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| U.S. EXPLOSIVE ORDNANCE |
| PART 6 - BOMBS AND BOMB FUZES |
| Chapter 20 - BOMB FUZES |
| Section 3 - NAVY-DESIGNED BOMB FUZES |
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AN-Mk 234 (Athwartship Hydrostatic) (Suspended from use) |
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Bombs |
Depth Bombs Mks 17, 29, 37, 38; AN-Mks 17 Mod 2, 41, 44, and 47 |
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Functioning |
Water pressure at depth set for 25, 50, 75, 100, or 125 feet of water |
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Armed condition |
Partially armed when arming wire is pulled and jump-out pins are ejected. Arming completed at 12 - 15 feet of water when primer and detonator are aligned with firing pin |
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Fuzes used with |
AN-M103, AN-Mk 219, or Mk 221 in nose; Mk 229 in tail in 650-lb. depth bombs |
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Over-all length, inches |
Firing assembly - 6.9; Extender assemblies - 9.9 |
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Body diameter, inches |
3.6 |
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Material |
Bronze, brass, steel, and aluminum |
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General: The fuze is essentially the same as the Athwartship Hydrostatic Fuze AN-Mk 224, being an athwartship fuze consisting of the pistolm booster, and booster extender. The firing assembly and booster extender are inserted in the athwartship tube of the depth bombs from opposite sides. The AN-Mk 234 differs from the AN-Mk 224 in that it has an external setting device and does not require disassembly to effect depth variati-ons in functioning. |
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The depth setting is accomplished by varying the amount the adjustable spring must be compressed by the hydrostatic piston as the bellows expand. If a deep setting is de-sired, the depth-setting collar is rotated so that a shallow step on the collar would be positioned under the spring-housed depth lug. Thus, the depth lug would engage the col-lar shortly after entering the water, and the bomb would have to sink farther before the water pressure could overcome the spring resistance. If a deep step were positioned un-der the lug, the hydrostatic piston could move farther before encountering resistance from the spring. Unitl the lug is engaged, the spring housing rides inward with the hy-drostatic piston; but as sson as the lug is engaged the spring housing no longer moves with the piston and the spring resistance must be overcome. |
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Operation |
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Action in booster extender: When the bomb is dropped from the plane, the arming wire to the booster extender is withdrawn from the jump-out pin. The jump-out pin is thrown out by its spring; the booster spindle is freed, and water is permitted to enter the hole created by the jump-out pin. The water expands the bellows until it overcomes the pres-sure of the spring acting against the locking slide and booster spindle. The locking balls are forced into an enlarged groove in the fuze, and the booster and slider aligner move inward, aligning the primer and detonator sliders, as described in the operation of the AN-Mk 224. |
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Action in pistol: As the arming wire pulls free, it extracts the plug and neoprene con-nector, permitting water to enter the fuze when the bomb is immersed in water. The wa-ter acts against the flanged base of the hydrostatic piston and, as the pressure increa-ses, expands below the bellows. The hydrostatic piston, adjustable spring, and spring housing all move inward until the depth lug engages the step on the depth-setting collar which has been positioned opposite it. At this point, the spring hosuing no longer moves inward. The hydrostatic piston continues to move inward under pressure of the water, but its movement is restricted by the resistance of the adjustable spring. Meanwhile, the movement of the hydrostatic piston compresses the firing spring; and, when the enlarged groove in the piston comes opposite the locking balls, the firing spring forces the balls out, forcing the firing pin against the primer. The primer fires the detonator, which sets off the sub-booster of tetryl, the booster, and the main charge. |
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Figure 366. Athwartship Hydrostatic Fuze AN-Mk 234 |
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