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| GERMAN UNDERWATERS ORDNANCE MINES |
| Chapter 6 - AIRCRAFT MINES - LUFTWAFFE |
| THE BMC MINE |
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This mine was developed for the Navy by the Luftwaffe in 1943-1944. Its prototypes, the BMA and BMB, were abandoned because of difficulties with the anchor, balance in flight, and streamlining. These difficulties were overcome, and the BMC in its final form included a seven-day delay rising clock. It is a moored, contact, Le Clanche cell horn mine, laid by aircraft or surface craft for offensive or defensive use in maximum depth of water of 450 feet, against surface craft. |
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Figure 67 – BMC Mine Afloat |
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Figure 68 – BMC Mine |
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Description of case: |
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Shape |
Two hemispheres, joined by a 22-in. cylindrical mid-sec-tion |
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Material |
Steel |
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Diameter |
26 in. |
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Length |
44 in. |
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Charge |
120 lb. cast hexanite |
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Description of External Fittings. |
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Horn |
Four, equally spaced around upper hemisphere, 11 in. from center |
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Coverplate |
8-in. diameter, in center of upper hemisphere, flush tpye, secured by 8 bolts |
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Base plate |
11-in. diameter, in center of lower hemisphere, flush type, secured by 16 bolts; fitted with mooring lever and An-chor-securing boss |
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Horn-release disc |
2-3/4 in. diameter, 1-3/8 in. above center of cover plate |
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Booster cover |
Oval-shaped, on cylindrical mid-section, 2-1/4 in. from anchor-securing flange, secured by set screw |
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Filling-hole |
4-1/4 in. diameter on lower hemisphere, 10-1/2 in. from center secured by four bolts |
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Figure 69 – BMC Mine – Cross Section |
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Figure 70– BMC Anchor |
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Operation. The mine takes depth by hydrostat. Mooring tension pulls out the mooring spindle against spring tension of the inside of the base plate. Withdrawal of the mooring spindle forces a catch upward, thereby actuating a horn-release rod which extends through the longitudinal axis of the case to the cover plate. Movement of this rod forces the horn-release disc upward, allowing the horns to snap our and lock in the "out" posi-tion, and closes the arming switch on the wiring panel. The mine is now armed. |
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When a horn is bent, the brass tube at the base of the horn breaks, allowing sea water to enter a Le Clanche cell under the horn, energizing it and producing a current sufficient to fire the detonator. |
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The only self-disarming device is the arming switch, which is designed to disarm the mine by opening the firing circuit upon release of mooring tension. |
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Figure 71 – BMC/S Mine |
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