Topic: Can this airplane lift off?

[bunghole]

I like pie.

What kind of pie?

I personally like a nice pecan pie.  There are many types of pies.  You have the pecan pie, the apple pie, peach pie (or cobbler), lemon meringue, coconut cream pie, lemon pie (of the non meringe variety), raspberry pie, rhubarb pie (delightful when done properly), key lime pie, mud pie, cherry pie, blueberry pie, etc.

I've found that the quality of a pie is about 75% crust.  Without a nice flaky crust, any filling is going to fall flat.

From Wikipedia:

A pie is a baked dish which is usually made of a pastry dough shell that covers or completely contains a filling of various sweet or savoury ingredients. Pies can be either "filled", where a dish is covered by pastry and the filling is placed on top of that, "top-crust," where the filling is placed in a dish and covered with a pastry/potato mash top before baking, or "two-crust," with the filling completely enclosed in the pastry shell. Pies can be a variety of sizes, ranging from bite-size to ones designed for multiple servings.

Reference to “pyes” as food items appeared in England (in a Latin context) as early as the 12th Century, but no unequivocal reference to the item with which the article is concerned is attested in the Oxford English Dictionary until the 14th century (Oxford English Dictionary sb pie).

Anyhoo...

[mystic_1]

"accelerates toward infinity as it tries to keep up with the wheels"


You keep saying this.  Why would the conveyor accelerate to infinity?

If the aircraft's ground speed is 50mph, the conveyor's speed is 50mph in the opposite direction.

Aircraft accelerates to 60mph.  Conveyor accelerates to match.  60mph.

Where do you see infinity?

mystic_1

[mlinder]

"accelerates toward infinity as it tries to keep up with the wheels"


You keep saying this.  Why would the conveyor accelerate to infinity?

If the aircraft's ground speed is 50mph, the conveyor's speed is 50mph in the opposite direction.

Aircraft accelerates to 60mph.  Conveyor accelerates to match.  60mph.

Where do you see infinity?

mystic_1

Again, even this does not matter, unless we know the friction of the bearings. Only the friction of the bearings is what causes the conveyor belt to have any effect on the motion of the plane.

[masonryman]

rhubarb pies are not even good unless they are a mix, strawberry rhubarb, excellent mix of sweet and tart. I also feel I must point out the slight that must be felt by the sugercream pie for not being mentioned.

Mark

[bunghole]

rhubarb pies are not even good unless they are a mix, strawberry rhubarb, excellent mix of sweet and tart. I also feel I must point out the slight that must be felt by the sugercream pie for not being mentioned.

Mark

I can't say I've ever even heard of such a pie.  More information please.  It sounds delightful!

[sangyo soichiro]

"accelerates toward infinity as it tries to keep up with the wheels"


You keep saying this.  Why would the conveyor accelerate to infinity?

If the aircraft's ground speed is 50mph, the conveyor's speed is 50mph in the opposite direction.

Aircraft accelerates to 60mph.  Conveyor accelerates to match.  60mph.

Where do you see infinity?

mystic_1

Because this is important to the understanding of where infinity comes from, I'm going to label it in a bold font.

How the runaway-conveyor scenario works:

Setup 1:
Imagine the conveyor adjusts itself to the speed of the plane relative to the ground.  This is the scenario where the wheels rotate at twice their normal speed.

Setup 2:
Imagine the conveyor adjusts itself to the speed mentioned above in setup 1 plus the reading on the plane's speedometer (which measures the speed relative to the conveyor itself).  In this case, the conveyor quickly speeds up to infinity.


Anyway, that's where infinity comes from.

[masonryman]

rhubarb pies are not even good unless they are a mix, strawberry rhubarb, excellent mix of sweet and tart. I also feel I must point out the slight that must be felt by the sugercream pie for not being mentioned.

Mark

I can't say I've ever even heard of such a pie.  More information please.  It sounds delightful!

  I think it might be a midwest/southern thing

[mlinder]

"accelerates toward infinity as it tries to keep up with the wheels"


You keep saying this.  Why would the conveyor accelerate to infinity?

If the aircraft's ground speed is 50mph, the conveyor's speed is 50mph in the opposite direction.

Aircraft accelerates to 60mph.  Conveyor accelerates to match.  60mph.

Where do you see infinity?

mystic_1

Because this is important to the understanding of where infinity comes from, I'm going to label it in a bold font.

How the runaway-conveyor scenario works:

Setup 1:
Imagine the conveyor adjusts itself to the speed of the plane relative to the ground.  This is the scenario where the wheels rotate at twice their normal speed.

Setup 2:
Imagine the conveyor adjusts itself to the speed mentioned above in setup 1 plus the reading on the plane's speedometer (which measures the speed relative to the conveyor itself).  In this case, the conveyor quickly speeds up to infinity.


Anyway, that's where infinity comes from.

Again, simply doesn't matter. The only eefect the conveyor belt has on movement of the plane is speed of conveyor belt through the friction of the wheel bearings. Frictionless, no movement. You want movement, we gotta have bearing friction.

