|
|
| GERMAN UNDERWATERS ORDNANCE MINES |
| Chapter 4 - CONTACT AND MOORED INFLUENCE MINES |
| THE UM MINES |
|
The UMA Mines. The first of this series was developed in 1928. It was a moored, contact, chemical- and switch-horn mine, laid by surface craft, intended for use primari-ly against submarines. In 1936 the prototype of this series became the UMA I when, after slight modifications in the case and mooring, the UMA II was introduced. In 1938 the UMA III appeared. Basically, it was the same as its predecessors, with improvements in the anchor and mooring spindle. |
|
Description of Case |
|
Share |
Spherical |
|
Material |
Steel |
|
Diameter |
32 in. |
|
Charge |
66 lb. block-fitted hexanite |
|
Description of External Fittings |
|
Horns |
Eight: one chemical, in center of upper hemisphere; four, chemical, equally spaced around upper hemisphere, 15½ in. from center; three, switch, equally spaced around lower hemisphere, 17 in. from center |
|
Base plate |
Standard type UMA |
|
Lifting eyes |
One 19 in. from center of upper hemisphere |
|
Lifting lug |
One, 160° from lifting eye, 19 in. from center of upper hemisphere |
|
Operation. The depth of the mine case its preset and determined by the amount of mooring cable used. Mooring tension rulls out the mooring spindle, closing the mooring safety switch, tripping the booster-release lever, and the mine is armed. |
|
The German UMA/K mine assembly was designed and developed in late 1942 to defend the sea approaches to Northern Europe from Allied attack. It replaced the EMG mine as-sembly, which was considered unsatisfactory for the defense of such waters, and was used operationally until 1944, when it was in turn replaced by the OMA/K. |
|
The UMA/K consists of a normal UMA mine case with the lower horns blanked off, a cast-iron 110-pound weight and a cast-iron anchor weighing 500 pounds. The assembly of the above components before and after laying is shown in Figures 35 and 36. |
|
The assembly is so designed that the mine case remains on the surface, regardless of the stage of the tide. It may be laid in depths of 85 to 165 feet. For depths of 85 to 150 feet, a 65-foot mooring cable is used between the mine case and weight: for depths of 100 to 165 feet, the mooring-cable length is increased to 85 feet. In both cases, the mooring cable between the anchor and weight is 165 feet in length. |
|
Figure 32 – UMA Mine Afloat |
|
|
|
Figure 33 – UMA Mine |
|
|
|
Figure 34 – UMA Mine - Cross Section |
|
|
|
Figure 35 – UMA/K Mine |
|
|
|
Figure 36 – UMA/K Mine |
|
|
|
|
