get my hands on/build the equipment for measuring the forces and what not though.
RE: How Stuff Works....Force vs Power.
You seem to be saying that it takes more POWER to move the tires down the road at a faster speed....it dosn't take more FORCE...but it DOES take more POWER? Let me know if I got that correct, because I am no physisistisisis.
Because it seems like you're saying that when the treadbelt speed increases, you'll need more POWER in order to remain at 0 IAS. And once you run out of this 'more power' thing, and the treadbelt keeps spinning faster and faster, don't you think -IAS will occur?
RE:deformable underlying surface
Remember....if it were a REAL plane, then it would be a REALLY REALLY REALLY big treadbelt....which would presumably have the same type of 'deformable underlying surface'....i dunno...maybe? Reletively speaking?
Hey, I appreciate your thoughtful responce...good luch with the experiment, hope it goes well.
What I found out is this:
If you have a plane that can go 10mph on static ground, then you will NOT be able to stop it with a 10mph treadbelt....I believe this has something to do with 'Static Thrust' vs 'Moving Thrust' or whatever the term is.
So, limited by a 'normal treadbelt' that can only go 10mph or so, and knowing that you can't use a 20oz 'Tribute' or other plane that is capeable of going 50+MPH ( that IS obvious to you, I can already tell)....we have to come up with some different ideas of how to prove this theory.
What I DID was this:
I found a small plane (Aero Ace), which BTW has 19grams of thrust from it's two tiny motor/prop combos.
I got some stable 'wheels' to strap on (leggo truck)
I tried to see if this contraption would propel itself on static ground (It DID!)
Did it go fast enough to take off from static ground? NO, too heavy...but that's ok, because I have a very 'slow' treadbelt. Even without the tonka wheels, this thing needs 10mph IAS to fly anyway...too fast for THIS treadbelt.
So what I did was find out if I could prevent forward IAS with the treadbelt. (I DID)
"WOW", I said...."how did that happen?"
Let's see if reducing the throttle will make the plane have -IAS. (It did)
Let's see if increasing thottle will make the plane have +IAS (It Did)
Let's see if adding weight will make the plane have -IAS. (It did)
Let's see if reducing weight will make the plane have +IAS. (It did)
Let's see if increasing treadbelt speed will make the plane have -IAS. (It did)
Let's see if reducing treadbelt speed will make the plane have +IAS. (It did)
So, it would appear that the speed of the treadbelt has something to do with something. Also the weight and the power of the plane.
I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used). And an even more powerful plane with a more faster treadbelt would result in the same....and an even MORE (well, you get the picture).
So, can a treadbelt prevent a plane from flying? I think it can....
Let me know how your experiment goes....I would like to hear about it.
Now I know your full of it.
I have done it and no matter how fast I set the treadmill, the plane sped up forward the same as if it were on still ground.
It's comments like the above which discredit you, Precuser.
We were using different planes. Does that not mean anything to you?
I believe you used a plane capable of 30+mph in static air.
That plane might need a 100+mph treadbelt. You DID remember to use a 100+MPH treadbelt, didn't you?
Remember the whole Static Thrust thing?
Yes quite sure, but it's a good point since for other objects that slides, like say a box, the initial friction coefficient you have to overcome to "get it moving" is a little higher than the friction coefficient for when the box is already sliding along, though once you've gotten it going the friction is indeed constant.*
QUOTE (adoucette+)
I would RESTATE that last line though.
So I think we can both agree on the fact that the actual Force that is AVAILABLE to hold the plane stationary on the conveyor is constant no matter how fast the conveyor is spinning?
I'm not quite following you there on the "available" modification of the statement? I mean that if you anchor the plane with a newton-measure-springy-thingamajig, it won't show an increase in the force needed to hold the plane.
Of course, the laws of friction is a model for how things work in general in "the big picture". In the small picture however, when the wheels and/or the underlying surface deforms ever so slightly the mathematics gets a bit more complicated and the dependencies more numerous. Now, I don't pretend to actually know this stuff, but I dug a few papers up and skimmed through them the best I could and in the case of the deformable underlying surface, the frictional coefficient did indeed increase a little for increasing speeds but then went back down again when the speed increased even more, it had something to do with how fast you were rolling vs. the speed at which the material bounced back after being deformed as far as I could tell. All this was for pretty small speeds though (a few m/s) - I'm guessing this might be something like that "increased friction coefficient for getting the box sliding" or something? Harder wheels rolling on harder surfaces deviates less from the model. Anyhow, if the law for rolling friction was more complicated, and especially if the effects of velocity specifically were not negligible (often when you roll stuff you get it up to speed after all), I'm pretty sure that That's what would be taught and used - so for all practical purposes the force is constant.
As for the model plane on the treadmill: that's a pretty cool experiment and I got a bunch of own ideas with skateboards and stuff I'm thickening about trying at the gym!
(Now that would be a fun sight and I'm sure people would wonder about what the heck I was doing and what kind of insane I was.) I'm thinking the treadmill/model-plane setup isn't exactly accurate or rather directly comparable to the big picture though (I'm sure it's accurate! It's a frikken live Test). I theorize that, for instance, when you make the treadmill spin faster, the belt "coming up" in the front of the loop gets "thrown up" more than when it goes slower since it's elastic. (I know it's a crappy explanation but it's the best I can do*heh*) That would create sort of a "hill" that the plane (or skateboard or wheeled cart) had to fight against. Also, the normal treadmill speeds I think are probably around in that area where the frictional force Is velocity dependent and before it starts going back down.. so that's a b***h Also, I'm thinking that the small wheels of the model is more sensitive to unevenness of the surface (perhaps deforms it more) etc. that might affect the experiment more. It's a pretty cool experiment though and should get things pointing in the right direction. If you get a hold of that mill again you should try and see if you can make the treadmill prevent the plane from taking off, that's what I would have done. I'm gonna give some more thought about doing that skateboard/treadmill experiment and film it. I just have to get my hands on/build the equipment for measuring the forces and what not though. RE: How Stuff Works....Force vs Power.
You seem to be saying that it takes more POWER to move the tires down the road at a faster speed....it dosn't take more FORCE...but it DOES take more POWER? Let me know if I got that correct, because I am no physisistisisis.
Because it seems like you're saying that when the treadbelt speed increases, you'll need more POWER in order to remain at 0 IAS. And once you run out of this 'more power' thing, and the treadbelt keeps spinning faster and faster, don't you think -IAS will occur?
RE:deformable underlying surface
Remember....if it were a REAL plane, then it would be a REALLY REALLY REALLY big treadbelt....which would presumably have the same type of 'deformable underlying surface'....i dunno...maybe? Reletively speaking?
Hey, I appreciate your thoughtful responce...good luch with the experiment, hope it goes well.
What I found out is this:
If you have a plane that can go 10mph on static ground, then you will NOT be able to stop it with a 10mph treadbelt....I believe this has something to do with 'Static Thrust' vs 'Moving Thrust' or whatever the term is.
So, limited by a 'normal treadbelt' that can only go 10mph or so, and knowing that you can't use a 20oz 'Tribute' or other plane that is capeable of going 50+MPH ( that IS obvious to you, I can already tell)....we have to come up with some different ideas of how to prove this theory.
What I DID was this:
I found a small plane (Aero Ace), which BTW has 19grams of thrust from it's two tiny motor/prop combos.
I got some stable 'wheels' to strap on (leggo truck)
I tried to see if this contraption would propel itself on static ground (It DID!)
Did it go fast enough to take off from static ground? NO, too heavy...but that's ok, because I have a very 'slow' treadbelt. Even without the tonka wheels, this thing needs 10mph IAS to fly anyway...too fast for THIS treadbelt.
So what I did was find out if I could prevent forward IAS with the treadbelt. (I DID)
"WOW", I said...."how did that happen?"
Let's see if reducing the throttle will make the plane have -IAS. (It did)
Let's see if increasing thottle will make the plane have +IAS (It Did)
Let's see if adding weight will make the plane have -IAS. (It did)
Let's see if reducing weight will make the plane have +IAS. (It did)
Let's see if increasing treadbelt speed will make the plane have -IAS. (It did)
Let's see if reducing treadbelt speed will make the plane have +IAS. (It did)
So, it would appear that the speed of the treadbelt has something to do with something. Also the weight and the power of the plane.
I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used). And an even more powerful plane with a more faster treadbelt would result in the same....and an even MORE (well, you get the picture).
So, can a treadbelt prevent a plane from flying? I think it can....
Let me know how your experiment goes....I would like to hear about it.
QUOTE (Precursor562+Feb 27 2007, 07:47 PM)
Now I know your full of it.
I have done it and no matter how fast I set the treadmill, the plane sped up forward the same as if it were on still ground.
It's comments like the above which discredit you, Precuser.
We were using different planes. Does that not mean anything to you?
I believe you used a plane capable of 30+mph in static air.
That plane might need a 100+mph treadbelt. You DID remember to use a 100+MPH treadbelt, didn't you?
Remember the whole Static Thrust thing?
QUOTE (adoucette+Feb 27 2007, 07:11 PM)
Nope, the constant speed prop changes the pitch to compensate for the headwind, (it doesn't move your power lever). Thus it maintains a constant thrust even as the plane accelerates.
