Airplane on a converter belt question.

[BCPVP]

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Since the plane is attached to the wheels, for ever little increment the plane tries to move forward, the conveyor belt will speed up and pull it back, assuming the tires don’t skid.

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Are you just [censored] with me?

The tires spin against the belt, having no effect on the movement of the rest of the plane. This is so elementary I'm having a hard time believing that you don't get it.

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There was a monster thread on this (I think in OOT) and there were many people who couldn't get over the fact that the wheels aren't driving the plane forward.

[Sharkey]

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The tires spin against the belt, having no effect on the movement of the rest of the plane.

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In the ideal case, the inertia of the plane is independent of what the wheels are doing, but if there’s the least friction in the whole ensemble, the conveyor belt will simply speed up however much is necessary to counteract the thrust of the engines.

[CORed]

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The wheels spin on an axle with very low friction (much lower than the tires against the belt). Thus, the tires spin with [are driven by] the belt, in either direction, at any speed, but the plane is still pulled forward by the engines.

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Of course, if the conveyor belt moves sufficiently fast, either the tires will overheat and blow out, the wheel bearings will burn out or the wheels thenselves will fly apart from centrifugal force, or sufficient frictional forces will be developed to slow the plane down. Of course, similar engineering consideratios will limit the maximum speed atainable by the conveyor belt.

[MidGe]

Once more,

For take-off only the relative airspeed is relevant. The undercarriage plays no role. Given a sufficiently strong head wind a small plane can take off with its wheel brakes locked and thus zero ground speed.

[Sharkey]

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Of course, if the conveyor belt moves sufficiently fast, either the tires will overheat and blow out, the wheel bearings will burn out or the wheels thenselves will fly apart from centrifugal force, or sufficient frictional forces will be developed to slow the plane down. Of course, similar engineering consideratios will limit the maximum speed atainable by the conveyor belt.

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Since none of the component specs are in evidence, that is an irrelevant argument.

[Sharkey]

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Once more,

For take-off only the relative airspeed is relevant. The undercarriage plays no role. Given a sufficiently strong head wind a small plane can take off with its wheel brakes locked and thus zero ground speed.

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The plane will never attain sufficient air speed because its acceleration is being reduced by friction with the conveyer belt.

[purnell]

From the OP:
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However, the plane is on a converter belt which is rigged to move/spin in the opposite direction of the plane at the exact speed of the wheels.

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BTW, WTF is a converter belt? It sounds suspiciously like something that might have been used during one of the inquisitions, in which case the whole discussion is moot. [img]/images/graemlins/crazy.gif[/img]

[CORed]

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Once more,

For take-off only the relative airspeed is relevant. The undercarriage plays no role. Given a sufficiently strong head wind a small plane can take off with its wheel brakes locked and thus zero ground speed.

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I'm not disputing that. I'm only pointing out that a backward moving conveyor belt does generate some frictional force on the wheels of the plane, which will increase with the speed of the conveyor belt, and the wheels of the plane cannot turn infinitely fast. Now, I'll admit that the conveyer belt would have to move bacwards at an undgodly speed to overcome the thrust of the jet engines. Actually, the whole excercise is pretty silly, because the notion of a conveyor belt that can increase it's speed instantaneously to match the forward speed of the plane is physically impossible. The conveyor belt has mass and therefore inertia, and it takes a force acting over time to accelerate it. The conveyor belt also presumably has a tnsile strength and that limits the rate of acceleration, because if the force accelerating it excedds its tensile strength the belt will break. As a practical matter, I don't think you could build a conveyor belt that could accelerate backwards fast enough to prevent a plane from taking off, or even come close to doing so, assuming anybody was foolish enough and had enough money to waste to try.

[Sharkey]

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From the OP:
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However, the plane is on a converter belt which is rigged to move/spin in the opposite direction of the plane at the exact speed of the wheels.

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BTW, WTF is a converter belt? It sounds suspiciously like something that might have been used during one of the inquisitions, in which case the whole discussion is moot. [img]/images/graemlins/crazy.gif[/img]

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Of course. The wheels and the conveyor belt have to move at the same speed under all circumstances, given that there’s no skidding. What about it?

A converter belt is like a girdle, I think.

[purnell]

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From the OP:
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However, the plane is on a converter belt which is rigged to move/spin in the opposite direction of the plane at the exact speed of the wheels.

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BTW, WTF is a converter belt? It sounds suspiciously like something that might have been used during one of the inquisitions, in which case the whole discussion is moot. [img]/images/graemlins/crazy.gif[/img]

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Of course. The wheels and the conveyor belt have to move at the same speed under all circumstances, given that there’s no skidding. What about it?

A converter belt is like a girdle, I think.

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The "What of it" is that if the belt is rigged to run at the same speed as the wheels [linear speed of a point on the belt equal to the instantaneous linear speed of a point on the perimeter of the tire], the belt never reaches a speed at which it will have a significant effect on the speed of the plane. [img]/images/graemlins/tongue.gif[/img]