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  1. #1
    Join Date
    Mar 2016
    Posts
    22
    Country: United States

    Default Insulation for Fireproof Safe

    Does anyone have an idea what the proper mix of alum powder and plaster should be in a fire resistant safe?

    Refractory cement would work but is if a different consistency than was originally used.

    Iím restoring a safe where the safe bottom was cut out.

    https://i.imgur.com/2wwSE5C.jpg

  2. #2
    Join Date
    Oct 2009
    Location
    Cleveland, Ohio USA
    Posts
    1,267
    Country: United States

    Default

    Finally finished making the friction fence assembly. Made a new brass tube and cut in a groove for an internal spring. Fortunately had the correct size gear but it had a large hole that needed filled. Used low temp "Tix" solder for the gear insert also made of brass. This insert needed 2 small internal steps to engage into the slots cut into the tube. This was done with hi temp silver solder. These steps tie the gear to the tube. I annealed the tube ends prior to bending them over so they wouldn't crack. So it is working more freely now. It is important to pay close attention when installing the drive cam onto the dial spindle, making sure the drive cam gear teeth engage into the fence gear. It is possible to trap the fence gear under the cam gear. Tightening the cam in this situation puts undue stress on the low temp solder used. Otherwise there is little stress on that solder joint and it should work fine.
    Attached Thumbnails Attached Thumbnails IMG_20180328_194228270_BURST000_COVER.jpg   IMG_20180328_194152561.jpg  

  3. #3
    Join Date
    Oct 2009
    Location
    Cleveland, Ohio USA
    Posts
    1,267
    Country: United States

    Default

    Maybe this pic is better
    Attached Thumbnails Attached Thumbnails IMG_20180328_202351875.jpg  

  4. #4
    Join Date
    Mar 2016
    Posts
    22
    Country: United States

    Default

    Looking forward to seeing the fence. I know how badly I burned it so Iím shocked that it could be rebuilt. Amazing work.

    On the topic of insulation, gypsum, lime and alum in a 4:2:1 ratio seems like it is not nearly as hard as the original material. The old articles I found called for 4:1:4 but sourcing alum powder is neither easy nor cheap. Still looking for suggestions.

  5. #5
    Join Date
    Jul 2014
    Posts
    50
    Country: Germany

    Default

    You could look through safe patents for fire insulation stuff.

  6. #6
    Join Date
    Sep 2004
    Location
    Devon UK
    Posts
    2,979
    Country: UK

    Default

    Quote Originally Posted by Cepasaccus View Post
    You could look through safe patents for fire insulation stuff.
    The alum was the active ingredient - the rest was normally just absorbent filling.
    the alum was sometimes in tin boxes in the fill.
    the alum released water in a chemical reaction on heating and the water turning into steam and escaping removed a lot of heat energy from the safe. It wasn't a barrier to anything except heat so the physical strength of the fill was not normally a feature of these fire resisting safes.

  7. #7
    Join Date
    Mar 2016
    Posts
    22
    Country: United States

    Default

    I actually found the ratio I referenced in an old hall patent. I also read that the alum was inserted in the mix as large pieces rather than as powder (which is what I purchased). I wasnít aware of the tin boxes. That still leaves me wondering what they used. I understand these werenít necessarily meant to be burglar proof but the original insulating material is harder than the mix I created.

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