Arthur
Look...when your plane increases prop pitch while in flight, it IS USING MORE POWER.
And I still don't know what your point is.
I am saying that when the plane is held static by whatever means, that static thrust is greater than the thrust generated while in flight....ALL OTHER THINGS BEING EQUAL.
You are bringing up a turboprop with variable pitch.....hey, why not use booster rockets...? You're missing the point!
Arthur
Look...when your plane increases prop pitch while in flight, it IS USING MORE POWER.
And I still don't know what your point is.
I am saying that when the plane is held static by whatever means, that static thrust is greater than the thrust generated while in flight....ALL OTHER THINGS BEING EQUAL.
You are bringing up a turboprop with variable pitch.....hey, why not use booster rockets...? You're missing the point!
The treadmill can’t counter the force of the engine thrust because the treadmill can’t apply a counter-force through free spinning wheels.
It takes off.
It takes off.
QUOTE (Johan_K+)
QUOTE (adoucette+)
I would RESTATE that last line though.
So I think we can both agree on the fact that the actual Force that is AVAILABLE to hold the plane stationary on the conveyor is constant no matter how fast the conveyor is spinning?
I'm not quite following you there on the "available" modification of the statement? I mean that if you anchor the plane with a newton-measure-springy-thingamajig, it won't show an increase in the force needed to hold the plane.
Correct.
Which means if you have sufficent thrust above this constant force applied by the conveyor belt, you will take off.
Since the trust of the plane is not limited in the OP, there is no problem ensuring you have sufficient thrust to accelerate while taking into account all factors that increase the drag on the aircraft with increasing speed.
Which means the Aircraft designers ALWAYS win.
The plane flys.
Arthur
We were using different planes. Does that not mean anything to you?
It obviously means nothing to you since the first quote was taken from an earlier post of yours. Also no one is denying that the belt could stop the plane from moving forward by creating resistance through the wheels bearings. We are simply trying to explain to you that the belt would have to be going extremely fast. Faster than anything made with todays technology could ever reach and faster than the plane which goes against the OP.
The plane I have (an actual store bought plane that is designed to fly) will reach a max speed although I can't remember what that speed was right now. The treadmill I used can reach a max speed more than twice the max speed of the plane (that much I do remember) and the plane could still pull itself forward. Through observation I could not see any difference in acceleration on or off the belt.
After the test which proved the plane could fly to have someone like yourself claim to have done it simply proves to me that A ) you didn't do it at all and are lying through your teeth or B ) as you have cleared up already, performed an experiment that is biased and unrealistic.
Then to turn around and contradict yourself as quoted above discredits you further.
It obviously means nothing to you since the first quote was taken from an earlier post of yours. Also no one is denying that the belt could stop the plane from moving forward by creating resistance through the wheels bearings. We are simply trying to explain to you that the belt would have to be going extremely fast. Faster than anything made with todays technology could ever reach and faster than the plane which goes against the OP.
The plane I have (an actual store bought plane that is designed to fly) will reach a max speed although I can't remember what that speed was right now. The treadmill I used can reach a max speed more than twice the max speed of the plane (that much I do remember) and the plane could still pull itself forward. Through observation I could not see any difference in acceleration on or off the belt.
After the test which proved the plane could fly to have someone like yourself claim to have done it simply proves to me that A ) you didn't do it at all and are lying through your teeth or B ) as you have cleared up already, performed an experiment that is biased and unrealistic.
Then to turn around and contradict yourself as quoted above discredits you further.
You have purposefully mis-quoted me:
I said: I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used).
You are loosing credibility faster than the speed of internet. You are a liar.
Also, you say that '
When in fact, this would place YOU in the MINORITY of FlyBoys....Most flyboys are saying that a treadbelt could NEVER prevent a plane from flying...because there is NOT ANY backwards force transmitted from the belt unto the plane.
So, it appears that you are in SERIOUS DISAGREEMENT with your fellow flyboys...you might want to clear that up with THEM.
What you just said is exactly what I am trying to say....a treadbelt WILL prevent a plane from flying....a VERY VERY FAST treadbelt.
BTW-your experiment was VERY weak...and also, I must point out for the billionth time....if your plane was going 5mph on static ground, you will need MUCH more than 5mph treadbelt...this is due to STATIC THRUST.
Try a 50mph treadbelt, or a slower plane to achieve my results....
First of all you should have said that in the first place and second such a conclusion would be completely false. I have used a more powerful plane than you AND a faster treadmill than you as it would appear. Yet had completely different results.
First of all you should have said that in the first place and second such a conclusion would be completely false. I have used a more powerful plane than you AND a faster treadmill than you as it would appear. Yet had completely different results.
You have purposefully mis-quoted me:
There was no mistaking what you said. It was very straight forward.
The original question calls for the belt to match the speed of the plane. NOT go any faster.
After a leave of absence you came back with some interesting things to say...
The original question calls for the belt to match the speed of the plane. NOT go any faster.
After a leave of absence you came back with some interesting things to say...
So yes, when the treadbelt speed is matching the plane’s wheelspeed, then the plane will have no airspeed. No fly. The faster the tires spin, the more overall force is transmitted from the treadbelt to the plane.
If you say the tires blow out, then it doesn’t fly, for obvious reasons. Still ‘No Fly’.
If you want to say that the treadbelt cannot go this fast, then you need to re-read the question…the only limit to the treadbelt’s speed is the plane’s speed (over the surface of the treadbelt, of course). Please show me where the plane’s speed is based on a ‘stationary outside observer’ you can’t because it does not.
So by this it would seem that you believe the belt can stop the plane from taking off within the specs of the OP. All because you say the plane's speed is determined by the speed of the planes wheels. You would have to believe this for the following to hold true...
All because the plane is on the ground and in contact with it? Well, belt in this case and not ground. What about a plane that is taking off of a belt that is coated with ice and instead of using wheels it has skates or how about a plane taking off of the water using floats and that water has a current. These planes don't have wheels and therefore don't have wheel speed. So you would measure the speed of the plane off of what they are passing over? Sorry but a sea plane that needs to reach 200 mph to achieve take off isn't going 225 mph when it takes off from a body of water with a 25 mph current going in the opposite direction. People have realized this and to explain it they use ' a stationary outside observer' as a fixed point of reference so you can 'see' the movement since some can't seem to grasp what the speed of the plane is.
Anyway that's alright because now you agree to be talking about the belt going faster than the plane in order to hold it back which you also agree is outside the OP which of course is a complete change in story while you desperately try to argue your point. A point you tried to make a while ago but your new story is counter arguative toward that original point. What your saying now and what you said then is a contradiction. So which is it?
First of all you should have said that in the first place and second such a conclusion would be completely false. I have used a more powerful plane than you AND a faster treadmill than you as it would appear. Yet had completely different results.
There was no mistaking what you said. It was very straight forward.
The original question calls for the belt to match the speed of the plane. NOT go any faster.
After a leave of absence you came back with some interesting things to say...
So by this it would seem that you believe the belt can stop the plane from taking off within the specs of the OP. All because you say the plane's speed is determined by the speed of the planes wheels. You would have to believe this for the following to hold true...
All because the plane is on the ground and in contact with it? Well, belt in this case and not ground. What about a plane that is taking off of a belt that is coated with ice and instead of using wheels it has skates or how about a plane taking off of the water using floats and that water has a current. These planes don't have wheels and therefore don't have wheel speed. So you would measure the speed of the plane off of what they are passing over? Sorry but a sea plane that needs to reach 200 mph to achieve take off isn't going 225 mph when it takes off from a body of water with a 25 mph current going in the opposite direction. People have realized this and to explain it they use ' a stationary outside observer' as a fixed point of reference so you can 'see' the movement since some can't seem to grasp what the speed of the plane is.
Anyway that's alright because now you agree to be talking about the belt going faster than the plane in order to hold it back which you also agree is outside the OP which of course is a complete change in story while you desperately try to argue your point. A point you tried to make a while ago but your new story is counter arguative toward that original point. What your saying now and what you said then is a contradiction. So which is it?
Liar, I DID say it in the first place....let me fill you in:
http://forum.physorg.com/index.php?showtop...ndpost&p=183037
And THAT is a DIRECT QUOTE....you can also go directly to the post with the link I've given you. What IS YOUR PROBLEM? So, do you realize that I DID say so in the FIRST place?????
2nd: You say you used a faster treadbelt than mine? Well, you didn't use a FAST ENOUGH treadbelt. Did you miss the part about how I recomended you use a 50mph treadbelt???
3rd: I NEVER said the belt was going faster than the plane. I said that if a plane could go 5mph on static ground, then it would need maybe a 50mph or faster treadbelt to be held at 0 IAS...this is due to STATIC THRUST.
And WHEN the plane IS at 0 IAS, it is a FACT that the plane's speed over the surface of the treadbelt EQUALS the speed of the treadbelt itself. JUST LIKE a runner on a treadbelt.
Besides, why are you still onto me? We AGREE NOW. You said it yourself...a treadbelt IS ABLE to prevent a plane from flying. NOW YOU ARE ON MY SIDE!!!
