quote Originally posted by Gokart Mozart: I already asked that...

Well, what if there was a full moon and three light bulbs were burnt out in Times Square? That's about as relevant to the original scenario.

quote Originally posted by Gokart Mozart: I already asked that...

No no Wait.... Okay.. how about if you put it upside down.. on a treadmill with a 100 knot headwind?

It would take even less space to take off. Who says there is no such thing as a dumb question.

quote Originally posted by Red88FF: It would take even less space to take off. Who says there is no such thing as a dumb question.

If if if uhhhh if uhhh.. wait... yeah. if uhh we tied it to a helicopter and a tredmill.. nah... never mind it wouldnt fly

Didn't the Wright brother's flyer have skids instead of wheels? Put these on your theoretical airplane if the wheels are confusing you. Once you overcome the frictional forces the plane will gain speed and take off. It doesn't matter how fast the conveyor is going.

Do you have some way of fashioning a rudimentary lathe?

quote Originally posted by TK: Do you have some way of fashioning a rudimentary lathe?

OH, that's not right!

quote Originally posted by Patrick: No. For the 1000th time, that is not correct. There is nothing stated in the above scenario which suggests the plane will remain stationary.

Actually it does. It says the treadmill is computer controled to COUNTERACT ANY forward motion. To me that says its stationary. The plane does not fly by thrust....thats what moves it forward. LIFT is what makes it fly. Lift is only generated by forward motion thru the air...... If its the way your saying, you could use 1,000 hp motor and it will fly without wings because the motor has the power. Im not arguing that there prob is not a treadmill that can really do that...but thats how its stated as I see it.

quote Originally posted by rogergarrison: [The original scenario] says the treadmill is computer controled to COUNTERACT ANY forward motion.

No, it does not. All it says is that the conveyor is controlled to move at the same speed as the airplane, but in the opposite direction.

It simply CANNOT effect the speed of the plane.


Nice, this again.

quote Originally posted by rogergarrison: Actually it does. It says the treadmill is computer controled to COUNTERACT ANY forward motion. To me that says its stationary

It does not say that at all. It says nothing about the conveyor counterating anything. All it says is the conveyor speed is the same as the plane's speed, only backwards. YOU are making the assumption that it counteracts the plane's velocity. It doesn't. Does your landing gear speed have any impact on your airspeed in flight? Why would it on the ground?

You know the plane's thrust comes from the air, not the ground - so the plane moves forward when you throttle up. As the conveyor moves backwards, how does that counteract the thrust from your engine? It doesn't. It simply means your landing gear are turning twice as fast. From your perspective in the cockpit, your ground speed is twice your air speed. (assuming no wind and your ground speed is read from a speedometer on the landing gear).

But the point is, you ARE moving. If you're moving, there's airflow over the wings and you can take off.

It's a physical impossibility for the conveyor to counteract your speed. The conveyor is going the same speed as the plane, only backwards. If the plane wasn't moving - the conveyor wouldn't be moving either.

So either the conveyor never moves, which means the plane can take off like it's on the ground. Or
The conveyor moves, which means the plane must be able to move - which means the plane can take off.

anyone who thinks the plane cannot take off - does the plane crash if it flys over a treadmill going the same speed in the opposite direction? if not - why not? now go the next step. the wheels are irrelevant.

Consider it this way.

The idea of the conveyor belt is basically a moving runway surface, right?

Instead of a conveyor belt, imagine you have an aircraft carrier with a 2 mile long flight deck. Assume there is no wind. Now, the aircraft carrier's engines use the same controls from the conveyor - that is, they are set to match the speed of your aircraft, but going backwards.

Your plane is on the flight deck and stationary. The aircraft carrier is stationary. The sea is calm (no drift). There is no wind.

You throttle up your plane to attempt to take off heading due North. As you do, the aircraft carrier begins moving due South as exactly the same speed as your plane.

When you get up to 100 mph heading 000, the aircraft carrier is doing 100 mph heading 180.
Relative to the flight deck, you're going 200 mph - your rate of departure - but you have an actual airspeed of 100 mph.

