The greatest question in the history of human kind.

[qaztwo]

Re: The greatest question in the history of human kind.

If you attach a rope to toy car and pull it it moves forward. Take that same car and place on conveyor and same results. Rolling friction is less then static friction might not even require more power to acc. And yes the wheels would be spinning faster, conveyor belt speed + forward movment. If you want the wheels to not move repeat experiment on ice and lock the wheels up plane will still take off.

 

[mudmagnet63]

Re: The greatest question in the history of human kind.

Jimminy Christmas

The prop pulling the plane through the air dont give a #### how fast the wheels are moving, if the wheels were rolling @ 2000 mph backwards it wouldnt make a crap they are FREEWHEELING

 

[SgtMaj]

Re: The greatest question in the history of human kind.

The engine (and prop) will pull the plane forward (on it's wheels) right up to the point that there is enough air movement over the wings to create lift.
If the wheels are going at the same speed as the conveyor belt, there is NO air movement over the wings (on a single prop airplane)
On a multi engine airplane, the propwash over the wing is not enough to lift the plane. It needs the lift from the rest of the wing.

On Myth busters, all they did was allow the wheels to go a LOT faster than the "Conveyer Belt"
They just forgot to look at their video's of when the planes actually lifted off.

I didn't think that was part of the premise of the original myth... especially since it would not be physically possible to accelerate the treadmill to the point where the plane wouldn't be moving forward, since the prop will pull the plane forward reguardless of how fast the treadmill is going or accelerating.

 

[oops!]

Re: The greatest question in the history of human kind.

i need to see the show.....

all i know is it requires air speed over the mainplaines to generate lift.....reguardless of what the wheels are doin.....and a single prop aint gonna generate that kind of airspeed over the whole surface of the wings

durn re runs

 

[SgtMaj]

Re: The greatest question in the history of human kind.

I got hit with the reruns too, so I didn't get to see it either, but as I understand it, the plane isn't stationary.

 

[QC]

Re: The greatest question in the history of human kind.

They (the other side) still don't get it . . . Nobody is saying the prop will blow enough air across the wings to create lift. The flippin' plane moves forward, ground speed increases, regardless of the speed of the wheels . . . OMG!

 

[oops!]

Re: The greatest question in the history of human kind.

im sorry qc...did you say the plane was moving????

i thought it was stationary on a treadmill......


i really need to see the show

oops

 

[Kenneth Brown]

Re: The greatest question in the history of human kind.

They (the other side) still don't get it . . . Nobody is saying the prop will blow enough air across the wings to create lift. The flippin' plane moves forward, ground speed increases, regardless of the speed of the wheels . . . OMG!

How does the plane move forward then? If it takes a speed of 73 mph to take off......... Never mind. Ya'll win, Mythbusters is now fake in my eyes and I'll still watch it for Kari.

 

[mudmagnet63]

Re: The greatest question in the history of human kind.

There is nothing to MAKE the plane stay stationary the wheels serv only to let the plane roll. Foreward thrust created by the prop has zero to do with wheels if it takes 73 mph to take off and the treadmill is set at 73 mph all that happens is the tires spin at 146 mph when the plane leaves the ground

 

[rotor_av8]

Re: The greatest question in the history of human kind.

OK, I'm a helicopter pilot but the principles of flight, believe it or not are still the same. The helicopter's wing is thrust into the air in a circular motion instead of the air being pushed straight in.

Here are the facts. Forget the wheels. A lifting wing needs airflow over it to provide lift. Without airflow there is no lift. Period. W/ enough HP a prop can create enough wing for lift without much foreward motion.

25 percent of lift is generated by air forced into the underside of an airfoil (wing) 75 percent of your lift is generated by the vaccuum(negative pressure) left on the top of the lifting wing. Look up the "venturi tube" and "bernoli's principal". Also look up how an airfoil works.....believe it or not a boat hull in the same idea....the lift in a boat is mostly generated not by the water forcing up but the negative pressure area created by the displacement of water.

Something has to generate this airflow. It can be foreward motion or wind generated by a propeller. Some powerful airplanes can generate enough airflow with minimal foreward motion just with the prop to lift off with a tiny bit of roll distance. These planes are used in Alaska a lot where they have tiny roll out areas like sandbars to land on. I think one kind is called a Cub.

