Type II Mine (DE)
The German Type II Mine was suitable for use from minelayers. This article is based, initially, on a British report on German mines from July, 1917.[2]
| Type II Mine | |
| Weight | 710 lbs. |
| Casing | 0.2 in. welded steel |
| Trigger | five impact horns, one being on top |
| Charge | 290 lbs. wet gun cotton |
| Primer | 12 oz. of unknown type |
| Detonator | 90 gr. fulminate of mercury |
| Buoyancy | 320 lbs. |
| Height | 46 in. |
| Diameter | 31.5 in. |
The charge was built up of hexagonal discs of 12 ounces weight packed in a hard wood medium. The primer was held in a drawn brass casing suitable to last at least 6 months in seawater by British estimates. It was of a substance more volatile than dry gun cotton and considerably smaller than that in the Type I mine.
Action of Laying and Detonation
German mines of Type I through V worked in the same manner. The mine and sinker went to the bottom together. After 10 or 20 minutes, a soluble plug dissolved to release the mine, which rose under its own buoyancy, trailing the tethering cable behind. When the hydrostatic depth gear in the mine determines that its proper depth has been attained, it fired to grip the mooring cable. After this, the depth gear and grip would be locked to prevent ratcheting upward with a rising tide. The British felt the depth gear was reliable and accurate.
When a contact horn was struck and bent, a glass tube of acid would break, and its contents would flow to a bichromate battery to energise it, causing the detonator to fire. This action was instantaneous.
Type II, Small
There was a smaller variant of this model for use by above-water minelayers, possibly only used in the Baltic. The Russians had recovered some and shared their discovery with the British.
| Type II Small, Mine | |
| Weight | 324 lbs. |
| Charge | 54 lbs. hexanite |
| Buoyancy | – |
| Height | 37 in. |
| Diameter | 25 in. |
Some of the Baltic mines laid by surface minelayers had horn extensions to increase their sensitivity.
Footnotes
Bibliography
- Admiralty (July, 1917). German Navy: Part IV, Section 3. Torpedoes, Mines, Etc. (C.B. 1182) The National Archives. ADM 186/228.
