Figure 1-5.—Mechanical long-delay fuze Mk 346 Mod 0.
setting shaft rotate past the minimum or maximum delay
setting without further rotation of the indicator dial or
damaging the mechanism.
The base end of the fuze houses the timer, firing pin,
detonator-rotor, lead-in, arming shaft, and the
functioning delay indicator dial. On the face of the base
end plate is the toothed cam, which operates as an
antiremoval device. The arming shaft moves forward at
impact to initiate the timer mechanism; this allows the
detonator-rotor to align with the firing pin and release
the antiremoval cam.
Operation
After the bomb is released from the aircraft, the
arming assembly is freed from the arming wire and
allowed to rotate. After approximately 45 revolutions
of the input shaft at 1,200 rpm or more, first stage arming
is complete. Usually this takes about 1.5 to 2 seconds.
Upon impact, the second stage arming is initiated, which
aligns the fuze firing train, starts the delay-to-burst
timer, and releases the antiremoval cam. After the
preselected time on the delay-to-burst timer has expired,
the bomb detonates.
NOTE: First stage arming must be completed
before impact, and impact must be sufficient to
initiate second stage arming.
Arming Assemblies Mk 3, 4, and 5 Mods
Mk 3, 4, and 5 arming assemblies are used with the
tail assemblies of LDGPs (except Mk 84) and Snakeye
weapons. They provide arming action for the Mk 346
fuze. The arming assemblies consist of a Mk 5 Mod 1
or Mod 2 fuze drive, an adapter, an appropriate drive
shaft, which couples to the input shaft of the fuze, and
a funnel guide. The Mod of the drive unit denotes the
Mod of the assembly.
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