4.21 FUSE IGNITION ----------------------- The oldest form of explosive ignition, fuses are perhaps the favorite type of simple ignition system. By simply placing a piece of waterproof fuse in a device, one can have almost guaranteed ignition. Modern waterproof fuse is extremely reliable, burning at a rate of about 2.5 seconds to the inch. It is available as model rocketry fuse in most hobby shops, and costs about $3.00 for a nine-foot length. Fuse is a popular ignition system for pipe bombers because of its simplicity. All that need be done is light it with a match or lighter. Of course, if the Army had fuses like this, then the grenade, which uses fuse ignition, would be very impracticle. If a grenade ignition system can be acquired, by all means, it is the most effective. But, since such things do not just float around, the next best thing is to prepare a fuse system which does not require the use of a match or lighter, but still retains its simplicity. One such method is described below: MATERIALS _________ strike-on-cover type matches electrical tape or duct tape waterproof fuse 1) To determine the burn rate of a particular type of fuse, simply measure a 6 inch or longer piece of fuse and ignite it. With a stopwatch, press the start button the at the instant when the fuse lights, and stop the watch when the fuse reaches its end. Divide the time of burn by the length of fuse, and you have the burn rate of the fuse, in seconds per inch. This will be shown below: Suppose an eight inch piece of fuse is burned, and its complete time of combustion is 20 seconds. 20 seconds ŻŻŻŻŻŻŻŻŻŻ = 2.5 seconds per inch. 8 inches If a delay of 10 seconds was desired with this fuse, divide the desired time by the number of seconds per inch: 10 seconds ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ = 4 inches 2.5 seconds / inch NOTE: THE LENGTH OF FUSE HERE MEANS LENGTH OF FUSE TO THE POWDER. SOME FUSE, AT LEAST AN INCH, SHOULD BE INSIDE THE DEVICE. ALWAYS ADD THIS EXTRA INCH, AND PUT THIS EXTRA INCH AN INCH INTO THE DEVICE!!! 2) After deciding how long a delay is desired before the explosive device is to go off, add about 1/2 an inch to the premeasured amount of fuse, and cut it off. 3) Carefully remove the cardboard matches from the paper match case. Do not pull off individual matches; keep all the matches attached to the cardboard base. Take one of the cardboard match sections, and leave the other one to make a second igniter. 4) Wrap the matches around the end of the fuse, with the heads of the matches touching the very end of the fuse. Tape them there securely, making sure not to put tape over the match heads. Make sure they are very secure by pulling on them at the base of the assembly. They should not be able to move. 5) Wrap the cover of the matches around the matches attached to the fuse, making sure that the striker paper is below the match heads and the striker faces the match heads. Tape the paper so that is fairly tight around the matches. Do not tape the cover of the striker to the fuse or to the matches. Leave enough of the match book to pull on for ignition. _____________________ \ / \ / ------ match book cover \ / | M|f|M ---|------- match head | A|u|A | | T|s|T | | C|e|C | |tapeH|.|Htape| | |f| | |#####|u|#####|-------- striking paper |#####|s|#####| \ |e| / \ |.| / \ |f| / \ |u| / |ta|s|pe| |ta|e|pe| |.| |f| |u| |s| |e| |.| |_| The match book is wrapped around the matches, and is taped to itself. The matches are taped to the fuse. The striker will rub against the matcheads when the match book is pulled. 6) When ready to use, simply pull on the match paper. It should pull the striking paper across the match heads with enough friction to light them. In turn, the burning matcheads will light the fuse, since it adjacent to the burning match heads. HOW TO MAKE BLACKMATCH FUSE: ----------------------------- Take a flat piece of plastic or metal (brass or aluminum are easy to work with and won't rust). Drill a 1/16th inch hole through it. This is your die for sizing the fuse. You can make fuses as big as you want, but this is the right size for the pipe bomb I will be getting to later. To about 1/2 cup of black powder add water to make a thin paste. Add 1/2 teaspoon of corn starch. Cut some one foot lengths of cotton thread. Use cotton, not silk or thread made from synthetic fibers. Put these together until you have a thickness that fills the hole in the die but can be drawn through very easily. Tie your bundle of threads together at one end. Separate the threads and hold the bundle over the black powder mixture. Lower the threads with a circular motion so they start curling onto the mixture. Press them under with the back of a teaspoon and continue lowering them so they coil into the paste. Take the end you are holding and thread it through the die. Pull it through smoothly in one long motion. To dry your fuse, lay it on a piece of aluminum foil and bake it in your 250 degree oven or tie it to a grill in the oven and let it hang down. The fuse must be baked to make it stiff enough for the uses it will be put to later. Air drying will not do the job. If you used Sodium Nitrate, it will not even dry completely at room temperatures. Cut the dry fuse with sissors into 2 inch lengths and store in an air tight container. Handle this fuse carefuly to avoid breaking it. You can also use a firecracker fuse if you have any available. The fuses can usually be pulled out without breaking. To give yourself some running time, you will be extending these fuses (blackmatch or firecracker fuse) with sulfured wick. HOW TO MAKE SULFURED WICK (---------------------------) Use heavy cotton string about 1/8th inch in diameter. You can find some at a garden supply for tieing up your tomatoes. Be sure it's cotton. You can test it by lighting one end. It sould continue to burn after the match is removed and when blown out will have a smoldering coal on the end. Put some sulfur in a small container like a small pie pan and melt it in the oven at 250 degrees. It will melt into a transparent yellow liquid. If it starts turning brown, it is too hot. Coil about a one foot length of string into it. The melted sulfur will soak in quickly. When saturated, pull it out and tie it up to cool and harden. It can be cut to desired lengths with sissors. 2 inches is about right. These wicks will burn slowly with a blue flame and do not blow out easily in a moderate wind. They will not burn through a hole in a metal pipe, but are great for extending your other fuse. They will not throw off sparks. Blackmatch generates sparks which can ignite it along its length causing unpredictable burning times.