The ONLY purpose you have on this thread now, is convincing the other FlyBoys that a treadbelt CAN impart force to a plane, and that force is GREATER as the SPEED of the treadbelt is increased. YOU BELIEVE THIS, RIGHT? You said:
And THAT is a DIRECT QUOTE....you can also go directly to the post with the link I've given you. What IS YOUR PROBLEM? So, do you realize that I DID say so in the FIRST place?????
2nd: You say you used a faster treadbelt than mine? Well, you didn't use a FAST ENOUGH treadbelt. Did you miss the part about how I recomended you use a 50mph treadbelt???
3rd: I NEVER said the belt was going faster than the plane. I said that if a plane could go 5mph on static ground, then it would need maybe a 50mph or faster treadbelt to be held at 0 IAS...this is due to STATIC THRUST.
And WHEN the plane IS at 0 IAS, it is a FACT that the plane's speed over the surface of the treadbelt EQUALS the speed of the treadbelt itself. JUST LIKE a runner on a treadbelt.
Besides, why are you still onto me? We AGREE NOW. You said it yourself...a treadbelt IS ABLE to prevent a plane from flying. NOW YOU ARE ON MY SIDE!!!
The ONLY purpose you have on this thread now, is convincing the other FlyBoys that a treadbelt CAN impart force to a plane, and that force is GREATER as the SPEED of the treadbelt is increased. YOU BELIEVE THIS, RIGHT? You said:
Also no one is denying that the belt could stop the plane from moving forward by creating resistance through the wheels
so, please point out exactly where I contradicted myself? See, you posted one accurate quote....and then used the SAME QUOTE to claim I was contradicting the first quote (which was the same quote)....so, what the fudge are you talking about?
The ONLY thing we disagree about is how the OP intends the plane's speed to be determined.
Oh, and we also disagree about what I said in this post:
http://forum.physorg.com/index.php?showtop...ndpost&p=183037
You claim I said this:
You also say that DEFINATLY I DID NOT say this:
You also say that DEFINATLY I DID NOT say this:
I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used).
So, please click on the link and now YOU tell ME what I really said:
I mean....you seem to have clearly lost you mind! Can you not read a post on the internet? Is your computer broken??? Are you missing WORDS? You have totally either missed my point, or you are trying to be clever, or you are ashamed that you are actually on my side, and now you have to convince the other flyboys that a treadbelt CAN prevent a plane from taking off.
OR, Maybe you can't quite comprehend STATIC THRUST...how a plane that moves at 2mph on static ground will need a 5-10mph treadbelt to prevent IAS. Do you not understand what 'Speed over static gound' is verses 'Speed over the surface of a moving treadbelt'?
Which is it?
I said that if a plane could go 5mph on static ground, then it would need maybe a 50mph or faster treadbelt to be held at 0 IAS...this is due to STATIC THRUST.
I'm seeing a complete contradiction within these two sentences and they were typed one directly after the other.
But according to you you never said the belt was going faster than the plane yet now your saying I need a treadmill that can reach speeds faster than my plane in order to keep it from not going anywhere. Also if the plane isn't going anywhere because the belt is holding it back how can it have speed? If the plane is just sitting on the belt trying to go somewhere but its not then belt is merely moving under a stationary plane. Key word is stationary as in not moving as in a velocity of 0 mph. The belt is however moving meaning the speed of the belt is greater than that of the plane and does not match the plane at all. In order for the belt to match the speed of the plane it would have to stop moving.
The truth is that the amount of resistance to move induced onto the plane as a result of the belt moving in the opposite direction whose speed matches that of the plane (in accordance with the OP) is so small under normal circumstances that under the conditions of the moving belt (which would merely double the wheel speed) the increase would be so small that there would be no noticeable difference between the plane on or off the belt.
But according to you you never said the belt was going faster than the plane yet now your saying I need a treadmill that can reach speeds faster than my plane in order to keep it from not going anywhere. Also if the plane isn't going anywhere because the belt is holding it back how can it have speed? If the plane is just sitting on the belt trying to go somewhere but its not then belt is merely moving under a stationary plane. Key word is stationary as in not moving as in a velocity of 0 mph. The belt is however moving meaning the speed of the belt is greater than that of the plane and does not match the plane at all. In order for the belt to match the speed of the plane it would have to stop moving.
The truth is that the amount of resistance to move induced onto the plane as a result of the belt moving in the opposite direction whose speed matches that of the plane (in accordance with the OP) is so small under normal circumstances that under the conditions of the moving belt (which would merely double the wheel speed) the increase would be so small that there would be no noticeable difference between the plane on or off the belt.
And WHEN the plane IS at 0 IAS, it is a FACT that the plane's speed over the surface of the treadbelt EQUALS the speed of the treadbelt itself. JUST LIKE a runner on a treadbelt.
First off a plane would not be like a runner. A plane pushes off the air to move forward and a runner pushes off of the ground. Place a treadmill in a room facing a doorway. Get on and start running at whatever setting. No matter how long you are running you are not going to go through that doorway. Hell the distance between you and the doorway will remain unchanged. This means you are not going anywhere and is occupying the same volume of space. Your speed is zero. Your legs on the other hand is a different story. They are moving at a rate equal to the treadmill's speed but since the belt is moving at that speed you do not go anywhere.
So what you describe above is exactly that. The belt is matching the speed of the plane's wheels however unlike the legs of a runner the speed of the plane's wheels is 50% depended on the speed of the belt. The speed of the runner's legs are 100% depended on the runner. The plane itself is not moving. It won't make it to the end of the conveyor belt. If it started out at the very center of the belt no matter how much time passes it remains at the center of the belt according to what you said above. Sorry but if the plane is not leaving the center of the belt then it has no speed and the belt is merely moving beneath the plane while making the plane's wheels go round. Since the belt matches the speed of the plane then the only way that belt is going to move is if the plane itself physically moves.
So if the plane is at 0 IAS then it isn't physically going anywhere so it has a velocity of 0 mph.
That is like say a sea plane that is tied down to a dock while floating on water with a 5 mph current has a speed of 5 mph. No it doesn't. The see plane isn't going anywhere and has a speed of 0 mph.
So the plane that is on the belt not moving while the belt moves underneath causing the wheels to spin at the same speed as the belt does not have any speed at all. It is simply a plane going at 0 mph with spinning tires whose spin is equal to and caused by the movement of the belt underneath.
I know exactly what static thrust is and I know it is irrelevant to the situation. When a plane is moving forward air approaches the propeller as a result. This will decrease the amount of thrust by decreasing the pressure difference between the leading side and tailing side of the propeller. When the plane is not moving (static conditions) is when you get static thrust. Since the belt is in contact with the wheels of the plane only then in no way can it have any effect on the propeller or surrounding air. This means that the static thrust can not be in any way effected by the belt. So before you mention something like static thrust to try and support your arguments it would help to know yourself what it is especially if you plan to ask someone else if they know what it is. So....
That is like say a sea plane that is tied down to a dock while floating on water with a 5 mph current has a speed of 5 mph. No it doesn't. The see plane isn't going anywhere and has a speed of 0 mph.
So the plane that is on the belt not moving while the belt moves underneath causing the wheels to spin at the same speed as the belt does not have any speed at all. It is simply a plane going at 0 mph with spinning tires whose spin is equal to and caused by the movement of the belt underneath.
I know exactly what static thrust is and I know it is irrelevant to the situation. When a plane is moving forward air approaches the propeller as a result. This will decrease the amount of thrust by decreasing the pressure difference between the leading side and tailing side of the propeller. When the plane is not moving (static conditions) is when you get static thrust. Since the belt is in contact with the wheels of the plane only then in no way can it have any effect on the propeller or surrounding air. This means that the static thrust can not be in any way effected by the belt. So before you mention something like static thrust to try and support your arguments it would help to know yourself what it is especially if you plan to ask someone else if they know what it is. So....
I said that if a plane could go 5mph on static ground, then it would need maybe a 50mph or faster treadbelt to be held at 0 IAS...this is due to STATIC THRUST.
this is NOT happening. Not only not the way or I should say 'why' (static thrust) as you mentioned here but also not at all with these low velocities.
So I think we can both agree on the fact that the actual Force that is AVAILABLE to hold the plane stationary on the conveyor is constant no matter how fast the conveyor is spinning?
I'm not quite following you there on the "available" modification of the statement? I mean that if you anchor the plane with a newton-measure-springy-thingamajig, it won't show an increase in the force needed to hold the plane.
Correct.
Which means if you have sufficent thrust above this constant force applied by the conveyor belt, you will take off.
Since the trust of the plane is not limited in the OP, there is no problem ensuring you have sufficient thrust to accelerate while taking into account all factors that increase the drag on the aircraft with increasing speed.
Which means the Aircraft designers ALWAYS win.
The plane flys.
Arthur
QUOTE (Atl5p+Feb 28 2007, 11:23 AM)
What I DID was this:
I found a small plane (Aero Ace), which BTW has 19grams of thrust from it's two tiny motor/prop combos.
I got some stable 'wheels' to strap on (leggo truck)
I tried to see if this contraption would propel itself on static ground (It DID!)
Did it go fast enough to take off from static ground? NO, too heavy...but that's ok, because I have a very 'slow' treadbelt. Even without the tonka wheels, this thing needs 10mph IAS to fly anyway...too fast for THIS treadbelt.
