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Good answerbut what is the load from the conveyor belt? ..
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there will be a frictive force proportional to the radial velocity of the wheels, which will be going twice as fast
Good answerbut what is the load from the conveyor belt? ..
![]()
there will be a frictive force proportional to the radial velocity of the wheels, which will be going twice as fast![]()
Assuming that there is (somehow ) a converyor belt which is travelling at the equal and opposite relative linear speed to the linear wheel speed; and therefore there is no slip, no other factors coming into play; and the plane is not moving relative to a fixed point on the ground (and therefore the airmass around it, then the plane will not take off. It has nothing to do with the propulsion mechanism of the airplane. Of course finding such a conveyor belt in real life is a problem.
But why would the plane not move relative to a fixed point on the groundThe wheel speed and the conveyor belt are actually totally irrelavent
Sorry, but the propulsion mechanism has everything to do with it ... i.e. the plane is being pushed or pulled through the air ... not being driven along the conveyor
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Becuase as long as the plane is in contact with the ground the forward propulsion of the plane mass is via the wheels. If the conveyor belt is moving the opposite direction, then the wheels will stay in exactly the same spot relative to the ground
It's not VTOL!
Why won't the plane move? The plane will move and it will take off![]()
Why will the plane move? It won't and it won't take off
From my understanding the conveyor belt will counter any forward wheel motion caused by the thrust of the plane's engines (see my previous analogy to runner on treadmill) ie the plane will remain stationary in space. Ergo no relative airflow, no lift vector, no take off-simples![]()
Not if the conveyor is moving at exactly the same speed as the wheels![]()
Why will the plane move? It won't and it won't take off
From my understanding the conveyor belt will counter any forward wheel motion caused by the thrust of the plane's engines (see my previous analogy to runner on treadmill) ie the plane will remain stationary in space. Ergo no relative airflow, no lift vector, no take off-simples
Even better analogy - imagine a car on a rolling road. If you then strap a pair of aerofoil sections onto the car, will it fly? No!!:nono:
Davek , the wheels have no drive. The conveyor moving in the opposite direction will simply make the wheels spins at twice as fast. The plane will continue to move forward, because the drive is through the jet propulsion through the air.
I made the same mistake..![]()
no the wheels will just turn faster as they are not connected to the drive. in theory they will turn twice as fast and make no difference to the aircrafts airspeed, but in reality as there is friction in the wheels the aircrafts airspeed will slow down but it will still take off providing in normal operating contitions it doesnt need full thrust to take offIf I taxy my plane along the runway using engine thrust (causing the wheels to turn and propel me forward) and then (imagine) the runway starts to roll towards me (like a conveyor belt) then the result will be me sitting in my aircraft stationary relative to space, no airflow, no lift. My wheels will turn and I will remain taxying along the moving runway but I will never take-off. If you think otherwise I need a clearer explanationThrust and lift are two different things.
PS I certainly don't understand the wheels going twice as fast stuff!
The plane will take off as normal so long as the wheels can withstand travelling at twice the rpm as usual during the takeoff run. Nothing else changes.
PS I certainly don't understand the wheels going twice as fast stuff!
The speed of the belt is exactly the same as the wheels.
For the plane to move relative to a fixed point the belt and wheels must travel at different speeds unless one slips relative to the other.
If the speed of the belt and speed of the wheels are the same then the plane does not move, no matter if it is wheel driven or not. This is why I said the wheel bearings would melt. Given the co-efficient of friction in wheel bearings the conveyor and wheels must move at an extremely high speed for the energy from a jet engine to be dissipated through friction.
For the plane to move relative to a fixed point the belt and wheels must travel at different speeds unless one slips relative to the other.
That's what I was thinking. If the plane has forward thrust from its engines, it is physically impossible for the conveyor belt to move at the same speed as the wheels. The wheels will move faster, and there's no two ways about it.
And then, yes, the plane will take off.
Why can't the belt travel at the same speed as the wheels?![]()
It can if the plane isn't moving, but as soon as there is forward thrust from the engines the plane will move forwards (irrespective of the speed of the belt) and the wheels will then be spinning faster than the belt is moving.
The same thing can't be said about the plane. It's not driven by anything that's in contact with the belt, so if the plane has forward thrust it will move forwards no matter what the belt is doing. But its wheels will be spinning faster than the belt. Physics dictate that.
So there.![]()
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Because if the wheels (assuming the wheels are driven, in this instance) accelerated to 10mph, then the plane would stay stationary. In order for the plane itself to accelerate to 10mph, the wheels have to be spinning faster than that.So if the plane accelerates from 0 to 10mph and the belt does the same, why would the wheels be going faster than 10 mph![]()
Sorry, but Physics dictate that the wheels will be exactly the same speed as the belt
because the thrust from the plane would always try and push the plane forwards, so the wheels will always move faster than the belt, which will then speed up but then thrust will push the plane and make the wheels turn faster. do you see where this is going? the wheels and belt would up at impossible speeds if this could happen
read arguements about this so many times but yes it would take off as proven by mythbusters
reasons are because no power goes to the wheels so the fact they are spinning backwards in essence makes no differences to the thrust produced by the engine so it will take of with no problems, would just mean that the wheels are travelling twice as fast as normal at take off.
Sorry, but Physics dictate that the wheels will be exactly the same speed as the belt
Surely thats not right unless the belt sped up with the plane, if the belt is set to say 50mph then the plane is moving forward at 50mph surely the wheels are doing 100![]()
But if the plane doesn't move then the belt doesn't move![]()
but that is physically impossibleBut the point is that the belt always matches the speed of the wheels
but that is physically impossible
but that is physically impossible
The only thing that dictates that the wheels will be the same speed as the belt is your original brief.
We can argue with your brief, but we can't argue with physics.![]()
but that is physically impossible
I keep telling him, be he won't listen.![]()
Because I'm right and your wrong![]()
kk back to the brief which way is the belt turning, does it pull the plane backwards (-ve v) or push it forwards (+ve v).
The speed of the wheels rel to the belt is (radVwheel*rad)-(Vbelt)
Vbelt=(radVwheel*rad) if going in same direction (pushing plane along) OR
Vbelt=-(radVwheel*rad) if going in opposite direction
1--1=2![]()
So, Why is it physically impossible care to elaborate![]()
Because if the wheels (assuming the wheels are driven, in this instance) accelerated to 10mph, then the plane would stay stationary. In order for the plane itself to accelerate to 10mph, the wheels have to be spinning faster than that.![]()
I already have! Twice!![]()