Airplane on Conveyor Belt Mythbusters 12/12

[Pjturbo]

This thread proves that old saying,"Half the population is below average."

Phil

 

[kansas transit]

i think Kari is HOT





clearly this is not a thread hijack because it is about mythbusters

AGREED 100%

 

[Scythian]

A jet engine generates thrust, but it doesnt move any air over the wings. Thus, no airspeed. A treadmill will NOT affect thrust, but it will offset the fact that the thrust would move the airplane forward, generating the lift required to make the airplane fly. If the jet engines could generate enough thrust to overcome gravity without the added help of lift, then the airplane would take off.
So take a small aircraft, and put really powerful engines on it (basically a rocket), it will work. Otherwise, it wont happen on any airplanes I know of.

How would a treadmill offset the thrust moving the aircraft forward? The aircraft isn't teathered....

 

[FJRay]

I love the video of the Cub doing the short take off. That guy is a well driller that lived across the road from me in Wash. and that is the way he takes off every day. I used to enjoy the private air shows every summer.

 

[Fred W]

How would a treadmill offset the thrust moving the aircraft forward? The aircraft isn't teathered....

It wouldn't.

That is the assumption that is being made here that blows this whole myth apart.

Running a treadmill forward or backward under the plane would not effect the plane's speed through the air. Relative ground speed doesn't matter.

Put it this way, as you bring the engine thrust up and the plane begins to move forward, running the conveyor belt in the direction of travel at the same speed would result in the wheels not turning, but the plane would still be traveling at the same speed through the air. Like wise, running the conveyor backwards would result in the wheels spinning twice the "normal" speed, but the plane speed through the air would be the same..

 

[Scythian]

How would a treadmill offset the thrust moving the aircraft forward? The aircraft isn't teathered....

It wouldn't.

That is the assumption that is being made here that blows this whole myth apart.

Running a treadmill forward or backward under the plane would not effect the plane's speed through the air. Relative ground speed doesn't matter.

Put it this way, as you bring the engine thrust up and the plane begins to move forward, running the conveyor belt in the direction of travel at the same speed would result in the wheels not turning, but the plane would still be traveling at the same speed through the air. Like wise, running the conveyor backwards would result in the wheels spinning twice the "normal" speed, but the plane speed through the air would be the same..

'zackly....

 

[xviper]

...So, You are stuck in a room with no windows and no doors.

There is a hole in the floor about a foot deep and just barely wider than the diameter of a table tennis ball. There is a table tennis ball at the bottom of the hole.

You have a fork, a wrench, and a long, thin plastic wire.

How do you get the ball out of the hole without damaging anything?

That's to easy, you piss in the hole untill the tennis ball floats to the top, no tools needed, well i guess some people call it there TOOL. Just gotta think outside the box. Stan

Brilliant! This must assume that you've not just peed and you've got enough piss to fill the hole (which he should have stated was a water tight tube). The fork, wrench and the wire was a decoy, unless you consider that the pee is damaging to the tube.

Another possibility (if there was a hole at the bottom of the tube to let air in) is to blow across the top of the tube (or hole as he called it). Bernoulli's principle would come into effect and pull the ball up the shaft of the tube. If you had enough breath, the ball would pop up above the hole and you grab it (or just blow it away). Again, the tools are a decoy.

 

[kansas transit]

...So, You are stuck in a room with no windows and no doors.

There is a hole in the floor about a foot deep and just barely wider than the diameter of a table tennis ball. There is a table tennis ball at the bottom of the hole.

You have a fork, a wrench, and a long, thin plastic wire.

How do you get the ball out of the hole without damaging anything?

That's to easy, you piss in the hole untill the tennis ball floats to the top, no tools needed, well i guess some people call it there TOOL. Just gotta think outside the box. Stan

Brilliant! This must assume that you've not just peed and you've got enough piss to fill the hole (which he should have stated was a water tight tube). The fork, wrench and the wire was a decoy, unless you consider that the pee is damaging to the tube.

Another possibility (if there was a hole at the bottom of the tube to let air in) is to blow across the top of the tube (or hole as he called it). Bernoulli's principle would come into effect and pull the ball up the shaft of the tube. If you had enough breath, the ball would pop up above the hole and you grab it (or just blow it away). Again, the tools are a decoy.

I used to know this young lady that could, ah err, never mind. Stan.

 

[xviper]

I used to know this young lady that could, ah err, never mind. Stan.

Mitzy Dupris ........................... She could smoke a cigarette .................................... oops, same as you, never mind.

 

[ionbeam]

...So, You are stuck in a room with no windows and no doors. There is a hole...get the ball out of the hole...

I don’t know how FJRottie got himself into this situation (see this post) I’ve PMed him a solution, I’m guessing that he is out trying it right now. Hopefully he can get his balls back.

 

[Scab]

This thread proves that old saying,"Half the population is below average."
Phil

That sounds a bit optimistic.

