Mythbusters - Anyone see something that will stop 6000 page threads?

NYSpeed Automotive NYSpeed Off Topic
241

Maybe this comparision will make more sense.

You’ve seen the moving walkways at the airport right? Basically a giant treadmill. Now put a handrail on both sides of the walkway and turn the walkway off. Put on a pair of roller blades and see how fast you can move along the stationary walkway using just your hands on the hand rail.

You can picture this right? Guy on rollerblades pulling himself along down the stationary conveyor, wheels spinning. Lets say he can go 5 MPH.

Now, as in the airplane question, we’re going to turn the conveyor on and have it match his top speed of 5mph. Remember, he’s not pushing with his feet, he’s simply using his arms to pull himself along, the same way a prop pulling the air would move an airplane.

Ok, so start off with our rollerblader simply holding the hand rails while we ramp the conveyor up to 5mph. You agree that he’s stationary right? That even though the conveyor is going 5mph the fact that he’s on rollerblades and holding on to the railing that isn’t moving makes him stationary right? So what happens when he pulls himself forward? He’s moving right? His arms are still capable of moving him at 5MPH, the treadmill is matching that 5mph going the opposite direction. End result, guy going 5mph through the airport, treadmill going 5mph, wheels going 10mph. Maybe he only his 4.95 MPH because the friction slows him down ever so slightly, but he’s still moving forward.

Now stop making him use his hands and put a big gas powered fan on his back. Do you understand that he’ll still go forward, just as he did when he was using his hands on the railing? Neither his hands nor the fan are pushing on the moving conveyor so they are not effected by it.

Finally, replace the guy with a fan on his back with a plane. It will still accellerate to takeoff speed. Lets say 50mph since Mythbusters is going to use an ultralight. Plane going 50mph one way, conveyor going 50mph the other, wheels going 100, plane has enough airspeed to take off.

If you don’t agree with any of this, exactly where did I lose you?

242

Wait…you are allowed to rollerblade through the airport?

http://content.answers.com/main/content/wp/en/thumb/8/83/200px-0330chewbacca.jpg

243

[quote=“JayS,post:241,topic:37377"”]

End result, guy going 5mph through the airport, treadmill going 5mph, wheels going 10mph. Maybe he only his 4.95 MPH because the friction slows him down ever so slightly, but he’s still moving forward.

[/quote]

the problem states that the treadmill can match the speed of the wheels. So please explain it in those terms

244

[quote=“sureshot007,post:242,topic:37377"”]

Wait…you are allowed to rollerblade through the airport?

[/quote]

Die

Better yet, go cut off Muscle50 and have him beat you up.

245

[quote=“boardjnky4,post:243,topic:37377"”]

the problem states that the treadmill can match the speed of the wheels. So please explain it in those terms

[/quote]

The walkway can go 10mph in the other direction and you would still be able to pull yourself at 5mph.

246

LOL this whole thing is just crazy and HILARIOUS with all the “technical” replys…

Here’s a 4th grade science experiment to prove how/why it will/wont.

You need:
A treadmill
A model car of some sort with free-spinning wheels
A piece of string

Tie the string to the front of the car

Place the car on the treadmill and hold the string out the front of the treadmill such that you are “holding” the car on the treadmill with the string

Turn on the treadmill.

You are now holding the car on the treadmill with the string; the wheels of the car are the going the same speed as the treadmill, correct?

Now pull on the string, can you pull the string? YOU ARE THE JET ENGINE THEN; the force moving the airplane/car has no relationship to wheel speed of the vehicle/treadmill.

The ONLY limitation I can see that will make it or not make is if the engines are powerful enough to overcome the doubling of rolling resistance of the wheels.

247

[quote=“JayS,post:241,topic:37377"”]

Maybe this comparision will make more sense.

You’ve seen the moving walkways at the airport right? Basically a giant treadmill. Now put a handrail on both sides of the walkway and turn the walkway off. Put on a pair of roller blades and see how fast you can move along the stationary walkway using just your hands on the hand rail.

You can picture this right? Guy on rollerblades pulling himself along down the stationary conveyor, wheels spinning. Lets say he can go 5 MPH.

Now, as in the airplane question, we’re going to turn the conveyor on and have it match his top speed of 5mph. Remember, he’s not pushing with his feet, he’s simply using his arms to pull himself along, the same way a prop pulling the air would move an airplane.

Ok, so start off with our rollerblader simply holding the hand rails while we ramp the conveyor up to 5mph. You agree that he’s stationary right? That even though the conveyor is going 5mph the fact that he’s on rollerblades and holding on to the railing that isn’t moving makes him stationary right? So what happens when he pulls himself forward? He’s moving right? His arms are still capable of moving him at 5MPH, the treadmill is matching that 5mph going the opposite direction. End result, guy going 5mph through the airport, treadmill going 5mph, wheels going 10mph. Maybe he only his 4.95 MPH because the friction slows him down ever so slightly, but he’s still moving forward.

Now stop making him use his hands and put a big gas powered fan on his back. Do you understand that he’ll still go forward, just as he did when he was using his hands on the railing? Neither his hands nor the fan are pushing on the moving conveyor so they are not effected by it.

