Chapter 5 - Aircraft Mines - SVK; The LM Mines: The LMD MineChapter 5 - Aircraft Mines - SVK; The LM Mines: Parachutes for the LMA and LMB Mines

LM - ZUS Z (34) B Bomb Fuze for LMB. The primary function of the fuze is to explo-de the mine as a delayed-action bomb if the mine does not reach a sufficient depth of water to depress the hydrostat before the clockwork completes its firing run-off.

Figure 58 – Detonator-Booster Assembly for LMB Mine

The fuze which is a modification of the German (34) A* bomb fuze is 4-1/16 inches long. The fuze body is of aluminum divided into four parts:


Contains the hydrostat and clockwork reelase pin

Clock housing

Encases the clockwork

Clock mounting

Contains firing mechanism and is the base to which clock-work is fastened

Gaine adapter

To which the gaine is threaded

The four sections are secured together by three cheese-headed screws. The additio-nal length of the fuze permits the insertion of only two picric-acid booster pellets, one annular and one solid.

Water-Entry System. The water-entry system consists of a channel drilled transver-sely through the fuze head with two off-set holes drilled at 90 degrees to it (See Figure 59). The uper entry hole allows water to enter the channel from under the hydrostatic-valve cover plate, and the lower entry hole allows the water to pass from the channel into the hydrostat chamber. The lower hole is displaced about 1/8 inches from the upper hole.

Hydrostat Assembly. The upper section of the fuze contains the hydrostat assembly, which consists of a steel plate with three holes, a bellows, a spring, a plunger, and a re-taining plug which screws into the fuze head, locking the whole assembly in place. The steel plate is secured to the fuze head by a small screw. This plate acts as a screen.

The open end of the bellows rests against the retaining plug and has a rubber ring seal around its flange to make a watertight joint. The spring is between the guide plug and the closed end of the bellows, so that hydrostatic pressure has to compress the bellows and spring as the plunger is depressed. The operation depth of the hydrostat is fifteen feet.

Clockwork and Firing Assembly. The principle of operation is the same as in the (34) A* although there are slight modifications. There is no selection of an "e" or "b" setting. The pin in the small nautilis-shaped cam is a fixed-position pin. The fuze will act as an anti-recovery device upon withdrawal from water.

Operation. Movement of the firing lever is controlled by an arrangement of cams ope-rated by a clockwork.

The clock run-off is divided into two periods:

A seven-second period to arm after the mine leaves the aircraft allows time for the parachute to open without danger that the parachute jerk will fire the fuze.

A 19-second period starts at impact with water or land. At the end of the 19 se-conds, the mine will be detonated by the fuze unless it has reached a depth sufficient to operate the hydrostat. In the latter case, the hydrostat piston will have been depressed far enough to prevent movement of the firing lever when it is released by the clockwork-controlled cam.

Figure 59 – LM – ZUS Z (34) B Bomb Fuze for LMB

Chapter 5 - Aircraft Mines - SVK; The LM Mines: The LMD MineChapter 5 - Aircraft Mines - SVK; The LM Mines: Parachutes for the LMA and LMB Mines