Plane

[Whereditgo]

Lets say the whole length of the conveyor is 10,000 times the circumference of the wheel.
One whole rotation of the conveyor will match 10,000 rotations of the wheel.
The ratio will always be 1 to 10,000 in terms of their rotations.

The observer might perceive the plane to be moving along the conveyor, but it is actually moving through the air above the conveyor.
The conveyor makes no difference to the plane, the plane moves as if the wheels were hovering 1mm above the conveyor.
The fact that it is 1mm lower than this and has contact with the conveyor, causes the wheels to turn. They do not skid in this scenario.
The wheels will match the conveyor at one rotation to 10,000 rotations whatever the conveyor speed and whatever the speed the plane is doing through the air, including being stationary in the air.
Hovering in the air, running along a normal runway or running along a conveyor - plane takes off in the same way.
There is no backward pressure from the wheels as there is with driven wheels or human feet. The wheels are passive.
View attachment 57002
The wheel does 10,000 rotations for every one rotation of the conveyor, if the conveyor belt's whole length is 10,000 times that of the circumference of the wheel.
And this remains the same, whatever the speed of rotation of the conveyor and/or the speed of the plane through the air above the conveyor.

The wheels to not "need" to rotate "faster" than the conveyor in order for it to move through the air above the conveyor.
That is the wrong choice of words to describe what is happening.
The conveyor's rotation and the wheel's rotation will always be the fixed ratio relative to each other.
The wheels can't "do more" they are passive and have no power.
The conveyor altering it's rotation speed will mean that the wheels alter their rotation speed - to match. They do this passively - they can not do otherwise.

The wheels move along a surface. It does not matter whether that surface is a solid static runway or a conveyor, the plane is not hindered.
And the wheels do not skid on the conveyor, it takes off as normal, with wheels' rotation perfectly matching the rotation of the conveyor in a fixed ratio.

Overcoming the perception that the wheels "must rotate faster" than the conveyor for it to move along the conveyor - can be difficult to do.
To do this - forget "moving along the conveyor" and replace with "moving through the air above the conveyor".
This should free the mind from how driven wheels behave.

The wheels are there merely because the plane does not hover.
But the plane behaves just about the same as a hovering one would do, if that hovering one lowered a wheel form itself to just touch the conveyor to make it turn.

Force of jet engine causes plane to move through the air. The wheel below is just a dangly thing of little importance.
(Of course it has some importance, but far less than a lot of people realise, because they perceive how driven wheels behave most of the time)

Surely that only remains true while the plane (or whatever the wheel is attached to) remains stationary, to move the wheel has to rotate faster than whatever it is in contact with - but that's not permitted, so it skids.

 

[RichA]

Lets say the whole length of the conveyor is 10,000 times the circumference of the wheel.
One whole rotation of the conveyor will match 10,000 rotations of the wheel.
The ratio will always be 1 to 10,000 in terms of their rotations.

The observer might perceive the plane to be moving along the conveyor, but it is actually moving through the air above the conveyor.
The conveyor makes no difference to the plane, the plane moves as if the wheels were hovering 1mm above the conveyor.
The fact that it is 1mm lower than this and has contact with the conveyor, causes the wheels to turn. They do not skid in this scenario.
The wheels will match the conveyor at one rotation to 10,000 rotations whatever the conveyor speed and whatever the speed the plane is doing through the air, including being stationary in the air.
Hovering in the air, running along a normal runway or running along a conveyor - plane takes off in the same way.
There is no backward pressure from the wheels as there is with driven wheels or human feet. The wheels are passive.
View attachment 57002
The wheel does 10,000 rotations for every one rotation of the conveyor, if the conveyor belt's whole length is 10,000 times that of the circumference of the wheel.
And this remains the same, whatever the speed of rotation of the conveyor and/or the speed of the plane through the air above the conveyor.

The wheels to not "need" to rotate "faster" than the conveyor in order for it to move through the air above the conveyor.
That is the wrong choice of words to describe what is happening.
The conveyor's rotation and the wheel's rotation will always be the fixed ratio relative to each other.
The wheels can't "do more" they are passive and have no power.
The conveyor altering it's rotation speed will mean that the wheels alter their rotation speed - to match. They do this passively - they can not do otherwise.

