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Would the plane take off?

Discussion in 'General Chat' started by imported_Nigma, Mar 21, 2006.

  1. chazzy
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    chazzy Member

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    totally agree re the speed relative to the conveyor being 320 if it needs 160 airspeed to lift off. /ubbthreads/images/graemlins/smile.gif

    I think it must be in the reading/interpretation!

    chas
  2. imported_hookie
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    imported_hookie Guest

    [ QUOTE ]
    [ QUOTE ]
    cough cough

    [/ QUOTE ]

    Idiots. /ubbthreads/images/graemlins/laugh_2.gif

    [/ QUOTE ]

    I'm worried why they just don't get it, even with highly qualified professors in physics agreeing with us!
  3. bainsyboy
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    bainsyboy Guest

    IM GOING UP THE PUB
    /ubbthreads/images/graemlins/beerchug.gif + /ubbthreads/images/graemlins/dancing.gif + /ubbthreads/images/graemlins/MexWave.gif + more /ubbthreads/images/graemlins/beerchug.gif = /ubbthreads/images/graemlins/blush2.gif = /ubbthreads/images/graemlins/vomit.gif

    But if we get around to the answer of the plane ill get back to you, but i reckon we will be talking birds & football
  4. NEiLS3LK51
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    NEiLS3LK51 Member

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    I have had enough of counter arguments, especially those that still give examples of things on a constant speed belt!

    Im going to build a model of this, that will generate a vertical lift off only for a propelled, air chucked over the wing model.
    When the air is dispersed away from the wing like a jet engine the model will not generate any lift. Neither type will move forwards on the belt.
    ie. traditionally generated air speed.

    For either case the model will be free runing on wheels like a real plane, although friction of the tyres to the belt will be exagerated
    as I will not be able to recreate the same force a real plane would make with a belt due to it being a little/light model and seeing it skid forwards
    as I have said before will be difficult to see when the thrust eventually overcomes this frictional force.

    Belt and propeller motors will be adjusted concurrently with some extra offset made to the belt motor to compensate for the inefficiency of the
    thrust generated by the propeller. So both the wheels and belt will move at roughly the same speed and the plane will go nowhere.
    It may be impossible to get them exactly the same speed so there may be some movement either way, but no increasing acceleration,
    like a real plane that takes off.

    I would expect some nonlinearity in the planes generated wheel speed compared to the belt speed over the range of input voltage to
    the motors due to inefficiency mentioned before, so some tweaks maybe required to the belts offset along the way to maintain a
    constant speed between the belt surface and the planes wheels.

    I will look to start middle next week as I actually do have some real work to do as well and the pub beckons now!

    Hookie, please forward my plans onto the academics who have been interested, I would be pleased to get some feedback.
  5. imported_hookie
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    imported_hookie Guest

    But the force applied is to the atmosphere! the wheels rotate but have apply no force to the plane as they have bearings! lol

    I'm off to the pub too, but doubt I'll talk football, just girls /ubbthreads/images/graemlins/wink.gif
  6. rickquattro
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    rickquattro Member

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    If the belt rotated and behaved re increasing speed etc, as in the question, but the direction of the belts rotation was reversed, ie. in the direction the plane was attempting to move , would the aircraft take off in half the time?

    Or would the passengers still receive vouchers for a delayed flight.....
  7. Mart
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    Mart Active Member

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    [ QUOTE ]
    If the belt rotated and behaved re increasing speed etc, as in the question, but the direction of the belts rotation was reversed, ie. in the direction the plane was attempting to move , would the aircraft take off in half the time?

    Or would the passengers still receive vouchers for a delayed flight.....

    [/ QUOTE ]

    Or would the plane over-run the belt, and crash!

    On the note of planes, did anyone hear the news of the Irish airline, that landed at the wrong airport! see below!

    link
  8. NEiLS3LK51
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    NEiLS3LK51 Member

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    [ QUOTE ]
    But the force applied is to the atmosphere! the wheels rotate but have apply no force to the plane as they have bearings! lol

    [/ QUOTE ]

    Exactly, the model will be pushed by propeller. So the force will be applied to the atmosphere.

