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View Diary: Pique the Geek 20130106: Magnesium -- Common and Essential (43 comments)

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  •  Back when I was young, (3+ / 0-)
    Recommended by:
    Translator, defluxion10, greenotron

    control line speed model airplanes were made of all wood.  Then somebody got the idea of making the belly pans out of magnesium.  They were expensive, but strong and lighter than their wood counterparts.  Then problems began to crop up.  Speed models are very light and streamlined, and have to take off on dollies, which drop off as the aircraft becomes airborne.  Now what goes up must come down, and the model lands on its belly, skidding along until it comes to a stop.  Takeoffs have to be from asphalt or concrete, because grass fields cannot be mowed closely enough or flat enough to accommodate the dolly.  Look at the short video below, and the problem with a pure (or mostly pure) magnesium belly pan will become readily apparent when it rubs the ground at close to 200 mph.

    You cannot put out a magnesium fire on a model airplane!

    Modern pans are made of less flammable alloy.  

    The general who wins the battle makes many calculations in his temple before the battle is fought. The general who loses makes but few calculations beforehand. - Sun Tzu

    by Otteray Scribe on Sun Jan 06, 2013 at 06:27:56 PM PST

    •  To be honest, I did not see the fire. (2+ / 0-)
      Recommended by:
      Otteray Scribe, defluxion10

      What I did see was sort of a bizarre, and humorous combination of a pole dance and a hammerthrow, with a very good Doppler effect in addition.

      Warmest regards,

      Doc

      I would rather die from the acute effects of a broken heart than from the chronic effects of an empty heart. Copyright, Dr. David W. Smith, 2011

      by Translator on Sun Jan 06, 2013 at 06:40:04 PM PST

      [ Parent ]

      •  This one did not catch on fire. (2+ / 0-)
        Recommended by:
        Translator, defluxion10

        It is one of the new alloys.  They quit using nearly pure magnesium back in the early 1960s after some really ugly fire episodes.  The other problem was in the workshop.  Castings came rough, and if the modeler got too aggressive with the grinding wheel, it was entirely possible to burn down the shop.

        The purpose of the pole is for making sure there is no cheating in competitions.  Note the little yoke on top.  When the flyer puts his or her hand in that, the judges know the distance from the center of the circle to the centerline of the airplane is exactly 60 or 70 feet, depending on the engine class being flown.  Otherwise timing would be meaningless.  They have to fly ten laps on the yoke for a heat to count.  That way, they get a ten lap average on the speed, and the speed is very easy to calculate, since they know the exact circumference of the circle, thus the distance flown.  

        The general who wins the battle makes many calculations in his temple before the battle is fought. The general who loses makes but few calculations beforehand. - Sun Tzu

        by Otteray Scribe on Sun Jan 06, 2013 at 07:05:48 PM PST

        [ Parent ]

      •  You may have noticed (2+ / 0-)
        Recommended by:
        Translator, defluxion10

        that when the pilot took his hand out of the yoke, you could see it jerk from the centrifugal force.  Do the math.  A model that size, at speed, will feel as if it is a bag of cement.  

        The general who wins the battle makes many calculations in his temple before the battle is fought. The general who loses makes but few calculations beforehand. - Sun Tzu

        by Otteray Scribe on Sun Jan 06, 2013 at 07:19:15 PM PST

        [ Parent ]

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