Chapter 7 - Submarine Laid Mines; The TM MinesChapter 7 - Submarine Laid Mines; The TM Mines: The TMB Mine

The TMA I Mine. This mine was the only moored mine of the series. Prior to the com-pletion of the M 2 magnetic unit, a contact pistol was designed for the mine. This pistol was a pendulum type styled after the Russian 1906 pistol used in the Russian mines M 12, M 26, and PLT. The evidence as to whether this pistol was used operationally is conflicting, the prisoners of war interrogated having voiced different opinions on the sub-ject. Since no documents were available, a definite answer to this question cannot be given.

The M 2 magnetic unit which was designed for the TMA proved unsatisfactory. Con-sequently, only a small quantity of TMA mines were laid. Toward the close of the war, the M 3 was adapted for use with this mine, so that existing stocks could be utilized.

Figure 100 – TMA Mine with Anchor, Ready for Laying

Figure 101 – TMA I Mine

Description of Case


Cylindrical, with hemispherical nose and tapered, finned tail


Aluminum (KSS)


21 in.


9 ft. 3-1/2 in.


475 lb. cast hexanite

External Fittings

Bowden wire channel

180° from top center line, extends full length of case

Positioning lugs

Five, on nose, 30°, 120°, 210°, 270°, and 300° respect-ively from top center line; 7 in. from center

Securing lugs

Two, on nose, 90° and 270° respectively from top center line; 7 in. from center

Mechanism plate

11 in. diam., on nose, secured by 15 studs; covered by fairing, 6 in. diam., which is cut away to permit access to the mooring eye and securing lugs

Safety latch

On lower fin, in line with bowden wire channel, spring-loa-ded controls bowden wire

Joning flange

5 ft. 6 in. abaft the nose, covered by two sections of semicircular sheathing, 2 in. wide


Four, 0°, 90°, 180°, and 270° from top center line, at after end; 2 ft. 4 in. long, 9 in wide

Operation. When the mine is launched, the safety latch springs out, pulling the bow-den wire. This unlocks the spindle of a hydrostatic clock. Water pressure depresses the clock spindle at a depth of 15 feet, starting the clock. The clock spindle, once depress-ed, is locked in. The clock runs off its delay setting, allowing the detonator to house in the booster, and the firing unit begins its arming cycle.

No self-disarming devices are fitted.

Figure 102 – TMA Mine – Cross Section

Figure 106 – TMA Mine Afloat

Chapter 7 - Submarine Laid Mines; The TM MinesChapter 7 - Submarine Laid Mines; The TM Mines: The TMB Mine