    They do have force to the plane as they are mechanically coupled to the planes body.
    The hub/axle of the wheel is fixed to the plane and so transfers a lateral force during ground
    conditions even if the wheel is free to rotate.

    This is I want to demonstrate in the experiment.
  9. fallmonk
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    fallmonk Turbo Sport

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    ANYBODY got a stinger missile i can blow this bloody plane up with !
  10. neversaydie
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    neversaydie Post Whore

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    is this the post whore thread?
  11. imported_hookie
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    imported_hookie Guest

    Cambridge University replied with an opinion -

    [ QUOTE ]
    what counts for a plane to take off is the speed of the air over the wings. in the ideal case of frictionless wheels, the wheels go faster but the plane is still accelerating since the jet engines' thrust is applied to the body and wings of the plane. so it seems to me that this plane will fly. of course a car where the force is applied to the road through the wheels would have some trouble.

    [/ QUOTE ]

    They highlight the point about the thrust/wheels thing, post goes on whoring and all!
  12. NEiLS3LK51
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    NEiLS3LK51 Member

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    Is this a direct quote, where it says frictionless wheels does it mean bearings or surface contact to the belt?

    If the wheels contact to the belt were frictionless there would be no point in an opposable conveyer belt at all, it could just be ice. I will not even bother to continue with my model if we now argue surface contact is ideally frictionless too!

    I don't think such a limited response should be credited as being Cambridge's, they are meant to be one of our countries finest Universities!!

    Only a few posts of the 8 pages or so have been post whoring so I wouldn't worry.

    p.s. I will build the model anyway.
  13. scoTTy
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    scoTTy Active Member

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    Does it really need a model? It's obvious. Put a plane on ice, concrete, water, snow, wood, conveyor belt, anything and it'll still bloody fly!
  14. NEiLS3LK51
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    NEiLS3LK51 Member

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    Yes it does, because its not obvious, will not fly except for the vertical lift off conditon of a propelled plane
    and the only way to prove this to you is to show you a video clip of it not flying at various levels of thrust!
  15. TDI-line
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    [ QUOTE ]
    is this the post whore thread?

    [/ QUOTE ]

    No bud, we don't do that now. /ubbthreads/images/graemlins/smirk.gif
  16. audi5e
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    audi5e Member

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    In the real world, it would be almost impossible to replicate the question. To instantly provide an equal but opposite force is going to be extremely difficult. As for the disbelievers, I agree with your arguments that the plane will fly if the wheels were allowed to skid or you put it on ice, then the the wheel and the surface would not be in equilibrium and so the wheel would be able to move at a faster rate than the surface.

    By the way, while the aircraft is on the ground and below flying speed, the wings are useless appendages. The thrust/propulsion acts on the air to create forward movement. However this forward movement is transfered via the wheels over the ground. Since the wheel and the conveyor are in equilibrium the body of the plane will remain stationary relative to the ground beside the conveyor.

    Someone used the analogy of a person pushing a shopping trolley on a moving surface, where I think everyone understood that you have to push the trolley, and no matter how fast you go, you cannot move forward relative to the ground next to the trolley if the conveyor is moving against you. The fact that the wheels are not driven directly is not that important. Thrust is being applied to the trolley and that thrust is being converted to forward motion via the wheels. Yes, in the case of a jet engine, the thrust is far greater but is still being applied to the body of the aircraft and converted to forward movement via the wheels. Remember that forward movement from the wing/flight only happens once airspeed is high enough.
  17. rickquattro
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    rickquattro Member

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    [ QUOTE ]


    Someone used the analogy of a person pushing a shopping trolley on a moving surface, where I think everyone understood that you have to push the trolley, and no matter how fast you go, you cannot move forward relative to the ground next to the trolley if the conveyor is moving against you. The fact that the wheels are not driven directly is not that important. Thrust is being applied to the trolley and that thrust is being converted to forward motion via the wheels. Yes, in the case of a jet engine, the thrust is far greater but is still being applied to the body of the aircraft and converted to forward movement via the wheels. Remember that forward movement from the wing/flight only happens once airspeed is high enough.

