Nose Fuze No. 849 Mks I and II (Service)

Description: The vane and vane assembly of the Fuze No. 849 Mk II consist of a vane cap, which is held by three reatining clips, the vanes, and the arming spindle. A steel ring is soldered to the retaining clips to prevent damage to the vanes, which are of sheet steel and are staked to the arming spindle. The spindle threads into the arming-vane support and down onto the ball-retaining cap, which holds four retaining balls in the groove in the top of the spring-loaded striker. A safety pin passes through the arming-vane support and the striker. Below the striker is a percussion cap which flashes down to the primary powder pellet. At right angles to the flash channel below the cap, is a vent hole and vent hole pellet. This vent hole leads to the outside, but is sealed by the outer cover in the unfired condition. At the outer end of the primary pellet chamber is a short powder pellet, which flashes through a flash channel in the fuze drum to the length of Bickford-type safety fuse contained in a lead foil sheath surrounding the fuze drum. A short fire hole leads from the safety fuse to the long powder pellets which lead to the magazion. The magazine is housed in the lower fuze body. On the outer side of the fuze is a scale graduated from 0 to 95 seconds, with an indicator which moves around it to set the fuze. A red sealing strip joints the outer cover and fuze body.

Operation: When the flare is put in the plane, the indicator on the side of the fuze is set at the desired delay. When released, the safety pin and vane cap are removed. As the flare falls, the vanes rotate and raise the arming spindle, allowing the ball-retaining cap to be moved away by the pressure of the balls holding up the spring-loaded striker. The striker is then freed and hits the percussion cap, which flashes down and fires both the vent-hole pellet and the primary powder pellet. The products of combustion break the seal of the vent hole in the outer body. The flash passes to the short powder pellet, and through the flash channel to the delay fuse. This burns in a clockwise direction, and flashes through the fire hole into the lower fuze body and then along the long powder pellets to fire the magazine.

Remarks: The No. 849 Mk III time-setting disc is calibrated from 0 to 70 seconds and includes a safe setting.

Figure 160 - Nose Fuze No. 849 Mk II