Author Topic: plane on a conveyor belt? (Read 19890 times)

APDrone · « **Reply #345 on:** January 26, 2007, 06:50:44 AM »

Quote

Originally posted by SteveBailey
so, the only way for the wheels to move is for the plane to move forward, we agree on that.

Based on what you are saying:

So the plane is now moving forward(wheels rolling), then it stops? It stops [ actually, never really started ] in relation to the world outside of the conveyor. If the engine is still generating thrust, the thrust is trying to move forward, which is translated into a rolling effect, which is countered. The only way for the wheel to stop spinning is if the engine is turned off ( or idled or whatever it takes to make the prop stop trying to go ) or the brakes are applied. If it was moving forward a 1 mph and then stopped, the wheels would then slow down right? By 1 mph? Then the conveyer would slow down right?

Look.. I have explained this stuff about 4 or 5 times and Eskimo has explained more often and better than I.

If you have a problem with my arguments, quote them and I will answer to those.

deSelys · « **Reply #346 on:** January 26, 2007, 07:36:45 AM »

Lol, i've just found this on a science-oriented forum:

More than 400 pages!

We're waaaaaaay behind!

WhiteHawk · « **Reply #347 on:** January 26, 2007, 08:01:40 AM »

Imagine if you are on a conveyor with a jet pack and you wnated to take off vertically, the conveyor would have no effect on that. Now imagine if we had a propeller and wings attached, the conveyor matches our IAS, we could never keep up, but if the engine was powerful enough it would drag us along the conveyor even though the conveyor was racing below our feet. Assuming the engine is ok for normal take-off, the only variable here is the drag factor of our feet on the conveyor. Intuitively, I would say that the drag increases as the speed of the conveyor increases. Lets say, we still cannot take off. Now, give me some cheap roller skates. Lets say, drag factor is reduced greatly, but still no take off. Now we get some primo wheels, drag factor is reduced dramatically, but alas, still not good enough. Now we goet some reverse magnetic boots that reduce the friction here to close to 0. Now it doesnt matter how fast the conveyor is running because we can practically levitate above it and take off happens. So there is really not enough information to answer this question. We need a drag variable for the wheels or if the wheels are sufficient, the plane will take off. This can be shown by reversing the conveyor and running it WITH the plane. If there is 0 drag, the wheels will simply not move at all and the plane will take off normally.

APDrone · « **Reply #348 on:** January 26, 2007, 08:08:41 AM »

Quote

Originally posted by deSelys
Lol, i've just found this on a science-oriented forum:

More than 400 pages!

We're waaaaaaay behind!

Go back to about page 4 of this thread and you will find:

Quote

Originally posted by Terror
From a Physics Forum on this exact topic:

459 Pages, 6876 replies!!

Physics Forum Thread

Hitech, this thread may just fill your HD space !!

Terror

Casca · « **Reply #349 on:** January 26, 2007, 08:48:21 AM »

Quote

Originally posted by deSelys
Lol, i've just found this on a science-oriented forum:

More than 400 pages!

We're waaaaaaay behind!

Just to point out...again...that the question in the thread cited is not the same question that precipitated this thread.

SteveBailey · « **Reply #350 on:** January 26, 2007, 09:54:29 AM »

Quote

Look.. I have explained this stuff about 4 or 5 times and Eskimo has explained more often and better than I.

Here's the simple truth and you agreed already, although you won't like it.

The only way for the wheel to start spinning.. THE ONLY way, is for the plane to start moving forward.(there is no thrust at the wheel)

If the plane does not move forward, the wheels never start spinning. In your model APdrone, the wheels magically begin turning yet the plane never moves to start the wheels turning in the first place.

That you guys continue to argue this is amazing to me.

Explain to me how the wheels start turning if the plane does not move forward? The conveyer matches the speed of the wheels. If the plane never moves as you state, the wheel speed muist be 0. Explain this.

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

APDrone · « **Reply #351 on:** January 26, 2007, 10:08:01 AM »

Quote

Originally posted by SteveBailey
Here's the simple truth and you agreed already, although you won't like it.

The only way for the wheel to start spinning.. THE ONLY way, is for the plane to start moving forward.(there is no thrust at the wheel)

If the plane does not move forward, the wheels never start spinning. In your model APdrone, the wheels magically begin turning yet the plane never moves to start the wheels turning in the first place.

That you guys continue to argue this is amazing to me.

Explain to me how the wheels start turning if the plane does not move forward? The conveyer matches the speed of the wheels. If the plane never moves as you state, the wheel speed muist be 0. Explain this.

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

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.

lukster · « **Reply #352 on:** January 26, 2007, 10:20:22 AM »

Forget about friction between the belt and the tire for a moment. Let's attach a very powerful motor (on a sliding rail) capable of producing a constant acceleration in the attached wheel's rotational speed. This is designed to lift the tire off the ground. That force would be transferred to the plane through the wheel's axle and could counter the plane's thrust if the acceleration were sufficent.

Too many conditionals in that scenario, forget I mentioned it.

