plane on a conveyor belt?

[Golfer]

"If I understood their madness then I would be insane too."

I said that 5 years ago and I think it clearly still applies.

[lukster]

Originally posted by Golfer
"If I understood their madness then I would be insane too."

I said that 5 years ago and I think it clearly still applies.

The force that causes the wheels to move in the direction the belt moves is the same force that will counter the planes thrust. The faster the belt increases speed, the more force applied.

I think some of you are just yanking our chain.

[moot]

It's only a matter of time for someone to build a model of sufficient scale..

[SteveBailey]

If the plane does not slow, the wheel will then be sped up to 2 RPS

Well according to you the plane does slow.  If the plane slows, this allows the conveyer to catch up to the wheels, thus no longer accelerating.  If the plans slows to a stop, as you claim, then the wheels are no longer going forward so there is no speed in the wheels for the conveyer to match. Since the conveyer has now caught up, and the plane is slowing to stop, the wheels will slow down.  Now the conveyer has to match the wheels, so the conveyer stops too.

Thus, according to you, the wheels will not be moving, the conveyer will not be moving, and the airplane will somehow be not moving even though it is at full throttle.

[Wes14]

Originally posted by SteveBailey
Well according to you the plane does slow.  If the plane slows, this allows the conveyer to catch up to the wheels, thus no longer accelerating.  If the plans slows to a stop, as you claim, then the wheels are no longer going forward so there is no speed in the wheels for the conveyer to match. Since the conveyer has now caught up, and the plane is slowing to stop, the wheels will slow down.  Now the conveyer has to match the wheels, so the conveyer stops too.

Thus, according to you, the wheels will not be moving, the conveyer will not be moving, and the airplane will somehow be not moving even though it is at full throttle.

 and pigs fly too? (no offense cops)

[lukster]

Originally posted by SteveBailey
Well according to you the plane does slow.  If the plane slows, this allows the conveyer to catch up to the wheels, thus no longer accelerating.  If the plans slows to a stop, as you claim, then the wheels are no longer going forward so there is no speed in the wheels for the conveyer to match. Since the conveyer has now caught up, and the plane is slowing to stop, the wheels will slow down.  Now the conveyer has to match the wheels, so the conveyer stops too.

Thus, according to you, the wheels will not be moving, the conveyer will not be moving, and the airplane will somehow be not moving even though it is at full throttle.

You think it's not possible for the engine to be at full power without rolling the wheels forward? Try tying together two planes facing opposite directions. Anywhere is fine but tie their axles together and you will most closely simulate the force being applied by an accelerating belt. If both planes are identical neither will move with engines at full power.

That's just one aspect of the problem. We can't go forward until you agree with this.

[lukster]

I think I can see what your having trouble with Steve. Remember, we are talking about a belt capable of accelerating (or decelerating) at tremendous speeds. A belt like that could be capable of producing 10,000 pounds of force in a millisecond if we define it's acceleration capabilty that high. The plane's engine moves the plane a millimeter and almost instantly the the belt is moving at thousands of miles per hour. This might result in the plane then moving backwards which causes the belt to slow possibly to a stop. Soon as our tiny slice of time advances the engines force is rexerted and the plane moves forward another millimeter, wham, there's the belt moving it back again.

To the uncalibrated eye it would appear the wheel is stationary while the engine is running full bore.


Thinking more on it the wheel could never stop, it would always spin forward but the plane could start and stop it's forward progress though that would depend on the response time (acceleration factor) of the belt. It's easy to get the two issues confused as I did there for a moment. You induced it though.

[WhiteHawk]

Originally posted by SteveBailey


Whitehawk, what happens to the plane... does it move at all?

Sure, the only way the plane would not move would be if the drag factor of the wheels between the plane and the conveyor is 100%.  Or if the plane were fixed to the conveyor.

[WhiteHawk]

Originally posted by APDrone
Then if it never moves at all, the plane still doesn't fly.

The question states the wheel speed is matched.. Assumingly instantly.  How it does that is not really part of the question. It just happens. That's the aggravating aspect to the whole question because we know that physics ( as we know it ) wont let that happen after the tolerance for heat, matter, friction, .. etc are exceeded.  

