Author Topic: Plane on a Treadmill (Read 19762 times)

Chopper Face 69 · « **Reply #30 on:** Feb 26, 2006, 10:25:31 PM »

No. That's crap. The reason for which the planes actually took off is because the treadmill was unable to keep up with the speed of the plane. The way these people seem to think the plan would take off is that the powet of the turbines pushing the plane would make it just fly forward and not stick to the treadmill. But the problem is you can't perfectly duplicate such a treadmill. If the plane is allowed to lose it's grip on the tread and move forward before going upwards, wich is the only way in which a plane can fly because upwards motion is only caused by the wind under the wings caused by the forward motion, then the speed of the plan is not all being compensated by the treadmill. It's just not able to keep up.

Rama · « **Reply #31 on:** Feb 27, 2006, 05:20:39 AM »

I think you are wasting your time. D would tell the Wright Brothers they where wrong, and would be completely serious about it.

Rodent of Unusual Size · « **Reply #32 on:** Feb 27, 2006, 09:47:44 AM »

First off, you're an idiot if you can't understand why it can't happen.

To reiterate, air has to move around the wings in order to create lift. And ths air must move at a speed that produces enough lift to actually pull the plane upwards. If the plane is accelerating forward while the ground is moving backwards, the plane is not moving and air will not move around the wings at a sufficient speed to generate the sufficient lift required to pick it up off the ground.

I don't give a crap where the thrust comes from. The fact is that it IS NOT MOVING, and thus there is not enough airflow to produce lift. And it doesn't matter if the wind is blowing, or how hard, because unless it's a fucking hurricane or tornado, it's not going to be strong enough to blow over the wings and lift it.

I work in a place that tests jet engines on a daily basis. If you strap a jet down and burn the engines, guess what? It doesn't lift. Same thing here, except instead of straps you have a treadmill keeping the thing stationary.

Now pull your head out of your ass and find something else to go on about.

IDE · « **Reply #33 on:** Feb 27, 2006, 03:18:23 PM »

EVERYBODY CHILLLLL OUTTT!!!

I'm gonna be running on a treadmill later tonight. I'll flap my arms when no one is looking and we'll settle this once and for all!

B E C K · « **Reply #34 on:** Feb 27, 2006, 03:55:27 PM »

Bring souvenirs.

Chopper Face 69 · « **Reply #35 on:** Feb 27, 2006, 05:35:22 PM »

Quote

EVERYBODY CHILLLLL OUTTT!!!

I'm gonna be running on a treadmill later tonight. I'll flap my arms when no one is looking and we'll settle this once and for all!

I'm not convinced you couldn't do so from a stationary position making you a human equivalent of a VTOL craft.

The D · « **Reply #36 on:** Feb 27, 2006, 10:04:32 PM »

I give up on you guys, you aren't reading the articles properly, you're not thinking properly. For one thing, the plane is not STICKING to the treadmill, it's resting on the treadmill on the wheels, which roll freely. The thrust is from the engines. The engines push it forward, the wheels spin backwards freely with the treadmill and don't impede on the plane's movement, and the plane's thrusted forward, air goes under the wings, and it takes off.

IDE · « **Reply #37 on:** Feb 27, 2006, 10:26:32 PM »

I flapped as hard as I could and nothing happened.

Case Closed.

Faye Valentine · « **Reply #38 on:** Feb 27, 2006, 10:34:55 PM »

is there someone here who actually cares about how planes fly? damnit i've heard about planes for my whole life.

Extra Zero · « **Reply #39 on:** Feb 27, 2006, 11:35:12 PM »

Quote

I flapped as hard as I could and nothing happened.

Case Closed.

ONE TRUTH PREVAILS!

Rodent of Unusual Size · « **Reply #40 on:** Feb 28, 2006, 11:04:58 AM »

Quote

I give up on you guys, you aren't reading the articles properly, you're not thinking properly. For one thing, the plane is not STICKING to the treadmill, it's resting on the treadmill on the wheels, which roll freely. The thrust is from the engines. The engines push it forward, the wheels spin backwards freely with the treadmill and don't impede on the plane's movement, and the plane's thrusted forward, air goes under the wings, and it takes off.

