PYRO5.TXT - Casings and General Construction, Part 2 This is part of a series of files on pyrotechnics and explosives. It's serious stuff, and can be really dangerous if you don't treat it seriously. For you kids out there who watch too many cartoons, remember that if a part of your body gets blown away in the REAL world, it STAYS blown away. If you can't treat this stuff with respect, don't screw around with it. Each file will start with a set of safety rules. Don't skip over them. Read 'em and MEMORIZE 'em!! At the beginning, there will be a set of general rules that always apply. Then there will be some things that you HAVE TO KNOW about the materials you will be using and making this time. Read it thoroughly before starting anything. Pyrotechnic preparations and explosives are, by their very nature, unstable, and subject to ignition by explosion or heat, shock, or friction. A clear understanding of their dangerous properties and due care in the handling of ingredients or finished products is necessary if accidents are to be avoided. Always observe all possible precautions, particularly the following: 1. Mix only small batches at one time. This means a few grams, or at most, an ounce or so. Don't go for big mixes -- they only make for bigger accidents. The power of an explosive cubes itself with every ounce. (9 Ounces is 729 times as powerful as one ounce.) 2. When weighing chemicals, use a clean piece of paper on the scale pan for each item. Then discard the used paper into a bucket of water before weighing the next ingredient. 3. Be a safe worker. Dispose of any chemicals spilled on the workbench or equipment between weighings. Don't keep open containers of chemicals on your table, since accidental spillage or mixing may occur. When finished with a container, close it, and replace it on the storage shelf. Use only clean equipment. 4. Where chemicals are to be ground, grind them separately, NEVER TOGETHER. Thoroughly wash and clean equipment before grinding another ingredient. 5. Mixing of batches should be done outdoors, away from flammable structures, such as buildings, barns, garages, etc. Mixes should also be made in NON METALLIC containers to avoid sparks. Glass also should not be used since it will shatter in case of an accident. Handy small containers can be made by cutting off the top of a plastic bottle three or four inches from the bottom. Some mixes may most conveniently be made by placing the ingredients in a plastic bottle and rolling around until the mixture is uniform. In all cases, point the open end of the container away from yourself. Never hold your body or face over the container. Any stirring should be done with a wooden paddle or stick to avoid sparks or static. Powdered or ground materials may also be mixed by placing them on a large sheet of paper on a flat surface and then rolling them across the sheet by lifting the sides and corners one at a time. 6. Never ram or tamp mixes into paper or cardboard tubes. Pour the material in and gently tap or shake the tube to settle the contents down. 7. Store ingredients and finished mixes where they will not be a fire hazard away from heat and flame. Finished preparations may be stored in plastic bottles which will not shatter in case of an accident. Since many of the ingredients and mixes are poisonous, they should be stored out of reach of children or pets, preferably locked away. 8. Be sure threads of screw top containers and caps are thoroughly cleaned. This applies also to containers with stoppers of rubber or cork and to all other types of closures. Traces of mixture caught between the container and closure may be ignited by the friction of opening or closing the container. Throughout any procedure, WORK WITH CLEAN CONDITIONS. 9. ALWAYS WEAR A FACE SHIELD OR AT LEAST SHATTERPROOF SAFETY GLASSES. Any careful worker does when handling dangerous materials. Be sure lenses and frames are not flammable. 10. Always wear a dust respirator when handling chemicals in dust form. These small particles gather in your lungs and stay there. They may cause serious illnesses later on in life. 11. Always wear gloves when working with chemicals. 12. Always wear a waterproof lab apron. 13. If you must work indoors, have a good ventilation system. 14. Never smoke anywhere near where you are working. 15. Make sure there are NO open flames present, and NO MOTORS (they produce sparks inside.) No hot water heaters, furnaces, or pilot lights in stoves!! Sparks have been known to very readily explode dust floating in the air. 16. ALWAYS work with someone. Two heads are better than one. 17. Have a source of water READILY available. (Fire extinguisher, hose, etc.) 18. Never, under any circumstances, use any metal to load chemicals or put chemicals in. Fireworks with metal casings are worse to handle than a live hand grenade. Never use any metal container or can. This includes the very dangerous CO2 cartridges. Many people have been KILLED because of flying fragments from metal casings. Again, please do not use metal in any circumstance. 19. Always be thoroughly familiar with the chemicals you are using. Some information will be included in each file, but look for whatever extra information you can. Materials that were once thought to be safe can later be found out to be dangerous stuff. 20. Wash your hands and face thoroughly after using chemicals. Don't forget to wash your EARS AND YOUR NOSE. 21. If any device you've built fails to work, leave it alone. After a half hour or so, you may try to bury it, but never try to unload or reuse any dud. 22. If dust particles start to form in the air, stop what you are doing and leave until it settles. 23. Read the entire file before trying to do anything. 