BOMBS USED IN:

No. 30

No. 37

FUNCTIONING

ARMED CONDITION

FUZES USED WITH

ARMING TIME

OVERALL LENGTH

MAX. BODY DIAMETER

COLOR

DESCRIPTION:

These fuzes are fundamentally the same, the pricipial difference between the No. 30 and No. 37 being in length, and the fact that, because of its additional length, No. 37 arming spindle is fitted with two universal joints. The differences between the variuos Mks of the No. 30 are explained in "REMARKS" below. The fuze body is of tubular sect-ion and is externally threaded at one end to receive a coupling nut with secures a tu-bular tail piece to the fuze body. Screwed into a flange on the fuze body is a locating pin for insertion into the slot in the exploder container of the bomb. The lower end of the fuze body is closed by a C.E. filled magazine, which has a thin bottom wall. The up-per end of the magazine is closed by a diaphragm having a fire channel communicating with the magazine, the fire channel being stemmed with C.E.

An arming vane is secured to the end of the arming vane spigot and a flanged arm-ing vane spindle supports a rotatable pinion and counter-weight. The pinion meshes with two gear wheels, one fixed to the tail piece and having 59 teeth, the other engag-ing the arming spindle is a locking rod projecting into and retaining a pivoted shutter in the unarmed position. The shutter contains a detonator and has a spring which forces it about its pivot to line up with the firing channel when the locking rod is withdrawn.

The fuze has two identical delay mechanisms, each consisting of a striker, a creep spring, an igniferous detonator, a delay pellet, and an adjoining powder pellet to positi-oned that the powder pellet extends over a flash channel, and one end of the delay pellet adjoins a firing hole which opens into the bottom of the striker chamber. The stri-kers are retained in the unarmed position by the arming spindle which is screwed into the sides of the strikers. Stop pins prvent the arming spindle and the striker from jamm-ing.

FUNCTIONING:

When the fuzed bomb is released, the safety clip is pulled free and the arming vanes rotate. The pinion is revolved around the fixed and rotatable gears, and because of the difference in the number of teeth, rotates the movable gear and hence the arming spindle once every 60 vane revolutions. As the arming spindle is rotated, it unthreads from the strikers and draws the locking rod out of the shutter. When the locking rod clears the shutter, its spring forces it about its pivot, lining the detonator up with the firing channel. The shutter is locked in this position by a pivoted, spring-controlled lock-ing pawl which snaps into position behind the shutter, the pawl being locking by a spring actuated plunger which moves down into a groove in the pawl. As the arming spindle clears the strikers, it slides upwards through the rotatble gear wheel. The fuze is now armed.

On impact the striker move downwards, overcoming the creep springs, and fire the ingiferous detonators, the flashes from which passes through the firing holes and ignite the delay pellets, which in turn ignite the powder pellets. The flashes from the powder pellets pass through the flash channel and the flash plug and ignite the detonator which, by igniting the C.E. in the stemmed fire channel, fires the C.E. in the magazine. Impact of the fuzed bomb with the light superstructure of the ship, or with the surface of the sea, is sufficient to cause the fuze to function.

REMARKS:

(1) The no. 30 Mk I includes a special and a normal delay. The arming mechanism is the same, but the delay mechanism differs in that the striker for the specical delay is, when released by the screwed arming spindle, supoorted by a shear wire. There is no creep spring beneath this pellet. The normal delay functions the fuze as decribed above, but the special delay functions when the fuzed bomb strickes 1 inch mild steel plate with a velocity of 500 ft. per sec. When this occurs, the wire supporting the stri-ker is sheared and the striker moves against and fires the ignifeorus detonator below it. The flash from the detonator passes through the firing hole to the delay pellet which ignites the powder pellet. The flash from the powder pellet passes through the flash channel and the flash plug and ignite the detonator, 5 grain, which by igniting the C.E. in the stemmed fire channel, fires the C.E. in the magazine.

(2) The No. 30, Mk I* is the same as the Mk II fuze as decribed above.

(3) The No. 30, Mk III is similar to the Mk II, except that it is fitted with a stirrup and a packing washer and has a fork secured to the safety clip to press the arming vane spigot firmly against the packing washer to form a water-tight joint while the fuzed bomb is being taxied over water.

(4) The fuzes are not capable of giving direct action; and bombs fuzed with them can, in an emergency, be dropped safety.