Which ones (if any) of these sentences are true?

[PeterBassett]

the propeller or engine of the plane transfers its energy into the wheels (whilst it is in contact with the ground) to get it moving forward.

NO IT DOESN'T!

It isn't a car. It doesn't power its wheels. It is a plane. It pushes on the air.

 

[bugbear]

the conveyor counteracts thrust through motion in the wheels of the plane. the point you are missing here is the wheels are the major effect.

But assuming the bearings in the wheels are reasonable, you can do what you like (via a conveyor, if you wish) to the rims, and no backwards/forwards force will be exerted on the axle.

You'll just spin the wheels.

Now, if we were talking about a (normal) car, which moves forwards by pushing against the ground with its wheels, yes, the conveyor would do all sorts of things.

But all the ground does to an aircraft is hold it up.

In the language of vectors; due to the bearings in the wheels, any force the conveyor applies via the wheels must have a 0 horizontal component.

BugBear

 

[PeterBassett]

In the language of vectors; due to the bearings in the wheels, any force the conveyor applies via the wheels must have a 0 horizontal component.

Bing!

 

[Dibs-h]

In the language of vectors; due to the bearings in the wheels, any force the conveyor applies via the wheels must have a 0 horizontal component.

Bing!

Yes I think the interaction between the planes wheel and belt is key - the more I read, and as Bugbear has said - no matter what speed you set the belt to, all it would do is spin the planes wheel faster and faster, i.e. zero horizontal force component on the "leg".

As stated in the article I linked to - if the plane doesn't move, i.e. no air over the wings, it won't lift off. But the bit above has got me wondering, in that if all the conveyor does is spin the wheel of the plane - effectively keeping it stationary - the application of thrust to the plane should push the plane forward, and effectively airborne.

It's this interaction between wheel & belt that's the awkward part.

Just my 2c worth.

Dibs

 

[Racers]

Hi. Mark

Planes that land on snow and ice have skids, so how thay take off, or sea planes they don't have wheels when they use water.

Pete

 

[RogerS]

Mark...your physics major is wrong. Sorry to tell it how it is !

You still haven't said if you agree with my dangling-plane analogy.

 

[PeterBassett]

What about a sea plane taking off upstream on a river.

It can't possibly fly. Physics say so! :lol:

 

[Racers]

Hi,

Dont forget the earth is spinning at 1000mph at the equator, so you will have to go faster than that to take off :wink: :wink:

Pete

 

[PeterBassett]

I hadn't thought of that. Ah well, back to the drawing board... :lol:

Anyway, everyone knows that planes fly from the combined will of the people on board. All the physics stuff has been made up by the military-industrial complex.

 

[RogerS]

I hadn't thought of that. Ah well, back to the drawing board... :lol:

Anyway, everyone knows that planes fly from the combined will of the people on board. All the physics stuff has been made up by the military-industrial complex.

You are absolutely right, Peter. Here's the proof.

Picture a 4 seater Cessna. Picture the size of the wings. Cessna flies at, what, 120 knots? OK. Now picture a jumbo. Flying speed - say 480 knots. OK...so that's 4x the number of passengers. 16 now. Now a jumbo can carry 416 passengers. Which means that the wings need to be 416/16 times larger than a cessna's. ie 26x the area of a Cessna's wings. Are they? I don't think so. Maybe 10x. And that's before we factor in all the cargo and luggage!

Ergo....as PB has said..it's only the will of the passengers that keeps them flying.

 

[PeterBassett]

I've changed my mind.

Rabid telepathic spider monkeys.

Aeroplanes are powered by the forced telepathic intervention of rabid spider monkeys.

The plane doesn't fly at all. That would be ridiculous.

The monkeys are whipped until they achieve a zen like state that enables them to make the passengers think they are in the air.

Then the passengers and their cargo are simply beamed to their destination airport via a star trek like transporter.

Thats why airports are so large. Giant underground spider monkey farms and vast whipping arenas.

Why haven't I realised this before?! It's so simple!

 

[Anonymous]

Mark

Are you winding us up?

Step One....

Imagine a long length of trackwork high up...bit like a gantry crane. With rails on. There is a trolley on these rails and this trolley can roll freely forward or backwards. Now dangle a plane beneath this trolley on a cable so that the plane is hanging in the air.

Now fire up the jet engines. What's going to happen? The plane is going to move forward under the thrust of its' engines. If you had a long enough set of rails then eventually the speed of the plane will generate enough lift from the airflow going over its' wings and it will fly.

Do you agree?

yes i do agree, but that isn't the case here at all!!

if the conveyor ensues that the plane essentially stays still (which it does).

How? The conveyor *can't* stop the plane from moving.

but the wheels do, thats the whole point.

lololol this is so comical, whilst the wheels which are attached to the plane in which have a downward force onto the conveyor have the major effect on this puzzler.

You have to add the wheels into the equation as they are there and in contact with the conveyor.

i know you are all trolling with me - come you can pack it in now!!

 

[Racers]

Hi, Mark

Hold a wheel by the axel on a running belt sander and tell my how much force you can feel.

Pete

 

[PeterBassett]

i know you are all trolling with me - come you can pack it in now!!

Ah, it's only in jest. :wink:

Seriously, Mark, can you explain, in your own words how the conveyor belt would stop the plane from accelerating forwards from the force applied by its prop/jet?

 

[Anonymous]

i understand your concept and i very nearly agree with it pete.

ok i'll try this one.

your in a sail boat and the wind is blowing you forward and the current (water) flowing in the exact opposite at the same force the wind is excting on your sails.

Do you move forward?

 

[PeterBassett]

Unfortunatley that is not the same system. The drag on the boat from the flow of water is large and well coupled.

The drag on the body of the aircraft from the moving conveyor is decoupled by the wheels and their bearings.

That is the purpose of the wheels. Do you see the difference there?

 

[Anonymous]

but the wheels have the weight of the plane pushing them down.

 

[Racers]

Hi, Mark

If the forces are cancling each other out then you will remain stationary.

But the friction in the wheel bearings of the plane are very small.

Pete

 

[PeterBassett]

but the wheels have the weight of the plane pushing them down.

I don't follow. This is the case when a plane takes off as normal from an airfield.

The wheels are free to rotate, that is their purpose.

 

[Anonymous]

i totally see where you are all coming from.

but you are forgetting the weight of the plane on the wheels its a downward pressure.