Anti-Vehicular Yardstick Mine

Japanese WWII Anti-Vehicular Yardstick Mine

This Japanese land mine, of Naval origin, is usually found buried in landing strips. Almost any vehicle will activate the mine, but its use as an anti-personnel device is limited since a pressure of approximately 336 pounds is necessary to set it off.

The mine consists of an oval shaped tube of sheet metal with a cap on both ends; an explosive charge comprising eight blocks of picric acid, each cast in a paper container and coated with paraffin; and four percussion type fuzes.

The picric acid blocks which are flattened on one side do not fill the mine completely. The space between the flat side of the blocks and the wall of the case accommodates the protruding heads of the fuzes which are inserted between blocks.

The percussion type fuze consists of a cylindrical body which houses the striker release plunger, a booster housing, and a striker housing. The two latter parts are identical in external appearance and screw into the sides of the main body diametrically opposite each other.

The striker release plunger, a split pin with an enlarged flat head, is positioned in the fuze body by a copper shear wire. A second hole 90 degrees from the shear wire hole accommodates a safety wire. The lower end of the plunger is split by a slot, the width of which is increased on the inner end.

The mine is held in an unarmed position by the safety wire which is inserted through a hole in one of the end caps, and extends the entire length of the mine. A spring clip on the cap holds the wire in place. When the mine is to be put into operation, the safety wire is removed and a burying plug is screwed into the hole in the cap to make the assembly waterproof. A thick tarry substance is applied to-the seams around the end caps probably for the same purpose.


Length (overall)        36 ins.
Diameter (oval) 3.35 x 1.8 ins.
Total weight 10.58 lbs.
Weight of mine 4.63 lbs.
Weight of filling 5.95 lbs.
Weight of each explosive block 3/4 lb.
Filling Picric acid
Weight of complete fuze .29 lb.
Color Brown outside; black lacquer inside

Japanese: p. 308.1 (March 1, 1945)

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