So what I did was find out if I could prevent forward IAS with the treadbelt. (I DID)
"WOW", I said...."how did that happen?"
Let's see if reducing the throttle will make the plane have -IAS. (It did)
Let's see if increasing thottle will make the plane have +IAS (It Did)
Let's see if adding weight will make the plane have -IAS. (It did)
Let's see if reducing weight will make the plane have +IAS. (It did)
Let's see if increasing treadbelt speed will make the plane have -IAS. (It did)
Let's see if reducing treadbelt speed will make the plane have +IAS. (It did)
No one is saying that if you have a very low powered aircraft you can't affect its IAS via a treadbelt.
That is NOT the issue with the OP.
All you did was get a very LOW POWERED aircraft, with barely any thrust, then added a set TONKA TRUCK wheels which were of course too much for the plane to actually fly with (thus outside of the OP) and then drew CONCLUSIONS from this ill thought out experiment.
In your version the DRAG from the wheels along with the added weight is just barely enough to make the plane move, so of course the treadbelt quickly overwhelms the limited thrust available, so OF COURSE in this VERY LOW POWER to WEIGHT/DRAG regimen, you can control the IAS via the treadbelt.
Such is NOT the case in typical aircraft.
It is most certainly NOT a constraint of the OP.
You need to try it with a plane which can not only take off with its wheels attached but then accelerate to well past the speed it lifts off at.
Arthur
I found a small plane (Aero Ace), which BTW has 19grams of thrust from it's two tiny motor/prop combos.
I got some stable 'wheels' to strap on (leggo truck)
I tried to see if this contraption would propel itself on static ground (It DID!)
Did it go fast enough to take off from static ground? NO, too heavy...but that's ok, because I have a very 'slow' treadbelt. Even without the tonka wheels, this thing needs 10mph IAS to fly anyway...too fast for THIS treadbelt.
So what I did was find out if I could prevent forward IAS with the treadbelt. (I DID)
"WOW", I said...."how did that happen?"
Let's see if reducing the throttle will make the plane have -IAS. (It did)
Let's see if increasing thottle will make the plane have +IAS (It Did)
Let's see if adding weight will make the plane have -IAS. (It did)
Let's see if reducing weight will make the plane have +IAS. (It did)
Let's see if increasing treadbelt speed will make the plane have -IAS. (It did)
Let's see if reducing treadbelt speed will make the plane have +IAS. (It did)
No one is saying that if you have a very low powered aircraft you can't affect its IAS via a treadbelt.
That is NOT the issue with the OP.
All you did was get a very LOW POWERED aircraft, with barely any thrust, then added a set TONKA TRUCK wheels which were of course too much for the plane to actually fly with (thus outside of the OP) and then drew CONCLUSIONS from this ill thought out experiment.
In your version the DRAG from the wheels along with the added weight is just barely enough to make the plane move, so of course the treadbelt quickly overwhelms the limited thrust available, so OF COURSE in this VERY LOW POWER to WEIGHT/DRAG regimen, you can control the IAS via the treadbelt.
Such is NOT the case in typical aircraft.
It is most certainly NOT a constraint of the OP.
You need to try it with a plane which can not only take off with its wheels attached but then accelerate to well past the speed it lifts off at.
Arthur
QUOTE (mggb2001+Feb 27 2007, 08:40 PM)
In response to number 4: The real question is; Have you ever tried running up a down moving escalator with rollerblades while wearing a jetpack?
mggb2001,
Read #3 again.
mggb2001,
Read #3 again.
QUOTE
I have concluded that the same results would occur with a more powerful plane
QUOTE (->
| QUOTE |
| I have concluded that the same results would occur with a more powerful plane |
We were using different planes. Does that not mean anything to you?
It obviously means nothing to you since the first quote was taken from an earlier post of yours. Also no one is denying that the belt could stop the plane from moving forward by creating resistance through the wheels bearings. We are simply trying to explain to you that the belt would have to be going extremely fast. Faster than anything made with todays technology could ever reach and faster than the plane which goes against the OP.
The plane I have (an actual store bought plane that is designed to fly) will reach a max speed although I can't remember what that speed was right now. The treadmill I used can reach a max speed more than twice the max speed of the plane (that much I do remember) and the plane could still pull itself forward. Through observation I could not see any difference in acceleration on or off the belt.
After the test which proved the plane could fly to have someone like yourself claim to have done it simply proves to me that A ) you didn't do it at all and are lying through your teeth or B ) as you have cleared up already, performed an experiment that is biased and unrealistic.
Then to turn around and contradict yourself as quoted above discredits you further.
I know many people who were convinced to switch from won't fly to fly. Does anyone know of someone who switched from fly to won't fly? I do not.
QUOTE (Precursor562+Feb 28 2007, 03:05 PM)
It obviously means nothing to you since the first quote was taken from an earlier post of yours. Also no one is denying that the belt could stop the plane from moving forward by creating resistance through the wheels bearings. We are simply trying to explain to you that the belt would have to be going extremely fast. Faster than anything made with todays technology could ever reach and faster than the plane which goes against the OP.
The plane I have (an actual store bought plane that is designed to fly) will reach a max speed although I can't remember what that speed was right now. The treadmill I used can reach a max speed more than twice the max speed of the plane (that much I do remember) and the plane could still pull itself forward. Through observation I could not see any difference in acceleration on or off the belt.
After the test which proved the plane could fly to have someone like yourself claim to have done it simply proves to me that A ) you didn't do it at all and are lying through your teeth or B ) as you have cleared up already, performed an experiment that is biased and unrealistic.
Then to turn around and contradict yourself as quoted above discredits you further.
You have purposefully mis-quoted me:
I said: I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used).
You are loosing credibility faster than the speed of internet. You are a liar.
Also, you say that '
QUOTE
Also no one is denying that the belt could stop the plane from moving forward by creating resistance through the wheels
When in fact, this would place YOU in the MINORITY of FlyBoys....Most flyboys are saying that a treadbelt could NEVER prevent a plane from flying...because there is NOT ANY backwards force transmitted from the belt unto the plane.
So, it appears that you are in SERIOUS DISAGREEMENT with your fellow flyboys...you might want to clear that up with THEM.
What you just said is exactly what I am trying to say....a treadbelt WILL prevent a plane from flying....a VERY VERY FAST treadbelt.
BTW-your experiment was VERY weak...and also, I must point out for the billionth time....if your plane was going 5mph on static ground, you will need MUCH more than 5mph treadbelt...this is due to STATIC THRUST.
Try a 50mph treadbelt, or a slower plane to achieve my results....
QUOTE
I said: I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used).
First of all you should have said that in the first place and second such a conclusion would be completely false. I have used a more powerful plane than you AND a faster treadmill than you as it would appear. Yet had completely different results.
QUOTE (->
| QUOTE |
| I said: I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used). |
First of all you should have said that in the first place and second such a conclusion would be completely false. I have used a more powerful plane than you AND a faster treadmill than you as it would appear. Yet had completely different results.
You have purposefully mis-quoted me:
There was no mistaking what you said. It was very straight forward.
QUOTE
BTW-your experiment was VERY weak...and also, I must point out for the billionth time....if your plane was going 5mph on static ground, you will need MUCH more than 5mph treadbelt...this is due to STATIC THRUST.
Try a 50mph treadbelt, or a slower plane to achieve my results...
Try a 50mph treadbelt, or a slower plane to achieve my results...
The original question calls for the belt to match the speed of the plane. NOT go any faster.
After a leave of absence you came back with some interesting things to say...
QUOTE (->
| QUOTE |
| BTW-your experiment was VERY weak...and also, I must point out for the billionth time....if your plane was going 5mph on static ground, you will need MUCH more than 5mph treadbelt...this is due to STATIC THRUST. Try a 50mph treadbelt, or a slower plane to achieve my results... |
The original question calls for the belt to match the speed of the plane. NOT go any faster.
After a leave of absence you came back with some interesting things to say...
So yes, when the treadbelt speed is matching the plane’s wheelspeed, then the plane will have no airspeed. No fly. The faster the tires spin, the more overall force is transmitted from the treadbelt to the plane.
If you say the tires blow out, then it doesn’t fly, for obvious reasons. Still ‘No Fly’.
If you want to say that the treadbelt cannot go this fast, then you need to re-read the question…the only limit to the treadbelt’s speed is the plane’s speed (over the surface of the treadbelt, of course). Please show me where the plane’s speed is based on a ‘stationary outside observer’ you can’t because it does not.
So by this it would seem that you believe the belt can stop the plane from taking off within the specs of the OP. All because you say the plane's speed is determined by the speed of the planes wheels. You would have to believe this for the following to hold true...
QUOTE
If you want to say that the treadbelt cannot go this fast, then you need to re-read the question…the only limit to the treadbelt’s speed is the plane’s speed (over the surface of the treadbelt, of course). Please show me where the plane’s speed is based on a ‘stationary outside observer’ you can’t because it does not.
All because the plane is on the ground and in contact with it? Well, belt in this case and not ground. What about a plane that is taking off of a belt that is coated with ice and instead of using wheels it has skates or how about a plane taking off of the water using floats and that water has a current. These planes don't have wheels and therefore don't have wheel speed. So you would measure the speed of the plane off of what they are passing over? Sorry but a sea plane that needs to reach 200 mph to achieve take off isn't going 225 mph when it takes off from a body of water with a 25 mph current going in the opposite direction. People have realized this and to explain it they use ' a stationary outside observer' as a fixed point of reference so you can 'see' the movement since some can't seem to grasp what the speed of the plane is.
