Final answer to the airplane on a long treadmill problem ...

[Ruiner]

1. I said that plane = dyno roller, treadmill = car. Please reread what i said.

2. Plane will take off on snow since there AREN'T any -A Velocity on X axis with -hp & -tq. Also, the snow will have enough friction for the plan to grip on. Treadmill has -A Velocity on X axis with -hp & -tq. It counters every +A velocity in the +X direction.

3. Plane doesn't require right velocity/speed to lift off, it requires enough lift force of the air movement. It relies on its speed to help it move ALONG the density of the air to cause enough lift. If the plan is to run on the space runway where there aren't any air, it will not have any vertical movement. It will move VERY fast on the outerspace runway, but not UP unless it has a thrust engine to push it up and changes its Y directional velocity. The plane can run at 500mph on the runway while the air is moving at the SAME velocity and SAME force and SAME direction as the plane, it still WILL NOT take off.

I don't believe it bet. But I understand your concept very well.

It's time for the Mythbuster to prove this.

A plane DOES require velocity/speed to lift. The speed of the air over the top of the wing vs over the bottom of the wing creates a pressure difference and that is what gives you lift.

Wrong on the bolded part. How can a treadmill counteract the FORWARD push of the engines by spinning the wheels of a plane? All it does is spin the wheels. Answer me that. I just busted your theory, btw...

[ShooterMcGavin]

As long as the wheels are free rolling (neutral), no, not really. There is a small amount of friction in the wheel bearings. If the plane's thrust matches that friction, exactly, then the plane will stay stationary. Once the plane's thrust passes that friction amount, the plane will move forward.

but the key is, what if said treadmill can accelerate constantly? F=ma, so whatever force is provided by engines, it can be equally matched and exceeded by the treadmill if it has enough acceleration, no?

[ATK_Designs]

A plane DOES require velocity/speed to lift. The speed of the air over the top of the wing vs over the bottom of the wing creates a pressure difference and that is what gives you lift.

Wrong on the bolded part. How can a treadmill counteract the FORWARD push of the engines by spinning the wheels of a plane? All it does is spin the wheels. Answer me that. I just busted your theory, btw...

Again, for the 3rd time.

The plane's wheels are the same thing as the dyno's roller. It outputs no pwr or tq.

The treadmill does output HP and TQ, in negative direction.


So imagine it this way, instead of having your porsche sexing up on top of the dyno, this time, the dyno is doing a reverse cowboy (on top) on your porsche :idb:

Also: I said that the plan doesn't require the RIGHT velocity, not that it doesn't require ANY velocity at all. I was, however, wrong in the mean that it does require the velocity. What I meant was that it Does not require the exact same *book* velocity to lift off. Each plane is different and also in each situation (atmosphere density)

[Ruiner]

Again, for the 3rd time.

The plane's wheels are the same thing as the dyno's roller. It outputs no pwr or tq.

The treadmill does output HP and TQ, in negative direction.


So imagine it this way, instead of having your porsche sexing up on top of the dyno, this time, the dyno is doing a reverse cowboy (on top) on your porsche :idb:

No, it is not the same:

The wheels on my car are powered by my engine... what are the wheels powered by on a plane?

Another example: Let's say that my car is on a dyno in neutral...and I have a jet engine attached to it. I crank up the engine, what happens to my car on the dyno?

[Ruiner]

Interlude, you do realize that the statement "The treadmill does output HP and TQ, in negative direction" is true, but that it is ONLY doing this on free-spinning wheels, right?

[ATK_Designs]

No, it is not the same:

The wheels on my car are powered by my engine... what are the wheels powered by on a plane?

Another example: Let's say that my car is on a dyno in neutral...and I have a jet engine attached to it. I crank up the engine, what happens to my car on the dyno?

Dude, the wheels of the plane are freespining. I was sampled backward. If you must match the plane/treadmill (motorized) example, you must attach the jet engine TO the dyno.

In that case you'll move the whole Dyno station backward. But in this subject, the car (treadmill) must have matching negative speed as the dyno wheels are putting.

Interlude, you do realize that the statement "The treadmill does output HP and TQ, in negative direction" is true, but that it is ONLY doing this on free-spinning wheels, right?

I was talking about the motorized treadmill.

So in this subject, the treadmill is free spinning and NOT motorized??:confused:

If so, you're 100% correct. It's the same as those air plane on the water. It WILL LIFT OFF.

[Ruiner]

I was talking about the motorized treadmill.

So in this subject, the treadmill is free spinning and NOT motorized??:confused:

If so, you're 100% correct. It's the same as those air plane on the water. It WILL LIFT OFF.

