Clothespin Time Delay Switch

Section VI

No. 8

A 3 to 5 minute time delay switch can be made from the clothespin 8witch (Section VII, No. 1) and a cigarette. The system can be used for initiation of explosive charges, mines, and booby traps.


  • Spring type clothespin
  • Solid or stranded copper wire about 1/18 in. (2 mm) in diameter (field or bell wire is suitable)
  • Fine string, about 6 inches in length
  • Cigarette
  • Knife


1. Strip about 4 inches (10 cm) of Insulation from the ends of 2 copper wires. Scrape copper wires with pocket knife until metal is shiny.

20 11 Clothespin Time Delay Switch

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.

20 21 Clothespin Time Delay Switch

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.

20 31 Clothespin Time Delay Switch

NOTE: Delay time may be adjusted by varying the burning length of the cigarette. Burning rate in still air la approximately 7 minutes per inch (2.5 cm). Since this rate varies with 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.

20 41 Clothespin Time Delay Switch

5. Tie string around rear of clothespin, 1/8 Inch or less from end. The clothespin may be notched to hold the string in place.

20 5 Clothespin Time Delay Switch

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.


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.

206 Clothespin Time Delay Switch

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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