You know WHY people use treadmills? Because they can WALK all day yet not GO anywhere. The same with a plane.

The engines do not propel the plane upwards, only forward. It's like a car on a dynometer...you can measure the powet output of the car at the rear wheels, but it's not "making wind" around it. If the plane is not "making wind" around it, there'll be no lift.

You could have Jesus AND Chuck Norris pushing it from behind, but if the treadmill can match that speed in the opposite direction, it's not going forward.

I'm not conceding this.

Rama · « **Reply #41 on:** Feb 28, 2006, 01:23:07 PM »

Jesus and Chuck Norris together? I'd pay to see that.

IDE · « **Reply #42 on:** Feb 28, 2006, 02:50:06 PM »

He's Jesus, lol.

Sam · « **Reply #43 on:** Feb 28, 2006, 03:52:42 PM »

As much as I am loathe to admit it, D's right on this one. It would take minimal additional thrust from the engines to overcome the opposing motion of the treadmill, mostly due to the effects of lost energy due to friction in the wheel bearings. When you stop to consider the fact that the wheels on the plane are essentially there to keep it from having to slide around on it's belly, the answer becomes rather obvious.

Let's put it this way:

Remove the wheels completely and allow the plane to be suspended by, I don't know, some anti grav unit that's only strong enough to lift it a few feet off the ground. The jet turbines engage and the air is compressed, fuel added and combusted,, then allowed to expand again, providing thrust (if you want I could go into the specifics of the Brayton cycle, but I doubt anyone's interested). All of this happens completely independent of any interaction with the ground. The ground could be screaming backwards at 2x the speed of sound and it wouldn't bother the jet. We're not worried about lift here, we're just talking about simple horizontal locomotion. (the lift comes as a result, but it's rather inconsequential to the heart of the problem)

Let's put the wheels back. Now the wheels, of course, are not the ideal suspension device the theoretical anti-grav unit is. There are inherrent innefficiencies, including the aformentioned friction. This would, indeed, cause some small amount of backwards force. But the magnitude of that force and the resulting motion is negligable compared to the thrust that the turbines can put out.

B E C K · « **Reply #44 on:** Feb 28, 2006, 08:44:31 PM »

Quote

Jesus and Chuck Norris together? I'd pay to see that.

I'm picturing Jesus clinging onto Chuck Norris' back, his fingers gripping the abundant amount of hair, and recoiling in horror as he realizes he's sinking.

Rama · « **Reply #45 on:** Mar 01, 2006, 03:21:49 AM »

I was kinda hoping for "Sidekicks 2."

Chopper Face 69 · « **Reply #46 on:** Mar 01, 2006, 06:00:00 AM »

Sam makes sense and I concende that his explanation makes me thing this would work. This isn't really in fitting with how the question was asked though as it seems that for every forward thrust there is a backward thrust on the plane stopping it in the same way by this threadmill. Like if the wheels were perfectlyfrictionless at the joints. I guess what's causing that way to make sense is the friction at the wheel's joint (whatever that's called) as well as a lack of proper adhession between the wheels and the treadmill.

None of these sites, and especially not the guy who's trying to explain it who doesn't understand it..., have made it make sense like he did.

Faye Valentine · « **Reply #47 on:** Mar 01, 2006, 08:22:51 AM »

well, he IS an engineer.

tomduo · « **Reply #48 on:** Mar 01, 2006, 08:54:49 AM »

It's kinda an ideal explanation, so to me I don't see it working. If it was possible, the miliary would be using it.

Rama · « **Reply #49 on:** Mar 01, 2006, 09:04:09 AM »

Yeah they wouldn't need to be investing millions into a VOTL NATO fighter if this actually worked. Besides you have to throw so many rules out the window to make it work and the question didn't really address that very well. It’d be like saying imagine you have a sub under water, but the rules of hydro dynamics don't apply.... Then really what's the point of it being underwater?

