12/12/2007 - the Conveyor Belt myth will be busted

AuntPeggy said:
What it comes down to is your definition of "The plane moves".

If your view is that the airplane's movement is relative to the moving belt beneath the wheels, then the answer is "NO!".

If your view is that the airplane's movement is relative to the ground under the moving belt, then the answer is "Yes, if you can get enough thrust to overcome the backward pull of the moving belt and attain rotation speed (relative to the ground beneath the belt)."

And, as many have noted, it is relative wind that provides lift.
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The question never says anything about wheels. The plane speed relative to the belt is the same speed relative to the ground. At liftoff the speed of the plane is 60 kts. North. The speed of the belt is 60 kts South.

thrust to overcome the backward pull of the moving belt What is it pulling on? The faster the belt goes the less it has to pull with. Thats why when your tires start to spin you let up to get them to grab again. The faster you make them go the less traction you get.

You can make up all kinds of things but the question was quite clear.

Dan
 
Arrrgh!!!!

Read a book on Kinematics, think about it a little, and then change your no vote to a yes.

~ Christopher
 
jwriteclub said:
Arrrgh!!!!

Read a book on Kinematics, think about it a little, and then change your no vote to a yes.

~ Christopher
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I need to get you to argue with my former boss, the dean of the college of science and mathematics with a PhD in Physics. He emphatically told me I was wrong and the plane wouldn't take off ;)
 
TMetzinger said:
Ya know, one could do this with an RC plane pretty easily.
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I thought about doing that, but I don't want to be banned from my gym for misusing their equipment :D

(I'm pretty sure the RC setup will be the small scale proof on Mythbusters)
 
FlyNE said:
Ok, guys. You're saying that if the ground moves aft the airplane will want to move aft. So on a normal takeoff where the ground remains stationary...why does the airplane not remain stationary?
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Fantastic argument! Thank you for that.
 
wbarnhill said:
I need to get you to argue with my former boss, the dean of the college of science and mathematics with a PhD in Physics. He emphatically told me I was wrong and the plane wouldn't take off ;)
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And did he tell you why he thought that? I'd love to see his force diagram. An assertion from a non-expert with a PhD means nothing to me. A reasoned argument from him, on the other hand, would be very interesting to see.

Everybody thinks of this in terms of relative motion. The important thing is to look for the net force. We're asking a question about acceleration. Newton taught us that the accleration will be equal to the net force divided by the mass. The mass is constant in any situation we're looking at, so we can ignore it.

The net force in the horizontal direction will be equal to the thrust minus any fluid drag and any rolling friction from the wheels. The friction drag is the same as in a normal take-off, as is the thrust. So all we have to ask ourselves is whether the rolling friction can possibly be greater than the thrust. The thrust is pretty huge, so most of us agree that, unless there's a bearing seizure, the thrust will dominate. As long as the thrust is even a pound more than the rolling friction, the aircraft will accelerate and eventually build up enough airspeed to take off.

I love that this topic is still going after literally years. Anybody know when it was first posted? I miss it when it's not around for a while.
 
SkyHog said:
9:00pm (unknown timezone) - We'll finally get to see an airplane successfully take off from a treadmill, turning in the opposite direction. From the description:

MythBusters
Air Plane Hour
TV-PG

Jamie and Adam take wing to test if a person with no flight training can safely land a 747 and if a plane can take off from a conveyor belt speeding in the opposite direction. Tory, Grant, and Kari jump on some Hollywood-inspired skydiving myths.
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So did the show go ahead? What happened?
 
Did anyone with a treadmill in the basement get a mini indoor RC plane for x-mas???

Take a video and kill this issue once and for all :)

Pete
 
wbarnhill said:
I need to get you to argue with my former boss, the dean of the college of science and mathematics with a PhD in Physics. He emphatically told me I was wrong and the plane wouldn't take off ;)
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The problem with most people that get it wrong is that they think too much. That's the beauty of the question.

