Magnetic-Dip needle - Submarine laid
♦ MK 12
Mines Mk 12 Mods 0 and 3, figure 1, are magnetic, needle-type, ground mines designed to be planted from 21-inch submarine torpedo tubes. The original design was based on a World War I German naval design. The mechanisms were designed to operate in either the northern hemisphere or the southern hemisphere, as necessitated by the magnetic poles. They were used in depths of from 16 to 125 feet of water against surface craft, and in depths up to 500 feet against submarines. If surface launching of a mine of the Mk 12 type was required, the Mod 0 or 3 was planted from the decks of surface craft using a jury rig.
Mine Mk 12 Mod 3 was an improved design of Mine Mk 12 Mod 0. It differed chiefly in the assembly of its electrical accessories and electrical connections:
a. In the Mod 0 most of the electrical accessories were attached to either the battery plate or battery cover and the connections were made by individual leads.
b. In the Mod 3 most of the electrical accessories were mounted on a panel as a subassembly and the electrical connections were made by plugs. These changes resulted in easier assembly, but did not alter the external appearance, safety features, or operational characteristics of the mine.
Mk 12 Mod 0 was loaded with either 1100 lbs. of TNT. or 1250 lbs. of TPX. The Mod 3 was loaded with either 1170 lbs. of HBX-1 or 1100 lbs. of TNT.
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Derick S. Hartshorn -