    [/ QUOTE ]

    Oh please.....

    The shopping trolly analogy works in the example above because the person standing on the belt is trying to provide forward motion via his feet, on the belt. Your comment about forward movement via the wheels of the plane is also incorrect. The force of the engines acts on the air behind the engine. No drive in any form is via the wheels...

    Propellor or jet, engine force acts on air behind the engine.
    Are wheels driving the aircraft forward. No
    Will the aircraft move forward. Yes

    On full power, on the imaginary belt, the only way the aircraft would not take off is if there were a tether on the tail of the plane to a fixed point, behind it...

    Send the question to Hammond at Braniac.....

    Loosing the will to live now...
  18. imported_hookie
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    imported_hookie Guest

    The only reason this thread is continuing is because a couple of folk don't understand about the whole engine applying force to the air behind it and the wheels having bearings on that because they are free to rotate do not transmit force very well to the body of the plane (It's for this reason that the rear wheel of a bicycle has a freewheel/cassette and not just a bearing, otherwise you'd be pedaling hard and getting nowhere fast....)
  19. rickquattro
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    [ QUOTE ]
    Cambridge University replied with an opinion -

    what counts for a plane to take off is the speed of the air over the wings. in the ideal case of frictionless wheels, the wheels go faster but the plane is still accelerating since the jet engines' thrust is applied to the body and wings of the plane. so it seems to me that this plane will fly. of course a car where the force is applied to the road through the wheels would have some trouble.

    [/ QUOTE ]

    Exactly! I have also sat on planes with the little LCD display with location/speed etc on it and said to my lass that the take off speed is the same as I have been on my bike on a track day..... I dont get to fly on my bike though as the power is driving THROUGH THE WHEELS !

    Lost the will to live now...
  20. Charlies604
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    Just waiting for my elastic band plane to arrive and we'll be off to tescos, the gym or sumwhere else with a big moving belt!!!!


    What about planes that take off from water by the way? Water isnt still.... they never have to say hold on guys cant fly today the tide is comin in not goin out!
  21. audi5e
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    audi5e Member

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    ok, let me ask a question, how does an aircraft with force applied on the air behind it, from a jet engine, move forward while it is still on the ground? It get's pushed right? from behind. And how is it getting to move forward? on the wheels, correct? (taken from the question) so what happens if the ground just keeps moving beneath the wheels? The plane tries to move forward because of the force applied by the air behind the jet engine which is acting on the aircraft and pushing it faster and faster, but all the while the belt just keeps on keeping up but in the opposite direction. Yes, absolutely, the belt and the wheels are going round at an incredible speed, but the body of the aircraft is staying still.

    By the way, if you remove the condition and say that they wheel can move faster than the belt then you will have flight.
  22. audi5e
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    audi5e Member

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    [ QUOTE ]
    Just waiting for my elastic band plane to arrive and we'll be off to tescos, the gym or sumwhere else with a big moving belt!!!!


    What about planes that take off from water by the way? Water isnt still.... they never have to say hold on guys cant fly today the tide is comin in not goin out!

    [/ QUOTE ]

    The plane skids over water, so all it has to do is overcome the rearward motion of the water.
  23. audi5e
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    Going to throw another useless piece of info into this. The jet engines do act on the air behind the plane, as stated. What I think would happen is that because air is a gas it can be displaced, so the more force you push out in terms of gas the more displacement takes place. If the aircraft were being pushed from an immovable object then equilibrium would be broken and the plane would take off.

    So take the man running on the conveyor pushing the trolley. He would not be able to overcome the conveyor. However if he were to push from beside the conveyor he would be able to overcome the conveyor because he is pushing against an immovable object, ie the ground.
    If you mounted a fan or propellor or jet on the trolley, the air behind would be displaced, ie movable. Since there is nothing solid to push against....

    ok, now my head is spinning.
  24. TDI-line
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    TDI-line Uber Post Whore

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    I cut my arm at work today.
  25. bainsyboy
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    bainsyboy Guest

    [ QUOTE ]
    I cut my arm at work today.

