Mk 29 Mods 0-3

Rocket uses in

Functioning

Fuzes found with

Arming speed, r.p.m.

Diameter, inches

Over-all length, inches

Weight, pounds

1.45 - 0.04

General: The Nose Fuze Mk 29 is used in both projectiles and the 5-inch spin-stabili-zed rocket. It functions on impact, with no delay.

Description: The fuze consists of four principal parts: (1) the base, which contains the relay detonator and holder and the interruptor unit; (2) the nose or detonator as-sembly, which contains the striker assembly and the detonator; (3) the plastic ogive; and (4) the flash tube, which is fitted in the center of the ogive and holds the nose and the base together. The firing-pin supporting cup is located beneath the firing pin, holding the striker away from the detonator, and a centrifugal interruptor separates the detona-tor from the relay detonator in the base of the fuze. Two types of interruptor assemblies have been employed. In the earlier model, the interruptor bore against the upper blade of a forked setting sleeve in the "Delay" or "Off" position and thus could not move into the sleeve and clear the flash channel. Rotating the sleeve 90° in either direction to the "S.Q." or "On" position removed the end of the forked blade from the interruptor, and centrifugal force could move the interruptor into the sleeve and out of the flash channel. The interruptor system of later models has been slightly altered. A cylindrical setting sleeve with an eccentric bore is employed. In the "Delay" or "Off" position, the eccentric bore is not aligned with the interruptor, and the interruptor cannot move into the sleeve and clear the channel. Turning the setting sleeve to the "S.Q." or "On" position aligns the bore with the interruptor, which can then be moved into the sleeve by centrifugal force.

Operation: When the fuzed rocket is loaded in the launcher, the setting key is turned to the "On" or "S.Q." position. When the rocket leaves the gun, centrifugal force moves the interruptor into the sleeve and clears the flash channel. On impact, the closing disc above the striker is forced down, the crush cup beneath the striker is crushed, and the striker is driven into the detonator. The flash travels through the open flash channel and initiates the relay detonator in the base of the fuze.

Remarks: The differences between Mods of this fuze are as follows:

No Mod - Dark green ogive, made of easily chipped asbestos plastic, unsuitable for storage and handling.

Mod 1 - Chip-proof, resin-impregnated cloth, yellow plastic ogive.

Mod 2 - Same as Mod 1, with strengthened flash channel.

Mod 3 - Like Mod 2, with longer nose cap extending to base and giving additional sup-port to flash channel. Brown plastic ogive.

This fuze will function on thin plate and on water at angles over 6°.

A disc 0.01 inch thick is incorporated between the relay detonator and the flash channel of the Mod 3. This prevents gas pressure, which sometimes leaks past the unar-med interruptor, from setting off the relay detonator, if the nose of the fuze is acciden-tally struck during handling.

Figure 147. Navy Nose Fuze (Rocket) Mk 29 Type