Sam · « **Reply #50 on:** Mar 01, 2006, 10:45:36 AM »

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Yeah they wouldn't need to be investing millions into a VOTL NATO fighter if this actually worked. Besides you have to throw so many rules out the window to make it work and the question didn't really address that very well. It’d be like saying imagine you have a sub under water, but the rules of hydro dynamics don't apply.... Then really what's the point of it being underwater?

If this "worked" it still wouldn't provide any useful advantage. You'd just be wasting energy running a treadmill and getting nothing but some waste heat generated by the friction in the bearings.

But the whole point is the treadmill wouldn't be useful at all; it's not like it allows the jet to build up a lot of thrust without moving forward. The jet moves forward and takes off as if nothing is going on underneath it.

As a fun little aside, the jet *would* get an insignificant boost forward if it was still on the ground when it got to the edge of the treadmill since the wheels would be rotating faster than the jet is moving forward. That tiny amount of kinetic energy (1/2*I*w^2, where I is the moment of inertia of the wheel and w is the angular velocity [in rad/sec]) would be transferred to the plane (1/2*m*v^2, where m is the mass of the plane and v is the linear velocity). Since the plane is so much more massive (m) than the wheel (I, which is directly related to the mass of the wheel and it's shape), the velocity increase is negligable.

But it's still there.

I hope you all took notes, there'll be an exam on Friday.

tomduo · « **Reply #51 on:** Mar 01, 2006, 11:00:08 AM »

Fuck this shit, I am a history student. Unless the production of this affects society, and it's use helps turn the tide of war or oppresses women, then maybe, otherwise fuck a 4chan for wasting my time over a useless and improbable innovation that has in no way aided soceity, and proved to do nothing more than bog it down. Shit, this needs more anime pr0n.

Sam · « **Reply #52 on:** Mar 01, 2006, 11:01:12 AM »

that being said, I almost wanted to argue the opposite side, since the attitude of the question and D's replies struck me as having a "Ha ha, I'm smarter than you" tone

tomduo · « **Reply #53 on:** Mar 01, 2006, 11:02:09 AM »

Just smile at the anime pr0n.

Sam · « **Reply #54 on:** Mar 01, 2006, 11:12:01 AM »

(I'm not smiling at the anime pr0n of the girls that look like they're 12, tops)

It also may help to look at the wheels in the extreme situations.

First, let's imagine the wheels as having an efficiency of zero. They're completely rusted in place, essentially no better than a concrete block strapped onto the belly of the plane. In this case the plane would move backwards as soon as the treadmill starts moving.
(translational --> 100% translational)

Next, imagine the wheel is an ideal component -- no friction in the bearings. Any kinetic energy transferred to the wheel by the treadmill at the contact surface is converted completely into rotational energy. The plane stands in one place and the wheels spin at a rate determined by the treadmill speed.
(translational --> 100% rotational)

Reality lies somewhere between.
(translational --> X% translational + Y% rotational)

...damn I'm a nerd. This is actually interesting to me.

tomduo · « **Reply #55 on:** Mar 01, 2006, 11:24:44 AM »

What anime chick looks of age? They're Japanese!

Plus, they have boobs.

Rama · « **Reply #56 on:** Mar 01, 2006, 11:30:52 AM »

I thought that the idea was to make them look 12....It's like what they are "into" over there. You get none of the guilt cause they arn't real. Clever loophole you cheeky bastards.

IDE · « **Reply #57 on:** Mar 01, 2006, 11:35:35 AM »

lolilicious!

tomduo · « **Reply #58 on:** Mar 01, 2006, 01:18:50 PM »

LOLIGASM!

Faye Valentine · « **Reply #59 on:** Mar 01, 2006, 01:41:57 PM »

I thought that kind of pics were prohibited in this board