will it take off?

[NewToy]

Congratulations!!! You and I were on the losing side of this debate until we thought about it for a while. Untilllll I thought of this example....

Put on some roller skates and stand on a treadmill. Hold a CO2 fire extinguiser under your arm and point it backwards. Have someone turn on the treadmill and fire off the fire extinguisher. You will shoot forward no matter what the speed of the treadmill, right? Except that according to the original question, the treadmill will match your wheel speed. In order to go anywhere forward, your wheels would have to turn faster than the surface of the treadmill. Soooo, I am back to the school of thought that this is a tough question.

Picture me am lying on the ground next to a mile long treadmill with my fingertip on the center of the hub of the airplane's wheel. If the wheel turns forward at all, the magic treadmill will turn in the opposite direction, so the hub of the wheel will never leave my finger, right? How could the plane gain any airspeed if it isn't leaving my finger?

I've changed my mind again, the plane won't fly because the wheel can never leave the spot next to my finger because the magic treadmill won't let it.

The wheels have noting to do with it except to hold the plane up and allow it to move. Go back to your original thought about the fire extinguisher and you will get it. Where is all the thrust energy going if not moving the aircraft? Back to basic physics again. The thrust isn't being transmitted to the wheels but to the surrounding air that isn't attached to the conveyor. You should have kicked the **** out of that joker that tried to run you over in the plane and stayed at work.
John

 

[MossRoad]

. I can't understant how the "no fly" contingent cannot grasp this.

Because we are taking the magic treadmill concept seriously.

 

[BTDT]

Ok, let's try this. Get your favorite hotwheels tractor. Put it on the treadmill in your workout room and turn it on while holding the tractor against the belt with your finger. The belt turns, the tractors wheels turn, and it pretty much stays under your finger. Now, duct tape a bottle rocket to the top of the tractor (facing in same direction as tractor), repeat above procedure. Light fuse. Explain to your significant other how your toy tractor imbedded itself in your sheetrock wall. Just don't tell here you heard this on TBN.

 

[Tom_Veatch]

...
You're standing at one of the plane's wing tips but off the conveyor. The plane revs up and starts moving forward. The conveyor kicks in and moves in the opposite direction. The wheels spin faster and faster but the conveyor does too. You're still at the plane's wing tip because the wheels nor plane hasn't had any forward travel, relative from where you're standing.
...

OK, tell me what's resisting the engine thrust? What holds the a/c back and keeps it from moving forward in response to the engine thrust? The wheels can't, they spin freely without putting any significant rearward drag on the a/c and, so far, nobody's mentioned any ropes or anything tying it to the ground. At least I assume the pilot unhooked the tie downs during his pre-flight inspection.

 

[NewToy]

Because we are taking the magic treadmill concept seriously.

I'm serious as well but you are missing the point. If the power was applied to the wheels you are correct but it's being converted to THRUST. Take the little childs toy with 5 or 6 ball bearings suspended with the strings. Pull one ball back and let her go, that energy causes a reaction making the other ball at the opposite end move. Now sit on a conveyor in Wal-Mart checkout and try it with an Estes rocket motor strategically placed in a DARK place on your person. Ignite the rocket motor and then you'll see.

John

 

[MossRoad]

Only if the planes engines are off. If engine produces thrust, it's up, up, and away

No such treamill exists. If the treadmill could match the wheel spin exactly, it would turn at the exact same moment the wheel turned, keeping it in the exact same place in relation to a point on the ground , no matter how much thrust you applied.

If the plane is standing still it has to overcome the friction with the ground to first get moving. Once it is moving, it can then pick up speed. It will never break this friction if the wheel makes no forward progress due to the magic treadmill. No initial forward motion means no forward motion ever due to the magic treadmill. Now, if the treadmil had a short delay in its initial reaction time, I would say, sure, it will constantly be trying to catch up and the plane will always be ahead and eventually take off. But we are assuming a magic treadmill that would never let the plane leave its initial spot to start with. Nope. No fly today.

 

[Tom_Veatch]

That reminds me of an old joke...

Q: What are the two most dangerous things in aviation?
A: Two doctors in a Bonanza!

So expensive only Doctor's could afford to buy them; who then spent more time talking to their brokers than they did maintaining their flight proficiency, ergo... "V-tailed Doctor Killers". Really a nice flying airplane, 'though.

 

[MossRoad]

Ok, let's try this. Get your favorite hotwheels tractor. Put it on the treadmill in your workout room and turn it on while holding the tractor against the belt with your finger. The belt turns, the tractors wheels turn, and it pretty much stays under your finger. Now, duct tape a bottle rocket to the top of the tractor (facing in same direction as tractor), repeat above procedure. Light fuse. Explain to your significant other how your toy tractor imbedded itself in your sheetrock wall. Just don't tell here you heard this on TBN.

First, sorry about those multiple posts... sometimes I hit the wrong key.

O.k. now I think you are just trying to get me to video tape something stupid!

 

[shaley]

They aren't flying, they are gliding.

I'm saying these fish have wings and the beat them pretty hard and fast. You can hear the flutter when the come out of the water. I'm just as amazed at the Tuna for learning how to nail them. Look at the size of the peck wings.

 

[MossRoad]

OK, tell me what's resisting the engine thrust? What holds the a/c back and keeps it from moving forward in response to the engine thrust? .....

The magic treadmill(which doesn't exist). Just like tying a plane to the ground with a rope, the magic treamill will keep the wheels in the same forward/backwards postion even though they are spinning. Man, the friction will be huge where the rubber meets the treadmill, but the plane will just sit there, blowing tons of air behind it, wheels spining freely on their hubs, making little windflow over the wings except for any prop wash. That's the fault with this situation... there is no magic treadmill that can react to the initial motion of that wheel on the vey first fraction of a turn without some time delay.

In the bottel rocket on a toy tractor scenario, it is a conventional treadmill, not a magic treadmill, so of course the toy tractor will get imbedded in my wall and make my wife happy.