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Can I call BS on this video

  1. May 25, 2013 #1
    People keep posting crazy videos about Saudis changing wheelsof a car when
    the car is still moving , but is on two wheel
    http://www.bbc.co.uk/news/world-middle-east-22664659

    It can be seen in this video

    Wouldn't a car's standard ( friction clutch one )differential not allow the wheel to remain stationary ( either the front wheel or rear wheel that is suspended in air has to move depending on whether the car is front wheel or rear wheel drive )

    Isn't it the whole point of a friction clutch differential , that both wheels HAVE to have power/motion\

    Please correct me if I am wrong , considering it's BBC who have put up this
     
  2. jcsd
  3. May 25, 2013 #2
    What do you mean can you call BS on it? You can see it with your eyes.

    EDIT: It's late and I may be talking crap, let me have a think. : /
     
    Last edited: May 25, 2013
  4. May 25, 2013 #3
    Well , let me rephrase it
    The Car would have some form of "limited slip differential" , which means both the raised wheel and the other wheel will be sort of forced to have equal power/velocity , wouldn't they
    In the video , the raised wheel doesn't move ( hence they can change the tires ) , ie differential isn't doing it's job

    So , my point is , either the car has some new form of differential ( I highly doubt ) or it's fake
     
  5. May 25, 2013 #4
    Well for starters, it's not fake. So lets set our minds out to how it can be achieved.

    The diff can't be locked in anyway, as the wheel would be spinning. So the diff must be open, however this would mean that power would be spun away. It also means that the wheel would be easy to lock with left foot braking.

    So an open diff with left foot braking allows power to be transmitted to the wheel that has the inertia of the car dragging it along, whilst keeping the wheel in the air stationary.

    :biggrin:
     
    Last edited: May 25, 2013
  6. May 25, 2013 #5

    OCR

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    The differential is actually 'doing it's job'.
    http://en.wikipedia.org/wiki/Differential_(mechanical_device)





    You got it... :approve:



    OCR
     
    Last edited by a moderator: Sep 25, 2014
  7. May 25, 2013 #6
    @Chirss
    well that's possible
    Thanks

    PS: I was hoping the video was fake and I could expose BAD journalism
     
  8. May 25, 2013 #7

    Danger

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    Just tune into Fox News; you'll have a lifetime supply to play with. :rolleyes:
     
  9. May 25, 2013 #8

    phinds

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    +1 on that :smile:
     
  10. May 28, 2013 #9
    I've seen it done in person. Google james smith, he is a stunt man
     
  11. May 31, 2013 #10
    I'm just a car enthusiast and not an automotive engineer, but I don't see why it can't just have a limited slip (locked) differential. If the differential is open, then I am certain that the wheel in the air would spin and the wheel on the ground would get no power. Same situation as having one wheel on snow or in mud and the other wheel on dry asphalt - i.e. the entire point of a locked differential.
     
  12. May 31, 2013 #11

    phinds

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    I'm not clear what your point is. Are you saying the video is a fake and the people who have seen it themselves are lying or the opposite?
     
  13. May 31, 2013 #12
    If you just wanted to drive off on two wheels, you'd just weld the diff up and be away, merry as you like. You can't do that if you want to do the wheel change stunt as well, as it requires the wheel in the air to be not rotating.
     
  14. May 31, 2013 #13
    Right, because of the wheel change stunt in particular, they need the OPEN differential. I understand now. Still don't get the left foot braking thing you mentioned though.

    I just didn't understand the confusion, since it seemed obvious to me that you could drive crooked like that if you simply had a locked differential. Now that I re-read the OP and responses, I see what they were getting at. The wheels in the air are NOT rotating at the same speed as the wheels on the ground, weird.
     
  15. Jun 1, 2013 #14

    OCR

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    That might not have been the best description, so we'll try...

    My bold...
    Actually, it's called differential braking and works like this...
    http://en.wikipedia.org/wiki/Differential_braking#Differential_braking

    Can also be called independent wheel braking.

    http://forums.off-road.com/jeep-sho...endent-brakes-poor-mans-locker.html#post21022


    In any case, the people in the video had to stop the right side wheels from turning... although there are other ways, they probably have a separate system for the right and left side brakes.

    And... they would probably use their left foot to push the brake control. (pedal)... :smile:



    OCR
     
    Last edited: Jun 1, 2013
  16. Jun 7, 2013 #15

    Danger

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    Hmm... those were called "cutting brakes" when I was a kid, and they were used only on dune buggies.
     
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