118. Improvised River Mine (Behelfs-Flusstreibmine)

a. Description. The improvised river mine (fig. 149) consists of a circular sheet-zinc case containing 44 pounds of explosive. The sheet-zinc case is 15 inches in diameter and 5 in-ches high, but when surrounded by its wooden jacket it is 17 3/4 inches in diameter and 6 1/4 inches high. Two carrying handles are attached to the wooden jacket. Near the bottom of the sheet-zinc case are two small, metal detonator tubes, diagonally opposite each other and closed by screws or leather plugs. Detonators are inserted to permit ac-tivation when the mine is to be used as a land mine.

(1)

Firing mechanism. A wooden contact rod about 4 1/2 feet long, with antennae at the top, is mounted vertically on a wooden floation buoy. Six wooden feelers, each 13 inches long, extend from the wooden floation buoy. The wooden floation bouy is secured to a metal firing rod which extends from the centrally located contact firing mechanism and protudes about 6 inches above it. The contact firing mechanism is mounted on a plate which screws into a well in the top of the sheet-zinc case. The joint between the metal firing rod and the contact firing mechanism is made water-tight.

(2)

Fuze mechanism. A clockwork delay mechanism is mounted ot the same plate as the firing mechanism and performs two functions. It arms the contact firing mecha-nism after 10 minutes, and it may explode the mine after a preset delay of from 10 minutes to 6 hours, in case the mine has not been detonated by contact by that time. The clockwork delay mechanism is wound by turning a winding ring on the pla-te in the direction of the arrow marked aufziehen (to wind). The selfdestruction de-lay period is set by turning a spring handle on the plate in the direction of the arrow marked Zündung in Std (firimg time in hours). A setting dial with graduation marks, each equal to 6 minutes, may be seen through a celluloid window. The delay arming mechanism is set (up to 10 minutes) by turning in the direction of the arrow marked Scharf in Min (arming time in minutes).

(3)

Arming lever. A curved arming lever, mounted on the plate, serves to release the clockwork delay mechanism. In the safe position, the end of the lever enters a groove marked sicher (safe). In the armed position, the end of the lever enters a groove marked scharf (armed), in which case the clock-work will be runing.

b. Employment. This mine is designed primarily for use against bridges, rafts, shipping, and similar targets.

c. Functioning. Any sideward movement against the antennae or wooden feelers is com-municated to the metal firing ring. The base of the firing rod pushes against the bushing of a spring-loaded striker. This allows a metal tongue to retract, releasing the striker against the percussion cap.

d. Neutralizing. This mine cannot be neutrailzed because of the very delicate mechanism. Extreme care should be taken to aviod touching the antennae or the wooden feelers. The mine should be destroyed either by small arms fire or by a rocket launcher aimed at the wooden floation buoy. Another method is to stretch a rope or wire across the stream downstream from the mine so that the mine will drift into it. If a bridge or other vital in-stallation is threatened by a mine which is lodged against it but still afloat, a line may be attached to one of the carrying handles and the mine towed very gently, from a distance of at least 100 yards, to a suitable demolition site. Since the attachment of the line to the carrying handle will be an exceedingly dangerous operation because of the pressure of the wooden feelers, this method should be adopted only in extreme cases.

Caution: The mine may also detonate according to the setting on the 6-hour clockwork delay mechanism. Once started, the clockwork delay mechanism cannot be stopped by turning the curved arming lever back to sicher (safe).

Figure 149. Improvised river mine.