[masonryman]

infinity; is there really such a thing, every thing has a limit and when it finds it, it ether stops or explodes.


nothing last or goes forever

[alltherightpills]

rhubarb pies are not even good unless they are a mix, strawberry rhubarb, excellent mix of sweet and tart. I also feel I must point out the slight that must be felt by the sugercream pie for not being mentioned.

Mark

I can't say I've ever even heard of such a pie.  More information please.  It sounds delightful!

[mlinder]

infinity; is there really such a thing, every thing has a limit and when it finds it, it ether stops or explodes.


nothing last or goes forever

We're talking theoretical, here. The values ∞ and 0 for 'f' can be used in theoretical physics.

[masonryman]

OK there it has been said, we are talking theory and in theory the prop can move enough atmosphere  to create enough lift for the plane to take off with out actually moving forward.

[mlinder]

OK there it has been said, we are talking theory and in theory the prop can move enough atmosphere  to create enough lift for the plane to take off with out actually moving forward.

Not if the prop doesnt pass air over the entire (or at least most of the) wing surface. And what prevents the plane from moving forward due to the props?

[masonryman]

well, according to some, the overwhelming friction in the wheel bearings

[mlinder]

If that were the case, as soon as the plane lifted statically, that resistance would disappear. The plane would then move forward.
This is kind of a moot point, however, since we don't know what the friction of the bearings are, and that friction is the only thing that matters in this question.

[masonryman]

I voted yes

[mlinder]

If the conveyor reaches ∞, then the bearing friction will reach ∞. Assuming that friction ≠ 0.

If the friction of the bearings is greater than the speed the props can pull the plane forward, the plane will end up going backwards.
If the friction of the bearings is less than the speed the props can pull the plane forward, it will move forward.
If the friction matches the speed the props can pull the plane forward, it will stay stationary.
If there were such a thing as -f, just running the conveyor belt would push the plane forward (kidding, actually, it would just cause the bearings to cool below ambient, far as I can tell.)

If there is no friction in the bearings, the plane wont move at all as the conveyor belt moves, while the plane is not 'on'. The wheels themselves will turn, but nothing else will move. Once the plane starts it's engines, it will move forward as if there were not a conveyor belt at all.
See why knowing the friction of the bearings is all important here?

[masonryman]

The plane could never move backwards if the conveyor only matched the speed of the wheels, as friction built and the wheels began to seize and slow the belt would slow as well. The motor would continue to pull at full force, the wheels would Begin to slide or lock up causing the plane to nose over and kill the engine.

What about humidity, it also plays a large part in the performance of many functions

[mystic_1]

Imagine the conveyor adjusts itself to the speed mentioned above in setup 1 plus the reading on the plane's speedometer (which measures the speed relative to the conveyor itself).

I didn't see where this new condition was stated before this post.  I checked back through several pages of the thread just to make sure.

mystic_1

[mlinder]

If the conveyor belt was designed to match in the opposite direction, and friction were in fact an issue, friction would reach ∞, and at that same instant, the conveyor belt would reach 0.
This is a a study not of the airplane engines power vs. the speed of the conveyor, this is a study of the airplane engines power vs wheel bearing friction.
Again, with no friction, plane would take off fine, regardless of whether the belt was at ∞ or not. Just wouldn't matter.

[mlinder]

We know only one of three variables needed to find out if a given plane can take off in this scenario.

The only one we know is maximum speed of conveyor belt. Thats ∞
We need: Airspeed required for take-off of this particular plane.
and: FRICTION OF WHEEL BEARING.
Again, if it's 0, it'll take off.
However, if the conveyor belt can reach ∞, and matches perfectly the relative speed of the airplane, it will never take off.

[Markcb750]

No friction or a small reasonable amount, as wheels and bearings provide.  

[mlinder]

No friction or a small reasonable amount, as wheels and bearings provide.  

No friction means the conveyor belt doesnt even have an effect on the plane. At all.
What is a reasonable amount?
And factually, even the 'tiniest' amount multiplied by ∞ is still ∞.
Are we saying the bearing has a static amount of friction? Meaning, no matter what the speed of the wheel turning, there is the same amount of friction?
At the end of the day, it doesn't matter. If the plane cannot move faster than the conveyor belt, due to bearing friction, it will never take off.

(of course, relatively speaking, with a speed of infinite, the conveyor belt would be infinitely large... so... no real need to go anywhere, cause, you know, you're everywhere already)

[masonryman]

Well the wheel bearing is obviously going to reach critical mass before the tread mill finds infinity (and where is the mobius strip on the keyboard) but who said that was the center of the question, I would be very interested in the amount of lift being created and how that lift affects your friction problem and how much it would raise the point of critical mass for the bearings in question

[masonryman]

We are not even discussing the point that most interest me. I have seen planes take off in a very short distance and I belive that distance is more about the time it take the engine/propellor to reach enough RPM to produce enough trust to lift the plane, I know in standard flight it is all about foward motion and lift but take off is not standard flight.

 I have seen many planes fly vertical and in that situation the lift is drag and is actualy hurting it's performance.