haha, the conveyor used is a tarp dragged by a toyota tundara. 2000ft tarp it looked like vs. some dinky plane.

 

The wheel bearings don't have much friction. I've seen videos of a dude pulling a full size boeing with his teeth. Unfortunately this is all I could find in a couple minutes...

http://video.aol.com/video-detail/man-pull...eeth/3329301055
http://video.aol.com/video-detail/tesoro-p...pull/2517385677

...anyways, if 20 guys can do this, then I'm sure hundreds of thousands of pounds of thrust/ horsepower can also manage quite well. That coupled with the fact that rolling friction is constant with speed means that it takes the same strength to hold that plane in place with the treadmill going 1 mph and 1000 mph....assuming that the wheels don't fail.

Give it a little bit of throttle, and God himself turning that treadmill cannot stop the plane on top. Unless the tires explode, which, if we can engineer a treadmill to withstand the force of God then we can engineer a wheel that can do that as well.

And in the end, the treadmill's job is simply to match the plane's speed, not to stop it. That means that if the plane is moving at takeoff speed (~180mph for 747, <5mph for model plane), then that's how fast the treadmill is moving backwards...and no faster. The wheels will spin a maximum of the equivalent of 360mph, and the thing will lfy. Not an impossible engineering feat by any means.

 

I think what you guys are trying to say is that the plane is just like a sun gear or roller skates: That the plane will just sit there. If you had a fixed object with a wheel resting on the treadmill, sure. But the implementation of thrust means that the plane will move at some rate forward.

The reason that you don't feel wind in you face is that you are NOT MOVING IN RELATION TO THE ROOM>>>

 

If the wings of the plane reach sufficient take off speed with respect to the air, it will take off. It wont matter what the wheels and treadmill are doing. It's all about the relative velocity of the wing and air.

If the treadmill goes as fast as the plane so that the velocities cancel out, then the speed of the plane with respect to the air is 0, and it will not take off.

 

If two trains drive past each other at equal but opposite speeds, they won't come to an immediate halt because their speeds "cancel out." If you want to extend a free-spinning wheel from one train to the next...their speeds still won't cancel out. If you want to pass one train over the other...still their speeds won't cancel out.

A plane on a treadmill is no different. Which law of physics dictates that their speeds cancel out? If they did, aircraft carriers would install treadmills instead of cables to arrest the planes coming in for landing. Probably treadmills would be a danger to aviation, because an airplane flying over a treadmill would fall out fo the sky since it's speed was canceled out.

It doesn't work that way. People need to hammer the idea out of their heads that a treadmill is used to cancel out the runner's speed. They also need to hammer out the idea that the runner is moving at whatever the treadmill says. He/ she is not. Shoot a radar gun at him to prove it to yourself. Give him a hand-held GPS unit. It will say 0, no matter what the treadmill claims.

 

Wrong..... the treadmill cancels out the wheels spin...not the velocity of the airplane and it's ability to move forward.

Thrust is generated from the engines, not the wheels. There is simply no connection between the treadmill and the engines.

Start the engines the plane moves forward, the wheels move forward.

Start the treadmill, the wheels move backwards with the treadmill, but the plane still moves forward as it's thrusted by the engines.

Why do the wheels initially move? Because of the thrust generated by the engines.
Can the Wheels stop without turning off the engines?....YES.

If the wheels are moving with the treadmill and you turn the treadmill off will the wheels still turn?.....YES.

Nothing that is happening with the wheels or below the airplane have anything to do with it's ability to move forward through the air due to the thrust from the engines.

 

that is true, but if the treadmill does go as fast as the wheels go the plane will not take off, the wheels are what connects the plane to the ground, the plane does not hover. So no matter how much thrust you have you are still not airborne because there is no wind to make the plane lift. If the plane was hovering then yes the wheels would have no effect. What causes lift is the air speed over the wings, if the plane is on the treadmill there is no wind speed, if the treadmill was a frictionless type of surface, like if the plane was going 100mph and the treadmill was going 100mph, and their speeds always contridicated eachother. But if the treadmill maxed out at 100mph and the plane could go faster than 100mph then yes if the plane could take off if we're talking about a infinitely long treadmill.

 

I can't believe some people just don't get this. An airplane needs zero feet of runway to take off if its windy enough - thats one reason why planes are tied to the ground when they're parked. What the wheels do is completely irrelevant.

 

If the treadmill is frictionless, what does its speed matter? There's no friction, thus no effect on the plane...

 

[QUOTE=esracer,Jan 30 2008, 05:35 PM] that is true, but if the treadmill does go as fast as the wheels go the plane will not take off, the wheels are what connects the plane to the ground, the plane does not hover.