Mk 29 Mods 0-3

Projectiles used in

Over-all length, inches

Diameter at nose, inch

Diameter at base of ogive, inches

Threaded length, inch

Threads

Weights, pounds

Material

Arming speed, r.p.m.

Description: The fuze consists of four principal parts: (1) the base, which contains the relay detonator and holder and the interrupter 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. A crush cup is located beneath the firing pin, holding the firing pin away from the detonator, and a centrifugal interruptor separates the detonator 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" od "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, 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. In either case, the end of the setting sleeve carries a slotted setting key.

Operation: When the fuzed projectile is loaded into the gun, the setting key is turned to the "On" or "S.Q." position. On set-back, the interruptor sits down in the flash chan-nel, but when the projectile 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 tavels 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:

Mod 0: Dark green ogive, made of easily chipped asbestos plastic, unsuitable for sto-rage and handling. This Mod is obsolete.

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

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

Figure 84. Point Detonating Fuze Mk 29 Mod 0