Jan 30 -- Mythbusters vs. Plane on a Treadmill (finally!) - Page 3 - JeepForum.com

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post #31 of 447 Old 01-22-2008, 09:46 AM
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Ok, we know the answer is NO, but with that rc plane that they are using they will probably be able to get it to work. because i had the exact same plane awhile ago and that thing could take off in a few feet. that big propellor can probably generate enough air over the wings to give it enough lift to take off. The main vairable in this experiment is air speed(over the wings) not ground speed.

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post #32 of 447 Old 01-22-2008, 09:49 AM
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Quote:
Originally Posted by ancestralworm
are you kidding me!

the force pushing a drag car forward is transmitted through the ground. an airplane is forcing air back in return pushing it forward. the tredmill can be set on a kabillion miles an hour but if it is not producing any wind resistance on the plane then it dont f-ing matter! the plane will move forward, reach its speed and lift off the ground!

why am i even arguing this? you should stick to something easier like tic tac toe.

ok smart ***, if the plane dosn't need to use the ground at all then why do they put wheels on them? oh wait that's because even though the plane's motor is pushing air, it still has to use the ground to move on until it get's enough speed to create lift, the weight of the plane rests on the ground.

to use yet another anolgoy to help you people understand, you can think of it as a jetcar. yeah it's power is comming from air being forced behind it, not through the wheels. but it can also be placed on a treadmill like the rc car in the above clip and will sit still.

i'm really starting to wonder how everyone who thinks it will take off passed high school.

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post #33 of 447 Old 01-22-2008, 09:54 AM
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Quote:
Originally Posted by TJ Tex
p.s. The friction on the wheels is negligable unless the brakes are applied.
Can you explain why? This is what most people think, but I have yet to see a real response as to why the friction of the spinning wheels doesn't matter.
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post #34 of 447 Old 01-22-2008, 09:54 AM
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Quote:
Originally Posted by red96jeep
ok smart ***, if the plane dosn't need to use the ground at all then why do they put wheels on them? oh wait that's because even though the plane's motor is pushing air, it still has to use the ground to move on until it get's enough speed to create lift, the weight of the plane rests on the ground.
So you're saying that the tiny amount of friction that comes through the wheels will resist the entire thrust of the engine?

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post #35 of 447 Old 01-22-2008, 09:56 AM
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Quote:
Originally Posted by red96jeep
ok smart ***, if the plane dosn't need to use the ground at all then why do they put wheels on them? oh wait that's because even though the plane's motor is pushing air, it still has to use the ground to move on until it get's enough speed to create lift, the weight of the plane rests on the ground.

to use yet another anolgoy to help you people understand, you can think of it as a jetcar. yeah it's power is comming from air being forced behind it, not through the wheels. but it can also be placed on a treadmill like the rc car in the above clip and will sit still.

i'm really starting to wonder how everyone who thinks it will take off passed high school.
Not all airplanes have wheels and they still take off. Explain that!
Did you pass high school?

Edit. Too slow - see plane above...
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post #36 of 447 Old 01-22-2008, 09:59 AM
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Quote:
Originally Posted by red96jeep
ok smart ***, if the plane dosn't need to use the ground at all then why do they put wheels on them? oh wait that's because even though the plane's motor is pushing air, it still has to use the ground to move on until it get's enough speed to create lift, the weight of the plane rests on the ground.

to use yet another anolgoy to help you people understand, you can think of it as a jetcar. yeah it's power is comming from air being forced behind it, not through the wheels. but it can also be placed on a treadmill like the rc car in the above clip and will sit still.

i'm really starting to wonder how everyone who thinks it will take off passed high school.
I told myself I was going to stop arguing in these threads...but I just can't help myself now.

1) They put wheels on to reduce friction making it easier for the plane to move. The wheels have nothing to do with speed...how the hell do you think planes stay in flight once they're in the air? Do you think that they'd really have planes taking off on their bellies?

2) Difference between cars/people and planes on treadmills is that with cars/people, the power is being transferred directly to the ground. The ground is the means by which it moves...whereas, with airplanes the air is the means by which it means.

Edit: And I guess I didn't fully read your example the first time through. But with your example, if power is supplied soley by the jets and the wheels are freely spinning, then yes, it will move.

3) I'm wondering how YOU could've passed high school.

Quick example: If you put rollerblades on and got on a treadmill and had it match your speed like the question, but had a rope to pull on, would you move forward? The answer is yes(pretty obvious). That is exactly like the plane example with the rope being the air and the rollerblades being the wheels. That's what they jets do...they basically pull the plane through the air like you would pull yourself forward with a rope.
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post #37 of 447 Old 01-22-2008, 10:00 AM
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Quote:
Originally Posted by red96jeep
ok smart ***, if the plane dosn't need to use the ground at all then why do they put wheels on them? oh wait that's because even though the plane's motor is pushing air, it still has to use the ground to move on until it get's enough speed to create lift, the weight of the plane rests on the ground.

to use yet another anolgoy to help you people understand, you can think of it as a jetcar. yeah it's power is comming from air being forced behind it, not through the wheels. but it can also be placed on a treadmill like the rc car in the above clip and will sit still.

i'm really starting to wonder how everyone who thinks it will take off passed high school.
First, I'm wondering how you passed high school with all the spelling and grammatical errors in your post.

Next, I will think of a jet car. Why don't they put large, dragster-style rear racing slicks on them? Because there is no need, the tires are only used to support weight, not gain traction or propel the vehicle.

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Quote:
Originally Posted by red96jeep
i'm really starting to wonder how everyone who thinks it will take off passed high school.
Quoted for effort. This one is REALLY gonna come back to bite you

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post #38 of 447 Old 01-22-2008, 10:08 AM
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Quote:
Originally Posted by red96jeep
i'm really starting to wonder how everyone who thinks it will take off passed high school.
when you get out of grade school they will try to teach you such things. watch some sesame street instead of WWF before the bus picks you up and it will probably help also. your parents must be proud.