Does this help at all, or make it more confusing?

Dons flamesuit:

I thought I read that they were going to match the forward speed of the plane with the treadmill basically making the airplane stay in place. Since the actual body of the plane (including the wings) would be going 0 mph there would be no lift, your just turning the wheels and not getting enough air over the wings to create lift. Even if the plane has a very low takeoff speed 0 just wont cut it. consider it like this:

You take a sailboat on a windless day and place a very large fan on its deck facing the sail, when you turn on the fan what would happen? The boat would remain motionless because the force of the wind blowing out of the fan is equal to the force the fan makes. ( I can never explain this stuff so it makes sense can someone help?). Now turn the fan around and see what happens.

Brad

quote Originally posted by twofatguys: Dons flamesuit: I thought I read that they were going to match the forward speed of the plane with the treadmill basically making the airplane stay in place. Since the actual body of the plane (including the wings) would be going 0 mph there would be no lift, your just turning the wheels and not getting enough air over the wings to create lift. Even if the plane has a very low takeoff speed 0 just wont cut it. consider it like this: You take a sailboat on a windless day and place a very large fan on its deck facing the sail, when you turn on the fan what would happen? The boat would remain motionless because the force of the wind blowing out of the fan is equal to the force the fan makes. ( I can never explain this stuff so it makes sense can someone help?). Now turn the fan around and see what happens. Brad

yes, go ahead and match the speed of the treadmill to the plane. if the planes not moving - neither is the treadmill. so, how does this help?
but - anyways - the plane will move. it will accelerate forward. the treadmill will accerate backwards. the wheels will be spinning.
what moves a plane forward? how does a treadmill affect this?

quote Originally posted by twofatguys: Dons flamesuit: I thought I read that they were going to match the forward speed of the plane with the treadmill basically making the airplane stay in place. Since the actual body of the plane (including the wings) would be going 0 mph there would be no lift, your just turning the wheels and not getting enough air over the wings to create lift. Even if the plane has a very low takeoff speed 0 just wont cut it. Brad

I guess were both just reading it wrong........ I dont read it as saying its spinning the wheels the other way....Im still seeing it say its keeping the plane from moving forward, regardless of how fast theyre spinning. I can see what there saying IF it was just setting on non powered rollers (they would be spinning as fast, in the opposite direction..but just as a result of the wheels moving), they would have no effect on it flying or not. It would def take off then. Ill just wait and see what happens on the 30th.

quote Originally posted by rogergarrison: I guess were both just reading it wrong........ I dont read it as saying its spinning the wheels the other way....Im still seeing it say its keeping the plane from moving forward, regardless of how fast theyre spinning. I can see what there saying IF it was just setting on non powered rollers (they would be spinning as fast, in the opposite direction..but just as a result of the wheels moving), they would have no effect on it flying or not. It would def take off then. Ill just wait and see what happens on the 30th.

how is the plane kept from moving forward? planes are NOT powered thru their wheels. otherwise they fall out the sky once they leave the ground.

quote Originally posted by Gokart Mozart: I already asked that...

Yes, it would. With noone at the controls, and with winds normally gusting, the plane would go out of control. But if you had a steady 100 knot wind, and were at the controls, you could get off the ground.

Would you mind answering my question...what makes a helicopter lift off the ground?

quote Originally posted by fierobear: Would you mind answering my question...what makes a helicopter lift off the ground?

Would you mind sticking to the original question? Would you mind not asking an irrelevent question? Would you mind saying why you think this is a relevant question or do you really not know? Would you mind going to Wiki and answer your own question?

quote Originally posted by Gokart Mozart: Would you mind sticking to the original question? Would you mind not asking an irrelevent question? Would you mind saying why you think this is a relevant question or do you really not know? Would you mind going to Wiki and answer your own question?

Then answer my question.

I just did.

quote Originally posted by Gokart Mozart: I just did.