 

[tinpusher]

I believe the theory is that if the treadmill is driven so that the wheel speed matches the airspeed at which the thrust would be driving the aircraft, the effective groundspeed would be zero and thus the aircraft would be relying solely on the thrust produced by the engine(s).
There qre some very powerful military aircraft that might be able to fly relying completely on the thrust produced by the engines, but....

So what do planes use to "fly" other than thrust produced by the engines? (which provides velocity to the airframe which causes the wings to create lift)

How could a ski-plane take off on snow if an airplane needs wheels driving it?

Right, the assumtion in the original question is that the treadmill will offset any forward movement, which in reality it wont. The airplane will simply drive off the treadmill (if there is enough friction), or nose dive into the ground (in a near frictionless environment).

The original question assumes incorrectly that the treadmill would offset any forward movement, and in that case the only way it would take off is if the thrust vs. weight ratio were great enough.

Assumptions.....thats where this thread took a nose dive......

 

[xviper]

and in that case the only way it would take off is if the thrust vs. weight ratio were great enough.

ONLY if that thrust was vectored downward. In the case of the treadmill, the thrust is vectored horizontally. The whole purpose of the treadmill is to prevent forward movement of the plane through space. Thrust vs. weight ratio is only relevant if the plane is pointed upwards (or thrust downwards) to any degree. If the plane was pointed at 90 degrees to horizontal (ie, nose of plane straight up, thrust straight down) then if thrust equals mass of the plane, the plane would then weigh ZERO at that moment. Add one more pound of thrust and the plane will rise. If the plane is pointed at anything less than 90 degrees, Then by vector calculations, it would take much more thrust than the weight of the plane to make it rise. When thrust is horizontal to the pull of gravity, it can be infinite. The plane will not rise so long as the treadmill can keep up. When it can't keep up, the plane will move forward relative to the ground, airspeed will increase to the point where it will allow the wings to produce lift. Once the treadmill can no longer keep, the parameters of the experiment just changed.

Vectoring always involves 2 components - vertical and horizontal. When thrust is completely horizontal, the vertical component is ZERO (ie, no lift from thrust). In this case, the plane must rely upon horizontal movement through air so that Bernoulli can do his magic.

We, as motorcyclists deal with vectoring all the time, but we deal with it on different plane (no pun intended). When we lean into a turn, 2 component vectors are always at work - one is gravity acting vertically on the weight of the bike (and rider), the other is centrifugal force acting to push the bike to the outside of the turn. If we didn't have gravity, we would slide out of the turn. If we didn't have centrifugal force, we would be able to lean.

Did some of you guys fall asleep during physics class?

 

[Fred W]

The whole purpose of the treadmill is to prevent forward movement of the plane through space.

Please explain how the treadmill will prevent forward movement of any plane.

Did some of you guys fall asleep during physics class?

Apparently some of you did.

 

[tinpusher]

The whole purpose of the treadmill is to prevent forward movement of the plane through space.

Please explain how the treadmill will prevent forward movement of any plane.

Did some of you guys fall asleep during physics class?

Apparently some of you did.

It wont, but the original question assumes it would stop forward movement (otherwise there would be no point to having the treadmill). In reality, it would drive off the treadmill, or nose dive into the ground.

 

[xviper]

The whole purpose of the treadmill is to prevent forward movement of the plane through space.

Please explain how the treadmill will prevent forward movement of any plane.

Did some of you guys fall asleep during physics class?

Apparently some of you did.

As you apply thrust (either by propeller or by jet or rocket or fairy wings), the plane will begin to move forward. This forward movement is negated when you run the treadmill. The treadmill serves to keep the plane in the same position relative to the ground the treadmill is bolted to. The more thrust, the faster the treadmill runs. This is how the treadmill prevents the forward movement of the plane. The plane is NOT moving. The treadmill under it, is.

Certainly, you've run on an excercise treadmill? How are you able to NOT run into the front part of the treadmill? Answer: The treadmill is operating. You can maintain your position even if you run faster by simply making the treadmill operate faster. Thus, the treadmill is preventing your forward movement. YOU, are not moving forward. The treadmill under you is moving backwards. You can run as fast as you like. As long as you keep the treadmill operating at the same rate as you're running, you will go NOWHERE.

Nope, I was wide awake during physics class and I paid attention. Besides, "vectoring" was a whole other parameter that was being introduced into this discussion - a parameter that wasn't intended in the airplane on a conveyer belt experiment. It was the topic of vectors that I was relating to physics and staying awake for.

So, when is this episode of Mythbusters? I checked the programming for Mythbusters and I didn't see an episode that dealt with this topic.

 

[Fred W]

The whole purpose of the treadmill is to prevent forward movement of the plane through space.

Please explain how the treadmill will prevent forward movement of any plane.

Did some of you guys fall asleep during physics class?

Apparently some of you did.