If you look at the runway in plan or profile view, then start the plane moving. One is it moving relative to the ground? Two is it moving relative to the belt? If you want to say that it is moving only relative to the belt tell me what force is being used to move it. Now tell me why that same force will not move it relative to the ground. The only way your theory would work is if the force was through the wheels (Like on a car). You cannot move a PLANE relative to the belt with out moving it relative to the ground. If the plane now moves relative to the ground and the belt stop the plane. It is very simple, it is just as simple for you to tell me I'm wrong just show how the plane moves relative to the belt with out moving relative to the ground. It is not a trick question, your mind just looked at the question wrong. It is the same thing we are all taught in Ground School. A PLANE does not act the same as a CAR. You have to KNOW those differences to fly a plane SAFELY.

Dan
 
cwyckham said:
So did the show go ahead? What happened?
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The show will not prove anything to the group that says the plane will not fly if it moves only relative to the belt. Because that is their only argument. And because a plane cannot move relative to only the belt it cannot be proven.

Dan
 
TMetzinger said:
Ya know, one could do this with an RC plane pretty easily.
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The Mythbusters are going to do exactly that. They're putting an RC plane on a conventional exercise treadmill.

I fear that the "full size" test might be lacking. They came close to falling off the wagon on the Airplane Special, and they seem to have found a pilot who does not get it. And with them putting a real plane on a paper roll (or whatever) runway pulled by a truck you'll always have the clueless saying the truck couldn't pull fast enough.
 
The key question for the naysayers is how does ANY plane land without crashing? Did you know that the wheels are not spinning AT ALL before touch down? How can it get down the runway? :D
 
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mikea said:
The Mythbusters are going to do exactly that. They're putting an RC plane on a conventional exercise treadmill.

I fear that the "full size" test might be lacking. They came close to falling off the wagon on the Airplane Special, and they seem to have found a pilot who does not get it. And with them putting a real plane on a paper roll (or whatever) runway pulled by a truck you'll always have the clueless saying the truck couldn't pull fast enough.
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What would be cool is if they had a real good operator and have the plane just go very slow until everyone said "See I told you so" then firewalled it and took off. By the way what channel is it on? I have Dish network.

Dan
 
stingray said:
What would be cool is if they had a real good operator and have the plane just go very slow until everyone said "See I told you so" then firewalled it and took off. By the way what channel is it on? I have Dish network.

Dan
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Discovery Channel.
 
mikea said:
The problem with the video is the camera has a narrow view, so it looks like something you could do with a race car - increase the throttle to match the treadmill, which is NOT what's he doing but the point isn't obvious. *sigh*
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The problem with the videos is that the author claims the airplane on the treadmill will fly and then shows us 11 minutes of the airplane on the treadmill NOT FLYING. I want a refund.

Regards,
Joe
 
Well, you can't expect a toy airplane to take off in 4 feet or however long that is. But it moves forward, it builds airspeed, and that's what counts.
 
Tomahawk674 said:
Well, you can't expect a toy airplane to take off in 4 feet or however long that is. But it moves forward, it builds airspeed, and that's what counts.
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Yeah, but in this demo - at least the second one - the plane moves forward and backwards (relatively) and only builds (relative) speed a little. As I'm saying if you had the hands of a safecracker on the throttle you could do the same apparent demo with an RC car, which invalidates the point.
 
Tomahawk674 said:
Well, you can't expect a toy airplane to take off in 4 feet or however long that is. But it moves forward, it builds airspeed, and that's what counts.
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What I can't tell is what is driving that airplane. Its wheels or a prop.
 
Both planes are actually flyable toy planes; first one used a matchbox car for wheels, ala Wright brothers trolley, second plane has it's own wheels. You can See him accelerate the treadmill while holding the same ammount of throttle on the plane, and the plane stays stationary. The different in friction from 3 to 9 mph isn't enough to "pull" the plane back. As soon as he adds more power plane beats friction and moves forward.
 