Anyway that's alright because now you agree to be talking about the belt going faster than the plane in order to hold it back which you also agree is outside the OP which of course is a complete change in story while you desperately try to argue your point. A point you tried to make a while ago but your new story is counter arguative toward that original point. What your saying now and what you said then is a contradiction. So which is it?
QUOTE (Precursor562+Feb 28 2007, 04:17 PM)
First of all you should have said that in the first place and second such a conclusion would be completely false. I have used a more powerful plane than you AND a faster treadmill than you as it would appear. Yet had completely different results.
There was no mistaking what you said. It was very straight forward.
The original question calls for the belt to match the speed of the plane. NOT go any faster.
After a leave of absence you came back with some interesting things to say...
So by this it would seem that you believe the belt can stop the plane from taking off within the specs of the OP. All because you say the plane's speed is determined by the speed of the planes wheels. You would have to believe this for the following to hold true...
All because the plane is on the ground and in contact with it? Well, belt in this case and not ground. What about a plane that is taking off of a belt that is coated with ice and instead of using wheels it has skates or how about a plane taking off of the water using floats and that water has a current. These planes don't have wheels and therefore don't have wheel speed. So you would measure the speed of the plane off of what they are passing over? Sorry but a sea plane that needs to reach 200 mph to achieve take off isn't going 225 mph when it takes off from a body of water with a 25 mph current going in the opposite direction. People have realized this and to explain it they use ' a stationary outside observer' as a fixed point of reference so you can 'see' the movement since some can't seem to grasp what the speed of the plane is.
Anyway that's alright because now you agree to be talking about the belt going faster than the plane in order to hold it back which you also agree is outside the OP which of course is a complete change in story while you desperately try to argue your point. A point you tried to make a while ago but your new story is counter arguative toward that original point. What your saying now and what you said then is a contradiction. So which is it?
Liar, I DID say it in the first place....let me fill you in:
http://forum.physorg.com/index.php?showtop...ndpost&p=183037
QUOTE
So, it would appear that the speed of the treadbelt has something to do with something. Also the weight and the power of the plane.
I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used). And an even more powerful plane with a more faster treadbelt would result in the same....and an even MORE (well, you get the picture).
I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used). And an even more powerful plane with a more faster treadbelt would result in the same....and an even MORE (well, you get the picture).
And THAT is a DIRECT QUOTE....you can also go directly to the post with the link I've given you. What IS YOUR PROBLEM? So, do you realize that I DID say so in the FIRST place?????
2nd: You say you used a faster treadbelt than mine? Well, you didn't use a FAST ENOUGH treadbelt. Did you miss the part about how I recomended you use a 50mph treadbelt???
3rd: I NEVER said the belt was going faster than the plane. I said that if a plane could go 5mph on static ground, then it would need maybe a 50mph or faster treadbelt to be held at 0 IAS...this is due to STATIC THRUST.
And WHEN the plane IS at 0 IAS, it is a FACT that the plane's speed over the surface of the treadbelt EQUALS the speed of the treadbelt itself. JUST LIKE a runner on a treadbelt.
Besides, why are you still onto me? We AGREE NOW. You said it yourself...a treadbelt IS ABLE to prevent a plane from flying. NOW YOU ARE ON MY SIDE!!!
The ONLY purpose you have on this thread now, is convincing the other FlyBoys that a treadbelt CAN impart force to a plane, and that force is GREATER as the SPEED of the treadbelt is increased. YOU BELIEVE THIS, RIGHT? You said:
QUOTE (->
| QUOTE |
| So, it would appear that the speed of the treadbelt has something to do with something. Also the weight and the power of the plane. I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used). And an even more powerful plane with a more faster treadbelt would result in the same....and an even MORE (well, you get the picture). |
And THAT is a DIRECT QUOTE....you can also go directly to the post with the link I've given you. What IS YOUR PROBLEM? So, do you realize that I DID say so in the FIRST place?????
2nd: You say you used a faster treadbelt than mine? Well, you didn't use a FAST ENOUGH treadbelt. Did you miss the part about how I recomended you use a 50mph treadbelt???
3rd: I NEVER said the belt was going faster than the plane. I said that if a plane could go 5mph on static ground, then it would need maybe a 50mph or faster treadbelt to be held at 0 IAS...this is due to STATIC THRUST.
And WHEN the plane IS at 0 IAS, it is a FACT that the plane's speed over the surface of the treadbelt EQUALS the speed of the treadbelt itself. JUST LIKE a runner on a treadbelt.
Besides, why are you still onto me? We AGREE NOW. You said it yourself...a treadbelt IS ABLE to prevent a plane from flying. NOW YOU ARE ON MY SIDE!!!
The ONLY purpose you have on this thread now, is convincing the other FlyBoys that a treadbelt CAN impart force to a plane, and that force is GREATER as the SPEED of the treadbelt is increased. YOU BELIEVE THIS, RIGHT? You said:
Also no one is denying that the belt could stop the plane from moving forward by creating resistance through the wheels
so, please point out exactly where I contradicted myself? See, you posted one accurate quote....and then used the SAME QUOTE to claim I was contradicting the first quote (which was the same quote)....so, what the fudge are you talking about?
The ONLY thing we disagree about is how the OP intends the plane's speed to be determined.
Oh, and we also disagree about what I said in this post:
http://forum.physorg.com/index.php?showtop...ndpost&p=183037
You claim I said this:
QUOTE
I have concluded that the same results would occur with a more powerful plane
You also say that DEFINATLY I DID NOT say this:
QUOTE (->
| QUOTE |
| I have concluded that the same results would occur with a more powerful plane |
You also say that DEFINATLY I DID NOT say this:
I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used).
So, please click on the link and now YOU tell ME what I really said:
QUOTE
So, it would appear that the speed of the treadbelt has something to do with something. Also the weight and the power of the plane.
I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used). And an even more powerful plane with a more faster treadbelt would result in the same....and an even MORE (well, you get the picture).
I have concluded that the same results would occur with a more powerful plane (when a more faster treadbelt is used). And an even more powerful plane with a more faster treadbelt would result in the same....and an even MORE (well, you get the picture).
I mean....you seem to have clearly lost you mind! Can you not read a post on the internet? Is your computer broken??? Are you missing WORDS? You have totally either missed my point, or you are trying to be clever, or you are ashamed that you are actually on my side, and now you have to convince the other flyboys that a treadbelt CAN prevent a plane from taking off.
OR, Maybe you can't quite comprehend STATIC THRUST...how a plane that moves at 2mph on static ground will need a 5-10mph treadbelt to prevent IAS. Do you not understand what 'Speed over static gound' is verses 'Speed over the surface of a moving treadbelt'?
Which is it?
QUOTE
I NEVER said the belt was going faster than the plane.
QUOTE (->
| QUOTE |
| I NEVER said the belt was going faster than the plane. |
I said that if a plane could go 5mph on static ground, then it would need maybe a 50mph or faster treadbelt to be held at 0 IAS...this is due to STATIC THRUST.
I'm seeing a complete contradiction within these two sentences and they were typed one directly after the other.
QUOTE
You say you used a faster treadbelt than mine? Well, you didn't use a FAST ENOUGH treadbelt. Did you miss the part about how I recomended you use a 50mph treadbelt???
But according to you you never said the belt was going faster than the plane yet now your saying I need a treadmill that can reach speeds faster than my plane in order to keep it from not going anywhere. Also if the plane isn't going anywhere because the belt is holding it back how can it have speed? If the plane is just sitting on the belt trying to go somewhere but its not then belt is merely moving under a stationary plane. Key word is stationary as in not moving as in a velocity of 0 mph. The belt is however moving meaning the speed of the belt is greater than that of the plane and does not match the plane at all. In order for the belt to match the speed of the plane it would have to stop moving.
The truth is that the amount of resistance to move induced onto the plane as a result of the belt moving in the opposite direction whose speed matches that of the plane (in accordance with the OP) is so small under normal circumstances that under the conditions of the moving belt (which would merely double the wheel speed) the increase would be so small that there would be no noticeable difference between the plane on or off the belt.
QUOTE (->
| QUOTE |
| You say you used a faster treadbelt than mine? Well, you didn't use a FAST ENOUGH treadbelt. Did you miss the part about how I recomended you use a 50mph treadbelt??? |
But according to you you never said the belt was going faster than the plane yet now your saying I need a treadmill that can reach speeds faster than my plane in order to keep it from not going anywhere. Also if the plane isn't going anywhere because the belt is holding it back how can it have speed? If the plane is just sitting on the belt trying to go somewhere but its not then belt is merely moving under a stationary plane. Key word is stationary as in not moving as in a velocity of 0 mph. The belt is however moving meaning the speed of the belt is greater than that of the plane and does not match the plane at all. In order for the belt to match the speed of the plane it would have to stop moving.
The truth is that the amount of resistance to move induced onto the plane as a result of the belt moving in the opposite direction whose speed matches that of the plane (in accordance with the OP) is so small under normal circumstances that under the conditions of the moving belt (which would merely double the wheel speed) the increase would be so small that there would be no noticeable difference between the plane on or off the belt.
