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  1. #51
    Join Date
    Nov 2014
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    614
    Country: Bulgaria

    Default Copper content

    How much copper is needed to achieve the effect?

  2. #52
    Join Date
    Dec 2009
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    1,261
    Country: United States

    Default

    Quote Originally Posted by Chubby View Post
    How much copper is needed to achieve the effect?
    None, actually. Mosler added thin copper bands merely as decoration when they started marketing Donsteel. Whether it originated with Mosler or not, the legend sprang up that an actual copper layer was sandwiched between steel layers with the effect of thwarting torch attacks by conducting heat away faster than the torch could heat things up. There is no mention of a copper layer in patents, and no mention in a paper Mosler published on Donsteel. Also no mention that I can find in period trade journals or news reports. I also had a chance to tap on the copper band of an actual Donsteel door (Kansas City Public Library) and it was distinctly hollow.

    Mosler continued to sell doors with a copper band (or two bands) even after they discontinued Donsteel. Think of it as a sort of trademark. I'm sure they were glad of the legend, as were their customers; it may have deterred a burglary attack here and there.

  3. #53
    Join Date
    Dec 2009
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    1,261
    Country: United States

    Default Reversal

    Based on recent discoveries (see http://www.antique-locks.com/showthr...Scrap-or-Value) I need to reverse my stand on Donsteel doors! Lack of evidence caused me to conclude that Mosler did not use copper in the door, and that the visible stripe was just a decorative trim. Wrong! Now that the insides of a door have been exposed it is clear that copper was poured into spaces in the door and that this works very well at thwarting torch attacks. The visible copper strip is indeed decorative.

    What about the non-Donsteel doors (after about 1930) with a copper trim? I suppose the door is made from a more conventional steel alloy rather than Donsteel, but Mosler may have continued offering copper-filled doors.

    Exactly how the interior space (for the copper) was designed is still unknown. A good assumption would be that these are not simple flat-faced sandwiches. The front and back at least need protrusions into the copper to hold it all firmly together. The steel faces may even have been joined with integral-cast "pillars" leaving voids for the copper.

    While I was clearly wrong, I'm glad to see that Mosler built such tough doors that live up to legend.

  4. #54
    Join Date
    Aug 2013
    Posts
    1,372
    Country: Wales

    Default

    Wylk there's the same subject on the two different threads going on here! That's pretty much what I mentioned over on the recent 'old Mosler bank vault' thread:

    "I think they might have a bit of fun dealing with that copper layer as its not just about the thermal conduction of the copper itself, but also surface area for maximum heat transfer. Like the cooling fins on an engine head allowing maximum convection to the surrounding air, it's the same here but for conduction through the metals instead. I'd be amazed if it's just a smooth sided slab of copper, got a feeling it'll be interlocked at least to the outer door slab if not the the sides as well, which might mean more comedy entertainment when they can't cut it or get it out..."

  5. #55
    Join Date
    Oct 2009
    Location
    Cleveland, Ohio USA
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    1,279
    Country: United States

    Default

    At this point, it would be interesting to put an oxygen lance on that door. IIRC Mosler claimed it would hold up against it.

  6. #56

    Default

    Quote Originally Posted by Doug MacQueen View Post
    At this point, it would be interesting to put an oxygen lance on that door. IIRC Mosler claimed it would hold up against it.

    A friend ran across this description of Donsteel, supposedly from the 1999 official Mosler history:



    “Donsteel” frustrated burglars
    “Donsteel” and “Donmetal”, named after the Mosler sales manager of that time, J.G. Donaldson, were special metal alloys that had tremendous resistance to drills and torches. The alloys were used in the construction of vault doors, lock housings, and some money safes. A famous test of Donsteel’s resistance to torches was conducted on October 14, 1924 at the Hamilton plant and witnessed by many prominent citizens, law enforcement officials, bankers and the press. Test technicians used an oxygen lance, five tanks of oxygen and 45 feet of pipe in an attempt to penetrate a two inch thick plate of Donsteel. After the test, witnesses testified that:

    “There was not even a blister on the surface thereof.”


    Mosler organized the Guardian Metal Products Company in 1921 to manufacture Donsteel. A building with a 10,000 lb. traveling crane was built at the south end of Building No. 8 in which high-temperature electric furnaces were installed. However, the sale of Donsteel and Donmetal products did not meet volume expectations and the equipment was sold in 1930. The space was needed to heat-treat small money safes which were then very popular with gasoline stations and chain stores.

    BBE.

  7. #57
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    Dec 2009
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    1,261
    Country: United States

    Default

    Quote Originally Posted by BBE View Post
    A friend ran across this description of Donsteel, supposedly from the 1999 official Mosler history:
    That was posted in this thread back on January 28, 2013.

  8. #58

    Default

    Quote Originally Posted by wylk View Post
    That was posted in this thread back on January 28, 2013.
    Sorry, missed it.
    BBE.

  9. #59
    Join Date
    Dec 2009
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    1,261
    Country: United States

    Default

    A current eBay auction (https://www.ebay.com/itm/253528253113) has answered the question of how much copper goes into a door. The auction is for a 1948 bid by Mosler for Federal Reserve bank vault doors (for Seattle and Portland). One of the diagrams shows it's quite a lot:

    Click image for larger version. 

Name:	Fed Reserve proposal 11.jpg 
Views:	18 
Size:	223.2 KB 
ID:	19831

    A short discussion appears earlier in the bid:

    Click image for larger version. 

Name:	Fed Reserve proposal 6.jpg 
Views:	19 
Size:	342.0 KB 
ID:	19832

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