Tail Fuzes No. 895 Mk II (Service)

Description: The fuze is similar to the Fuze No. 895 Mk I, except that the method of arming is altered. The Fuzes No. 895 Mk II are armed by the rotation of the vanes and tie-rod incorporated in the standard British tail assembly. The tie-rod engages the T-bar of the fuze and rotates the centrifugal arming mechanism. This mechanism consists of a spindle, to which the T-bar is attached, with its lower portion enlarged and grooved to form two circular plates located above the other about ¼ inch apart. The central column of this spindle is drilled from the bottom to allow insertion of the arming plunger, which is supported by a plunger holder threaded into the top cap of the fuze. Two semicircular weights are located between the two plates formed from the enlarged portion of the spindle. A projecting point on the flat edge of each of these weighs blocks any upward movement of the arming plunger. Each weight is held inward by a U-shaped stirrup. The stirrups themselves are each held tightly against the sides of the plates by an arming spring. Two screws, located 180° apart, penetrate the circular plates of the spindle. One end of each arming spring is fastened to one of these screws, and the other end of the spring is attached to one of the stirrups. Each screws also serves as a pivot for one of the weights and the corresponding stirrup. A nut threaded to the upper end of each screw completes this assembly. A guide pin is set into the top surface of each weight. Each pin rides in a groove cut in the upper circular plate on the spindle and also is loca-ted in a slot cut in each end of a diamond-shaped safety bar. This safety bar fits freely around the upper portion of the spindle. A safety pin engages the T-bar penetrates the cover of the fuze, and passes down along the outside of one of the stirrups. The safety pin thus holds one of the weights securely in position during storage and transit.

Operation: In the unarmed position, the arming plunger is prevented from rising by the projecting point of the two weights. The weights are held in position both by the arming springs and the safety pin.

The safety pin is removed when the fuze is assembled in the bomb. When the bomb is released from the plane, the arming vanes and tie-rod in the tail, which engages the T-bar, rotate the spindle. The centrifugal force imparted by the rotation of the spindle cau-ses the weights to pivot outwarts against the action of the stirrups and arming spring. As the weights move outwards, the central hole in the base of the spindle is completely cleared, allowing the arming plunger to move upward when hydrostatic action causes the striker in rise. Before arming is fully completed, the weights have moved out far enough so that a groove in the end of each weight is engaged by the edge of a stirrup. When rotation of the vanes ceases, the weights are thus prevented from returning to their ori-ginal position.

The purpose of the safety bar is to prevent either of the weights from moving out-wards as the result of a hard jolt or jar on the side of the fuze after the safety pin has been removed. Except for centrifugal action, any force causing one of the weights to move outward will cause the other weight to move inward, and the net effect of the force will be equalized through the safety bar, with the result that neither weight will move.

Once the weights have moved out and locked in position, the fuze is fully armed. Ex-cept for the offset detonator, subsequent functioning is identical to that described for the Fuze No. 895 Mk I.

Remarks: The designation given to Fuzes No. 895 Mk II includes the nominal depth setting. The Fuze No. 895/18 Mk II, having an 18 ft. depth setting, is used in the A.S. 100-lb. Bomb Mk VI, and replaces the No. 895A Mk I. The Fuze No. 895/23 Mk II, having a 23-ft. depth setting, is used in the A.S. 250-lb. Bomb Type C. The Fuze No. 895/30 Mk II, having a 30-ft. depth setting, is used in the A.S. 600-lb. Bomb Mk I.

The greater depth setting are accomplished by substitution of heavier striker springs, or by an additional spring placed between the top cap of the fuze and the spring hous-ing.

Figure 177 - Tail Fuze No. 895 Mk II