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post #39 of 447 Old 01-22-2008, 10:11 AM
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Quote:
Originally Posted by dopod
Can you explain why? This is what most people think, but I have yet to see a real response as to why the friction of the spinning wheels doesn't matter.
It has been years since I have studied this stuff in college and in the military when I fixed flight controls on jets for 9 years, but I'll give it a shot.

The surface of the tire/wheel is rolling on the treadmill. Since the wheels are free spinning, the friction between the tire and road doesn't slow the wheel down at all. It just keeps the wheels rolling straight instead of sliding sideways while rolling. That's why planes don't have caster type wheels. The only friction that can slow the plane down is the friction of the wheel spinning around the axle. This friction is very very small, since the wheel has greased bearings in the joint between the axle and the wheel.

As far as the inertia of the wheel, the wheel is a very small weight compared to the whole plane and pilot. The energy to get the little wheels spinning is tiny compared to the thrust required to move the plane forward. The extra energy of the wheels spinning twice as fast as the treadmill will only slow the plane down a couple of MPH.

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post #40 of 447 Old 01-22-2008, 10:11 AM
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Quote:
Originally Posted by Vaj
So you're saying that the tiny amount of friction that comes through the wheels will resist the entire thrust of the engine?

but... what if the snow were moving in the other direction... at the same speed?

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post #41 of 447 Old 01-22-2008, 10:24 AM
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Quote:
Originally Posted by TJ Tex
The extra energy of the wheels spinning twice as fast as the treadmill will only slow the plane down a couple of MPH.

The treadmill must match the wheel speed though. I understand that, under normal circumstances, the wheels have very little friction, and that they use greased bearings.

But this is a hypothetical conveyor belt, not a real life one. So it must match the wheel speed, which will cause the wheels to move faster, which will cause the conveyor to match them again, which will cause them to move faster, etc.

It depends on how long the conveyor belt takes to match the speed of the wheels. If it's instantaneous, than the wheels and treadmill will accelerate to infinity instantly. I think it's safe to say that a wheel moving at infinity rpm would have quite a bit of friction.
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post #42 of 447 Old 01-22-2008, 10:28 AM
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Quote:
Originally Posted by Vaj
So you're saying that the tiny amount of friction that comes through the wheels will resist the entire thrust of the engine?

no, what i'm saying is that the thrust of the engine pulls the plane foward. it pushes on the wheels bacause gravity pulls down on the plane and put's all of it's weight on the wheels. so when the thrust pulls the plane foward the wheels are what's allowing the plane to movefoward(or skis like you pictured). but when that foward movement is cancled out by the runway moving in the oppsite direction at the same speed the plane will be at full throttle and producing thrust, but it will not be moveing anywhere. it will be pushing foward, the treadmill will be moveing back and the wheels that are the meadien for the two will be moveing at twice the speed of the treadmill (or what the plane would be moveing at). and as we all know planes need air moveing over the wings at a certent speed to create lift so it can take off. the engine does not create lift, it creates thrust that allows lift to happen when not opposed. so like i've been saying and thinking the whole time with no air moveing over the wings their will be no lift and no plane takeing off.


that's all i'm gonna be saying because frankly i'm tired of saying the same thing over and over knowing i'm right buy not getting throught to you. we will all descover that i'm right on the 30 when the myth buster do the expirment, as long as they truly do match the planes foward speed in the oppsite direction with the treadmill then what i'm saying will be right, and you all should go cry yourselvs to sleep lol

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post #43 of 447 Old 01-22-2008, 10:31 AM
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post #44 of 447 Old 01-22-2008, 10:33 AM
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Quote:
Originally Posted by red96jeep
no, what i'm saying is that the thrust of the engine pulls the plane foward. it pushes on the wheels bacause gravity pulls down on the plane and put's all of it's weight on the wheels. so when the thrust pulls the plane foward the wheels are what's allowing the plane to movefoward(or skis like you pictured). but when that foward movement is cancled out by the runway moving in the oppsite direction at the same speed the plane will be at full throttle and producing thrust, but it will not be moveing anywhere. it will be pushing foward, the treadmill will be moveing back and the wheels that are the meadien for the two will be moveing at twice the speed of the treadmill (or what the plane would be moveing at). and as we all know planes need air moveing over the wings at a certent speed to create lift so it can take off. the engine does not create lift, it creates thrust that allows lift to happen when not opposed. so like i've been saying and thinking the whole time with no air moveing over the wings their will be no lift and no plane takeing off.


that's all i'm gonna be saying because frankly i'm tired of saying the same thing over and over knowing i'm right buy not getting throught to you. we will all descover that i'm right on the 30 when the myth buster do the expirment, as long as they truly do match the planes foward speed in the oppsite direction with the treadmill then what i'm saying will be right, and you all should go cry yourselvs to sleep lol
Holy ****! Have you even passed 7th grade yet? IMO, you should really brush up on your physics and English skills.

BTW, when it does take off, you're most likely going to ***** about it and say something along the lines of "zomg teh conveyor wasn't movin teh saim speid as da plane!"
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post #45 of 447 Old 01-22-2008, 10:34 AM
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the friction between the wheels and conveyor belt are negligable. spinning wheels have nothing to do with lift/air speed. Who care how fast the belt is moving because the plane is still staying in one spot( if it were to match the belt speed). The plane on the belt is only going to produce lift over the section of the wing that is right behind the propeller, which is not enought air to produce enough lift for takeoff. Why would engineers make wings 20+ ft long if the lift over a 5 ft span is enough to fly the thing?

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