Chapter 7 - Submarine Laid Mines; The TM Mines: The TMA I MineChapter 7 - Submarine Laid Mines; The TM Mines: The TMC Mine
GERMAN UNDERWATERS ORDNANCE MINES
Chapter 7 - SUBMARINE-LAID MINES
THE TM MINES

The TMB Mine. There are five models of this mine, TMB I, TMB II, TMB III, TMB (S) and TMB (mit Aufstriebskörper). These cases differ from each other as follows:

Description of Case

 

TMB I - II

TMB III

TMB (S)

Material

KSS

KSS

KSS

Weight (lb.)

1,625

1,475

1,600

Main charge (lb.)

1,230

925

1,230

Length (over-all)

92 in.

92 in.

103 in.

Shape

Cylindrical, with hemispherical ends. Deflecting fin on tail door.

External Fittings

Positioning lug

On top center line, 3 ft. 9-1/2 in. abaft the nose

Hydrostatic clock

6-in. diam., on top center line, 5ft. 6-1/2 in. abaft the nose, secured by keep ring.

Booster-release-mechanism

4-in. diam., on top center line, 4 ft. 5 in. abaft the nose, secured by keep ring

80-day-clock
cover plate

8-in. diam., on top center line, 3 ft. 2 in. abaft the nose, secured by keep ring

Detonator
cover plate

4-3/4-in. diam., 180° from top center line, 4 ft. 6-1/2 in. abaft the nose, secured by keep ring

Filling holes

Two: one, 5-in. diam., threaded to nose; one, 6-in. diam., 90° from top center line, 4 ft. 6-1/2 in. abaft the nose; secured by four screws

Safety-bar clamp

On top center line at after end

Figure 103 – TMB (S) Mine

The TMB I differs from the TMB II only in the method of constructing and securing the unit compartment. Whereas in the TMB I the unit compartment was cast aluminum (KSS) bolted into position, the compartment in the TMB II was all welded. The TMB III had a larger unit compartment than the TMB II, which accounts for the differences in weight. The TMB II and TMB III may be identified externally by the annular rabbet on the after end of each case. The widths of these rabbets are 3-1/2 in. and 11-1/4 in. respectively. Their purpose is to facilitate expulsion of the mine from the compressed-air discharge type topedo tubes used by the German. The TMB (mit Auftriebskörper) utilizes either the TMB II or the TMB III mine case with buoyancy floats bolted to each end. It was design-ed for demolition of enemy bridges, docks, etc.; and was laid by specially trained swim-mers.

These mine cases were fitted with following mine influence units:

TMB I - II

TMB III - S

M 1

DM I

A 2, A 2st

MA 2/3

AT 3

 

The TMB (mit Auftriebskörper) employed only a delay clock for firing, although influ-ence units could be fitted if desired.

Operation. When the mine is launched, a spring-loaded safety bar is released from the top center line of the case, thereby unlocking the hydrostatic clock and booster- release mechanism. Water pressure depresses the clock spindle and operates the booster-release mechanism, respectively, at a depth of 15 feet, starting the clock and allowing the booster to house over the detonator. The clock runs off its delay setting, and the firing unit begins its arming cycle.

Figure 107 – TMB Mine – Cross Section

The only self-disarming device is the 80-day-clock, which may be fitted to sterilize the mine at the end of its set period by shorting out the battery.

Chapter 7 - Submarine Laid Mines; The TM Mines: The TMA I MineChapter 7 - Submarine Laid Mines; The TM Mines: The TMC Mine