Author Topic: plane on a conveyor belt? (Read 26190 times)

john9001 · « **Reply #150 on:** January 21, 2007, 05:50:20 PM »

if your conveyor belt can move at infinite speed, then my airplane wheels have no drag, no matter how fast your belt moves my wheels will keep up , but the thrust from my engines will still push the airplane forward.

the wheels will have no effect. Freewheeling.

what if your belt was covered with ice?

lukster · « **Reply #151 on:** January 21, 2007, 05:53:09 PM »

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Originally posted by john9001
if your conveyor belt can move at infinite speed, then my airplane wheels have no drag, no matter how fast your belt moves my wheels will keep up , but the thrust from my engines will still push the airplane forward.

the wheels will have no effect. Freewheeling.

what if your belt was covered with ice?

What about the black hole created by the infinite speed belt? It'll suck the universe into it and we'll all die, very slowly.

JB88 · « **Reply #152 on:** January 21, 2007, 05:58:48 PM »

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Originally posted by lukster
What about the black hole created by the infinite speed belt? It'll suck the universe into it and we'll all die, very slowly.

thank god. this is starting to get painful.

Mini D · « **Reply #153 on:** January 21, 2007, 06:01:31 PM »

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Originally posted by eskimo2
For such a system to work, it would have to function like an automobile cruise control. If the plane moves forward an inch the conveyor speeds up faster and faster until the plane moves back to its original position. If the plane falls back an inch, the system backs off a bit.

No.. it wouldn't work like that at all. It couldn't work like that. How would you back the plane up by moving at the same speed as the wheel? Fundamentally, this perfect system would have to know exactly how fast the wheel is turning and react to it instantly (0 seconds..). This perfect system would have to function with an imperfect wheel to generate the friction.

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If this system could accelerate the rotation of the wheels beyond anything realistic (they hold together and don’t overheat, etc.) then the system could prevent the plane from moving forward purely by the energy being loaded into the wheels.

The system would not accelerate the wheels. It cannot. The motion of the plane is the only thing that can accelerate the wheels. That is the premise of it "reacting".

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Try this: Clamp your belt sander onto a table upside down, perfectly level, and turn it on. Now drop a ball or wheel onto the belt. Watch what happens. Read my post above; hitech gets it. I wouldn’t be surprised if no one else does.

That is not the same scenario at all. You are generating the engergy and propulsion with the belt. In the scenario described, the belt is reacting to motion not causing it. Once again, the reactionary state would make it incapable of stoping the forward momentum of the aircraft in a frictionaless wheelbearing scenario.

The inertia on the tire is generated by the motion of the aircraft, not by the belt.

Fundamentally, the belt would never see the tire move. since the tire is not being driven. It would actually feel a reverse thrust caused by the friction of the wheel and spin the opposite direction.

eskimo2 · « **Reply #154 on:** January 21, 2007, 06:05:44 PM »

I’d like to be the first to apologize to APDrone. Although he didn’t explain how the conveyor could keep the plane from moving forward, he was right. If the conveyor prevents the plane from moving forward, it won’t fly.

If such a system were real, it would literally explode in a second or two. If it had infinite strength and power and the aircraft wheels and bearings didn’t create heat and also had infinite strength, however, it would work.

Debonair · « **Reply #155 on:** January 21, 2007, 06:10:55 PM »

no it wouldnt

Mini D · « **Reply #156 on:** January 21, 2007, 06:13:37 PM »

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Originally posted by eskimo2
I’d like to be the first to apologize to APDrone. Although he didn’t explain how the conveyor could keep the plane from moving forward, he was right. If the conveyor prevents the plane from moving forward, it won’t fly.