No, the treadmill is motorized, but the wheels of the plane are free spinning. The treadmill has torque, but it ONLY applies it to wheels that are free spinning.

Your dyno question was wrong in a sense. The wheels on the car would need to be free spinning (in neutral) as well. Will the dyno work and apply torque to the car if the car is in neutral? Nope. Just like the treadmill will not apply torque to the plane if the wheels are free spinning.

[ATK_Designs]

No, the treadmill is motorized, but the wheels of the plane are free spinning. The treadmill has torque, but it ONLY applies it to wheels that are free spinning.

Your dyno question was wrong in a sense. The wheels on the car would need to be free spinning (in neutral) as well. Will the dyno work and apply torque to the car if the car is in neutral? Nope. Just like the treadmill will not apply torque to the plane if the wheels are free spinning.

Oh okay,

but I was NOT talking in the sense that your car is in neutral + jet engine, no, not that.

I was talking about the plane's wheels = the same as the dyno's rollers.
And the treadmill = the car itself.

Lift up or not is based on air pressure. if there aren't any, plane will not lift off. Also, the treadmill will adjusting its negative velocity accordingly to the plane's.

Using the car vs dyno was a bad example. It was only to show you that the treadmill does output torque and HP in negative X direction to cancel out the free rolling velocity in positive X direction.

[Ruiner]

Oh okay,

but I was NOT talking in the sense that your car is in neutral + jet engine, no, not that.

I was talking about the plane's wheels = the same as the dyno's rollers.
And the treadmill = the car itself.

Lift up or not is based on air pressure. if there aren't any, plane will not lift off. Also, the treadmill will adjusting its negative velocity accordingly to the plane's.

Using the car vs dyno was a bad example. It was only to show you that the treadmill does output torque and HP in negative X direction to cancel out the free rolling velocity in positive X direction.

HOW is it cancelling the forward velocity, though?

Answer these questions for me:
- The treadmill is only spinning the wheels of the plane, yes?
- The wheels of the plane are free rolling, yes?
- Can spinning free rolling wheels cancel out the forward velocity of the plane?

I want you to think about that last question really hard... It actually makes the wheels spin faster. Look below:

[3kgtdrvr]

wow, that was a lot to read and really confusing to lol i didnt even get halfway before i gave up but i think as long as the plane it moving foward it should take off. if the treadmill can move and not pull the plane with it = 0 resisance or friction between the wheels and the treadmill and inside the wheels or wheel bearing so the treadmill can spin and the plane stay still so that 100% of the force of the engines goes towards pushing the plane then it should take off without any problem. damn good question though! really got me thinking

[Ruiner]

wow, that was a lot to read and really confusing to lol i didnt even get halfway before i gave up but i think as long as the plane it moving foward it should take off. if the treadmill can move and not pull the plane with it = 0 resisance or friction between the wheels and the treadmill and inside the wheels or wheel bearing so the treadmill can spin and the plane stay still so that 100% of the force of the engines goes towards pushing the plane then it should take off without any problem. damn good question though! really got me thinking

Even with friction in the wheel bearings, the plane's thrust will easily overcome that...

[Xan]

The propellers provide the thrust. Tricky question first time you hear it.

[ShooterMcGavin]

but the key is, what if said treadmill can accelerate constantly? F=ma, so whatever force is provided by engines, it can be equally matched and exceeded by the treadmill if it has enough acceleration, no?

ruiner? anything?

[Ruiner]

ruiner? anything?

The treadmill matches the SPEED of the plane, not the thrust. The tread mill can be moving at 100,000knots while the plane is going at 100knots. It WOULD NOT matter. It would ONLY make the wheels spin at 100,100knots. NOTHING MORE. Guys, the wheels would spin faster, but that would not change the thrust up the engines.

The treadmill in NO way can counteract the THRUST of the engines.

[JennB]

You are correct.

It's much simpler than it sounds. So many people think in terms of cars when there really isn't a relation. Cars are moved by their wheels, planes are not. The wheels on the plane might as well not even be there, they have no effect at all on the movement of the plane. The engines move it through the air and will do that it the wheels are spinning or if the plane is on water even.



(I'm sure something like that has been said at one point, but damn this thread is long)

[Ruiner]

You are correct.

It's much simpler than it sounds. So many people think in terms of cars when there really isn't a relation. Cars are moved by their wheels, planes are not. The wheels on the plane might as well not even be there, they have no effect at all on the movement of the plane. The engines move it through the air and will do that it the wheels are spinning or if the plane is on water even.