Tomahawk674 said:
Well, you can't expect a toy airplane to take off in 4 feet or however long that is.
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I had no such expectation. My expectation was that if one wants to prove that an airplane on a treadmill can take off, one would design an experiment that included flight as a potential outcome. One would then conduct the experiment with apparatus appropriate for the task. The experiment in the video is simply more talk and hand-waving.

Tomahawk674 said:
But it moves forward, it builds airspeed, and that's what counts.
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Counts for what? The experiment proves that a toy car with a toy airplane strapped to its back can go faster than a home treadmill. My dog can go faster than a home treadmill. He doesn't take off, though. (Well, he does if he's chasing a rabbit and getting him back takes forever, but I digress.) The problem at hand is not "Can a vehicle go faster than a treadmill?" but, quoting from the original problem statement, "Will the plane take off or not?"

Regards,
Joe
 
Joe B said:
I had no such expectation. My expectation was that if one wants to prove that an airplane on a treadmill can take off, one would design an experiment that included flight as a potential outcome. One would then conduct the experiment with apparatus appropriate for the task. The experiment in the video is simply more talk and hand-waving.

Counts for what? The experiment proves that a toy car with a toy airplane strapped to its back can go faster than a home treadmill. My dog can go faster than a home treadmill. He doesn't take off, though. (Well, he does if he's chasing a rabbit and getting him back takes forever, but I digress.) The problem at hand is not "Can a vehicle go faster than a treadmill?" but, quoting from the original problem statement, "Will the plane take off or not?"
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Right, Joe! It takes a stream of logic to know that if the plane can go however fast it wants, it can go fast enough to fly. The problem is the naysayers apparently don't have the brain wiring to follow the logic stream. :mad:
 
A conveyor belt large enough for an RC to take off is not easily accesible, that I know of, specially one that is supposed to relatively fast...
 
Tomahawk674 said:
A conveyor belt large enough for an RC to take off is not easily accesible, that I know of, specially one that is supposed to relatively fast...
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We'll see. It looks like Jamie and Adam do this very demo with a gym treadmill and an RC plane as the first proof of concept, then go to an LSA(?) on roll of paper(?) pulled by Jamie in a pickup.
 
mikea said:
We'll see. It looks like Jamie and Adam do this very demo with a gym treadmill and an RC plane as the first proof of concept, then go to an LSA(?) on roll of paper(?) pulled by Jamie in a pickup.
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Not paper. A canvas of some sort
 
Tomahawk674 said:
A conveyor belt large enough for an RC to take off is not easily accesible, that I know of, specially one that is supposed to relatively fast...
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All you need is two or three in line with a small platform connecting them. Speed the last one to max second to last medium and the first slow. Or have the plane start on a board for the first 2 feet and have all 3 going as fast as they can go. Either way it will not matter, an RC will take off before it hits the last one. I wish my plane would get airborn as fast as those things can. I'm sure Mythbusters will use some kind of conveyor belt from a transfer system hooked to the rear axle of a truck that can make it turn pretty fast.

Dan
 
SPOILER! Re: 12/12/2007 - the Conveyor Belt myth will be busted

Sherlock Drones here....

Last night I spoke to Adam Savage, co-host of MythBusters. ...

But the real reason I talked to him was to find out about the next episode of MythBusters (airing this Wednesday). It tackles the famous "plane on a conveyor belt problem," that has pitted brother against brother and friend against friend for years.

To get to the bottom of the thought-problem, Adam and Jamie used a real plane, in this case a 400-lb ultralight, and a large conveyor belt. Did the plane take off? You'll have to wait until Wednesday to find out, but Adam said even the pilot guessed wrong

http://www.boingboing.net/2008/01/28/mythbusters-tackles.html#comments
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Being that we've seen the preview where the "pilot" says he thinks it won't take off, we know that it DOES FLY!

I say if the "pilot" has a Sport Pilot certificate, he has to burn it live on camera.
 
Reminder: Mythbusters/conveyor show airs tonight

...for real this time
 
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