Author Topic: Can this airplane lift off? (Read 31207 times)

333 · « **Reply #100 on:** April 02, 2009, 06:30:12 PM »

Quote from: Dukiedook on April 02, 2009, 06:17:59 PM

Well 333, if we take friction totally out of the equation how would the plane produce thrust?

With a propeller? Or a jet engine? The wheels don't have anything to do with getting a plane in the air on a asphalt runway. Except for that one in that James Bond(Roger Moore) movie where a AMC Matador sprouted wings and got away from Bond. And the jet engine probably had more to do with getting that thing airborne anyways.

That is, of course, if you believe a Matador can fly.

MCRider · « **Reply #101 on:** April 02, 2009, 06:31:18 PM »

Quote from: Dukiedook on April 02, 2009, 06:17:59 PM

Look, if you are going to take everything mythbusters does as fact, well I don't know what to say.
I have watched the show when I get a chance and some of their experiments take wild assumptions and are not scientifically accurate.

Case in point: trying to prove that an army of soldiers in lockstep could not take down a bridge. The experiment they ran was very flawed. The plane one I didn't get to see, the clip the guy ran on this thread didn't show how the whole experiment was run.

Well 333, if we take friction totally out of the equation how would the plane produce thrust?

The clip is a short version of a longer one which is easily accessed in the margin where they line up other clips similar to the one being featured. I saw it as i was curious to see the rest of the experiement as well. They got a super long tarp to act as the conveyor belt. They rigged up a towbar to a pickup truck. The plane was a smaller stunt plane with a low take off speed. Ready set go, the truck accelerates to 30mph in one direction dragging the tarp under the plane, which accelerates to 30mph in the other direction and then promptly takes off. There was no resistance to the plane moving forward, the pilot did not think it would take off. They interviewed him afterwards and he was shocked. It performed as though the wheels and the tarp made no difference...because they don't. My guess is simply the wheels were turning at 60mph.

The power that makes the plane move forward is directed to the air, not the ground, as it would be on a car with driven wheels.

Don't make it any harder than it needs to be. Its a trick puzzle but its completely sensical once you separate the desire to see the plane as a car.

Bob Wessner · « **Reply #102 on:** April 02, 2009, 06:36:04 PM »

I'm off to bed. Can't wait to see how many pages we're at tomorrow.

Nice brain teaser though.

Duke McDukiedook · « **Reply #103 on:** April 02, 2009, 06:36:21 PM »

So how did they know the tarp was moving as fast as the wheels?

Sam Green Racing · « **Reply #104 on:** April 02, 2009, 06:38:05 PM »

Quote from: Samcr750 on April 02, 2009, 05:40:34 PM

Here ya go Dukie, try this one.

The conveyor belt reacts to the planes wheel speed and the conveyor and wheels are traveling at 700mph but the plane is not under power so is not going anywhere.
The friction in the wheel bearings and between the tyre and the belt would cause the plane to move backwards.
If the friction could be overcome, the plane would remain stationary.
Here we go. The wheels and belt are doing 700mph. A fly on the flight deck decides it needs to pee and the toilet is at the rear of the plane. The fuselarge is 330 feet long and it takes the fly 3.75 seconds to get there.

For Dukie only, what was the average speed of the flys flight ?

Sam.

Seems Dukie didn't want to solve this one, anyone ?

Sam.

Steve F · « **Reply #105 on:** April 02, 2009, 06:41:19 PM »

Quote from: Dukiedook on April 02, 2009, 06:17:59 PM

Well 333, if we take friction totally out of the equation how would the plane produce thrust?

You're joking, I hope.

Retro Rocket · « **Reply #106 on:** April 02, 2009, 06:43:12 PM »

Hmmmm, maybe "common sense" isn't that common....

Mick

Duke McDukiedook · « **Reply #107 on:** April 02, 2009, 06:43:41 PM »

No, please explain to me in a frictionless environment how either engine would produce thrust.

333 · « **Reply #108 on:** April 02, 2009, 06:43:56 PM »

The scary thing is, no. He probably isn't.

Markcb750 · « **Reply #109 on:** April 02, 2009, 06:44:40 PM »

Just to add combustibles

[youtube=425,350]VyR2E1QGTCk[/youtube]

Duke McDukiedook · « **Reply #110 on:** April 02, 2009, 06:46:10 PM »

Nothing scary boys, just explain it with sound science theory.

333 · « **Reply #111 on:** April 02, 2009, 06:48:03 PM »

You people are reading too much into this. It is not a friction less environment. There is only no friction between the wheels and the rolling belt. Or a asphalt runway. At least not enough to affect the planes ability to take off and fly. The original question posed only a weird conveyor belt. All the other laws of physics still apply.

Gravity. It's the law.