(I'm sure something like that has been said at one point, but damn this thread is long)

How come their minds cannot grasp this concept? I see that you are about my age...perhaps it comes with age and schooling? I dunno...

[speedminded]

The treadmill matches the SPEED of the plane, not the thrust. The tread mill can be moving at 100,000knots while the plane is going at 100knots. It WOULD NOT matter. It would ONLY make the wheels spin at 100,100knots. NOTHING MORE. Guys, the wheels would spin faster, but that would not change the thrust up the engines.

The treadmill in NO way can counteract the THRUST of the engines.

lemme help you out with the porsche on the dyno analogy....imagine a vehicle on the dyno in neutral...the wheels are free spinning just as a planes wheels are. Now imagine if that car was not strapped down on the dyno, it should remain free wheeling on top of the rollers even if power were applied to the dyno (like a treadmill) in turn causing the wheels to spin. Ok so now you would have a car sitting there with wheels spinning but not going anywhere (ever seen anyone spin 2 basketballs on top of each other or a man running on a floating barrel or log in the water?) Same idea, one causes the other to spin but since the bottom one is stationary neither go anywhere.

Anyways, back to the car on the dyno...it's not strapped down and no power is being supplied to the wheels. Now imagine if you had 4 people or even just one person run and push the back of the vehicle...is the car still going to go forward? yes. Now if you turn on the engines of the plane is it going to go anywhere? yes.

[JennB]

How come their minds cannot grasp this concept? I see that you are about my age...perhaps it comes with age and schooling? I dunno...

It's just hard to make the separation of concepts.

We're probably both very logical people so it's easier for us to understand.



Now emotions, I don't understand. Math and science, I'm on it.

[ATK_Designs]

all of this, with pictures and all; yet, you forgot the weight & Gravity.

I'm not going to try and argue any further. It's infact very simple. All engineers that I know also say that the plan will not take up.

remember,

1. Air plane thrust engine give it +X Velocity
2. Plane's weight give it -Y Velocity
3. Gravity weight adds to that -Y velocity
4. Treadmill gives enqual -X Velocity.

So, I will not trying to be precise, but instead be very simple about it, you have

X - 2Y = Plane's velocity
-X = Treadmill Velocity

Put them on the equation, you still end up with -2Y. You need Possitive Y to give it lifts. That above is not entirely correct equation since you'd have to factor in a lot more, however, it'll just yield extra -Y velocity, of which would further strengthen the concept.

X & Y are X-Y Axis of directionals

Anyone know physics can always tell this. I'm not saying I'm right since I'm also an engineer, but if a bunch of others senior engineers who said the same thing as I am, there must be a common.

I don't want to argue anymore if you don't understand. Have a good day.

[Vteckidd]

ill bet $1000 that the plane WOULD fly. Ruiner find the video that the kids made with the skateboard. that is all the proof you need.

the wheels arent driving the plane forward. The ENGINES in the rear are. an the plane will achieve thrust an lift off

[Vteckidd]

Anyways, back to the car on the dyno...it's not strapped down and no power is being supplied to the wheels. Now imagine if you had 4 people or even just one person run and push the back of the vehicle...is the car still going to go forward? yes. Now if you turn on the engines of the plane is it going to go anywhere? yes.

EGGSFUCKINGZACTLY

[speedminded]

all of this, with pictures and all; yet, you forgot the weight & Gravity.

I'm not going to try and argue any further. It's infact very simple. All engineers that I know also say that the plan will not take up.

remember,

1. Air plane thrust engine give it +X Velocity
2. Plane's weight give it -Y Velocity
3. Gravity weight adds to that -Y velocity
4. Treadmill gives enqual -X Velocity.

So, I will not trying to be precise, but instead be very simple about it, you have

X - 2Y = Plane's velocity
-X = Treadmill Velocity

Put them on the equation, you still end up with -2Y. You need Possitive Y to give it lifts. That above is not entirely correct equation since you'd have to factor in a lot more, however, it'll just yield extra -Y velocity, of which would further strengthen the concept.

X & Y are X-Y Axis of directionals

Anyone know physics can always tell this. I'm not saying I'm right since I'm also an engineer, but if a bunch of others senior engineers who said the same thing as I am, there must be a common.

I don't want to argue anymore if you don't understand. Have a good day.

Let's make it simple, the treadmill in no way what so ever will ever prevent the plane from moving forward...no matter what. Therefore gravity, lift, thrust, etc. everything is EXACTLY the same as if it were on a tarmac. Period.

Ask those same engineers if it's possible to drive into the back of a moving truck, just as KITT did in Knight Rider or the SSR does on it's commercial where it does a 180° onto the trailer...

