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Seriously now, can it take off or not? What do you think?
Regarding the plane on the belt question, do you really think the plane will take off or not?
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RE: Seriously now, can it take off or not? What do you think?
Well, if we are talking about a "normal" airplane, with normal power to weight ratio, meaning no 3D power to weight or to put it simple, just an ugly stick with a .40 engine... no, I would not think so. But if you have at least 2:1 power to weight and the plane is capable of taking of fron your hand without throwing it... yes it problably will take off.
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RE: Seriously now, can it take off or not? What do you think?
It's airspeed that determines take off, so while the treadmill speed may be impressive, the airspeed over most of the wing would be pretty close to zero.
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RE: Seriously now, can it take off or not? What do you think?
What?!!!!!!!:eek:
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RE: Seriously now, can it take off or not? What do you think?
IT IS ALWAYS BETTER TO POST IN AN EXISTING THREAD THAN START YOUR OWN
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RE: Seriously now, can it take off or not? What do you think?
IT IS ALWAYS BETTER TO POST IN AN EXISTING THREAD THAN START YOUR OWN The reason I wanted the poll is because I could not, for the life of me, believe that anyone could seriously be on the "no" side of this question, and therefore the one or two still arguing for it (and arguing pretty vaguely, I might add) must be trolls. I thought, perhaps wrongly, that a poll would help us identify if there really any members worth trying to convince. By the way, my eyesight is fine, thank you. Phil |
RE: Seriously now, can it take off or not? What do you think?
How could the plane take off if it were on a treadmill that kept pace with the movement of the plane so that the plane wasn't moving relative to the ground?
Any thrust generated by an engine is used to get it moving so that there is enough airflow over the wings to get it to lift off (unless there is enough thrust for a vertical take off, but I didn't think that's what we were talking about). If the forward movement is 'erased', then you can't get to a lift off speed. It's like the opposite of a catapult launch, instead of the forward speed added to the movement of the plane which helps take off in a shorter distance, the treadmill launch removes the chance for a take off. That's why we need the runway. If planes could take off from a treadmill, we could save valuable real estate, put those 747's on a big treadmill, let them spool up and get a good go on the belt and watch them take off from zero ground speed. I didn't follow the other thread--I guess I still need convincing. |
RE: Seriously now, can it take off or not? What do you think?
Time Pilot,
If the catapult were connected through rotating wheels the plane would just sit there. But it has a hook. Likewise, if you hook the back of the plane to the runway with a hook, it won't move. But the plane is sitting on wheels with bearings, movement of the tires doesn't matter. It's movement of air that makes the plane move. That comes from propeller thrust. Rutan just made a flight in a rocket powered plane that took off from a runway. Do you think it would sit still on a treadmill? Nope, don't think so. It doesn't care what the wheels are doing either. The wheels aren't propelling the plane down the runway. It doesn't matter what they are doing. Larry |
RE: Seriously now, can it take off or not? What do you think?
Okay. I get it now, and by tomorrow, I hope I'm feeling a little less stupid. [:-]
ORIGINAL: LarryC Time Pilot, If the catapult were connected through rotating wheels the plane would just sit there. But it has a hook. Likewise, if you hook the back of the plane to the runway with a hook, it won't move. But the plane is sitting on wheels with bearings, movement of the tires doesn't matter. It's movement of air that makes the plane move. That comes from propeller thrust. Rutan just made a flight in a rocket powered plane that took off from a runway. Do you think it would sit still on a treadmill? Nope, don't think so. It doesn't care what the wheels are doing either. The wheels aren't propelling the plane down the runway. It doesn't matter what they are doing. Larry |
RE: Seriously now, can it take off or not? What do you think?
Wheels will me moving twice as fast, but it will take off in almost the same distance as normal. The only reason it is a little longer is because the wheels spinning faster should add just the slightest bit of drag more than normal. Other than that, they make NO difference.
Now if it was in a wind tunnel and the AIRSPEED was adjusted like the treadmill it would be a different story. |
RE: Seriously now, can it take off or not? What do you think?
Time Pilot is right it cant fly....picture yourself...with a hang glider on your back...on the same treadmill....while you might be running as fast as you can...youre not moving relative to the ground...so no air is moving over you're glider..its the air moving over the wings that matters...
As you read the next paragraphs, keep in mind, when I refer to verical and horizontal directions, Im talking about the planes X and Y axis...not the ground... Also ( i just read LarryC's post) its not the engine that provides lift...the engine propells the planes horizontal axis...not vertical...think of it this way...if the air generated by the engine is what provided lift...when you hooked your legs behind youre planes tail and full throttled it...IF THE ENGINE PROVIDED LIFT...the plane would rise verticly although not moving foward. This is why planes require a runway also...even though the planes egine is at full throttle...the plane needs to reach a certain airspeed before it leaves the ground. Now Im sure some one is goning to read this and talk about hovering saying somthing like "when youre hovering the engine provides lift and youre not moving foward" Thats true...but the plane is pointed strait up, therefore the engine is providing (yet again) FOWARD thrust not along the planes vertical axis. CK |
RE: Seriously now, can it take off or not? What do you think?