MCRider · « **Reply #112 on:** April 02, 2009, 06:49:58 PM »

Quote from: Dukiedook on April 02, 2009, 06:36:21 PM

So how did they know the tarp was moving as fast as the wheels?

"When the runway senses the wheels moving, the runway will match the speed of the airplane's wheels, but in the opposite direction."

So on "go" the pilot floors it and the truck floors it. They show the truck speedo at 30mph. They switch back to the plane and its lifting off.

You can argue the finer points of the experiemnt all you want.

But had the plane stood still the criteria would have had the truck stay still too. But the plane immediately began moving forward, so did the truck. Fact is, even if the truck went 2 or 20 times faster than the plane, the plane would have still moved forward at its regular takeoff pace and would have taken off.

I guess you could say what if the plane was faster than the truck? I don't think so, but i don't know. But I'm sold on the concept. Its all over YouTube, everybody's in on it and the split is about as it is here, 2 yes for every 1 no.

I'm done.

Duke McDukiedook · « **Reply #113 on:** April 02, 2009, 06:57:16 PM »

Quote from: MCRider on April 02, 2009, 06:49:58 PM

Quote from: Dukiedook on April 02, 2009, 06:36:21 PM
So how did they know the tarp was moving as fast as the wheels?

You can argue the finer points of the experiemnt all you want.

Meh, those pesky finer points...

Markcb750 · « **Reply #114 on:** April 02, 2009, 06:57:42 PM »

The Myth Busters did way better then simple equations...

I maybe misunderstanding you but unless you are going to state that premise of the question differently your theory of how the wheels of the aircraft and the system that propels the aircraft interact is incorrect.

Air is accelerated rearward, by the prop or the turbine, this acceleration is reacted to by the aircraft which responds by accelerating forward. the wheels impede the forward acceleration a little, but not much. Issac Newton provided the three laws for mathematically predicting it.

333 · « **Reply #115 on:** April 02, 2009, 06:58:49 PM »

Check this out. It flew!

http://www.terrafugia.com/

MCRider · « **Reply #116 on:** April 02, 2009, 07:07:50 PM »

At the 2:30 mark or so is the key. The plane's forward thrust is not tied to the wheels. period.

Short of tying the 2 vehicles together electronically, I'd say it was a pretty good demo.

Caaveman82 · « **Reply #117 on:** April 02, 2009, 07:31:49 PM »

Quote from: MCRider on April 02, 2009, 07:07:50 PM

At the 2:30 mark or so is the key. The plane's forward thrust is not tied to the wheels. period.

Short of tying the 2 vehicles together electronically, I'd say it was a pretty good demo.

HEY!!!

You said you were done!!!!

MCRider · « **Reply #118 on:** April 02, 2009, 07:55:56 PM »

Oops.

Caaveman82 · « **Reply #119 on:** April 02, 2009, 08:00:20 PM »

It's okay... I won't tell,

Gordon · « **Reply #120 on:** April 02, 2009, 08:53:00 PM »

Why am I not surprised that I come back after several hours and this thread has taken on a life of its own?

I've already strained my gray matter enough trying to explain this as best I can, and don't have any more energy to try again tonight. I managed to get one person to see the light, and that's plenty for me.

Once someone has dug their heels in on something like this, no amount of explanation or numbers crunching will convince them otherwise until they see it with their own eyes, and since I don't have a gigantic conveyor belt or an airplane, there's not much else I can do.

Dukie, I've been enjoying this discussion, so please don't take it personally that I disagree with your position. Also, please don't take my lack of desire to continue trying to convince you that you are incorrect as any kind of sign that I'm beginning to think you may not be.

I'll check back in tomorrow at lunch and see how things are progressing.

Joel · « **Reply #121 on:** April 02, 2009, 09:08:26 PM »

Quote from: Dukiedook on April 02, 2009, 06:00:43 PM

I hear ya Mason, but when people say the wheels don't figure into the equation, they are wrong. Bearings generate heat and friction which in turn will create drag and more drag, no matter how well engineered.

The question is what kind of velocities and forces are we talking about here.

The drag from the spinning wheels is negligible which is why the plane takes off. If the conveyor speed equals the airplane's air speed, the wheels will simply spin at twice the normal rate and the plane will still take off when it reaches the proper speed. Because there is no set relationship between the airspeed of the plane and the rotational speed of the wheels, the conveyor can't prevent the plane from taking off.

mystic_1 · « **Reply #122 on:** April 03, 2009, 04:57:37 AM »

Air speed != Ground speed.

mystic_1

Markcb750 · « **Reply #123 on:** April 03, 2009, 05:06:01 AM »

what does "!=" mean?

cb650 · « **Reply #124 on:** April 03, 2009, 05:07:57 AM »

Airspeed does not = groundspeed

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Can this airplane lift off?

Author Topic: Can this airplane lift off? (Read 31207 times)

Markcb750

Markcb750

Markcb750