[fight club]

Let's make it simple, the treadmill in no way what so ever will ever prevent the plane from moving forward...no matter what. Therefore gravity, lift, thrust, etc. everything is EXACTLY the same as if it were on a tarmac. Period.

Ask those same engineers if it's possible to drive into the back of a moving truck, just as KITT did in Knight Rider or the SSR does on it's commercial where it does a 180° onto the trailer...

its very possible. ive done it loads of times... in spyhunter.

[ATK_Designs]

Let's make it simple, the treadmill in no way what so ever will ever prevent the plane from moving forward...no matter what. Therefore gravity, lift, thrust, etc. everything is EXACTLY the same as if it were on a tarmac. Period.

Ask those same engineers if it's possible to drive into the back of a moving truck, just as KITT did in Knight Rider or the SSR does on it's commercial where it does a 180° onto the trailer...

They can just stop working since they're earning well over 6-figure incomes.

About the car on the dyno, please read what I said TONS of time before, it's the UPSIDE DOWN Example.

Treadmill = car = output tq & hp
Plane = Dyno = no tq/hp - free wheelies.

YOU CANNOT STRAP A THRUST ENGINE ONTO THE CAR AND COMPARE IT, since it'd be the same as strapping the engine onto the treadmill.

I said that using it was a bad example since I don't know how dyno works (whether it actually can spin its roller or not).

[speedminded]

They can just stop working since they're earning well over 6-figure incomes.

I sure hope it's not in aeronautical engineering!

[speedminded]

They can just stop working since they're earning well over 6-figure incomes.

About the car on the dyno, please read what I said TONS of time before, it's the UPSIDE DOWN Example.

Treadmill = car = output tq & hp
Plane = Dyno = no tq/hp - free wheelies.

YOU CANNOT STRAP A THRUST ENGINE ONTO THE CAR AND COMPARE IT, since it'd be the same as strapping the engine onto the treadmill.

I said that using it was a bad example since I don't know how dyno works (whether it actually can spin its roller or not).

See my dyno example, it explains it perfectly.

[ATK_Designs]

I sure hope it's not in aeronautical engineering!

They're mixed, some of them are Telcom, hardware, and some work for Lockheed Martin. When I asked them this question, they laughed and said that this been discussed a longggggg time ago, even before I was born. It was one of the trick to stir up the discussions.

[{X}Echo419]

What would stop the plane from moving if it applied thrust from its engines?

because the Plance is not going anywhere.

it's the wind passing over the wings(called drag) and making the plane fly.

ya know what you can do(maybe) but a remote controled air plane on a treadmill put the threadmill on full speed then put the plane on it and try to fly it.
the plane will probally fall off or at best stay on the treadmill and not gain "any" altitude".

[fight club]

all of this, with pictures and all; yet, you forgot the weight & Gravity.

I'm not going to try and argue any further. It's infact very simple. All engineers that I know also say that the plan will not take up.

remember,

1. Air plane thrust engine give it +X Velocity
2. Plane's weight give it -Y Velocity
3. Gravity weight adds to that -Y velocity
4. Treadmill gives enqual -X Velocity.

So, I will not trying to be precise, but instead be very simple about it, you have

X - 2Y = Plane's velocity
-X = Treadmill Velocity

Put them on the equation, you still end up with -2Y. You need Possitive Y to give it lifts. That above is not entirely correct equation since you'd have to factor in a lot more, however, it'll just yield extra -Y velocity, of which would further strengthen the concept.

X & Y are X-Y Axis of directionals

Anyone know physics can always tell this. I'm not saying I'm right since I'm also an engineer, but if a bunch of others senior engineers who said the same thing as I am, there must be a common.

I don't want to argue anymore if you don't understand. Have a good day.

your weight on earth is the force of gravity upon any material object. you cant factor it in twice.

[ATK_Designs]

See my dyno example, it explains it perfectly.

I read that, it's different than my example.

However, you forgot the fact that you need people pushing it and perfect horizonal movement, NOT having any UP force, while the dyno rollers are motorized AND rolling in separate direction - NOT freewheeling.

That's why I said that using the car & Dyno was a bad example. Since it has different factors, for example: Dyno's rollers doesn't act the same as treadmill since it doesn't have full surface movement but rather, spot movement.

Oh well, believe what you want,

I'm tired of all this typing.

Edit; cherry kool aid you're correct, I forgot, I factored it twice. Thanks for correcting.

[speedminded]

They're mixed, some of them are Telcom, hardware, and some work for Lockheed Martin. When I asked them this question, they laughed and said that this been discussed a longggggg time ago, even before I was born. It was one of the trick to stir up the discussions.

