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Which is better to create a vacuum? Air or water?

  1. Mar 18, 2009 #1
    I have recently used a car dent removal device, which creates a vacuum round the device by sucking the air out however it did not work very effectively. I was wondering if it would be better if the vacuum was placed over the dent, filled with water and air in the vacuum was released through a valve and then use a pump to suck the water out of the vacuum, resulting in the dent being pushed back out.
    Any comments or feedback would be most appreciated
    Thanks
     
  2. jcsd
  3. Mar 18, 2009 #2

    mgb_phys

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    The limit with a vacuum is that you can only apply 1 atmosphere of pressure (15psi) - so you could do the same by putting an extra atmosphere of air/water pressure on the other side.
    But the advantage of vacuum is that it holds itself onto the metal - if you used high pressure on the back then you need some way of holding the system against the car.
    There is also a problem that getting at the back of the dent is normally harder!
     
  4. Mar 18, 2009 #3

    Danger

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    You can't beat the good old 'Morgan Knocker'.
    You used to have to drill a hole in a panel and attach the slide-hammer with a screw, but the newer approach is to weld a pin to the metal, then grind it off after straightening.
     
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