The wheels move along a surface. It does not matter whether that surface is a solid static runway or a conveyor, the plane is not hindered.
And the wheels do not skid on the conveyor, it takes off as normal, with wheels' rotation perfectly matching the rotation of the conveyor in a fixed ratio.

Overcoming the perception that the wheels "must rotate faster" than the conveyor for it to move along the conveyor - can be difficult to do.
To do this - forget "moving along the conveyor" and replace with "moving through the air above the conveyor".
This should free the mind from how driven wheels behave.

The wheels are there merely because the plane does not hover.
But the plane behaves just about the same as a hovering one would do, if that hovering one lowered a wheel form itself to just touch the conveyor to make it turn.

Force of jet engine causes plane to move through the air. The wheel below is just a dangly thing of little importance.
(Of course it has some importance, but far less than a lot of people realise, because they perceive how driven wheels behave most of the time)

Rotation ratio isn't relevant. The conveyor belt's length isn't relevant.
A direct drive gearing ratio of 1:1 relates to transfer speed. The touching surfaces of the two components move at the same speed, but only if both are fixed.
If one is not fixed then it is free to change speed. If its position relative to the other changes then its speed must also have changed.

I'm happy to accept the very good conclusion of the XKCD dude that it's an issue of perception and completely pointless trying to change anyone's mind.

 

[Voyager EMH]

Surely that only remains true while the plane (or whatever the wheel is attached to) remains stationary, to move the wheel has to rotate faster than whatever it is in contact with.

It does rotate faster if the thing it is in contact with is stationary. Normal runway is not rotating. Wheel is rotating faster then zero.

On the moving runway/conveyor, free your mind from "moving on the conveyor". The plane moves through the air above the conveyor.
The wheel does not need to overcome anything the conveyor is doing - "rotate faster" does not happen - wheel merely reacts passively to match the conveyor - it cannot "go faster" than it.

The "rotate faster", "go faster" are the wrong words to describe what is happening.
The wheel responds passively to the conveyor and matches its rotation in a fixed ratio of circumference of wheel to length of conveyor.
It cannot "go faster" or "rotate faster" than this fixed ratio.
If the conveyor increases or decreases its rotation then the wheels will do the same - matching passively. The progress of the plane through the air will continue unaffected.

It might be better to start with thinking about a hovering plane whose wheels are 1mm above the conveyor. Obviously unaffected. Plane takes off.
Repeat with the same plane with hovering at first with a wheel on a stick that just touches the conveyor. Same thing. But the wheel will rotate.
Whether the plane is stationary or moving through the air, exactly the same points of the wheel will touch exactly the same points on the conveyor.

With a jumbo jet, it might be the concept of the weight of the plane that could be making you think that there is something to be "overcome" to make the plane move.
Or that something has been overcome now that the plane is moving - and that "overcoming" is wheels rotating faster than the rotation of conveyor.
With a plane stationary on a normal runway the plane does have to "overcome" friction to move.
With a plane stationary on a conveyor that "overcoming" friction has already been done. Any increase in power will cause the plane to move through the air.
Plane moves through the air above the conveyor - wheels and conveyor have matching rotation at a fixed ratio.

The action of the wheel is a passive one. It has not to "do" anything. It can not "do" anything but react passively.

 

[RichA]

@Voyager EMH are you back on the absinthe?

 

[Whereditgo]

Where is this friction you speak of? Rolling resistance not friction do you mean?

I still maintain that for whatever the wheel is attached to travel, it has to travel more distance than the conveyor in the same period of time. The wheel is still acting passively, it just has to increase its rotational speed relative to the conveyor for the axle to move (or skid in the puzzle).

 

[Voyager EMH]

Rotation ratio isn't relevant. The conveyor belt's length isn't relevant.
A direct drive gearing ratio of 1:1 relates to transfer speed. The touching surfaces of the two components move at the same speed, but only if both are fixed.
If one is not fixed then it is free to change speed. If its position relative to the other changes then its speed must also have changed.

I'm happy to accept the very good conclusion of the XKCD dude that it's an issue of perception and completely pointless trying to change anyone's mind.