SteveBailey · « **Reply #353 on:** January 26, 2007, 10:23:23 AM »

Quote

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

So your answer to my debate is: since it never moves it doesn't fly. how exactly does the conveyer keep the plane from moving? The conveyer matches the wheel speed... that means the wheels have to turn first, even if for an instant. Which means the plane has to move forward.

You are getting somewhere if you would heed our discussion instead of worrying about "winning".

Think about the initial question. The conveyer matches the "speed" of the wheels, not the thrust of the airplane. If the thrust of the plane is 1000 pounds at first push to full throttle, are you saying the conveyer thrusts back against the wheels at 1000 pounds? If so, what does this have to do with wheel speed, which was the original posit?

Again, the conveyer matches the speed of the wheel. The only way for the wheels to move is for the plane to move forward. What stops the plane from rolling forward and how?

lukster · « **Reply #354 on:** January 26, 2007, 10:26:43 AM »

Quote

Originally posted by SteveBailey
So your answer to my debate is: since it never moves it doesn't fly. how exactly does the conveyer keep the plane from moving? The conveyer matches the wheel speed... that means the wheels have to turn first, even if for an instant. Which means the plane has to move forward.

You are getting somewhere if you would heed our discussion instead of worrying about "winning".

Think about the initial question. The conveyer matches the "speed" of the wheels, not the thrust of the airplane. If the thrust of the plane is 1000 pounds at first push to full throttle, are you saying the conveyer thrusts back against the wheels at 1000 pounds? If so, what does this have to do with wheel speed, which was the original posit?

Again, the conveyer matches the speed of the wheel. The only way for the wheels to move is for the plane to move forward. What stops the plane from rolling forward and how?

Steve, your missing the point of one perspective of this situation allowed by the ambiguity in the question. The force applied through acceleration of the wheel may meet or exceed the thrust of the plane if we apply no limitation to how fast the belt can accelerate. for the sake of argument let's say the belt is capable of accelerating from 0 to 1,000,000 mph in one second. That should be plenty fast enough to keep the wheel from moving maybe one inch, stop, one inch, stop, one inch stop. how will the plane ever reach a fast enough airspeed to liftoff at that rate?

SteveBailey · « **Reply #355 on:** January 26, 2007, 10:30:51 AM »

Quote

Originally posted by lukster
Steve, your missing the point of one perspective of this situation allowed by the ambiguity in the question. The force applied through acceleration of the wheel may meet or exceed the thrust of the plane if we apply no limitation to how fast the belt can accelerate.

The initial question doesn't say anything about force.

Let's say our plane has a take off speed of 100 MPH. The plane begins to move forward at 1 mph, the conveyer counters the wheel speed and spins against the tires at 1 mph right? OK so the net velocity of the wheels is 2 MPH, 1 MPH for the rotation of the wheels, and 1 MPH for the forward movement of the plane, agreed?

lukster · « **Reply #356 on:** January 26, 2007, 10:39:34 AM »

My last actually combined the two issues and was inapplicable. The belt would slow it's acceleration only when the plane was moved backwards. The plane would move forward of it's initial starting ponint only once.

The part you are refusing to acknowledge or understand is that from one perspective the wheel moves and the belt moves in the opposite direction. This then causes the wheel to turn that much faster which avalanches into a velocity limited only to the speed of light in theory. We can control how much force is applied as a counter to the plane's thrust by controlling the rate at which the belt/wheel accelerate into oblivion.

john9001 · « **Reply #357 on:** January 26, 2007, 10:47:06 AM »

the belt can not apply any force to the plane , all the belt can do is spin the wheels.

SteveBailey · « **Reply #358 on:** January 26, 2007, 10:47:55 AM »

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The plane would move forward of it's initial starting ponint only once.

What stops the plane from moving forward? I ask you this.... again.

and explain exactly how the conveyer accerates off into infinity.

If the plane isn't moving forward as your model states, why can the conveyer never match the wheels speed? If the wheel is merely spinning and not moving forward, how is it possible not to match it's speed? Explain this please.

lukster · « **Reply #359 on:** January 26, 2007, 10:54:10 AM »

Quote

Originally posted by SteveBailey
What stops the plane from moving forward? I ask you this.... again.

and explain exactly how the conveyer accerates off into infinity.

If the plane isn't moving forward as your model states, why can the conveyer never match the wheels speed? If the wheel is merely spinning and not moving forward, how is it possible not to match it's speed? Explain this please.

Here's the premise. The plane moves forward and the wheel is now spinning forward at 10rpm. The wheel monitor senses this and tells the belt to move in the opposite direct at 10rpm. Since the A/C engine is applying thrust at least holding the plane in place or moving forward for now, the belt now moving in the opposite direction at 10rpm causes the wheel to rotate at 20 rpm. The wheel monitor/belt controller senses this and speeds the belt to 20rpm, this increases the wheel to 40 rpm. The rate at which the belt is allowed to accelerate to it's max speed determines the force applied to the plane countering it's thrust.