We have the FINAL ANSWER!

im pretty sure the wheel bearings would burn up or tires would shred before it even got close to takeoff speed :)
 
I still say let's get ourselves a gov't research grant and build one. I volunteer to do a lot of the design work and construction..and be the pilot.
 
tonycondon said:
im pretty sure the wheel bearings would burn up or tires would shred before it even got close to takeoff speed :)
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It depends on if it's a high wing or a low wing...

The conveyor belt will create its own boundary layer, so that as it accelerates, it will drag the air along and over the wing of the aircraft. If the conveyor is long enough and the wing is close enough to the ground, you're in business. This then gets you up and into ground effect in the boundary layer. As soon as your wheels are up, you can accelerate forward as you normally would without the conveyor dragging you back due to the friction in your wheel bearings.

The idea aircraft for this would be a motorglider with bicycle gear and a pusher prop as the stall speed is very low and the wing is very close to the ground. Of course, the wing runner would get one heck of a workout.

Chris
 
not if the wingrunner wasnt standing on the conveyor belt, but off to the side.

this whole thing was hashed out in probably one of the longest thread in board history Chris. I dont have a link handy but im sure you can find it. was pretty fun to read through. consensus came out that the friction from wheel bearings would not be high enough to keep the airplane from taking off normally. wheels would just be spinning twice as fast as normal at liftoff.
 
STOP THE MADNESS
Beat_Dead_Horse.jpg

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now scott, its been a good 3 or 4 months since this subject was last revived. I think its more than enough time to prompt a full review of the subject.
 
tonycondon said:
not if the wingrunner wasnt standing on the conveyor belt, but off to the side.

this whole thing was hashed out in probably one of the longest thread in board history Chris. I dont have a link handy but im sure you can find it. was pretty fun to read through. consensus came out that the friction from wheel bearings would not be high enough to keep the airplane from taking off normally. wheels would just be spinning twice as fast as normal at liftoff.
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Yeah, I know it's a common one. It went to a few hundred posts on the red board back when I was a member over there. I hadn't thought of the boundary layer argument at the time, though. I'm sure nobody wants to start the madness again, but hey, you started it! :)

(But just because I can't help myself, I think your analysis is incorrect. It seems to me that it's a positive feedback loop and you'll quickly hit infinite wheel speed. If you take off at 60, you're moving forward at 60 throught the air (ignoring boundary layer effects). You say your wheels then need to go at 120. That means that the conveyor is going 60 backwards. However, the problem says that the wheel and conveyor speeds are matched, so the conveyor would have to double in speed at this point. If the aircraft is moving forwards, the conveyor will just keep speeding up.)

Ok, forget you read that last bit, people are going to hate me for going down this road again. I'm going to have to do a search for the old thread on this board to see where I've gone wrong.

Chris
 
tonycondon said:
this whole thing was hashed out in probably one of the longest thread in board history Chris. I dont have a link handy but im sure you can find it. was pretty fun to read through. consensus came out that the friction from wheel bearings would not be high enough to keep the airplane from taking off normally. wheels would just be spinning twice as fast as normal at liftoff.
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Actually, the question in the other thread is different. It says that the conveyor matches aircraft speed, which I take to be equal to the speed compared to non-moving ground. The question in the cartoon that started this thread says that it matches the wheel speed. I take that to be the tangential velocity of the wheel (i.e. the speed the aircraft would normally be going on the ground for that wheel rotation rate).

The former problem means that the aircraft takes off easily with the wheels spinning twice their normal speed. The new problem means that you have a positive feedback loop and you blow up your wheels, fall down onto the conveyor and shoot off the back like in the movies with treadmills.

Chris
 
Trying to resist adding to the madness..........failed

The quiz was revived because places like the New York Times columnist David Poque picked it up and as always keep getting it wrong...and it takes another post somewhere to point out where he's wrong and multple comments hash the same "insights."

It's amazing that some I found eventually hit every explanation I tried to make the problem and explanation obvious, like imagine a seaplane or a ski plane.. when I posted those it went zipping directly overhead. When you can't see it, you cannot see it.

http://www.boingboing.net/2006/12/11/airplanetreadmill_pr.html
 
Heh... I wonder how much money I could make if I made a video explaining the answer in such a way that anyone would smack their foreheads and go "OH!!!!" and simply let people purchase it from me. I figure 5 minute video at the most, sell viewing rights for a buck a pop, and simply kick back and watch the money roll in. (Surprised Rod Machado hasn't done something like this :D)
 
wbarnhill said:
Heh... I wonder how much money I could make if I made a video explaining the answer in such a way that anyone would smack their foreheads and go "OH!!!!" and simply let people purchase it from me. I figure 5 minute video at the most, sell viewing rights for a buck a pop, and simply kick back and watch the money roll in. (Surprised Rod Machado hasn't done something like this :D)
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There are some on YouTube but they're just kids screaming and just like they posts they're wrong.

The Mythbusters have been asked to take it on many times but they will ask exactly how they can do an experiment to prove the solution.
 
I'm just waiting for the FAA to put this on the private pilot knowledge exam. That will force instructors to cover it in ground school (at least those who don't just teach memorization skills).
 
mikea said:
There are some on YouTube but they're just kids screaming and just like they posts they're wrong.

The Mythbusters have been asked to take it on many times but they will ask exactly how they can do an experiment to prove the solution.
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I figure the mythbusters could make a scale model, using r/c planes (Grant's area) and a scale model variable speed conveyor belt (Adam and Jamie could get that done easy I bet). Perhaps put some measuring equipment on the R/C plane to measure the forward motion, wirelessly sending this data to the controller for the conveyor belt. There'd be a slight delay, but I doubt to the point that it'd be an issue.

Hell, set the conveyor on full, then just set the R/C airplane on it and go full throttle. When it takes off effortlessly, bam, done.

Of course, I like my idea of standing on a skateboard with a rope tied off in front of me, then getting the person to realize that the propeller pulls on the air (the rope), and then to prove my point, no matter how fast they set the treadmill/conveyor belt, I just tug on the rope. Like I said, hand to forehead moment.
 
wbarnhill said:
I figure the mythbusters could make a scale model, using r/c planes (Grant's area) and a scale model variable speed conveyor belt (Adam and Jamie could get that done easy I bet).
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Well, in April Grant is going to be speaking at the college at which I work; maybe I'll try to ask him about it!
 
actually it would be an excellent question for the written exam, no joking.
 
tonycondon said:
actually it would be an excellent question for the written exam, no joking.
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You thought I was joking? No, but it'll bring down the average score :(. Heavens, we might actually teach students how to REASON? (Bruce, sound like anywhere you've been? :yes: )
 
gprellwitz said:
Well, in April Grant is going to be speaking at the college at which I work; maybe I'll try to ask him about it!
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Make sure the remote control part is mentioned over and over. The tech in him will shoot forth and he shall beg the producers to do it. :D
 
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