So then it dives into an argument about when is the thrust applied to when and where and by how much.

Which is not part of the question.

Bottom line, again, is that if wheel speed is matched by a counter speed which leaves the net speed being zero, then necessary airspeed is never achieved and flight is not attained.

Plane doesn't fly.

Period.

End of sentence.

End of argument.

That would be true, if the vessel were wheel driven.   a Race car on an ice slick covered in baby oil would have trouble making any headway.   A jet car would not.

[lukster]

Originally posted by WhiteHawk
Sure, the only way the plane would not move would be if the drag factor of the wheels between the plane and the conveyor is 100%.  Or if the plane were fixed to the conveyor.

Well you bring in an interesting consideration, static friction vs kinetic though it's not all that influential in this scenario. When a plane is stationary and it's wheels are not spinning the friction between the tire and ground is greater than when the tire is moving. A plane that locks it brakes and applies full power is less likely to influence the motion of the plane than say a plane that is moving with full power and locks it's wheels. However, in neither case can a plane's engine accelerate the plane with the tires skidding.

You have to see that our belt can accelerate so fast that the tire cannot spin fast enough to keep up and so will skid.

[Golfer]

Lukster I hate to even try to wrap my head around and come to an agreement with you about anything on this subject matter but...

You do understand that how fast an airplane wheel is spinning has no bearing on how it's being propelled through the fluid (Air) by its own producer of thrust, whether that be propeller or jet engine?

You also keep going back to eskimo's videos and your agruments ARE valid if the vehicle atop the conveyor was being driven by the wheels.  Airplanes are not driven in any way shape or form by their wheels as is a motorcycle, car or bicycle.  Eskimos videos are not representitive of this instance because the sander is the bit applying the force to the little wheels.  You're looking at a reaction which doesn't exist in the pemise of the question.  The whole question goes back to wheel speed and wheel speed alone.  In order to have any wheel speed the aircraft, producing at least breakaway thrust, has to move.  Once the aircraft starts moving (propelling itself through its fluid, in this case...air) it's not stopping because the covneyor is acting upon the wheels...because that has no bearing on what causes the airplane to move.


What would happen in this case...

You have a conveyor built into a swimming pool.  You sink a cart into our pool placing it atop the cart.  Fix a boat to the cart anchoring it solidly.



Same deal...the wheel speed of the cart is sensed by the treadmill and immediately and equally opposes the wheel speed by matching it exactly and instantly.  Because the boats thrust comes from propelling itself through a fluid (in this case...water as opposed to air) I ask you the same question...what happens with the boat?  I submit to you that it will move regardless of force applied by the conveyor.

If you agree with this then please tell me WHAT THE HECK IS THE DIFFERENCE!!!!!!

[lukster]

You might even suppose that you have a plane with tremedous thrust capable of accelerating even as the tires are being ground to nothing. I simply increase the belt speed to chew up your landing gear and plane itself. You could define a friction coefficient to the tires  so low that a high powered engine could still accelerate against a belt approaching light speed but then the black hole will hold you in place.

There is no escape, Buhahahahahaa!!!!

[Golfer]

You're allowed to agree that it will fly, lukster.  It's not too late for that.

[WhiteHawk]

Originally posted by APDrone
At your request to 'heed our discussion', I will continue.





You're probably right in that there may be some actual initial movement,  then the conveyor would match the rotational speed and it would bring net movement back to 0. It really depends on the tolerances of the equipment used. With laser scanning and such, it could even be down to a billionth of an inch. The wheel would still be spinning and constantly accelerating, but this speed, whatever it is at a given time is matched, as stated.  Any additional acceleration would be starting with 0 net speed.  

I think I see where you're going with this.. in that, eventually, the aircraft may inch its way across the conveyor and eventually be liberated from it... at which point the normal physics kick in and it takes off normally..

Unless it is in AH's world and hits the customary tree or hill at the end of the runway.

oops

[lukster]

Golfer, no need to complicate the issue with a boat. Eskimo's first video with the belt grinder demonstrated that there is a force applied to the free spinning wheel in the direction of the belt motion. Watch it and explain to me or yourself why the object moves and then returns to it's original position. Then let's talk.