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| U.S.N.B.D. - BRITISH LAND MINES AND FIRING DEVICES |
| FIRING DEVICES |
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DIAMETER |
5/16 in. |
BRITISH SWITCH |
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LENGTH |
5 in. |
NO. 10
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WEIGHT |
1-1/2 oz. | |
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MATERIAL |
Aluminum and copper. | |
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COLOR |
Unpainted. | |
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Mk I |
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(SERVICE) |
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USE: |
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This device is designed to explode a demolition charge by delayed action. |
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DESCRIPTION: |
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This switch consists essentially of a housing tube made up of two parts, a thin cop-per sleeve containing a glass vial of corrosive liquid, and a thin aluminum sleeve, hous-ing a spring loaded striker retained by a retaining wire. This retaining wire is attached to the upper end of the striker and fastened to the top of the copper sleeve. A fuse adap-ter and percussion cap are crimped into the base of the switch, and a safety bar pier-ces the housing tube between the striker and the percussion cap. Inspection holes are provided just above the holes for the safety bar. |
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FUNCTIONING: |
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When the copper sleeve is crimped and the glass vial broken, the corrosive liquid is allowed to attack the retaining wire. When this wire is eaten through, the striker spring drives the striker into the percussion cap. |
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INSTALLING & ARMING: |
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Refer to the table included with each box of switches, and select the proper delay. Look through, or pass a nail through the inspection holes to see that the striker has not fallen and is not resting on the safety bar. Connect the explosive charge to the fuse adapter. A service detonator may be crimped directly over the adapter, or instantan-eous or safety may be used by crimping an adapter sleeve over fuse adapter and crimp-ing fuse in sleeve. Crimp the copper sleeve flat, without bending or fracturing the sleeve. Withdraw the safety strip. Do not leave safety strip behind, as its color will in-dicate to the enemy the delay time of the switch. Always use two switches for each important charge, to guard against risk of failure. |
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DISARMING: |
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This switch cannot be disarmed safely. If it is essential to disarm, insert the safety bar or a nail through the inspection holes, or cut the fuse connecting the switch to the explosive charge. After inserting the safety bar, remove the switch from the charge. |
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REMARKS: |
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1. If you can see through the inspection holes or insert a nail through them, the striker is cocked. If the sleeve has been crimped, discard the switch. If the sleeve is in-tact, unscrew the cap to see whether the glass vial is intact. If so, the switch may be re-used. |
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2. The time of delay are indicated by the colors of the safety bars. The following table, subject to 25% variation either way, shows the variation of the delay times with the temperature: |
| DEGREES C. | RED | WHITE | GREEN | YELLOW | BLUE | DEGREES F. |
| -20 | 75 min. | 19 hr. | 3½ days | 10 days | --- | -4 |
| -10 | 63 min. | 13 hr. | 2½ days | 5 days | --- | 14 |
| 0 | 43 min. | 5 hr. | 16 hr. | 28 hr. | --- | 32 |
| 10 | 31 min. | 2-3/4 hr. | 8 hr. | 18 hr. | 34 hr. | 50 |
| 15 | 27 min. | 2 hr. | 5-3/4 hr. | 12 hr. | 24 hr. | 59 |
| 20 | 23 min. | 1½ hr. | 4 hr. | 9 hr. | 20 hr. | 68 |
| 25 | 19 min. | 1¼ hr. | 3 hr. | 6 hr. | 15 hr. | 77 |
| 37½ | 12½ min. | 3/4 hr. | 1½ hr. | 3 hr. | 6 hr. | 99½ |
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43 |
9½ min. |
34 min. |
80 min. |
2 hr. |
5 hr. |
109½ |
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