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Re: 11112: cooling attempt to prevent warping

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  • demondoppel
    Going to try another technique, of reducing the time of welding, and shorten the welds considerably while using the LN2, so that the metal will not heat much
    Message 1 of 2 , Jan 17, 2006
      Going to try another technique, of reducing the time of welding, and
      shorten the welds considerably while using the LN2, so that the metal
      will not heat much at all.

      I was making welds sometimes, 3/4 to 1 inch long while using the LN2.
      I was defeating the cooling process by keeping the weld time/length
      too long.

      Something that I had to learn through trial and error ;)

      Other than that, the cone which was done, is under about 50/1000 for
      the 11 inch (about 10.95 after hammering into circular shape).

      It will have to be discarded, since it didn't achieve the diameter.

      Aside from this, no focus has been made on the frame or rings. They
      appear to be fine, as well as the osc table.

      Matt



      --- In hameltech@yahoogroups.com, "demondoppel" <mattihorn@i...>
      wrote:
      >
      > Okay, tried this new technique for welding the skins together.
      > I used LN2 (liquid nitrogen) to cool the entire cone, prior to
      welding.
      > It worked, and the LN2 stayed in the cone, about 1 litre, for a
      > duration of at least 30 minutes. Enough time to weld the cone skins
      > together.
      > The warping factor was reduced dramatically, but still there was
      some
      > occurring. I did not have the LN2 all the way up to the lip. It was
      > sitting about 10 cm (4 inches below the lip). This is probably why
      the
      > warping occurred.
      > Estimate about 3 litres of LN2 would be required to fill the entire
      > cone to top.
      > It's about timing, since the boil off is steady. If a cloud of
      vapour
      > gathers above the LN2, it slows down.
      > The entire cone becomes a big frosty.
      > The welding discolourations appear to be narrower, since the
      heating
      > is reduced. Of course, if the arc is applied too long, the warping
      > factor increases. again it's about timing.
      > The lip of the cone still tends not to uniform, there is some
      > distortion which will have to be removed through hammering, which
      is
      > another problem for keeping the edge of the cone true. Careful work
      of
      > course.
      > THe biggest cone being the most difficult, and then getting easier
      for
      > the middle and then much easier for the smallest. In fact the
      smallest
      > reveal the least amount of warping.
      >
      > That's it for now.
      > Matt
      >
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