    [/ QUOTE ]


    If TDI stands on the spot and flaps his arms really fast like really really fast like a humming bird would he be able to fly, How much you weigh TDI? as this will play a major part in this experiment.
  26. rickquattro
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    TDi, cant take part in the experiment, he has cut his arm and also has a note from his mum saying that he can't take part in flying experiments until his arm is better.

    He can however continue with "Live Art", as long as he holds the brush with his other hand.
  27. audi5e
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    Actually I was wrong in my last post. The plane's wheels and the conveyor would instantly hit infinity if I tried to move the aircraft by pushing against an immovable object. In other words the aircraft has also become an immovable object!

    So how much does TDi weigh? :)
  28. imported_hookie
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    imported_hookie Guest

    The plane took off and landed at it's destination whilst audi5e was still thinking about it /ubbthreads/images/graemlins/tongue.gif
  29. NEiLS3LK51
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    I have a plane built but still waiting on parts for the runway belt.
  30. Mart
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    Mart Active Member

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    Plane has run out of fuel now! So cannot take off, infact the belt got stuck on, and the plane has now come off the back of it, and has exploded, so cannot take off!
    Sorry guys!
  31. imported_hookie
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    imported_hookie Guest

    Easy way to check, use skateboard with fan attached as first test, measure speed, then set conveyor belt at same speed and place satebosrd on it, if it moves a plane would fly as it proves the one vector is greater than the other.
  32. rickquattro
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    TDi, hope your arm's a bit better today. Poor little soldier....
  33. audi5e
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    Yeah yeah yeah, but how much does he weigh?
  34. bainsyboy
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    bainsyboy Guest

    Rickquattro class reply mate
  35. chazzy
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    Audi5e, re the air "giving" not important, its the engine throwing air out the back, its the same effect as recoil on a machine gun, but instead of a load of bullets its ejecting loads of air particles going really fast,
    Or in momemtum speak, its gives the air a momentum in a negative direction (backwards) so the plane gains momentum in a positive direction, it moves slower than the air going out the back due to its greater mass.
    Chas (Now back at school after 3 weeks browsing forums!)
  36. TDI-line
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    TDI-line Uber Post Whore

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    About 90 KG.
  37. rickquattro
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    [ QUOTE ]
    About 90 KG.

    [/ QUOTE ]

    Is that with both legs on the scales or are you really a bloated pie fiend who lifts one leg up when getting weighed to appear lighter ?

    Q. By the way, where would you have to go to find out how heavy one of TDi's pie's is?

    A. Somewhere, over the rainbow.... weigh a pie..... ahem.

    I feel a cat/pie avatar interface scenario imminent...
  38. pwnorman
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    [ QUOTE ]
    About 90 KG.

    [/ QUOTE ]whats with the kg fatboy /ubbthreads/images/graemlins/lol.gifwere you trying to chop your arm off to stop eating those pie's bit drastic way of dieting. My folks have been on holiday and come back in the lenght of this debate asked the old man if he saw any large conveyor belt near manchester airport but saw nowt although he did mention a fat bloke standing on a belt in the terminal running the wrong way flapping his arms saying when asked he's cinducting an experiment for audi-sport just as he managed lift off, anyone here i wonder.
  39. TDI-line
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    TDI-line Uber Post Whore

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    Wheres the edit button. /ubbthreads/images/graemlins/burningmad.gif
  40. audi5e
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    [ QUOTE ]
    Audi5e, re the air "giving" not important, its the engine throwing air out the back, its the same effect as recoil on a machine gun, but instead of a load of bullets its ejecting loads of air particles going really fast,
    Or in momemtum speak, its gives the air a momentum in a negative direction (backwards) so the plane gains momentum in a positive direction, it moves slower than the air going out the back due to its greater mass.
    Chas (Now back at school after 3 weeks browsing forums!)

    [/ QUOTE ]

    Realised this after my post. Since the conveyor and wheel would hit infinity the plane body would not move anyway, so no flight.

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