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How Much Does Air "weigh"

Discussion in 'Anything Airgun Related' started by Spray1Mark, Jan 24, 2020.

  1. NIVEA

    NIVEA Not Banned Yet

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  2. jesim1

    jesim1 Kit bitch to the Stars

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    Every competent diver will tell you that you have to do a neutral buoyancy weight check at the end of a dive with an almost empty tank as your getting lighter all through the dive by breathing the air. Only by doing this can you be certain your not going to "pop up" because your underweighted and float to the surface :eek: Your estimate is spot on though :thumb:
     
  3. Gunfun

    Gunfun Engaging Member

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    I often wonder if airgun designers take advantage of the mass of air when designing the internals of airguns.

    Edward Turner (Triumph motorcycle engineer) used the mass of air to jump ahead of his competitors when designing the Speed Twin, it was in the 1930's when all engine designers were making intake ports and valves as big as possible so as to fill the cylinder as much as possible. What Edward Turner did was to make the intake port as long and narrow as possible because he realised this would increase the speed of the air/fuel mixture being pulled into the cylinder by the piston, and when the piston hit 'bottom dead center' the speed of the air/fuel mixture in the intake port would continue to fill the cylinder because of the air/fuels momentum, thus filling the cylinder with much more air/fuel compared to his competitors using large diameter intake ports.

    I was gobsmacked at Edward Turners genius for using something as seemingly insignificant as the weight of air/fuel to his advantage.
     
  4. MoggyM

    MoggyM FLM

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    Ask slimming world
     
  5. rich79

    rich79 Lovin the smell of cordite in the morning

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    I remember doing this at school, even using a 2lt plastic bottle with a small valve & pumping it up can show a difference.
    But I was only interested in lessons where you got to burn stuff.
     
  6. Zubar

    Zubar Engaging Member

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    It is certainly noticeable when diving. My twin 12s (24l) is a good 4kg heavier full.
    Another thing is my Ali 80 is an 11l Ali cylinder used as a stage sinks and hangs when full but will float when empty. Divers sometimes clip them to a line and send them up when used.
     
  7. Spray1Mark

    Spray1Mark Pro Poster

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    Diving? I quote!

    "you go in the water-shark's in the water"
    me I can't swim, don't need to, I live on the land, Great white sharks aren't dangerous it's all a lie, they are only dangerous if you are foolish enough to go in the sea!
     
  8. Spray1Mark

    Spray1Mark Pro Poster

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    You mean like the chemistry teacher?
     
  9. Spray1Mark

    Spray1Mark Pro Poster

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    I use carbon 12L 300 bar cylinders, they weigh about 6kg, approx 1kg more than the 9L carbon cylinders, however the advantage is effectively lost due to the extra weight of the air volume.
     
  10. psychosomatic gardener

    psychosomatic gardener Busy Member

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    Yes but at 10 m its 2 bar absolote pressure
     
    jesim1 likes this.
  11. psychosomatic gardener

    psychosomatic gardener Busy Member

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    Boyles law states that for every metre below the sea level pressure increases by .1 of a bar...
    So the surface pressure is 1 bar or 14.7 psi we are born to it we will die to it so if you were at the diving limit of 50m breathing air the pressure woud be 5 bar+ the surface pressure =6 bar..
    Or if you wer at 35 metres the absolote pressure would be 4.5 bar..
    May not mean a lot but if you had carbon monoxide in your tank of 1 ppmillion thats safe but 5 ppm is toxic at 5 bar so go past 40 metres and your stuffed..
     
  12. TrickyDicky

    TrickyDicky Life in the slow lane

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    That's also to do with valve timing (overlap) as you can do the same with scavenging IE lag between the exhaust opening and the inlet closing and using the outgoing exhaust flow to draw in more air.
     
  13. edtwozeronine

    edtwozeronine Donator

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    What would you rather have dropped on you, a ton of feathers or a ton of lead?
     
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  14. Wild Bill

    Wild Bill co2 Pistol Enthusiast & Western fan

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    That obvious. :thumb: But it depends if the feathers are all packed in one package. Both weight the same but obviously feathers would spread out over the fall.:D
     
    Last edited: Jan 25, 2020
    jesim1 likes this.
  15. The Ecologist

    The Ecologist Engaging Member

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    Feathers. I'd be banking on air resistance helping out. Wouldn't be happy if you've compressed them into a really really tight ball though!
     
  16. Wild Bill

    Wild Bill co2 Pistol Enthusiast & Western fan

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    Here is another one for you:

    A tanker carrying 37,500 ltrs of aviation fuel. Lets say the fuel weighs 37,500 kg. It is loaded at 12 degrees C. But overnight the ambient temperature increases to 30 degrees causing the 37,500 ltrs of fuel to expand to 38,500 ltrs, so an increase of a 1000 ltrs. Does the actual weight of the fuel increase though? ;)
     
  17. The Ecologist

    The Ecologist Engaging Member

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    Without trying to Google the answer I'm going to say the weight wouldn't change. However the weight would differ between 37,500 ltrs of oil at 12 degrees C and 37,500 ltrs of oil at 30 degrees C. Yay or Nay?
    Barry
     
  18. edtwozeronine

    edtwozeronine Donator

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    They'd both have to be in some sort of container I'm afraid, most people pick the feathers not assuming such.
     
  19. The Ecologist

    The Ecologist Engaging Member

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    OK then - where do you weigh a pie?
     
  20. Wild Bill

    Wild Bill co2 Pistol Enthusiast & Western fan

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    Quite correct. The weight stays the same despite their now being 1000 ltrs more fuel. :thumb:

    As for your question about oil, I am not sure. Because your qty of oil remains the same.
     

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