Rotation ratio isn't relevant. The conveyor belt's length isn't relevant.

Yes.
Too much fixating on describing the wheel's passive response as a determining factor to the plane moving through the air. It is not a determining factor.

If one is not fixed then it is free to change speed.

Yes, the wheel is free to change its "speed of rotation".

The wheel has not changed its position on the conveyor. The same points of the wheel will always match the same points on the conveyor.
With the plane moving through the air then the wheel has changed its position in the air (or world outside the conveyor) and that is how and why the plane takes off as normal.

That change-of-position-through-the-air type of speed should be described separately from wheel rotation speed.
Through the air speed is the plane through the air.
Rotation speed of wheel is a passive one and so can be ignored as it is irrelevant to the plane's takeoff.

 

[Voyager EMH]

Where is this friction you speak of? Rolling resistance not friction do you mean?

I still maintain that for whatever the wheel is attached to travel, it has to travel more distance than the conveyor in the same period of time. The wheel is still acting passively, it just has to increase its rotational speed relative to the conveyor for the axle to move (or skid in the puzzle).

The "more distance" is the distance through the air. The distance on the conveyor will always be the same for one rotation of the wheel = circumference of wheel.

The plane moves through the air. The axle moves through the air. The wheel has motion though the air. That is all the plane's movement through the air.

The wheel's rotational motion on the conveyor is fixed to one circumference length for each turn. That is why the plane takes off.
Wheel/conveyor interaction is not a determining factor for motion through the air. That is why the plane takes off.

 

[Voyager EMH]

@Voyager EMH are you back on the absinthe?

No, not "back" on it.

Anyway, good Voyager episode just started on Sky Mix.
Bye for a while.

 

[Whereditgo]

The "more distance" is the distance through the air. The distance on the conveyor will always be the same for one rotation of the wheel = circumference of wheel.

The plane moves through the air. The axle moves through the air. The wheel has motion though the air. That is all the plane's movement through the air.

The wheel's rotational motion on the conveyor is fixed to one circumference length for each turn. That is why the plane takes off.
Wheel/conveyor interaction is not a determining factor for motion through the air. That is why the plane takes off.

Post #860 shows it perfectly, but I will have another go.

If the conveyor is moving towards the plane at 1m/s and the wheel is 1m in circumference the wheel will rotate at 1 revolution per second.

If the conveyor maintains the 1 m/s speed and the plane starts to move forwards at 1 m/s then, provided the wheel remains in contact with the conveyor, the wheel will rotate at 2 revolutions per second.

I don’t understand what you are trying to say in your last paragraph.

 

[Voyager EMH]

From the OP,

"The conveyor belt .......... match the speed of the plane's wheels .... "

conveyor speed - tangential speed of wheel.

Task: Describe how these two are always the same no matter what speed the conveyor is doing or when the conveyor is in a process of speeding up?

Answer: Because one rotation of the wheel will always be across one-wheel's-circumference-length on the conveyor.

Illustration:
In the two panda drawings, the wheels make the same number of rotations before meeting the panda, whether the plane remains stationary or moves through the air.
While the plane is stationary, the speed of conveyor is 1km/h and the tangential speed of the wheel is 1km/h.
When the plane is moving through the air above at 1km/h, the relative speed of the conveyor beneath the wheel is 2km/h and the tangential speed of the wheel is also 2km/h.
That is how the conveyor speed can be described as matching the wheel's speed. And in the OP - it does state this.

If the OP is the wrong way to describe what is happening (and there is an obvious case for this) - then we have to scrub the OP - rewrite it - and start over.
But that won't alter the reality that the speed of the conveyor and the speed of the wheels (however described) does not prevent the plane from taking off.

(After Voyager last night we watched episode 3 of Miss Austen. Didn't have any Absinthe so had to make do with Drambuie. Today I was mostly engaged with a screw in a tyre, changing to a spare wheel and going down the tyre-shop. Good news was that the puncture was repairable and they charged £26 only)

 

[RichA]

"The conveyor belt .......... match the speed of the plane's wheels .... "

conveyor speed - tangential speed of wheel.

Task: Describe how these two are always the same no matter what speed the conveyor is doing or when the conveyor is in a process of speeding up?