Fundamentally, anything that is capable of preventing a plane from moving foward will cause it not to fly. It's just that a conveyer that reacts to the motion of the tire will not do that.

eskimo2 · « **Reply #157 on:** January 21, 2007, 06:17:31 PM »

Clearly the wording in the question is screwy; it seems focused on a car. If you interpret the question as stated: “This conveyor has a control system that tracks the plane's wheel speed and tunes the speed of the conveyor to be exactly the same but in the opposite direction, similar to a treadmill.”, such a device is impossible. If, however, the conveyor does not try to match the wheel speed “exactly”, but speeds up to whatever speed is necessary to keep the plane from moving, it would work in theory.

eskimo2 · « **Reply #158 on:** January 21, 2007, 06:18:20 PM »

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Originally posted by Mini D
Fundamentally, anything that is capable of preventing a plane from moving foward will cause it not to fly. It's just that a conveyer that reacts to the motion of the tire will not do that.

But if it reacts to the motion of the plane...

eskimo2 · « **Reply #159 on:** January 21, 2007, 06:23:05 PM »

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Originally posted by Mini D

The inertia on the tire is generated by the motion of the aircraft, not by the belt.

The whole point of the theoretical argument is that the motion of the belt loads the tire with huge rotational inertia.

Mini D · « **Reply #160 on:** January 21, 2007, 06:38:02 PM »

If the belt is reacting, it cannot generate inertia. The inertia must come solely from the motion of the aircraft.

The fundamental principle is quite simple... you must create enough resistance to counter 60,000 lbs of thrust. All of this resistance must be trasfered at the bearings of the wheel. It is the absolute only contact point between the aircraft and the spinning wheel. In addition, the belt would also have to transfer this much energy to the wheels.

The fundamental concept is wrong. Once the craft starts moving, the wheels aren't a factor outside of catostrophic failure.

Another little experiment for you to do: Take a belt sander and put it on a piece of paper and turn it on. Note what direction the paper goes. Then put the belt sander on the piece of paper again and push it forward with your hand and note what direction the paper goes. Put the same belt sander on a frictionless wheel and turn it on... it will stay stationary. Put it on a frictionless wheel and push it with your hand... it will move forward. Fundamentally, this is the exact same scenario being described.

eskimo2 · « **Reply #161 on:** January 21, 2007, 06:38:19 PM »

If you had to build such a device in real life, it would be controlled much like an automobile’s cruise control. Cruise controls are not perfect, they react to imperfections in speed. As soon as the wheel moves/rolls forward on the conveyor, it has a higher speed than the conveyor. At this point, the conveyor reacts by speeding up. This is where it goes nuts and its rpm gains thousands or millions of rpms per second. The energy being loaded into the wheel would be equal to the power of the engine and would gain energy every second.

Mini D · « **Reply #162 on:** January 21, 2007, 06:47:56 PM »

You're putting infinity up against a constant. As long as the aircraft had fuel supplied, it would keep genering a fixed energy that would be cumulative at the wheel. The belt would litterally have to be capable of "infinity" speed.

Mini D · « **Reply #163 on:** January 21, 2007, 06:52:20 PM »

PS.. you have to assume the absence of friction. Given that scenario, the belt and the wheel would both instantly go to infinite speed and the fuselage of the plane would start moving.

eskimo2 · « **Reply #164 on:** January 21, 2007, 06:56:42 PM »

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Originally posted by Mini D
Put the same belt sander on a frictionless wheel and turn it on... it will stay stationary. Put it on a frictionless wheel and push it with your hand... it will move forward. Fundamentally, this is the exact same scenario being described.

Dropping a ball or wheel onto an inverted belt sander is frictionless when it comes to bearings. The ball will rotate and shoot off of the sander. When the ball hits the belt, it starts rotating. But since it is only gaining rotational energy at the bottom, were it contacts the belt, the imbalance of force will move the ball back off the sander. Hold it steady for an instant while it gets up to speed and you could then let go and it would stay in place; this is because it is no longer accelerating rotationally.

This is not about friction. It is about rotational acceleration and energy. It takes energy to make things spin, even without friction.