FAIL

quote Originally posted by Gokart Mozart: Would you mind sticking to the original question? Would you mind not asking an irrelevent question? Would you mind saying why you think this is a relevant question or do you really not know? Would you mind going to Wiki and answer your own question?

I'm trying to get you to think through this and understand how and why you are mistaken about the conveyor. If your mind is made up, and you don't want to learn, just say so.

quote Originally posted by 84Bill: If if if uhhhh if uhhh.. wait... yeah. if uhh we tied it to a helicopter and a tredmill.. nah... never mind it wouldnt fly

rofl this thread is so stupid but entertaining!

quote Originally posted by Pyrthian: how is the plane kept from moving forward? planes are NOT powered thru their wheels. otherwise they fall out the sky once they leave the ground.

because the treadmill is pushing opposite the direction of thrust. If the wheels ever left the treadmill, that thrust would move it forward and produce lift under the wings. The use of wheels, skids, skis or any other supporting device is irrevelent if anything prevents any forward movement.

Helicopters have a rotary 'wing'. Their engine spins the blades / wings to produce lift. No forward motion is necessary.

[This message has been edited by rogergarrison (edited 01-09-2008).]

So, Roger...What is wrong with this? It isn´t a theory, I actually did a mock-up. Try it yourself!! Get a spring scale. tie one end to anything that freewheels.Watch the scale reading as you pull the scale. It will show a higher reading at the moment you over come inertia. And then it will remain constant, at slightly below the initial reading, when you overcome inertia. Once it is moving, you can pull it as fast as you like..the reading on the scale will remain virtually the same...LOOK!!!>>>>VVVVV...

quote Originally posted by fierofetish: Here is the definitive article!! When the conveyor belt is stationary, so is the plane. And the forces described in the picture are nil. Start the conveyor belt. As the tethering mast/rope initially have to overcome inertia, the load on the tethering pylon is greater, until the wheels start turning.It then decreases, once inertia is overcome, and remains steady.By a VERY crude experiment, I have worked out the coefficient of inert mass weight to actual force to overcome the inertia OF that weight..it is roughly, 7%.of the weight of the object, in ft/lbs. In other words if the plane weighs 1000lbs, it will exert 70 ft/lbs of load on the tethering pylon to keep the plane in place.NOW!!!!! Replace the tether mast AND ROPE with an engine and propeller, exerting 70ft/lbs of THRUST on the STATIONARY AIR surrounding the plane, and the plane will STILL stand still!! NOW...if you speed the conveyor belt up by 100%...does the load on the tether, or the engine/propeller increase by 100%? NO, IT DOESN¨T! It increases at a rate of 7%, not 100%. And so, even if the conveyor belt can speed up to 10000 mph, it does NOT exert more force on the tether at a greater rate than 7%. So, by that equation, if it takes 70 ft/lbs of thrust to keep it stationary, it will only take the normal thrust, PLUS the 70 ft/lbs, to enable the plane to move forward, and take off. Nick

Q.E.D. ad infinitum ... and some people still don't get it.

Let's try this: Stipulate that the "speed" of the airplane is defined by a GPS device attached to its fuselage and that the "speed" of the conveyor is defined by a GPS device attached to its upper surface. (i.e., in both cases "speed" is with respect to the same fixed external reference) In doing this I am not imposing a new condition upon the original statement of the problem, merely clarifying it.

[This message has been edited by Marvin McInnis (edited 01-09-2008).]

quote Originally posted by rogergarrison: because the treadmill is pushing opposite the direction of thrust. If the wheels ever left the treadmill, that thrust would move it forward and produce lift under the wings. The use of wheels, skids, skis or any other supporting device is irrevelent if anything prevents any forward movement. Helicopters have a rotary 'wing'. Their engine spins the blades / wings to produce lift. No forward motion is necessary.