Answer: Because one rotation of the wheel will always be across one-wheel's-circumference-length on the conveyor.

By that rationale, if I lie stationary and face down on the ground while MrsA rolls up my back in her roller skates, as each rotation of the roller skate wheels will be across one wheel's circumference length on my back, the speed of the wheels and the speed of my back must match.
But I don't believe that to be correct.

Have you checked the methanol content of the Drambuie?

 

[Voyager EMH]

By that rationale, if I lie stationary and face down on the ground while MrsA rolls up my back in her roller skates, as each rotation of the roller skate wheels will be across one wheel's circumference length on my back, the speed of the wheels and the speed of my back must match.
But I don't believe that to be correct.

Have you checked the methanol content of the Drambuie?

You are stationary on the ground. This does not meet the criteria of the OP.
To meet the criteria of the OP you would have to speed up and match the tangential speed of the rollerskates' wheels.

 

[RichA]

You are stationary on the ground. This does not meet the criteria of the OP.
To meet the criteria of the OP you would have to speed up and match the tangential speed of the rollerskates' wheels.

Same issue though. If I match the wheel speed she's stationary. If she's moving forwards then the tangential speed of the rollerskates' wheels has to be faster than I'm slithering.

 

[Voyager EMH]

Same issue though. If I match the wheel speed she's stationary. If she's moving forwards then the tangential speed of the rollerskates' wheels has to be faster than I'm slithering.

If the roller skates wheels are moving you have to moving also to meet the OP criteria. You stationary and wheels moving is not the OP.
If you are both stationary the speeds are the same.

The OP states the speeds are the same - or maybe - can be described in some way as the same.

"Wheels have to be faster" is something other than the OP.

 

[SocketRocket]

Average White Band anyone?

I'm thinking of giving it up for music and a free electric band

 

[Whereditgo]

If the roller skates wheels are moving you have to moving also to meet the OP criteria. You stationary and wheels moving is not the OP.
If you are both stationary the speeds are the same.

The OP states the speeds are the same - or maybe - can be described in some way as the same.

"Wheels have to be faster" is something other than the OP.

Correct, and why the OP is worded as it is, to make the scenario impossible and generate discussions like this one. The OP worded as it is expects the relative (your word not the OP's) difference between the conveyor and the wheel tangential speed to remain at zero, "perfectly counteracting their rotation".

 

[Voyager EMH]

Correct, and why the OP is worded as it is, to make the scenario impossible and generate discussions like this one. The OP worded as it is expects the relative (your word not the OP's) difference between the conveyor and the wheel tangential speed to remain at zero, "perfectly counteracting their rotation".

Which is why the only way the OP works for me is to think of the tangential speed of the wheels (not the rotational speed or the speed through the air - do not bring these into the discussion) as always being the same as the conveyor speed.
"The opposite direction" - we can possibly allow this, if we consider the top of the wheel as being "in the opposite direction" to the conveyor. The direction of movement of the top of the wheel is usually thought of as its direction.
The point where the the wheel and the conveyor are touching - the rotation of the two are moving in the same direction - and at the same speed according to the OP.

 

[RichA]

Which is why the only way the OP works for me is to think of the tangential speed of the wheels (not the rotational speed or the speed through the air - do not bring these into the discussion) as always being the same as the conveyor speed.
"The opposite direction" - we can possibly allow this, if we consider the top of the wheel as being "in the opposite direction" to the conveyor. The direction of movement of the top of the wheel is usually thought of as its direction.
The point where the the wheel and the conveyor are touching - the rotation of the two are moving in the same direction - and at the same speed according to the OP.

What is the difference between tangential speed and rotational speed of a wheel?
Same thing, Shirley?

 

[Voyager EMH]

Number of revolutions in a time period. For example RPM - revolutions per minute?

Speed that a point on the rim of a wheel is doing in a tangential direction.

These are two different things as far as I can tell.

 

[Whereditgo]

What is the difference between tangential speed and rotational speed of a wheel?
Same thing, Shirley?

Imagine you and your mate are sat on one of the old fashioned roundabouts you used to get in playgrounds, you sit as close to the centre as you can, while he is sat on the outside edge. You are both rotating at the same rate, but he is travelling much faster than you.