And WHEN the plane IS at 0 IAS, it is a FACT that the plane's speed over the surface of the treadbelt EQUALS the speed of the treadbelt itself. JUST LIKE a runner on a treadbelt.
First off a plane would not be like a runner. A plane pushes off the air to move forward and a runner pushes off of the ground. Place a treadmill in a room facing a doorway. Get on and start running at whatever setting. No matter how long you are running you are not going to go through that doorway. Hell the distance between you and the doorway will remain unchanged. This means you are not going anywhere and is occupying the same volume of space. Your speed is zero. Your legs on the other hand is a different story. They are moving at a rate equal to the treadmill's speed but since the belt is moving at that speed you do not go anywhere.
So what you describe above is exactly that. The belt is matching the speed of the plane's wheels however unlike the legs of a runner the speed of the plane's wheels is 50% depended on the speed of the belt. The speed of the runner's legs are 100% depended on the runner. The plane itself is not moving. It won't make it to the end of the conveyor belt. If it started out at the very center of the belt no matter how much time passes it remains at the center of the belt according to what you said above. Sorry but if the plane is not leaving the center of the belt then it has no speed and the belt is merely moving beneath the plane while making the plane's wheels go round. Since the belt matches the speed of the plane then the only way that belt is going to move is if the plane itself physically moves.
So if the plane is at 0 IAS then it isn't physically going anywhere so it has a velocity of 0 mph.
QUOTE
And WHEN the plane IS at 0 IAS, it is a FACT that the plane's speed over the surface of the treadbelt EQUALS the speed of the treadbelt itself.
That is like say a sea plane that is tied down to a dock while floating on water with a 5 mph current has a speed of 5 mph. No it doesn't. The see plane isn't going anywhere and has a speed of 0 mph.
So the plane that is on the belt not moving while the belt moves underneath causing the wheels to spin at the same speed as the belt does not have any speed at all. It is simply a plane going at 0 mph with spinning tires whose spin is equal to and caused by the movement of the belt underneath.
I know exactly what static thrust is and I know it is irrelevant to the situation. When a plane is moving forward air approaches the propeller as a result. This will decrease the amount of thrust by decreasing the pressure difference between the leading side and tailing side of the propeller. When the plane is not moving (static conditions) is when you get static thrust. Since the belt is in contact with the wheels of the plane only then in no way can it have any effect on the propeller or surrounding air. This means that the static thrust can not be in any way effected by the belt. So before you mention something like static thrust to try and support your arguments it would help to know yourself what it is especially if you plan to ask someone else if they know what it is. So....
QUOTE (->
| QUOTE |
| And WHEN the plane IS at 0 IAS, it is a FACT that the plane's speed over the surface of the treadbelt EQUALS the speed of the treadbelt itself. |
That is like say a sea plane that is tied down to a dock while floating on water with a 5 mph current has a speed of 5 mph. No it doesn't. The see plane isn't going anywhere and has a speed of 0 mph.
So the plane that is on the belt not moving while the belt moves underneath causing the wheels to spin at the same speed as the belt does not have any speed at all. It is simply a plane going at 0 mph with spinning tires whose spin is equal to and caused by the movement of the belt underneath.
I know exactly what static thrust is and I know it is irrelevant to the situation. When a plane is moving forward air approaches the propeller as a result. This will decrease the amount of thrust by decreasing the pressure difference between the leading side and tailing side of the propeller. When the plane is not moving (static conditions) is when you get static thrust. Since the belt is in contact with the wheels of the plane only then in no way can it have any effect on the propeller or surrounding air. This means that the static thrust can not be in any way effected by the belt. So before you mention something like static thrust to try and support your arguments it would help to know yourself what it is especially if you plan to ask someone else if they know what it is. So....
I said that if a plane could go 5mph on static ground, then it would need maybe a 50mph or faster treadbelt to be held at 0 IAS...this is due to STATIC THRUST.
this is NOT happening. Not only not the way or I should say 'why' (static thrust) as you mentioned here but also not at all with these low velocities.
Hello again
RE: How Stuff Works....Force vs Power.
You seem to be saying that it takes more POWER to move the tires down the road at a faster speed....it doesn't take more FORCE...but it DOES take more POWER? Let me know if I got that correct, because I am no physicists.
Yes that is Exactly correct - it takes more power but the force is constant. Now I realize that that sounds like a bunch of humbug and is kind of counter-intuitive*heh*, but it's because "power" and "force" means about the same in every-day language I suppose, but in the world of nerdy physicists it very different. It's like this:
Power is the amount of work you do divided by the time you do it in. P = W/t. Work is Force times distance, W = F*s, so, P = F*s/t, and we know that s/t is the same as velocity. So it takes more Power to go faster because you push with the same amount of Force but for a longer distance in the same amount of time
Yes that is Exactly correct - it takes more power but the force is constant. Now I realize that that sounds like a bunch of humbug and is kind of counter-intuitive*heh*, but it's because "power" and "force" means about the same in every-day language I suppose, but in the world of nerdy physicists it very different. It's like this:
Power is the amount of work you do divided by the time you do it in. P = W/t. Work is Force times distance, W = F*s, so, P = F*s/t, and we know that s/t is the same as velocity. So it takes more Power to go faster because you push with the same amount of Force but for a longer distance in the same amount of time
Because it seems like you're saying that when the tread belt speed increases, you'll need more
POWER in order to remain at 0 IAS. And once you run out of this 'more power' thing, and the
tread belt keeps spinning faster and faster, don't you think -IAS will occur?
I'm not quite sure what the term IAS stands for.. "something Air Speed"?. Since the force required to keep the plane stationary is the same though no matter how fast the belt is spinning, you won't have to increase the power output from the engine. The place where you "grip" to get your force from with the plane is the air and that is stationary, the Belt has to increase its speed though and hence the power output. (that'll be some heck of a mill turn it upside down and use it as a tank 
) So even though you increase the power output of the mill, you don't have to do the same with the plane.
RE:deformable underlying surface
Remember....if it were a REAL plane, then it would be a REALLY REALLY REALLY big tread belt....which would presumably have the same type of 'deformable underlying surface'....i dunno...maybe? Relatively speaking?
I have thought about that but I really don't think so since for instance the belt would have to be longer to fit the plane on it etc. so the "hill" wouldn't reach all the way to the plane anyway etc. and even if it did, it would not affect the plane as much cause it's so much more massive compared to the "hill" than the small plane is.
I have thought about that but I really don't think so since for instance the belt would have to be longer to fit the plane on it etc. so the "hill" wouldn't reach all the way to the plane anyway etc. and even if it did, it would not affect the plane as much cause it's so much more massive compared to the "hill" than the small plane is.
Let's see if reducing the throttle will make the plane have -IAS. (It did)
Let's see if increasing throttle will make the plane have +IAS (It Did)
Let's see if adding weight will make the plane have -IAS. (It did)
Let's see if reducing weight will make the plane have +IAS. (It did)
Let's see if increasing tread belt speed will make the plane have -IAS. (It did)
Let's see if reducing tread belt speed will make the plane have +IAS. (It did)
In the first four cases it shouldn't be that big of a surprise at what happends since for instance adding weight increases the rolling resistance and hence you would need to have a bigger power output from the plane to match it. As for the tread belt speed I would guess that it has to do with what I talked about earlier with the rolling resistance being affected at low speeds - but Also, with the Lego wheels (Love the idea!), they are so frikken small and they also have grooves in them haven't they, so I'm thinking that they would be affected by minute things much much more than big wheels. (small things affect things in the small more than they affect things in the large I mean.).
I have concluded that the same results would occur with a more powerful plane (when a more faster tread belt is used). And an even more powerful plane with a more faster tread belt would result in the same....and an even MORE (well, you get the picture).
I get your idea but I don't agree. when you scale things up all the small things that affect things doesn't get "scaled with it", so for a real plane where the power output is.. a lot higher, and also the possible ground speed before lifting, bigger wheels etc. ,the rolling frictional force is going to be constant as well so you will only have to apply a constant "throttle", or whatever they call it on a plane, to keep the plane stationary.
I get your idea but I don't agree. when you scale things up all the small things that affect things doesn't get "scaled with it", so for a real plane where the power output is.. a lot higher, and also the possible ground speed before lifting, bigger wheels etc. ,the rolling frictional force is going to be constant as well so you will only have to apply a constant "throttle", or whatever they call it on a plane, to keep the plane stationary.
Let me know how your experiment goes....I would like to hear about it.
It's still in the "it would be cool to" - stage, but if I ever get around to I'll post the link to the video for sure
I'm thinking that the question has been reinterpreted a number of times though so that different people are probably talking about different things. What I mean though is that "Would a treadmill be able to prevent a plane from lifting by spinning in the opposite direction of the planes travel?" (Which I think is what the questioneer meant when he wrote the question).
I'm seeing a complete contradiction within these two sentences and they were typed one directly after the other.
