Nose Fuze No. 700 Mks I and II (Service)

Rockets used in

Action

Armed condition

Arming time

Body diameter

Over-all length

Color

Description: The Fuze Mk I consists of a brass fuze body, a brass cap, an upper time ring, and a lower time-setting ring.

The brass nose cap has a flat top with five perforations, the center one leading to the striker recess and the remaining four leading to the recess accommodating the plun-ger. In this nose cap are located the striker and the striker spring. The spring is enclosed in an aluminum alloy plunger. Supporting the striker and the plunger are two brass pawls, pivoted in a pawl housing which is screwed into the bottom of the nose cap.

Pivoted in a recess in the fuze body is a safety lever, the upper arm of which interve-nes between the striker and the percussion cap in the unarmed position. The lower end of the lever is rectangular in cross section and fits into a spring-loaded catch. The outer end of the catch engages a recess in the time setting ring when the fuze is set on SAFE. A turning movement is imparted to the safety lever when the outer end of the catch lea-ves the recess in the time-setting ring, thus removing the upper lever arm from beneath the striker.

A flash channel leading to the upper time ring is located beneath the percussion cap. A second channel leads from the lower time-setting ring to the charge of gunpowder in the base of the fuze. Leading from the top of the fuze body through to the base of the fuze is a third channel provided for the escape of air pressure.

Operation: When the time-setting ring is moved from the safe position, the safety catch moves out of its recess and rotates the safety lever from under the striker.

During the acceleration period of the rocket, air enters the perforations in the top of the brass cap. The pressure built up inside the fuze forces the plunger down over the striker. The lower edge of the plunger, bearing or the outer end of the pawls, causes their inner ends to lift the striker and compress the striker spring. This movement conti-nues until the inner ends of the pawls are rotated clear of the striker, which is then dri-ven into the percussion cap, initiating the delay train in the upper time ring. This, in turn, ignites the delay train in the lower time-setting ring, which burns for the required period and then initiates the gunpowder charge in the base of the fuze. The explosion of the gunpowder charge intiates the Gaine No. 13, which is located in the adapter ring below the fuze.

Remarks: Fuze No. 700 Mk II is identical to the Fuze Mk I, except that the striker, pawls, and spring are somewhat modified, and the safety lever assembly is omitted.

The Fuzes Mk I and Mk II are pyrotechnic time fuzes, designed for antiaircraft purpo-ses Variable settings, from 0 to 30 seconds, are obtained by rotating the time-setting ring. The time settings are indicated by mumbered graduations, subdivided into ¼-se-conds intervals, engraved on the fuze body below the time-setting ring.