Finally, replace the guy with a fan on his back with a plane. It will still accellerate to takeoff speed. Lets say 50mph since Mythbusters is going to use an ultralight. Plane going 50mph one way, conveyor going 50mph the other, wheels going 100, plane has enough airspeed to take off.

If you don’t agree with any of this, exactly where did I lose you?

[/quote]

this is a very well conceived point! for those of you who didn’t understand before you should have a better understanding now.

Iwould think the point of using a real life treadmill to make planes take off would be to cut down on runway space thats the only real benefeit i can see. But as stated somewhere
If it’s not broken then there is no need to fix it.

248

[quote=“sureshot007,post:245,topic:37377"”]

The walkway can go 10mph in the other direction and you would still be able to pull yourself at 5mph.

[/quote]

if wheels and and treadmill are going the same speed, doesnt that mean that you would be standing still?

i would think that in order to move in the forward direction, the wheels would always have to be spinning slightly faster then the treadmill. I am not doubting that the plane would move, more doubting that the conveyor belt would instantly keep up and/or the validity of that part of the question.

249

[quote=“boardjnky4,post:248,topic:37377"”]

if wheels and and treadmill are going the same speed, doesnt that mean that you would be standing still?

[/quote]

yes you would be! but thats where the jet engines come in making you go forward, or your arms pulling you along the handrail to overcome the standing still factor.

250

since the wheels are free spinning, the actual wheel speed plays no role.

One prediction for the show, though. I predict a massive bearing failure on at least one wheel that leaves something for the doubters to hang on to.

251

[quote=“97FormulaWS-6,post:246,topic:37377"”]

LOL this whole thing is just crazy and HILARIOUS with all the “technical” replys…

Here’s a 4th grade science experiment to prove how/why it will/wont.

You need:
A treadmill
A model car of some sort with free-spinning wheels
A piece of string

Tie the string to the front of the car

Place the car on the treadmill and hold the string out the front of the treadmill such that you are “holding” the car on the treadmill with the string

Turn on the treadmill.

You are now holding the car on the treadmill with the string; the wheels of the car are the going the same speed as the treadmill, correct?

Now pull on the string, can you pull the string? YOU ARE THE JET ENGINE THEN; the force moving the airplane/car has no relationship to wheel speed of the vehicle/treadmill.

The ONLY limitation I can see that will make it or not make is if the engines are powerful enough to overcome the doubling of rolling resistance of the wheels.

[/quote]

this is my point tho. car standing still means that conveyor belt speed and wheel speed are the same. so in THEORY, if the treamill can match the wheel speed INSTANTANEOUSLY(which is more or less impossible) the plane would have a very difficult time moving in the forward direction.

252

And this is why you work for CIT.

253

[quote=“boardjnky4,post:251,topic:37377"”]

this is my point tho. car standing still means that conveyor belt speed and wheel speed are the same. so in THEORY, if the treamill can match the wheel speed INSTANTANEOUSLY(which is more or less impossible) the plane would have a very difficult time moving in the forward direction.

[/quote]

in this case yes then the conveyor would need to be set at a constant speed then in order to counter that.

254

[quote=“XH TNTA,post:253,topic:37377"”]

in this case yes then the conveyor would need to be set at a constant speed then in order to counter that.

[/quote]

i think it would be more proper if you took an 80grit Belt Sander and tried accelerating your face along it in the opposite direction. :burnin:

why do i get the feeling you’re Cuban Crisis?

255

guys i’m not doubting the plane here, i know that fucker is gonna move no matter what. Im just trying to understand the wheels speed vs. treamill speed thing.

is it true that if the wheel speed is equal to the treamill speed that means that it is standing still?

256

I typed a response, but it made too much logical sense, and hence would be wasted in this thread. Nevermind.

257

[quote=“LAFENGAS,post:254,topic:37377"”]

i think it would be more proper if you took an 80grit Belt Sander and tried accelerating your face along it in the opposite direction. :burnin:

why do i get the feeling you’re Cuban Crisis?

[/quote]

ROTFLMAO!!!

258

[quote=“LAFENGAS,post:254,topic:37377"”]

i think it would be more proper if you took an 80grit Belt Sander and tried accelerating your face along it in the opposite direction. :burnin:

why do i get the feeling you’re Cuban Crisis?

[/quote]

if that was the case, from reading other said thread then i would be opposing not agreeing with you :smash2:
and this guy says it perfectly

[quote=“Jskrapper,post:39,topic:37439"”]

Basically I am saying the treadmill will never be able to keep up with the planes desired wheelspeed. The experiment will be flawed because of design of the treadmill will limit it’s speed, the plane will slowly start to move forward, and then rapidly pick up speed…then take off.

The plane will fly.

In prfect conditions, no airflow over wings = no airspeed = no takeoff. This would have to be one hell of a treadmill that can move at unimaginable speeds with ZERO friction. This is the flaw in the test.

[/quote]

259

[quote=“sureshot007,post:256,topic:37377"”]

I typed a response, but it made too much logical sense, and hence would be wasted in this thread. Nevermind.

[/quote]

i know that the wheel speed is neglegable, and that is why i do not doubt that the plane will take off. just trying to understand what happens between the wheels and treadmill. thats all.

you guys are mistaking why i am asking this question.

260

[quote=“sureshot007,post:252,topic:37377"”]

And this is why you work for CIT.

[/quote]

correction, thats why i failed out of mechanical engineering