TM 31-210
Improvised Munitions Handbook
| Section VI |
No. 8 |
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CLOTHESPIN TIME DELAY SWITCH |
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| A 3 to 5 minute time delay switch can be made from the clothespin switch (Section VII, No. 1) and a cigarette. The system can be used for initiation of explosive charges, mines, and booby traps. | |
| MATERIALS REQUIRED: | |
| Spring type clothespin | |
| Solid or stranded copper wire about 1/16 in. (2 mm) in diameter (field or bell wire is suitable) | |
| Fine string, about 6 inches in length | |
| Cigarette | |
| Knife | |
| PROCEDURE: | |
| 1. Strip about 4 inches (10 cm) of insulation from the the ends of 2 copper wires. Scrape copper wires with pocket knife until metal is shiny. |
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2. Wind one scraped wire tightly on one jaw of the clothespin, and the other wire on the other jaw so that the wires will be in contact with each other when the jaws are closed. |
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| 3. Measuring from tip of cigarette, measure a length of cigarette that will correspond to the desired delay time. Make a hole in cigarette at this point, using wire or pin. |
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| NOTE: Delay time may be adjusted by varying the burning length of the cigarette. Burning rate in still air is approximately 7 minutes per inch (2.5 cm). Since this rate varies with the environment and brand of cigarette, it should be tested in each case if accurate delay time is desired. | |
| 4. Thread string through hole in cigarette. |
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| 5. Tie string around read of clothespin, 1/8 inch of less from end. The clothespin may be notched to hold the string in place. |
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| NOTE: The string must keep the rear end of the clothespin closed so that the jaws stay open and no contact is made between the wires. | |
| HOW TO USE: | |
| Suspend the entire system vertically with the cigarette tip down. Light tip of cigarette. Switch will close and initiation will occur when the cigarette burns up to and through the string. |
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| NOTE: Wires to the firing circuit must not be pulled taut when the switch is mounted. This could prevent the jaws from closing. | |
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