The German fuze Wgr.Z. 50 + is a direct action and graze fuze with provision for allways action should flight be abnormal, and is used in the 32 cm incendiary rocket and 28 cm and 30 cm H.E. rockets. It is identified by the marking "Wgr.Z. 50 +" stamped in the body above the flange. *The overall length of the fuze with cap is 2 inches and its diameter across the threads is 1.4 inches. It is provided with a cap and safety pin.

The fuze consists of a body, needle, needle holder, two centrifugal bolts, expanding spring ring, creep spring, detonator and holder, inertia collar, centreing washer, base plug, cap and safety pin.

The body is of aluminium 2.5 inches in length. Externally below the flange, it is screw-threaded for insertion in the rocket. Above the flange, it is coned and has a flat top. A circumferential groove is cut in the coned portion to accommodate an expanding spring ring. Internally the body is bored in three diameters, to form chambers 0.6 inch and 1.1 inches in diameter respectively, and an internal flange at the base.

The needle is of steel and provided with a head; it is held in the needle holder by a scre-wed plug. The needle holder is of aluminium formed with an external flange at its base; it is recessed and screwthreaded to receive the head of the needle and securing plug. The needle and holder are assembled from the inside of the fuze body so that the head of the holder protrudes from the top; its upward movement is limited by the flange on the hol-der which bears against the internal flange in the body. The needle is retained in this po-sition by a safety pin and two centrifugal bolts and is protected by a cap.

The cap is of thin metal, cone shaped with a flat top; it is pierced horizontally to receive the safety pin.

The safety pin passes through the cap, fuze body and the needle holder. The pin is pre-vented from falling out by a piece of wire passing through a hole at one end and secured by a lead seal.

The two centrifugal bolts are cylindrical in shape and slotted at one end. They are parti-ally housed in two radial channels and protrude to support the neelde holder on its un-derside, thereby preventing the needle being forced on to the detonator. The bolts are retained in position by a thin expanding spring ring which engages the slots and fits into the circumferential groove in the fuze body.

The detonator holde is of steel, cylndrical in shape and bored in three diameters to form an internal flange separating two recesses. The recess at the top accommodates the point of the needle, and the flange provides a seating for one end of the creep spring which surrounds the needle. The recess below the flange accommodates the detonator, which is secured by a screwed plug with central flash hole. The plug is secured by a re-taining pin let into a radial hole in the body of the detonator holder. The base of the plug is coned and fits into an inertia collar.

The inertia collar is of steel, cylindrical in shape and bored centrally to form a flash hole. The flash hole has a coned opening at the top to match and accommodate the coned portion of the plug in the detonator holder. The diameter of the collar is considerably less than that of the chamber which accommodates it. The collar is centred by five upturned strips cut in a brass centring washer which is a close fit in the chamber. The chamber is closed by a screwed base plug with central flash hole.

The safety pin is withdrawn and the cap removed. The needle is separated from the de-tonator by the centrifugal bolts which are retained in the closed position by the expand-ing spring rings.

The centrifugal bolts swing outwards under centrifugal action, overcoming the expanding spring ring, thereby permitting the needle and detonator holder to move towards one another. The creep spring prevents creep action. On impact the needle is forced on to the detonator by direct action. On graze the detonator is carried forward on to the needle, or it may be forced on to the needle by a side-ways movement of the inertia col-lar. The flash from the detonator passes through the central fire channel in the inertia collar and base plug to a gaine in the shell, which in turn detonates the shell filling.

Fig. 7