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17649RE: [7mm NGA] Hornby Toby 0-6-0 chassis

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  • Richard Coney
    Jul 8 12:12 PM
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      Mazak, or "Pot Metal" as it is often referred, is a Zinc based alloy used for casting and a British developed variant of Zamak, a family of <http://en.wikipedia.org/wiki/Alloy> alloys developed in the USA in the 1920s, with a base metal of <http://en.wikipedia.org/wiki/Zinc> zinc and alloying elements of <http://en.wikipedia.org/wiki/Aluminium> aluminium, <http://en.wikipedia.org/wiki/Magnesium> magnesium, and <http://en.wikipedia.org/wiki/Copper> copper. As Brian says, it rots. It's not a nice stuff and any impurities can start to destroy it relatively quickly. It was used for many automotive parts, and maybe still is to some extent, before plastics. From our point of view as modellers, it was used to make Dinky Toys' diecast model cars and ships, early examples of which are famously susceptible to "metal fatigue" as the surfaces erupt and the castings warp. Classic car enthusiasts hate the stuff as it gets brittle, cracks, crumbles, is very hard to rejoin once broken. It was used to make many of the chromed trim parts on old cars. The metal bubbles up through the plating and ruins the parts. It's very difficult to repair and re-plate without leaving signs of said repair. Basically, it's a horrible material, but its use is widespread, and it is still, I understand, a relatively cheap material to use. Class dismissed! (Actually, it's all laid out for you in Wikipedia!) Quite interesting though!



      From: 7mmnga@yahoogroups.com [mailto:7mmnga@yahoogroups.com]
      Sent: 08 July 2014 19:39
      To: 7mmnga@yahoogroups.com
      Subject: Re: [7mm NGA] Hornby Toby 0-6-0 chassis

      On 08/07/2014 09:02, DAVID TILLETT davidtillett@... [7mmnga]
      > I have the same problem with mine. Guess it must be the content of the
      > alloy, as they simply appear to turn to dust.

      This sounds as if the alloy could be Mazak, which is very prone to
      crumbling after a while, a phenomenon know as "Mazak rot". I believe it
      is due to using cheap alloy which has impurities in it; probably
      recycled material.

      Brian Rumary

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