But according to you you never said the belt was going faster than the plane yet now your saying I need a treadmill that can reach speeds faster than my plane in order to keep it from not going anywhere. Also if the plane isn't going anywhere because the belt is holding it back how can it have speed? If the plane is just sitting on the belt trying to go somewhere but its not then belt is merely moving under a stationary plane. Key word is stationary as in not moving as in a velocity of 0 mph. The belt is however moving meaning the speed of the belt is greater than that of the plane and does not match the plane at all. In order for the belt to match the speed of the plane it would have to stop moving.
The truth is that the amount of resistance to move induced onto the plane as a result of the belt moving in the opposite direction whose speed matches that of the plane (in accordance with the OP) is so small under normal circumstances that under the conditions of the moving belt (which would merely double the wheel speed) the increase would be so small that there would be no noticeable difference between the plane on or off the belt.
First off a plane would not be like a runner. A plane pushes off the air to move forward and a runner pushes off of the ground. Place a treadmill in a room facing a doorway. Get on and start running at whatever setting. No matter how long you are running you are not going to go through that doorway. Hell the distance between you and the doorway will remain unchanged. This means you are not going anywhere and is occupying the same volume of space. Your speed is zero. Your legs on the other hand is a different story. They are moving at a rate equal to the treadmill's speed but since the belt is moving at that speed you do not go anywhere.
So what you describe above is exactly that. The belt is matching the speed of the plane's wheels however unlike the legs of a runner the speed of the plane's wheels is 50% depended on the speed of the belt. The speed of the runner's legs are 100% depended on the runner. The plane itself is not moving. It won't make it to the end of the conveyor belt. If it started out at the very center of the belt no matter how much time passes it remains at the center of the belt according to what you said above. Sorry but if the plane is not leaving the center of the belt then it has no speed and the belt is merely moving beneath the plane while making the plane's wheels go round. Since the belt matches the speed of the plane then the only way that belt is going to move is if the plane itself physically moves.
So if the plane is at 0 IAS then it isn't physically going anywhere so it has a velocity of 0 mph.
That is like say a sea plane that is tied down to a dock while floating on water with a 5 mph current has a speed of 5 mph. No it doesn't. The see plane isn't going anywhere and has a speed of 0 mph.
So the plane that is on the belt not moving while the belt moves underneath causing the wheels to spin at the same speed as the belt does not have any speed at all. It is simply a plane going at 0 mph with spinning tires whose spin is equal to and caused by the movement of the belt underneath.
I know exactly what static thrust is and I know it is irrelevant to the situation. When a plane is moving forward air approaches the propeller as a result. This will decrease the amount of thrust by decreasing the pressure difference between the leading side and tailing side of the propeller. When the plane is not moving (static conditions) is when you get static thrust. Since the belt is in contact with the wheels of the plane only then in no way can it have any effect on the propeller or surrounding air. This means that the static thrust can not be in any way effected by the belt. So before you mention something like static thrust to try and support your arguments it would help to know yourself what it is especially if you plan to ask someone else if they know what it is. So....
this is NOT happening. Not only not the way or I should say 'why' (static thrust) as you mentioned here but also not at all with these low velocities.
Without reading your entire post, I can clearly see you are having trouble with the whole ‘relating plane’s speed to surface of treadbelt’.
I would recommend you re-read the thread so that you can understand how we have a difference of opinion as to ‘how’ the plane’s ‘speed’ is determined.
I relate it to a runner on a treadbelt. NOT because the runner pushes off the treadbelt, and the plane ‘pushes’ off the air. But because the runner and the plane are both TRAVELING over the surface of the treadbelt. This has nothing to do with how the propulsion takes place. This has to do with the fact that an object which is ‘using’ a treadbelt usually bases it’s speed via the surface of the treadbelt.
So once we are relating the plane’s speed to the treadbelt’s surface (again, keep up…this is where we have difference of opinion), and when the treadbelt is preventing plane IAS (you AGREE this can happen) you will have a situation where the plane’s speed (over the treadbelt’s surface) equals exactly the ‘speed of the treadbelt’.
Once again, just as a runner judges his speed via his speed over the surface upon which he is traveling, so shall the plane. When this happens, and this speed equals the treadbelt speed, then 0 IAS WILL occur….just like the runner who can keep watching that TV. He has SPEED over the surface of the treadbelt…just like the plane has a ‘speed’ over the treadbelt.
Once again, this has NOTHING to do with where that propulsion force is applied…..I’m NOT talking about how propulsion is applied….once again, this is NOT about how propulsion is applied…..can I say it one more time….. this is NOT about how propulsion is applied.
This is about relating speed to the surface upon which it is traveling.
Anyways….we have a difference of opinion as to how the plane’s speed is derived. That’s OK….I have no problem with that. Why?
Because you agree with me that a treadbelt CAN prevent a plane from flying…..now please…try to convince your fellow flyboys of this fact….we are done here.
QUOTE
RE: How Stuff Works....Force vs Power.
You seem to be saying that it takes more POWER to move the tires down the road at a faster speed....it doesn't take more FORCE...but it DOES take more POWER? Let me know if I got that correct, because I am no physicists.
Yes that is Exactly correct - it takes more power but the force is constant. Now I realize that that sounds like a bunch of humbug and is kind of counter-intuitive*heh*, but it's because "power" and "force" means about the same in every-day language I suppose, but in the world of nerdy physicists it very different. It's like this:
Power is the amount of work you do divided by the time you do it in. P = W/t. Work is Force times distance, W = F*s, so, P = F*s/t, and we know that s/t is the same as velocity. So it takes more Power to go faster because you push with the same amount of Force but for a longer distance in the same amount of time
QUOTE (->
| QUOTE |
RE: How Stuff Works....Force vs Power. You seem to be saying that it takes more POWER to move the tires down the road at a faster speed....it doesn't take more FORCE...but it DOES take more POWER? Let me know if I got that correct, because I am no physicists. |
Yes that is Exactly correct - it takes more power but the force is constant. Now I realize that that sounds like a bunch of humbug and is kind of counter-intuitive*heh*, but it's because "power" and "force" means about the same in every-day language I suppose, but in the world of nerdy physicists it very different. It's like this:
Power is the amount of work you do divided by the time you do it in. P = W/t. Work is Force times distance, W = F*s, so, P = F*s/t, and we know that s/t is the same as velocity. So it takes more Power to go faster because you push with the same amount of Force but for a longer distance in the same amount of time
Because it seems like you're saying that when the tread belt speed increases, you'll need more
POWER in order to remain at 0 IAS. And once you run out of this 'more power' thing, and the
tread belt keeps spinning faster and faster, don't you think -IAS will occur?
I'm not quite sure what the term IAS stands for.. "something Air Speed"?. Since the force required to keep the plane stationary is the same though no matter how fast the belt is spinning, you won't have to increase the power output from the engine. The place where you "grip" to get your force from with the plane is the air and that is stationary, the Belt has to increase its speed though and hence the power output. (that'll be some heck of a mill
turn it upside down and use it as a tank ) So even though you increase the power output of the mill, you don't have to do the same with the plane.QUOTE
RE:deformable underlying surface
Remember....if it were a REAL plane, then it would be a REALLY REALLY REALLY big tread belt....which would presumably have the same type of 'deformable underlying surface'....i dunno...maybe? Relatively speaking?
I have thought about that but I really don't think so since for instance the belt would have to be longer to fit the plane on it etc. so the "hill" wouldn't reach all the way to the plane anyway etc. and even if it did, it would not affect the plane as much cause it's so much more massive compared to the "hill" than the small plane is.
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RE:deformable underlying surface Remember....if it were a REAL plane, then it would be a REALLY REALLY REALLY big tread belt....which would presumably have the same type of 'deformable underlying surface'....i dunno...maybe? Relatively speaking? |
I have thought about that but I really don't think so since for instance the belt would have to be longer to fit the plane on it etc. so the "hill" wouldn't reach all the way to the plane anyway etc. and even if it did, it would not affect the plane as much cause it's so much more massive compared to the "hill" than the small plane is.
Let's see if reducing the throttle will make the plane have -IAS. (It did)
Let's see if increasing throttle will make the plane have +IAS (It Did)
Let's see if adding weight will make the plane have -IAS. (It did)
Let's see if reducing weight will make the plane have +IAS. (It did)
Let's see if increasing tread belt speed will make the plane have -IAS. (It did)
Let's see if reducing tread belt speed will make the plane have +IAS. (It did)
In the first four cases it shouldn't be that big of a surprise at what happends since for instance adding weight increases the rolling resistance and hence you would need to have a bigger power output from the plane to match it. As for the tread belt speed I would guess that it has to do with what I talked about earlier with the rolling resistance being affected at low speeds - but Also, with the Lego wheels (Love the idea!), they are so frikken small and they also have grooves in them haven't they, so I'm thinking that they would be affected by minute things much much more than big wheels. (small things affect things in the small more than they affect things in the large I mean.).
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I have concluded that the same results would occur with a more powerful plane (when a more faster tread belt is used). And an even more powerful plane with a more faster tread belt would result in the same....and an even MORE (well, you get the picture).
I get your idea but I don't agree. when you scale things up all the small things that affect things doesn't get "scaled with it", so for a real plane where the power output is.. a lot higher, and also the possible ground speed before lifting, bigger wheels etc. ,the rolling frictional force is going to be constant as well so you will only have to apply a constant "throttle", or whatever they call it on a plane, to keep the plane stationary.