The point I was trying to get at with the helicopter was that a propeller is similar enough to the helicopter's rotor for this illustration. The rotor pulls the helicopter off the ground. A propeller pulls the airplane forward. Neither cares what is happening below, as long as nothing is physically holding the helicopter down or physically hold the airplane in place. A tread mill CANNOT hold an airplane in place as long as the airplane's wheels can spin freely, as they normally do.

Look at it another way. A helicopter will lift off the treadmill. Turn the rotor sideways, shrink it, stick it on the front of the airplane, and the airplane moves forward until lift happens. Very similar principle.

I just cannot believe this is so difficult for people to understand and accept. There is NO WAY a treadmill can keep an airplane with freely-spinning wheels from moving forward. It CAN'T, regardless of any magical, mystical "control system".

quote Originally posted by rogergarrison: because the treadmill is pushing opposite the direction of thrust. If the wheels ever left the treadmill, that thrust would move it forward and produce lift under the wings. The use of wheels, skids, skis or any other supporting device is irrevelent if anything prevents any forward movement. Helicopters have a rotary 'wing'. Their engine spins the blades / wings to produce lift. No forward motion is necessary.

lol - I really hope you are just being silly

got 10 pages of people showing why the thrust & the treadmill are not at all connected.

I'm just glad that I don't have to serve on a jury with a couple of these guys.

quote Originally posted by Pyrthian: lol - I really hope you are just being silly got 10 pages of people showing why the thrust & the treadmill are not at all connected.

They are connected.

The problem is hard numbers. Don't tell me it won't work, show me why not. Fierofetish is the only one with hard data to show why it would fly. I was the only one to show why not.

quote Originally posted by Gokart Mozart: They are connected. The problem is hard numbers. Don't tell me it won't work, show me why not. Fierofetish is the only one with hard data to show why it would fly. I was the only one to show why not.

I've already posted video of it showing the plane will fly. You still don't get it.

And you still avoid answering my question.

quote Originally posted by Gokart Mozart:

Stupendous!!!

LOL!

quote Originally posted by Gokart Mozart: They are connected. .

They are NOT connected. The only thing that can effect the thust propellers ability to move an object that can be moved in this manner is air, period.

I hate to say it because for the most part this thread has gone along peacefully. OK, I won't say it, but you all know it!

Friction. tires on ground, bearings in wheels
speed of wheels
gravity and weight of plane
They are connected.
Why have these been ignored?

[This message has been edited by Gokart Mozart (edited 01-10-2008).]

quote Originally posted by TennT: The only way the belt could give a backward force to the plane (to stop forward motion) is if there is enough rolling resistance (between tires and belt) or bearing friction to give resistance, right? The conveyor needs a resistance to "push" against to counter the prop thrust. No resistance, no force, plane flies. Conveyor could run supersonic, but to counter the force generated by the prop, you'd need opposing force. Only thing available is friction/resistance of tires/bearings, it is not?

FFetish actually measured the rolling friction to boot. Wasn't it 70 lbs. rolling?

Me thinks you be the devil's advocate (sorta liked that movie).

Sign posted over one of my parts salesmen's office:
"Before you wrestle with pig in mud,
Remember that the pig enjoys it"


tg

[This message has been edited by TennT (edited 01-10-2008).]

quote Originally posted by Gokart Mozart: Friction. tires on ground, bearings in wheels speed of wheels gravity and weight of plane They are connected. Why have these been ignored?

They haven't been ignored. They aren't a strong enough force to keep the plane from moving forward. If they were, a plane couldn't lift off a standard RUNWAY. Think about it, Gokart.

[This message has been edited by fierobear (edited 01-10-2008).]

quote Originally posted by Gokart Mozart: Friction. tires on ground, bearings in wheels speed of wheels gravity and weight of plane They are connected. Why have these been ignored?

The stall speed for our Grumman Yankee is 60 Knots = 69.1 MPH

The treadmill will be turning the wheels at 149.8 MPH when the aircraft lifts off at 65 kts (74.9 mph) and climbs away like a home sick angel at about 2000 feet per minute @ 80 kts or 92 mph.

TEH plane will fly