Since they are all engineers and have the money why don't they build me a small scale version of this situation: a treadmill not much more than 10-12' long should be sufficient and a radio controlled airplane capable of some sort of remote start...

[fight club]

no problem!

[JennB]

http://www.straightdope.com/columns/060203.html

[ShooterMcGavin]

read this, it's an avaitor/engineer POV on this whole thing, it's lengthy but it explains in full detail:

http://www.avweb.com/news/columns/191034-1.html

[ShooterMcGavin]

The treadmill matches the SPEED of the plane, not the thrust. The tread mill can be moving at 100,000knots while the plane is going at 100knots. It WOULD NOT matter. It would ONLY make the wheels spin at 100,100knots. NOTHING MORE. Guys, the wheels would spin faster, but that would not change the thrust up the engines.

The treadmill in NO way can counteract the THRUST of the engines.

correct, that's not what i was saying and i'm acknowledging this is a departure from the original question. the followup question involves whether or not a treadmill could be designed to match the FORCE (or acceleration) of the plane. in which case, wouldn't the answer be yes?

[swiftblaze]

In regards to Echo's post,

The remote control plane idea is flawed because it needs to travel a longer distance in order to generatete enough lift to take off. I can guarantee you that the plane will move forward. As stated earlier, stand on a treadmill with rollerskates and hold on to the front bar. Set the treadmill to a high setting and attempt to pull yourself forward. You will be able to very easily. This contradicts your previous statements stating that the "plance" will not move forward. The wheels are freely spinning and do not affect the thrust pushing the plane forward. A remote control plane will move forward on the treadmill fine, but it does not have near enough distance to take off. On the other hand, a treadmill the size of a runway will provide adequate distance for a plane to be able to take off.

I have an interesting idea. This same giant treadmill can be used in the car scene as well. If you place a car on a treadmill while in neutral and attach a jet engine in the trunk, will it move forward? Yes! The wheels are not providing any power whatsoever. The jet engine mounted in the trunk of the car will push the car foward against the treadmill since the wheels are only acting as a contact point between the car and the ground. The car can gain quite a bit of speed as well. Now, image if you have an airplane capable of producing twice the amount of thrust as that single jet engine mounted in the back of the car. Understand where I am coming from? The wheels are merely a contact point and are needed to provide control and reduce friction. A plane would not be able to take off very well on a runway while resting on its belly. The free spinning parts allow for this to happen. However, a plane will be able to take off on ice without landing gear. The ice will not provide enough resistance to prevent the plane from taking off or catching on fire. Hell, planes take off from water all the time without landing gear.

I have another interesting idea to consider. Let's say you replaced the wheels of the plane with a flat surface the provides no friction whatsoever. Will the plane move forward with the engines at full throttle? YES! The treadmill will spin freely under this "frictionless" material and will not effect the speed of the plane moving forward. I know this is a lengthy response, but I hope this will eliminate some of the doubts from others who are skeptical about the whole plane vs. treadmill idea. Next time you go to an airport with motorized walkways, bring some rollerskates and hold on to the railing. Then, have a friend behind you try to push you the opposite direction of the motorized sidewalk. You will receive many crazy looks, but you WILL move forward.

This is just my on this question.

Chris

[SNapper]

lol how is a plane gunna take off without air passing over it's wings?

[speedminded]

lol how is a plane gunna take off without air passing over it's wings?

jesus christ people, the conveyor/treadmill IN NO WAY prevents the aircraft from moving forward...it is NO DIFFERANT than a runway.

With that said, how does the airplane get on the conveyor and is it already moving or what? With no problems at all the plane could taxi on to a moving conveyor and in no way would it effect the motion of the airplane...just like if you were on a bicyle and road up to a running treadmill, did a wheelie and put the front wheel on the conveyor belt....would it throw the bicycle backwards? NO Could you continue to ride forward (up to the rear wheel, but not touching the rear wheel)? YES.

In order to ride up on the tread mill you would have to match the rear wheel speed to the treadmills speed, why? because the bicycles rear wheel powers the bicycle...The wheels on a plane DO NOT propel the aircraft.

[swiftblaze]

lol how is a plane gunna take off without air passing over it's wings?

LOL. I'm in a hurry at work and neglected to mention that in my post. The plane will be taking off under the same conditions as those from a stationary runway since all variables will remain the same, and the aircraft does not rely on power to the wheels to take off. The wheels are free spinning and will not slow the planes forward momentum caused by thrust from the jet engines.

[ShooterMcGavin]

READ THE ARTICLE IN THE LINK, answers all your questions, i promise.