Aircraft and conveyor belt (again)

[Trazor]

Having given even more thought to this, it becomes obvious that the plane must always be moving forward towards take off speed, for the conveyor to match that speed.

Remember the conveyor must match the speed of the plane, so if the plane does not move the conveyor will not move. Therefore the plane must be moving forward for the conveyor to react to it.

 

[Softus]

I don't remember any disagreement about what happens when the wheel speed increases to infinite. IMHO the bearings would break up, or the tyres would explode, before the aircraft reached take-off velocity.

If you accept that the aircraft does take off, then the maximum wheel speed attainable is twice that of take off speed, no greater speed than that needs to be considered.

I accept that it would take off only if we disregard what I believe to have been an unintentional ambiguity in the OP, wherein the conveyor speed was defined as matching the wheel speed instead of the aircraft speed.

As soon as you allow the definition to be that the speed matches the wheel speed, then you have the paradox (sic.), wherein both the wheels and conveyor will instantaneously reach infinite speed as soon as the plane moves from its resting position.

 

[Softus]

Having given even more thought to this, it becomes obvious that the plane must always be moving forward towards take off speed, for the conveyor to match that speed.

I concur.

Remember the conveyor must match the speed of the plane...

You can't remember it, because the OP wasn't 100% clear on this point.

...so if the plane does not move the conveyor will not move. Therefore the plane must be moving forward for the conveyor to react to it.

Both of things are true in either of the interpretations of the OP.

 

[solo]

 

[Softus]

LMAO

 

[blondini]

Ok Softus, sorry. Maybe the term 'having a go' was wide of the mark. It's easy to misinterpret postings when you don't know someones character etc. Take this as a compliment, you would be formidable in the House of Commons.

I don't see any ambiguity in the OP. This conveyor belt has a control system that tracks the aircraft's wheels speed and tunes the speed of the conveyor belt to be exactly the same as the wheels, but in the opposite direction. I don't see how you could misinterpret this? The only problem I can see in it, is that if the aircraft is actually moving forward is impossible for the runway to match the wheel speed of the aircraft. It can only play catch unless an equilibrium is achieved where the drag from the conyeyor, (I know this is a moot point)is able to arrest the forward thrust from the engines.

You seemed quite adamant before, that the wheel speed would only be double the aircraft speed:

Me: Are you confusing wheel speed with forward speed or air speed of the aircraft?

You: No. I can scarcely believe that you don't understand this.

blondini wrote:
If the aircraft were travelling forward relative to a fixed point at a speed of 100mph and the conveyor was travelling backwards at the same speed, then yes the wheel speed would be 200mph. However the OP states that the conveyor will match the wheel speed of the aircraft, not the speed of the aircraft itself.

Softus: The wheel speed is directly proportional to the aircraft speed. If the aircraft doubles its speed, then the wheels double in speed.

blondini wrote:
it is theoretically possible for the rolling resistance to increase to a point where it achieves equilibrium with the engine thrust which does have a limit.

Softus: No - it's possible only in your imagination, which is not the same as being theoretically possible. However, a theory can be proven by showing the working, so if you have such a theory then please show the working.

blondini wrote:
It would have to be be extremely fast, but not necessarily infinite.

Softus: No it wouldn't - it would have to be twice as fast as normal. Whatever speed the plane is moving, if the conveyor matches either plane or wheel speed, then the wheels will be rotating twice as fast as they would if there were no conveyor there.


Working out the theory you asked for, I was going to try but the thread got locked. Maybe it could be roughly worked out, but I'll pass on that for now. Practical experimentation is also possible but I don't have a treadmill.

Final observation as I need to go to bed. There's no need for the wheelspeed to reach infinity to break the plane. Aircraft tyres are designed for high speeds, but they would be the weakest component. How fast do you think they could go before failing?

 

[Softus]

Final observation as I need to go to bed. There's no need for the wheelspeed to reach infinity to break the plane. Aircraft tyres are designed for high speeds, but they would be the weakest component. How fast do you think they could go before failing?

I assure the Right Honourable member for Newcastle upon Tyne that I have no knowledge of the said maximum capability, but I trust that the House is prepared for this question to be the subject of a working committee, and for the findings to be presented at a later sitting.

 

[solo]

Harumph!

 

[megawatt]

I think Blondini's an escapee from a rest home ... Thanks for sharing a piece of your mind with us all.

You can't have a great deal left

 

[kevnurse]

I've come in late on this discussion but as flying is my profession, I've read through the whole debate and I find it difficult to believe that there can be any disagreement over fundamental aerodynamics.

I have one question to ask megawatt:

Regardless of wheel speed and conveyor belt speed (which we are told, are equal), does the aircraft move forward relative to the ground surrounding the belt (or the air, if you wish; I'm assuming no headwind component)? The answer to this question is the crux of the matter.

Thanks.

 

[blondini]

Final observation as I need to go to bed. There's no need for the wheelspeed to reach infinity to break the plane. Aircraft tyres are designed for high speeds, but they would be the weakest component. How fast do you think they could go before failing?

I assure the Right Honourable member for Newcastle upon Tyne that I have no knowledge of the said maximum capability, but I trust that the House is prepared for this question to be the subject of a working committee, and for the findings to be presented at a later sitting.

Is there an expert witness who could enlighten us?

I believe that the jet powered car which a certain Mr Hammond crashed so spectacularly was using aircraft tyres due to their high speed capacity. Furthermore, the much faster vehicles developed by a certain Mr Noble may not use tyres at all but runs on solid wheels. There being no aircraft tyre available that could would be capable of surviving the speeds attained by said vehicles.

 

[Trazor]

Is there an expert witness who could enlighten us?

Yes I have one here...

He said the Titanic was unsinkable.
He said Thalidomide was safe.
He said millions would die, due to mad cow disease.
He allowed the building of homes on flood plains.
He said 30 years ago we were in for a mini ice age.
I think he now runs Northern Rock.

What was the question again............

 

[billyo]

go by balloon, then u will know what the bang was

 

[megawatt]

KevNurse Wrote:

I have one question to ask megawatt:
Regardless of wheel speed and conveyor belt speed (which we are told, are equal), does the aircraft move forward relative to the ground surrounding the belt (or the air, if you wish; I'm assuming no headwind component)? The answer to this question is the crux of the matter.

Yes

 

[luke_vibert_uk]

KevNurse Wrote:

I have one question to ask megawatt:
Regardless of wheel speed and conveyor belt speed (which we are told, are equal), does the aircraft move forward relative to the ground surrounding the belt (or the air, if you wish; I'm assuming no headwind component)? The answer to this question is the crux of the matter.

Yes

Yes what?...Yes, you acknowledge that you recognise you are wrong?

Not the most informative, intuitive or descriptive of answers…