Topic: Can this airplane lift off?

[Steve F]

The wheels allow forward movement of the plane to get airflow over the wings which create lift.
No forward movement, no fly. The theoretical conveyor belt prevents forward movement and matches the thrust of the engine, pound per pound.
The bearings push on the axle, which in turn moves the plane in the rearward direction, they don't just rotate.

But the conveyor belt DOESN't prevent forward movement that's the whole thing right there. Its as if the plane was suspended by little hovercraft feet. It doesn't matter what the wheels do. It doesn't matter what the pavement does. The thrust of the engine is completely independent of the wheels. The wheels are not geared to the engine.

You'll wake up someday and smack your forehead... could've had a V8! I did.

Here Here!  I can't beleive that some people just don't get the fact through their heads that the wheels are there only to allow the plane to roll on the "conveyor".

[Duke McDukiedook]

Caave, I don't care to do the math, I got my degree.
Gordo can run the #'s if he wants to, I admitted it is possible, I would like to see him disprove me with fancy numbers though.

That doesn't mean my initial evaluation was wrong either though.
If the belt could produce enough speed to keep the plane from moving forward, it ain't gonna fly no matter how much thrust you can produce.

[MCRider]

Caave, I don't care to do the math, I got my degree.
Gordo can run the #'s if he wants to, I admitted it is possible, I would like to see him disprove me with fancy numbers though.

That doesn't mean my initial evaluation was wrong either though.
If the belt could produce enough speed to keep the plane from moving forward, it ain't gonna fly no matter how much thrust you can produce.

Now we're getting into the "if frogs had wings they'd fly" area. First of all, the belt can't produce enough speed to keep the plane from moving forward, the wheels will just turn faster.

And the spec in the question was to just match the wheel speed. You can't go throwing in variables.

[Sam Green Racing]

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.

[MCRider]

Soichiro is da debil!

[shacolaid]

Steve, Why does the plane not take off with the wheel brakes on and the engine at full throttle?  The propeller has to overcome the movement of the conveyor and create enough forward thrust. If that happens, then the conveyor is not moving at the same speed as the plane.  

[Steve F]

propellers give an airplane foward thrust not lift. so if an airplane is on a conveyor belt running at the same speed as the airplane, the airplane is going 0 mph. This means no air flow over the wings to create lift. This is why aircraft carriers have steam catupault systems and runways. I am not sure of the stall speed of the airplane shown on the video but i know it is faster than 0 mph, more like 80 to 90 mph.  An airplane will not fly below its stall speed it will go into a flat spin and fall from the sky like a rock.

           

[Caaveman82]

I actually see both sides of the coin, because this is just one of those annoying word problems like they used to give us in 5th grade. Only a little more advanced in the actual math department. It really depends on how you read the question...

In one aspect Dukie is absolutely right. The way the question was worded it is open to interpritation. Dukie assumes that the question was implying that the plane would have 0 forward movement. Gordon and MC were not. So that's really the issue here.

I knew that english minor would come in handy at some point...

[masonryman]

Can the conveyor turn fast enough to negate the trust of an engine that is perpetually pushing against a stationary atmosphere?

[Duke McDukiedook]

Increase in speed of belt will increase friction on tires (more drag) which will heat up the bearings which will create more friction and higher belt speed will push the plane back with greater force (translation force will push on bearings which will in turn push the plane back). Don't forget drag from the wings.

The question is do you have more thrust than those forces working against it combined?

Please tell me where this logic is flawed?

[Steve F]

Caave, I don't care to do the math, I got my degree.
Gordo can run the #'s if he wants to, I admitted it is possible, I would like to see him disprove me with fancy numbers though.

That doesn't mean my initial evaluation was wrong either though.
If the belt could produce enough speed to keep the plane from moving forward, it ain't gonna fly no matter how much thrust you can produce.

Geez, Dukie,  The speed of the conveyor will only affect the wheel rotation on the plane.  Picture this....a plane on the conveyor being held in place buy a person on either side of the plane.  The conveyor starts to move, the wheels do too at the same feet-per-minute rate as the conveyor, but no air movement over the wing.  The guys start walking the plane, the wheels are turning faster than the conveyor feet-per-minute, and the air starts to flow over the wing.  If these guys were fast enough they could get the plane airborne, while the wheels just spin like mad.

[masonryman]

Increase in speed of belt will increase friction on tires (more drag) which will heat up the bearings which will create more friction and higher belt speed will push the plane back with greater force (translation force will push on bearings which will in turn push the plane back). Don't forget drag from the wings.

The question is do you have more thrust than those forces working against it combined?