ORIGINAL: ArmedZagi Time Pilot is right it cant fly....picture yourself...with a hang glider on your back...on the same treadmill....while you might be running as fast as you can...youre not moving relative to the ground...so no air is moving over you're glider..its the air moving over the wings that matters... As you read the next paragraphs, keep in mind, when I refer to verical and horizontal directions, Im talking about the planes X and Y axis...not the ground... Also ( i just read LarryC's post) its not the engine that provides lift...the engine propells the planes horizontal axis...not vertical...think of it this way...if the air generated by the engine is what provided lift...when you hooked your legs behind youre planes tail and full throttled it...IF THE ENGINE PROVIDED LIFT...the plane would rise verticly although not moving foward. This is why planes require a runway also...even though the planes egine is at full throttle...the plane needs to reach a certain airspeed before it leaves the ground. Now Im sure some one is goning to read this and talk about hovering saying somthing like "when youre hovering the engine provides lift and youre not moving foward" Thats true...but the plane is pointed strait up, therefore the engine is providing (yet again) FOWARD thrust not along the planes vertical axis. CK Saw ZZ Top do their "Recycler" tour, back in the Michael Jackson moonwalk days. They actually had a treadmill on the stage, they'd saunter to their right, the treadmill would carry them backwards, looked like they were moonwalking. Not that that has anything to do with it, either. Dave Olson |
RE: Seriously now, can it take off or not? What do you think?
ORIGINAL: ArmedZagi picture yourself...with a hang glider on your back...on the same treadmill....while you might be running as fast as you can...youre not moving relative to the ground...so no air is moving over you're glider..its the air moving over the wings that matters... CK |
RE: Seriously now, can it take off or not? What do you think?
Yall are forgeting that no matter how fast the plane TRIES to move...the treadmill keeps pace...
Here is the original question ORIGINAL: bentwings *** Brain Teaser *** Imagine an airplane is on the beginning of a massive conveyor belt, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation. There is no wind. Can the plane take off? ...any extra thrust the plane recives will make the plane roll faster... Correct? Yes...however since the treadmill is moving the same speed as the planes wheels "at any given time" the planes airspeed will still be ....0 and with 0 airspeed...that plane aint goin nowhere... CK |
RE: Seriously now, can it take off or not? What do you think?
Armed ==
Think about this carefully...ok i have time. you are assuming the wheels need to make contact with the ground for an airplane to accelerate. if that were so, we wouldn't need jets or props at all to fly. we'd just keep propelling the wheel in mid air for an airplane to continue to fly including accelerating in the air. if the conveyor made a difference, then we'd need some sort of "hard surface in the sky" to make contact with the wheels for the airplane to keep moving while in the air. |
RE: Seriously now, can it take off or not? What do you think?
I never said the wheels provide thrust...but until a plane has enough airspeed to get airborne...the wheels are going to be on the ground and causing friction.
CK |
RE: Seriously now, can it take off or not? What do you think?
in essence, you are saying the wheels of an airplane provide thrust. a car applies thrust through its wheels. the propelling wheels on a car are NOT freewheeling whereas an airplane does it differently.... and has freewheeling wheels.
that's why we use wheels to lessen friction on land airplanes. an opposite running conveyor belt can't possibly provide as much friction as wheels with the brakes locked on stationary hard tarmac!!!! if you are trying to stop the plane from moving forward, it's better to lock the wheels than the elaborate setup the question poses...and it's still not adequate to stop the craft. an engine, powerful enough, will drag locked wheels on a hard tarmac till takeoff speed is established. if the wheels never catch up to the plane's forward motion because of "conveyor effect", that's fine, the thrust is what's controlling forward motion here and everything else can come along for the ride....even if it means the wheels get dragged at some point. a;; that stuff about friction etc just complicates matters needlessly. THRUST is controlling and not the other way around -( wheels for cars, jet blast or props for airplanes) ......whatever the wheels on a landplane are doing....they either get along with the program or come for a cruise. |
RE: Seriously now, can it take off or not? What do you think?
I suppose it really all depends on how you take the question...but I still think the way its worded means that no matter how much power the plane has...it will stay in the same spot...
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RE: Seriously now, can it take off or not? What do you think?
i guess it does depend. will it help if the question had said a boat with wheels with a conveyor belt under the wheels while in water?
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RE: Seriously now, can it take off or not? What do you think?
Yes but that isnt the question now is it...lol :D
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RE: Seriously now, can it take off or not? What do you think?
:D:D:D
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RE: Seriously now, can it take off or not? What do you think?
Well its been ...interesting...but Im gonna call it a night and go watch tv...Im taping "The Triangle" ...Love that show...talk to you later.
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RE: Seriously now, can it take off or not? What do you think?
It'll TAKE OFF !
No matter the plane is not moving .... but it's still throwing back air and generating thrust. This is somewhat similar to a wind tunnel. Where the plane is stationary but it is actually flying. |
RE: Seriously now, can it take off or not? What do you think?
There is a 67 page thread on this on rcgroups it is running about 54% "no" (the correct answer, BTW)
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RE: Seriously now, can it take off or not? What do you think?
I REALLY wish we could get a wager on this, so many rapid "yes it will fly" guys, they would bet anything. MUCH money to be made!!
Kind of like betting Knick fans during Michael Jordan's days in Chicago...oh those were good times. |
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