RE: Can It Take Off??  
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RE: Can It Take Off?? - 12/3/2005 1:20:29 AM   
iron eagel



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From: Middleboro, MA, USA
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quote:

ORIGINAL: danny03

I respectfully disagree, the way I see it since the wheels are free to rotate there is no force holding the aircraft still, thereby allowing the aircraft to move forward allowing airflow over the wings. The only thing that the belt is doing is spinning the wheels faster.


Dany03 Hit the nail on the head, all the belt will do is make the wheels spin faster.
I have stood by the wingtip of a J3 going into a 40 kph headwind at take off, it climbed out like a helicopter. Airplanes do not care about ground speed ( how fast they move relative to the ground) just air speed. And like I said before the belt moving under the aircraft will produce air movement of some kind. The wheels may spin like He## but the plane will fly! No mater what the airplane will respond to the thrust of the engine, the wheels just keep the prop from getting broke and the belly from getting dents.

_____________________________

The Wrights never crashed, they only had hard landings. I 've had some hard landings myself. AMA EAA AOPA revver #185

(in reply to danny03)
       Post #: 26

RE: Can It Take Off?? - 12/3/2005 1:30:56 AM   
starwoes



Posts: 121
Joined: 10/6/2005
From: Maple Heights, OH, USA
Status: offline 		this focus on wheels i believe is getting outrageous. in fact, to see this clearly, i think you must discount the value of weight. for one, assume the plane is suspended on an infinite rope.......eg, a clothesline is hooked up where there's a pulley on the clothes line which is connected to the cg of the plane such that, the plane's wheels barely touch the threadmill...aircraft is perfectly balanced and suspended above the threadmill but with enough wheel contact (friction to spin the wheels). any increase or decrease in threadmill speed results in an increase or decrease in wheel speed.

spin the threadmill alone and see what happens. l'm sure the wheel will duplicate what the argument is about without a resultant increase in airspeed of the craft. now turn on the jets of the aircraft or the props of the aircraft and see what happens. the airplane will accelerate down the rope...threadmill or no threadmill. in fact, the wheels and threadmill can spin like mad and it wouldn't make a bit of a difference. i believe that's why we rely on wheels to propel cars and thrust to propel aircrafts.

in any case, i believe a seaplane trying like mad to match the current of a river will probably result in zero airspeed and thus...no fly..

(in reply to dick Hanson)
       Post #: 27

RE: Can It Take Off?? - 12/3/2005 1:39:40 AM   
iron eagel



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From: Middleboro, MA, USA
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quote:

ORIGINAL: starwoes

this focus on wheels i believe is getting outrageous. in fact, to see this clearly, i think you must discount the value of weight. for one, assume the plane is suspended on an infinite rope.......eg, a clothesline is hooked up where there's a pulley on the clothes line which is connected to the cg of the plane such that, the plane's wheels barely touch the threadmill...aircraft is perfectly balanced and suspended above the threadmill but with enough wheel contact (friction to spin the wheels). any increase or decrease in threadmill speed results in an increase or decrease in wheel speed.

spin the threadmill alone and see what happens. l'm sure the wheel will duplicate what the argument is about without a resultant increase in airspeed of the craft. now turn on the jets of the aircraft or the props of the aircraft and see what happens. the airplane will accelerate down the rope...threadmill or no threadmill. in fact, the wheels and threadmill can spin like mad and it wouldn't make a bit of a difference. i believe that's why we rely on wheels to propel cars and thrust to propel aircrafts.

in any case, i believe a seaplane trying like mad to match the current of a river will probably result in zero airspeed and thus...no fly..

Yes indeed the wheels and or how fast they turn are no matter to the airplanes movement.

_____________________________

The Wrights never crashed, they only had hard landings. I 've had some hard landings myself. AMA EAA AOPA revver #185

(in reply to starwoes)
       Post #: 28

RE: Can It Take Off?? - 12/3/2005 2:22:16 AM   
da Rock



Posts: 6130
Joined: 10/11/2005
From: western, NC, USA
Status: online 		How on earth is the conveyor belt possibly going to do anything to the airplane. It has no purchase, no leverage. If it was going to hold back the a/c it would have to do it THROUGH the tire. And if it grips the tire, the tire will turn. No leverage to the airplane through the wheel bearings at all. AND the problem says the conveyor is going to try and keep up with the wheel! So it isn't even going to try and hold anything back.

But truth is, the airplane couldn't care less what the conveyor does or the tires for that matter. It's going to go where the thrust pulls it as soon as thrust > drag.

What actually happens in this "puzzle" is that the airplane starts to move forward as soon as thrust is greater than drag. When it begins to accelerate forward, the tire starts to turn, and the conveyor matches it's rotation by matching the turn and winds up accelerating along under the airplane. Hope the ground crew had walked back to the ramp.

(in reply to iron eagel)
       Post #: 29

RE: Can It Take Off?? - 12/3/2005 2:57:01 AM   
BWooster



Posts: 244
Joined: 10/19/2002
From: Edmonton, AB,
Status: offline 		The airplane does not care what the wheels do: absolutely true, unless the wheels generate friction to prevent the airplane from gaining airspeed, i.e. hold the airplane back.

This thought exercise amounts to taking off with the brakes locked. In order for the aircraft to take off, its airspeed must rise. (Assuming calm air, its groundspeed will equal its airspeed. But if the conveyor turns only as fast as the wheels, it cannot gain any ground speed, unless it drag its wheels.

