plane on a conveyor belt?

[2bighorn]

Originally posted by eskimo2
Chuck’s plane lost nothing to rotational inertia and took off first and in the least distance.

Didn't you say that planes were balanced accordingly and that planes with lighter wheels had heavier airframes for the same amount?

[eskimo2]

Golfer,

In our question, why do your believe the conveyor will move at 100 knots if the plane is also moving at 100 knots?  How can that result in the conveyor matching the wheels’ speed?

[eskimo2]

Originally posted by 2bighorn
Didn't you say that planes were balanced accordingly and that planes with lighter wheels had heavier airframes for the same amount?

2Bighorn,

When the three planes take off, Al’s and Bob’s planes wheels are spinning, right?

[Golfer]

Why?

Because an airplane isn't a car.  An airplane doesn't depend on the tires contact to the ground to propel itself forward.  Thats what engines and propellers are for.  An airplane only needs the wheels to spin in order to pull or push itself through the air.  What the ground is doing under the airplane has no bearing whatsoever on whether or not the airplane will fly if the wheels are allowed to spin.

If your treadmill acts independently of the airplane and was not dependant on the wheels to provide a starting point (the conveyor matches the wheel speed...remember?  It doesn't just go maximum effort on its own...its reacting to the wheels not acting upon them) for the conveyor speed then your paper shoe drop thing would apply.

Given the question...you've presented a solution to a problem that doesn't exist.

[Golfer]

Originally posted by eskimo2
Golfer,

In our question, why do your believe the conveyor will move at 100 knots if the plane is also moving at 100 knots?  How can that result in the conveyor matching the wheels’ speed?

You're putting words in my mouth eskimo.  Allow me to quote myself...

I "get" that the treadmill continually accelerates because when the wheels start to spin the conveyor matches...effectively doubling the wheel speed which in turn it has to match resulting in an exponential acceleration of the wheels.

Just because you're cancelling out what the wheels are doing (and still spinning) you still have the fact that the airplane is producing thrust to deal with.  Nothing you do with a treadmill or the wheels if allowed to spin will have an effect on the airplane propelling itself through a fluid (air)

[2bighorn]

Originally posted by eskimo2
When the three planes take off, Al’s and Bob’s planes wheels are spinning, right?

Chuck's machine weighs exactly the same (diff mass distribution tho), has same lift, same drag, same friction, same thrust, yet it magically takes off in least distance?

Congrats, you just invented perpetual motion machine...

[eskimo2]

Golfer,

I really don’t think that you get the idea then.  Did you see the cylinder move rapidly to the left in the last video?  If it had a cart hooked up to it that weighed the same as the cylinder, it would have accelerated at half the rate, right?  But what if the shoe didn’t drop at 1 Gee?  What if the paper conveyor was accelerated at 2 Gees?  It would be pulled to the left at the same rate as the cylinder accelerated by the 1 Gee conveyor.  Numbers still too small for you?  Fine, hook a cart up to it that weighs 999 times as much, accelerate the conveyor at 1000 Gees and the 1000x cart would be pulled to the left at the same rate as the cylinder accelerated by the 1 Gee conveyor.  See a pattern here?  

The only limiting factor here is the coefficient of friction between the tires and the treadmill.  Lock the brakes of a plane and drag it with a big truck.  The amount of force that it takes to drag the plane (break it loose) is the maximum potential of opposing power that can be applied.

Yes, a plane’s engines can create a substantial opposing force.  I’ve stated long ago that any plane that can take off with its brakes locked may take off on the super treadmill.  Most planes cannot produce that kind of force.  If the super treadmill wanted to, it could push a plane backwards at a pretty good acceleration rate even with the airplanes engines on full power.

[eskimo2]

Originally posted by 2bighorn
Chuck's machine weighs exactly the same (diff mass distribution tho), has same lift, same drag, same friction, same thrust, yet it magically takes off in least distance?

Congrats, you just invented perpetual motion machine...

2Bighorn,

Al’s plane’s wheels have a rotational energy state of 2X because they weigh 2X and are spinning at 50 mph.  Bob’s plane’s wheels have a rotational energy state of 1X because they weigh 1X and are spinning at 50 mph.  Chucks plane’s wheels have an energy state of 0 because they have no mass.  How do you account for the different states of rotational energy in the wheels of the airplanes?  Don’t you see a conflict here when it come to conservation of energy?  If you think that the planes took off all together you have to be able to explain how their wheels have different states of energy.

[eskimo2]

Golfer,

Read the story and my responses to 2Bighorn.

[2bighorn]

Originally posted by eskimo2
If you think that the planes took off all together you have to be able to explain how their wheels have different states of energy.