Please tell me where this logic is flawed?

I'm a bricklayer not an engineer, I was asking.


As far as the rotation of the wheels go there are bearings that will spin at stupid high speed whit nearly no heat

[Duke McDukiedook]

Steve, you just contradicted yourself there. You said the wheels will spin faster than the belt, Sochiro said the belt matched the wheels velocity no matter how fast they went.

[Duke McDukiedook]

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.

[masonryman]

Well if you wanted to make wild assumptions we could say it was a areobatic plane with flaps in full

[Markcb750]

No they aren't irrelevent. If the thrust from the motor is greater than the friction forces created from the weight of the plane on the bearings and wheels from rotation and translation due to forces exerted by the belt, the plane will fly. The wheels and friction forces from them figure into the equation.

Plane in a river flowing will fly due to thrust forces being greater than drag forces from water on the skids.
 

All aircraft accelerate at a rate related to its mass and the net forces on the aircraft. Wheel friction is a small part of these forces.  it is calculated by the aircraft designers, but not significant compared to the basic Acceleration=force thrust/mass

The math is pretty simple but what is important is that the forces at the wheel are tiny relative to the weight of the plane, this is how people pull 10 dump trucks with their teeth.

[Steve F]

Steve, you just contradicted yourself there. You said the wheels will spin faster than the belt, Sochiro said the belt matched the wheels velocity no matter how fast they went.

I don't care what Sochiro said.  I'm giving up on all the nay-sayers that the plane can't get airborne....I just can't believe that something this simple is controversial.  The plane will F##%1$g fly! DAAAAAAM this is frustrating.  That's why the mythbusters had a good episode over this subject because some people just can't visualize the physics.

[333]

What I can't believe is that in only 7 to 8 hours, this thread has grown wings and it has taken off.  I only read the first page(and last), but I can't believe some can't get it right.  So, let me try.

If the wheels are truly "free wheeling"(not pushing the plane forward, not braking) the plane will take off and fly.  The conveyor belt has no affect on the plane, as there is no real connection(forwards or backwards) between the belt and the plane.  And you can't compare a seaplane, as the water in contact with the sponsons creates considerable drag compared with wheels on the ground.

You'd think someone started an oil thread.





Hmm.  I wonder what kind of oil they are using in that plane?

[Sam Green Racing]

and are there any guns on it?

Sam

[Caaveman82]

How many passangers are there?

Is there an improper luggage ratio? Did some one have two carry on bags?

More info needed to compute!

[Markcb750]

What I can't believe is that in only 7 to 8 hours, this thread has grown wings and it has taken off.  I only read the first page(and last), but I can't believe some can't get it right.  So, let me try.

If the wheels are truly "free wheeling"(not pushing the plane forward, not braking) the plane will take off and fly.  The conveyor belt has no affect on the plane, as there is no real connection(forwards or backwards) between the belt and the plane.  And you can't compare a seaplane, as the water in contact with the sponsons creates considerable drag compared with wheels on the ground.

You'd think someone started an oil thread.





Hmm.  I wonder what kind of oil they are using in that plane?

synthetic  


The difference between the a seaplane and a wheeled plane is my point. The friction/drag is much higher on the pontoons, and the planes still take off.

No matter how fast the conveyor is moved, the wheels make it like pulling a tablecloth from under a dish. The key is the mass of the dish.

[Caaveman82]

What I can't believe is that in only 7 to 8 hours, this thread has grown wings and it has taken off.  I only read the first page(and last), but I can't believe some can't get it right.  So, let me try.

If the wheels are truly "free wheeling"(not pushing the plane forward, not braking) the plane will take off and fly.  The conveyor belt has no affect on the plane, as there is no real connection(forwards or backwards) between the belt and the plane.  And you can't compare a seaplane, as the water in contact with the sponsons creates considerable drag compared with wheels on the ground.

You'd think someone started an oil thread.





Hmm.  I wonder what kind of oil they are using in that plane?

synthetic  


The difference between the a seaplane and a wheeled plane is my point. The friction/drag is much higher on the pontoons, and the planes still take off.

No matter how fast the conveyor is moved, the wheels make it like pulling a tablecloth from under a dish. The key is the mass of the dish.

That is ludacris! A dish does not have a jet engine!

[Duke McDukiedook]

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 fully, the clip the guy ran on this thread didn't show how the whole experiment was run (like 30 seconds).

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

[Markcb750]

Damn...





It's a great clip, very informative.


A well thought out experiment!

[Caaveman82]

This thread makes me fear for the shameless thread.

I predict by the end of the weekend, this thread will have the highest post count out of ANY forum out there....