So, it can take off, but only if the propeller thrust is greater than the resistance of the wheel- conveyor friction.



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RE: Can It Take Off?? - 12/3/2005 3:16:52 AM   
da Rock



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From: western, NC, USA
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quote:

This thought exercise amounts to taking off with the brakes locked


Actually the only direction the a/c could roll the tires would be clockwise. And when they start to roll clockwise, the conveyor is going to start running in the opposite direction. And that direction is the same one the a/c is taking off. So the wheels aren't going to turn and are going to sit still on a conveyor that's hauling a.... a couple of non-turning wheels that're attached to an a/c that's taking off.

(in reply to BWooster)
       Post #: 31

RE: Can It Take Off?? - 12/3/2005 3:25:08 AM   
da Rock



Posts: 6130
Joined: 10/11/2005
From: western, NC, USA
Status: online 		You know what's so funny about this puzzle?

It's original description is flawed.

Look at what it actually says about the direction of the wheel's rotation and what the conveyor does. I've been playing with it to stir the pot, but it's time to blow it out.

The original description says the tire's going to rotate clockwise right? A couple of problems with this. And it says the conveyor is going to match the tires direction in the opposite direction. An obvious problem with this.

(in reply to da Rock)
       Post #: 32

RE: Can It Take Off?? - 12/3/2005 3:29:04 AM   
da Rock



Posts: 6130
Joined: 10/11/2005
From: western, NC, USA
Status: online 		BTW, isn't it the F-14 that has an afterburner control with stages? It's like a gearbox with different gears, only 1st gear is less afterburner and 2nd is a little more etc. And the reason for this shifting deal is because if the sucker is firewalled while the a/c is sitting still the a/c will rip the gear off the plane even if the brakes are OFF because the drag on the wheels even when rolling free is greater than the strength of the gear!!!!!

Now we know where this teaser came from.

(in reply to da Rock)
       Post #: 33

RE: Can It Take Off?? - 12/3/2005 3:56:12 AM   
3dbob37n


 

Posts: 297
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Status: offline 		This thing can drive you nuts!
Anyway, all of you guys are forgetting one thing: The conveyor belt is moving in the opposite direction from the rotation of the wheels and is automatically adjusting itself to the speed that the wheels rotate. This being the case, the model would not accelerate. Because of this, it can never reach flying speed.
Let's discount some of the super powered airplanes and just consider that this is an ordinary model airplane with normal power. We all know that if you have enough power the model will bounce a couple of times and break free. But this would not be as described.
Summed up, the converyor belt is moving at the same speed as the wheels which will give no forward motion to the model. It can't fly.
Ah gee, who started this????? Do we finally get an answer?????

3dbob

(in reply to BMatthews)
       Post #: 34

RE: Can It Take Off?? - 12/3/2005 4:11:32 AM   
iron eagel



Posts: 1137
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From: Middleboro, MA, USA
Status: offline 		The typical glow powered model has a thrust to weight ratio of two to one, I do not care what the wheels are doing the airplane will move forward belt or not.
LOL

_____________________________

The Wrights never crashed, they only had hard landings. I 've had some hard landings myself. AMA EAA AOPA revver #185

(in reply to 3dbob37n)
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RE: Can It Take Off?? - 12/3/2005 4:25:17 AM   
Phlip



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quote:

Anyway, all of you guys are forgetting one thing: The conveyor belt is moving in the opposite direction from the rotation of the wheels


Doesn't matter which direction the belt turns. Either the wheels will not turn, or turn faster. Doesn't matter. Plane accelerates and flys either way!



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RE: Can It Take Off?? - 12/3/2005 4:27:43 AM   
Phlip



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quote:

This thing can drive you nuts!


It's not this thing that's driving me nuts.

Or are you just playing with us?


_____________________________

If the truth were self-evident, eloquence would be unnecessary.
Cicero (106 - 43 BC)

(in reply to 3dbob37n)
       Post #: 37

RE: Can It Take Off?? - 12/3/2005 4:37:40 AM   
iron eagel



Posts: 1137
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From: Middleboro, MA, USA
Status: offline 		Phlip, thanks for the drawing perhaps that will get the point across.
Although you are from MA maybe they will think it is just another "liberal" point of View
LOL

< Message edited by iron eagel -- 12/3/2005 4:39:51 AM >

_____________________________

The Wrights never crashed, they only had hard landings. I 've had some hard landings myself. AMA EAA AOPA revver #185

(in reply to Phlip)
       Post #: 38

RE: Can It Take Off?? - 12/3/2005 4:45:01 AM   
3dbob37n


 

Posts: 297
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From: Franklin,, NC, USA
Status: offline 		So when do we get the answer?
Is the engine even running?
If you can open the doors after landing, it was a good landing.

3dbob

(in reply to iron eagel)
       Post #: 39

RE: Can It Take Off?? - 12/3/2005 4:52:21 AM   
iron eagel



Posts: 1137
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From: Middleboro, MA, USA
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quote:

ORIGINAL: 3dbob37n

If you can open the doors after landing, it was a good landing.

3dbob

I like the way you think!
Keep the shiney side up. LOL

_____________________________

The Wrights never crashed, they only had hard landings. I 've had some hard landings myself. AMA EAA AOPA revver #185

(in reply to 3dbob37n)
       Post #: 40

RE: Can It Take Off?? - 12/3/2005 4:57:15 AM   
Flyfalcons