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I have concluded that the same results would occur with a more powerful plane (when a more faster tread belt is used). And an even more powerful plane with a more faster tread belt would result in the same....and an even MORE (well, you get the picture). |
I get your idea but I don't agree. when you scale things up all the small things that affect things doesn't get "scaled with it", so for a real plane where the power output is.. a lot higher, and also the possible ground speed before lifting, bigger wheels etc. ,the rolling frictional force is going to be constant as well so you will only have to apply a constant "throttle", or whatever they call it on a plane, to keep the plane stationary.
Let me know how your experiment goes....I would like to hear about it.
It's still in the "it would be cool to" - stage, but if I ever get around to I'll post the link to the video for sure
I'm thinking that the question has been reinterpreted a number of times though so that different people are probably talking about different things. What I mean though is that "Would a treadmill be able to prevent a plane from lifting by spinning in the opposite direction of the planes travel?" (Which I think is what the questioneer meant when he wrote the question).
QUOTE (Precursor562+Feb 28 2007, 07:51 PM)
I'm seeing a complete contradiction within these two sentences and they were typed one directly after the other.
But according to you you never said the belt was going faster than the plane yet now your saying I need a treadmill that can reach speeds faster than my plane in order to keep it from not going anywhere. Also if the plane isn't going anywhere because the belt is holding it back how can it have speed? If the plane is just sitting on the belt trying to go somewhere but its not then belt is merely moving under a stationary plane. Key word is stationary as in not moving as in a velocity of 0 mph. The belt is however moving meaning the speed of the belt is greater than that of the plane and does not match the plane at all. In order for the belt to match the speed of the plane it would have to stop moving.
The truth is that the amount of resistance to move induced onto the plane as a result of the belt moving in the opposite direction whose speed matches that of the plane (in accordance with the OP) is so small under normal circumstances that under the conditions of the moving belt (which would merely double the wheel speed) the increase would be so small that there would be no noticeable difference between the plane on or off the belt.
First off a plane would not be like a runner. A plane pushes off the air to move forward and a runner pushes off of the ground. Place a treadmill in a room facing a doorway. Get on and start running at whatever setting. No matter how long you are running you are not going to go through that doorway. Hell the distance between you and the doorway will remain unchanged. This means you are not going anywhere and is occupying the same volume of space. Your speed is zero. Your legs on the other hand is a different story. They are moving at a rate equal to the treadmill's speed but since the belt is moving at that speed you do not go anywhere.
So what you describe above is exactly that. The belt is matching the speed of the plane's wheels however unlike the legs of a runner the speed of the plane's wheels is 50% depended on the speed of the belt. The speed of the runner's legs are 100% depended on the runner. The plane itself is not moving. It won't make it to the end of the conveyor belt. If it started out at the very center of the belt no matter how much time passes it remains at the center of the belt according to what you said above. Sorry but if the plane is not leaving the center of the belt then it has no speed and the belt is merely moving beneath the plane while making the plane's wheels go round. Since the belt matches the speed of the plane then the only way that belt is going to move is if the plane itself physically moves.
So if the plane is at 0 IAS then it isn't physically going anywhere so it has a velocity of 0 mph.
That is like say a sea plane that is tied down to a dock while floating on water with a 5 mph current has a speed of 5 mph. No it doesn't. The see plane isn't going anywhere and has a speed of 0 mph.
So the plane that is on the belt not moving while the belt moves underneath causing the wheels to spin at the same speed as the belt does not have any speed at all. It is simply a plane going at 0 mph with spinning tires whose spin is equal to and caused by the movement of the belt underneath.
I know exactly what static thrust is and I know it is irrelevant to the situation. When a plane is moving forward air approaches the propeller as a result. This will decrease the amount of thrust by decreasing the pressure difference between the leading side and tailing side of the propeller. When the plane is not moving (static conditions) is when you get static thrust. Since the belt is in contact with the wheels of the plane only then in no way can it have any effect on the propeller or surrounding air. This means that the static thrust can not be in any way effected by the belt. So before you mention something like static thrust to try and support your arguments it would help to know yourself what it is especially if you plan to ask someone else if they know what it is. So....
this is NOT happening. Not only not the way or I should say 'why' (static thrust) as you mentioned here but also not at all with these low velocities.
Without reading your entire post, I can clearly see you are having trouble with the whole ‘relating plane’s speed to surface of treadbelt’.
I would recommend you re-read the thread so that you can understand how we have a difference of opinion as to ‘how’ the plane’s ‘speed’ is determined.
I relate it to a runner on a treadbelt. NOT because the runner pushes off the treadbelt, and the plane ‘pushes’ off the air. But because the runner and the plane are both TRAVELING over the surface of the treadbelt. This has nothing to do with how the propulsion takes place. This has to do with the fact that an object which is ‘using’ a treadbelt usually bases it’s speed via the surface of the treadbelt.
So once we are relating the plane’s speed to the treadbelt’s surface (again, keep up…this is where we have difference of opinion), and when the treadbelt is preventing plane IAS (you AGREE this can happen) you will have a situation where the plane’s speed (over the treadbelt’s surface) equals exactly the ‘speed of the treadbelt’.
Once again, just as a runner judges his speed via his speed over the surface upon which he is traveling, so shall the plane. When this happens, and this speed equals the treadbelt speed, then 0 IAS WILL occur….just like the runner who can keep watching that TV. He has SPEED over the surface of the treadbelt…just like the plane has a ‘speed’ over the treadbelt.
Once again, this has NOTHING to do with where that propulsion force is applied…..I’m NOT talking about how propulsion is applied….once again, this is NOT about how propulsion is applied…..can I say it one more time….. this is NOT about how propulsion is applied.
This is about relating speed to the surface upon which it is traveling.
Anyways….we have a difference of opinion as to how the plane’s speed is derived. That’s OK….I have no problem with that. Why?
Because you agree with me that a treadbelt CAN prevent a plane from flying…..now please…try to convince your fellow flyboys of this fact….we are done here.
QUOTE (Johan_K+Feb 28 2007, 11:02 PM)
Hello again
Yes that is Exactly correct - it takes more power but the force is constant. Now I realize that that sounds like a bunch of humbug and is kind of counter-intuitive*heh*, but it's because "power" and "force" means about the same in every-day language I suppose, but in the world of nerdy physicists it very different. It's like this:
Power is the amount of work you do divided by the time you do it in. P = W/t. Work is Force times distance, W = F*s, so, P = F*s/t, and we know that s/t is the same as velocity. So it takes more Power to go faster because you push with the same amount of Force but for a longer distance in the same amount of time
I'm not quite sure what the term IAS stands for.. "something Air Speed"?. Since the force required to keep the plane stationary is the same though no matter how fast the belt is spinning, you won't have to increase the power output from the engine. The place where you "grip" to get your force from with the plane is the air and that is stationary, the Belt has to increase its speed though and hence the power output. (that'll be some heck of a mill turn it upside down and use it as a tank ) So even though you increase the power output of the mill, you don't have to do the same with the plane.
I have thought about that but I really don't think so since for instance the belt would have to be longer to fit the plane on it etc. so the "hill" wouldn't reach all the way to the plane anyway etc. and even if it did, it would not affect the plane as much cause it's so much more massive compared to the "hill" than the small plane is.
In the first four cases it shouldn't be that big of a surprise at what happends since for instance adding weight increases the rolling resistance and hence you would need to have a bigger power output from the plane to match it. As for the tread belt speed I would guess that it has to do with what I talked about earlier with the rolling resistance being affected at low speeds - but Also, with the Lego wheels (Love the idea!), they are so frikken small and they also have grooves in them haven't they, so I'm thinking that they would be affec
Yes that is Exactly correct - it takes more power but the force is constant. Now I realize that that sounds like a bunch of humbug and is kind of counter-intuitive*heh*, but it's because "power" and "force" means about the same in every-day language I suppose, but in the world of nerdy physicists it very different. It's like this:
Power is the amount of work you do divided by the time you do it in. P = W/t. Work is Force times distance, W = F*s, so, P = F*s/t, and we know that s/t is the same as velocity. So it takes more Power to go faster because you push with the same amount of Force but for a longer distance in the same amount of time
I'm not quite sure what the term IAS stands for.. "something Air Speed"?. Since the force required to keep the plane stationary is the same though no matter how fast the belt is spinning, you won't have to increase the power output from the engine. The place where you "grip" to get your force from with the plane is the air and that is stationary, the Belt has to increase its speed though and hence the power output. (that'll be some heck of a mill
turn it upside down and use it as a tank ) So even though you increase the power output of the mill, you don't have to do the same with the plane.I have thought about that but I really don't think so since for instance the belt would have to be longer to fit the plane on it etc. so the "hill" wouldn't reach all the way to the plane anyway etc. and even if it did, it would not affect the plane as much cause it's so much more massive compared to the "hill" than the small plane is.
In the first four cases it shouldn't be that big of a surprise at what happends since for instance adding weight increases the rolling resistance and hence you would need to have a bigger power output from the plane to match it. As for the tread belt speed I would guess that it has to do with what I talked about earlier with the rolling resistance being affected at low speeds - but Also, with the Lego wheels (Love the idea!), they are so frikken small and they also have grooves in them haven't they, so I'm thinking that they would be affec