Type I Mine (DE)

Type I Mine

Moored

Horns
This early design did not always function

The German Type I Mine was an early type laid in the Scarborough Raid and off Ireland. This article is based, initially, on a British report on German mines from July, 1917.

Characteristics
Weight	560 lbs.
Casing	0.2 in. welded steel
Trigger	five impact horns, one being on top
Charge	180 lbs. wet gun cotton
Primer	1 lb. 11 oz. dry gun cotton
Detonator	90 gr. fulminate of mercury
Buoyancy	250 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.

The British had recovered Type I horns bent fully 30 degrees back with their glass tube undamaged within. The later Type mines had an improved design, seemingly introduced to address this insensitivity.

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.

Bibliography

• Admiralty (July, 1917). German Navy: Part IV, Section 3. Torpedoes, Mines, Etc. (C.B. 1182) The National Archives. ADM 186/228.