They have all the same total mass, different mass distribution, hence difference in energy for a particular part ie wheels.

The heavier wheels with more inertia (more angular momentum) are attached onto lighter airframes with less inertia (less kinetic E), or
the lighter wheels with less inertia (less angular momentum) are attached onto heavier airframes with more inertia (more kinetic E).

Total E needed to lift them up and fly is the same. Just because some of the E ain't as visible it doesn't mean it ain't there.

[Golfer]

I've read the stories.

The wheels are along for the ride on the airplane and again...like your example of the pull string toy cars don't apply to an airplane the way I think you hope.

How...how how how...do you overcome the thrust applied by an airplane capable of propelling itself through the air by applying a equal opposite force to the wheels?

Telling me a story about bob tom and joe taking off in formation isn't going to do it.  Telling me look at a 2 second blurb of a shoe falling won't cut it either.  Your examples are not what the question asks.  They're fine examples for showing how a conveyor underneath some objects affects them but that isn't the question.  You're solving problems that aren't applicable to the question.

The question has the conveyor matching the speed of the wheels effectively taking the wheels out of the equation.  The wheels, still spinning and presumably holding together while they accelerate through the speed of light, don't don't don't don't don't don't have anything to do with the airplane allowing itself to accelerate as long as they're allowed to spin.

It doesn't matter what equal opposing force you apply to the wheels...you're cancelling out the wheels.  It would work wonders if you had a car on your treadmill.  Your examples are perfect for a car.  You'd have to have an effect on the fluid (air) surrounding the airplane to make it not fly.


You never did answer what I asked a few pages ago...

Why or why not are you able to dyno test an airplane at your friendly neighborhood automotive engine shop?  Tell me how your plan to do that and I'll start listening to you.

[Toad]

Wait.... is this done with the tray tables in the up or down position? That's key.

[eskimo2]

Originally posted by Golfer
I've read the stories.

The wheels are along for the ride on the airplane and again...like your example of the pull string toy cars don't apply to an airplane the way I think you hope.

How...how how how...do you overcome the thrust applied by an airplane capable of propelling itself through the air by applying a equal opposite force to the wheels?

Telling me a story about bob tom and joe taking off in formation isn't going to do it.  Telling me look at a 2 second blurb of a shoe falling won't cut it either.  Your examples are not what the question asks.  They're fine examples for showing how a conveyor underneath some objects affects them but that isn't the question.  You're solving problems that aren't applicable to the question.

The question has the conveyor matching the speed of the wheels effectively taking the wheels out of the equation.  The wheels, still spinning and presumably holding together while they accelerate through the speed of light, don't don't don't don't don't don't have anything to do with the airplane allowing itself to accelerate as long as they're allowed to spin.

It doesn't matter what equal opposing force you apply to the wheels...you're cancelling out the wheels.  It would work wonders if you had a car on your treadmill.  Your examples are perfect for a car.  You'd have to have an effect on the fluid (air) surrounding the airplane to make it not fly.


You never did answer what I asked a few pages ago...

Why or why not are you able to dyno test an airplane at your friendly neighborhood automotive engine shop?  Tell me how your plan to do that and I'll start listening to you.

You can’t dyno an airplane for the same reason you can’t get electricity from a light bulb.


The wheels are not out of the equation, they are the equation.  When the wheels and plane and conveyor are still, the speed matches.  If they are all in the same spot where they started and are spinning, the speed matches.  

If the plane moves a foot, however, its wheel moves a foot.  So, the conveyor moves how far?  A foot?  Fine, when the conveyor moves a foot it also moves the wheel.  Now the wheel has moved two feet but the conveyor has moved only one.  That’s not the same distance which means its not the same speed either.  So if the conveyor were to move two feet, the wheel would have moved three.

Move the plane 100 feet down the conveyor:  It does not matter if the conveyor has spun 100 feet or 1,000,000 feet, the conveyor is 100 feet behind and therefore has not been traveling at the same speed!

[FiLtH]

Rpm...was that a coal or wood fired boiler on that electric train?  

[hitech]

Originally posted by 2bighorn
Not sure if you mean the same, but formula bellow should work since both are expressed in unit of force

Friction = ((plane mass + wheel mass) * gravitational acceleration) * bearing rolling friction coefficient) divided with number of bearings (one per wheel)


rolling friction coefficient is about 0.025 for very low quality radial friction only bearings (creates most of the friction)

I'm not talking about the quantity (your equations are fine). Would you agree the rolling friction is generating a torque about the axle?  

If you do agree. Just draw a sketch how this axle torque is turned into drag of the plane, I.E. force (not torque) that slows the plane.