Mk 66 Mod 0

Projectiles used in

Over-all length, inches

Thread

Materials

Weight, pounds

Description: This fuze is very much like the Point Detonating Fuze Mk 29 Mod 3, with the addition of the rotor for detonator safety. It has the firing pin and crush cap in the nose, the flash channel, the interruptor device, the rotor assembly, and the magazine. The rotor contains a lead azide detonator and is held in place by two detents. The boos-ter magazine contains 6.7 grams of black powder in a water-tight vinylite cup. A vinylite cup is cemented onto the base of the fuze to prevent the holes in the metal cover from abrading the silk powder bags in the W.P. load as the fuze is inserted.

An aluminum disk 0.010-inch thick between the relay detonator and the rotor housing is another safety feature. It prevents pressure from an accidental detonation in the nose from getting to the rotor after leaking past the unarmed interruptor - which the gas could do.

Operation: When the projectile is ready to be fired, the setting screw for the inter-ruptor is turned to the ON or SQ ("Super-Quick") position. Up to this time the interruptor, in the OFF position, has blocked the flash channel so that accidental crushing of the cup, setting off the detonator, could not set off the booster charge. On set-back, the interruptor sits down in the flash channel; but, as creep takes over, the centrifugal force moves the interruptor into the sleeve, clearing the flash channel.

Centrifugal force also moves the detents holding the rotor out, allowing the lead counterweights in the rotor, through centrifugal force, to rotate the rotor until the stop pins rest against the edge of the holes in the housing, thus lining up the second detona-tor under the flash channel. The fuze in now fully amred, and, on impact, the crush cap collpases, allowing the firing pin to set off the detonator, sending the flash down the open tube, which in turn sets off the detonator in the rotor, and finally the black powder charge.

Remarks: The fuze will detonate on impact with ground, ½-inch wood, or 1/8-inch mild steel plate.

The Point Detonating Fuze Mk 66 was developed to give detonator safety in 5"/38 W.P. projectiles assemblies, which do not have auxiliary detonating fuze.

Figure 86. Point Detonating Fuze Mk 66 Mod 0