As you apply thrust (either by propeller or by jet or rocket or fairy wings), the plane will begin to move forward. This forward movement is negated when you run the treadmill. The treadmill serves to keep the plane in the same position relative to the ground the treadmill is bolted to. The more thrust, the faster the treadmill runs. This is how the treadmill prevents the forward movement of the plane. The plane is NOT moving. The treadmill under it, is.

Certainly, you've run on an excercise treadmill? How are you able to NOT run into the front part of the treadmill? Answer: The treadmill is operating. You can maintain your position even if you run faster by simply making the treadmill operate faster. Thus, the treadmill is preventing your forward movement. YOU, are not moving forward. The treadmill under you is moving backwards. You can run as fast as you like. As long as you keep the treadmill operating at the same rate as you're running, you will go NOWHERE.

Nope, I was wide awake during physics class and I paid attention. Besides, "vectoring" was a whole other parameter that was being introduced into this discussion - a parameter that wasn't intended in the airplane on a conveyer belt experiment. It was the topic of vectors that I was relating to physics and staying awake for.

So, when is this episode of Mythbusters? I checked the programming for Mythbusters and I didn't see an episode that dealt with this topic.

Wrong. You are using the example of the running man and it's a bad example. A running man develops forward thrust from pusjing off against the treadmills belt. A plane, whether Jet drive or Prop drive, develops forward thrust by pushing against the air. Actually in a Jet is the displacement of air, but that is the same thing for our purposes. Therefore a conveyor belt will not have any effect on the thrust or the forward movement of the plane.

Oh, sorry, you are right, this has nothing to do with vectoring.

I think this Mythbusters is on tonight at 9PM

 

[tinpusher]

The whole purpose of the treadmill is to prevent forward movement of the plane through space.

Please explain how the treadmill will prevent forward movement of any plane.

Did some of you guys fall asleep during physics class?

Apparently some of you did.

As you apply thrust (either by propeller or by jet or rocket or fairy wings), the plane will begin to move forward. This forward movement is negated when you run the treadmill. The treadmill serves to keep the plane in the same position relative to the ground the treadmill is bolted to. The more thrust, the faster the treadmill runs. This is how the treadmill prevents the forward movement of the plane. The plane is NOT moving. The treadmill under it, is.

Certainly, you've run on an excercise treadmill? How are you able to NOT run into the front part of the treadmill? Answer: The treadmill is operating. You can maintain your position even if you run faster by simply making the treadmill operate faster. Thus, the treadmill is preventing your forward movement. YOU, are not moving forward. The treadmill under you is moving backwards. You can run as fast as you like. As long as you keep the treadmill operating at the same rate as you're running, you will go NOWHERE.

Nope, I was wide awake during physics class and I paid attention. Besides, "vectoring" was a whole other parameter that was being introduced into this discussion - a parameter that wasn't intended in the airplane on a conveyer belt experiment. It was the topic of vectors that I was relating to physics and staying awake for.

So, when is this episode of Mythbusters? I checked the programming for Mythbusters and I didn't see an episode that dealt with this topic.

I believe it's on tonight at 9p Central time.

Your "running on the tread mill" comparison is wrong. As stated earlier in this thread its not the wheels of the airplane pushing on the ground thats creating the forward movement (like our feet do, or a motorcycle). It's the pushing by thrust. The only thing the wheels are for is to reduce the friction with the ground, so the airplane can achieve enough velocity to achieve lift (a plane can not depart off a concrete runway, on its belly, too much friction).

 

[xviper]

It wont, but the original question assumes it would stop forward movement (otherwise there would be no point to having the treadmill). In reality, it would drive off the treadmill, or nose dive into the ground.

EXACTLY! Thank you!

If the plane is allowed to make forward motion, there is absolutely no point to this whole excercise.

Let's say a plane needs 60 mph to lift off. Put it on a treadmill running at 60 mph, with the propulsion system keeping up with that treadmill. Do you actually think that plane will lift off? It won't. There isn't 60 mph worth of AIR going over it's lifting surfaces (wings) to make the plane weightless. It will still need 60 mph of AIRspeed before it will fly. On a 60 mph treadmill, the AIRspeed is still ZERO. Therefore, NO lift. It would require the equivalence of 120 mph RELATIVE to the treadmill, thus RELATIVE to the ground the treadmill is bolted to, in order to get 60 mph of AIRspeed to take off. If a typical airplane that lifts off at 60 mph airspeed requires (and I'm guessing here) 300 feet of stationary runway to take off (no natural winds), on a treadmill operating at 60 mph, it would need that treadmill to be 300 feet. There goes the idea of building a bunch of giant treadmills at airports so you can get rid of runways.

 

[FJRottie]

Yes, piss in the hole is right and the ball will float to the top.

As far as the airplane on a conveyor goes, this is a mythbuster experiment to see if people really will tune into a certain TV program after much blabbering on the Intardnet about it.