Gyrocopters can do this too called a jump takeoff. A gyro has no power driving the main rotor only wind created by a airplane type prop that pushes.

I fly a helicopter and our takeoff is almost always 0 feet and 0 inches.

Common planes for short roll takeoffs are super cubs, zeniths and huskies.

Some video links:

http://www.youtube.com/watch?v=1tJuO16hRTk&feature=related
http://www.youtube.com/watch?v=H6ApIG7jIpk
http://www.youtube.com/watch?v=c99ZHZw97rU&feature=related
http://www.youtube.com/watch?v=3RPYWmdv174

Hope this helps. The prop makes the wind.....BTW I have not seen this video so if anyone finds it please link to it. Thanks,

-Rotor

 

[rotor_av8]

Re: The greatest question in the history of human kind.

When I say powerful airplanes I mean a high power to weight ratio.

Cool Fact: The helicopter is the only machine that takes more power to go slow (hover) and less power to go faster.

 

[SgtMaj]

Re: The greatest question in the history of human kind.

Rotor av8

I don't think the plane was stationary. I think it rolled down the moving runway to take off. (I havn't seen the vids either, but that is the premise of the so called "airplane on a treadmill")

 

[roadhog]

Re: The greatest question in the history of human kind.

hey, oops, Google mythbusters, then results, they've got the video on there. It's busted!!

 

[jsfinn]

Re: The greatest question in the history of human kind.

I saw the show and didn't think the plane was going to take off because I know there has to be air movement around the wings - specifically lift under the wings creating lift .... After reading some posts and seeing the show, I'm still confused how the plane could take off but I think I'm coming to the conclusion that:

The speed of the plane probably helps get air movement around the wings, but the prop alone pushing air around the wings actually makes it take off.

Does this make any sense?

 

[mudmagnet63]

Re: The greatest question in the history of human kind.

The foreward movement makes the plane takeoff just as if there were no treadmill. The treadmill ony serves to confuse the reader. the wheels of the plane are not controled by the motor like a car. The prop pulls the plane foreward regardless of what the wheels are doing

 

[Bass Man Bruce]

Re: The greatest question in the history of human kind.

The treadmill ony serves to confuse the reader. (end quote)


This is the crux of the discussion. The rest is just an airplane.
(this ignores the "friction" element on the wheels/pontoons but thats a digression)

 

[qaztwo]

Re: The greatest question in the history of human kind.

Angle of attack and money generate lift. Some airfoils can generate lift with a negative angle of attack some need positive. Aerobatic planes have symmetrical airfoils they fly just fine.

 

[QC]

Re: The greatest question in the history of human kind.

There is nothing to MAKE the plane stay stationary the wheels serv only to let the plane roll. Foreward thrust created by the prop has zero to do with wheels if it takes 73 mph to take off and the treadmill is set at 73 mph all that happens is the tires spin at 146 mph when the plane leaves the ground

Please, those of you who are still struggling with this, read the above mudmagnet quote. Read it over and over and over, and then when you get tired, read it again. That's the story, it is not about lift created by the propeller wash necessarily, it is that the plane goes forward because the wheels and propeller are not connected!!!!!!!!!!!!!! The wheels are idlers . . . They don't know what the wing, prop and the rest of the plane are doing. They don't care, they just spin and spin and then spin some more, just like your reading assignment . . .

 

[oops!]

Re: The greatest question in the history of human kind.

i just saw it.......thanks road hog.....

of course the plane flew.......he had forward momentum (sp)

(air speed over the main planes....wings..)

it doesnt matter what the wheels were doing....the pilot just did a regular take off...!!!!

in my opinion...that was a stupid myth.....i liked the donzie into the pole better.....

cant believe all the fuss bout that one.

i was under the impression that the plane was stationary and just the treadmill was moving....in that case the only thing that would cause the plane to take off....would be wind!!!!...lots of it....

oops

 

[mudmagnet63]

Re: The greatest question in the history of human kind.

Valum and a Crown on the rocks That will let u take off. sheesh


Mud