24. NEVER strike any mixture containing Chlorates, Nitrates, Perchlorates, Permanganates, Bichromates, or powdered metals don't drop them, or even handle them roughly. These rules may all look like a lot of silly nonsense, but let's look at one example. When the move "The Wizard of OZ" was made, the actress who played the good witch was severely burned when one of the exploding special effects got out of hand. The actress who played the bad witch got really messed up by the green coloring used on her face, and the original actor who played the Tin Man got his lungs destroyed by the aluminum dust used to color his face. The actor we know of as the tin man was actually a replacement. The point is, these chemicals were being used under the direction of people a lot more knowlegable of chemicals than you are, and terrible accidents still happened. Don't take this stuff lightly. *********************************** We'll only be using a few chemicals this time. Here's the list: Potassium Perchlorate KClO 4 A poisonous oxidizer, usually white but sometimes a slightly pink powder. Much more stable than its Chlorate brother, it can often be substituted for it to make a mixture safer. Sulfur S A yellow element that acts as a reducing agent. It burns at 250 degrees, giving off choking fumes. Purchase the yellow, finely powdered form only. Other forms are useless without a lot of extra and otherwise unecessary effort to powder it. Aluminum Powder Al An element added for brilliance and to speed up the burning rate of a mixture. A silvery powder, it often contains small amounts of finer dust that can be hazardous if stirred up in the air and inhaled. Not nearly as dangerous or as flammable as when in dust form, but still best to use with some caution. Sodium Salicylate HOC H COONa 6 4 A white powder that functions as a reducing agent. Not nearly as effective as other more common reducing agents, so used only when it gives a special advantage, as in whistles. Last time, we were discussing construction techniques for some small salutes. If you followed the directions carefully, you should have made some reasonably large noises. These little training salutes looked about the same size as an M-80 or a Silver Salute, but were nowhere nearly as powerful. This was intentional. Since these things are thoroughly nasty, we started small, though tried to keep it from becoming obvious. The larger the volume of space inside the tube, the more powder we can put in, and the more powerful it will be. Our training salutes had a 7/16" Inside Diameter, was 1 1/4" long, and had 1/4" end caps that take up space that then can't hold powder. The volume of a cylinder is V = Pi * R * R * L. R is one half of the inside diameter or 7/32". L is the tube length, minus the size of the two end caps, or 3/4". Pi is about 3.14. This gives us a volume of .113 square inches. A Silver salute has an Inside Diameter of 1/2", and an M-80 has an inside diameter of 9/16". Each of these has a length of 1 1/2", and uses only about a 1/8" end cap, because it used the rock-hard (and shrapnel producing) pyrotechnic cement we learned of last time, instead of the safer paper plugs we used. Applying the same formula, the silver salute encloses a volume of .245 square inches, or more than twice the volume of the training salute. The M-80 encloses a volume of .310 square inches, which is nearly three times that of the training salute. When we consider that explosive goes up roughly with the cube of the amount of explosive, we see that small changes in the dimensions of a salute can bring a huge change in its power. Of course, if you read the safety rules printed at the beginning of every one of these files, you will have figured that out for yourself. If you want to make larger salutes, and I just know you will, it would be a good idea to not use the pyrotechnic cement, and just make the casing a bit longer so that the paper end plugs can be used. You can do what you want, but if you perforate your eyeballs with splinters of pyrotechnic cement, you'll miss out on reading part 6 of this series, and that would really be a pity. Cherry Bombs Cherry bombs have been known to be terribly dangerous, largely because they tended to be coated with the pyrotechnic cement, often stretched out with cheaper sawdust. These have blinded a great many people. Their reputation has been further smeared by street punks who dip cherry bombs in glue, then in BB's, and let them dry into little anti-personnel grenades for hurling into rival street gangs. The sheer stupidity of such an action can't be adequately expressed. We'll talk about a safer way to make and use these items. Cherry bombs start with two small paper cups, one of which fits inside of the other, to make a crude ball. The smaller ball gets a hole poked in it, and the fuse inserted and glued in place. The smaller cup is then filled about halfway with flash powder, the salute powder mentioned last time works nicely, and the larger cup is glued in place. In the old days, the ball was then held by the fuse and dipped in the pyrotechnic cement, and set aside to harden. Instead, without letting the glue on the two cups dry, cover the entire ball with several layers of glue-soaked paper strips. Make the strips of brown kraft paper (supermarket paper bags will do) about 2 inches long and a quarter of an inch wide. These have to be pressed with your fingers onto the outside of the cups. The entire thing should end up covered with four or more layers of the paper strips. It's best to put on all the layers at once. If by any chance the thing should go off while you're making it, the soggy paper will just split open, and you'll get burned. But once you let some of the layers dry, you have a potentialy explosive device and could be damaged severely if it went off. Making the little paper cups is an interesting exercise in ingenuity. Since dealers in pyrotechnic materials will sell these cups for less than ten cents a set, (for smoke bombs only, of course!!) they're hardly worth the effort to make yourself. But if your funds are limited, or you just enjoy doing it yourself, we'll look at a couple of ways to do it. A piece of soaking-wet brown kraft paper can be formed over a round bulge or into a rounded impression. If two or three such sheets are formed over or stuffed into such a shape, with a layer of glue between each, they'll dry into nice cup shapes. Controlling the shapes of the cups can be tricky, but the outside cup must be able to fit snugly over the inside one. If it's too small, it won't fit at all, and if it's too big, it will be hard to glue to its mate. If you think about it, you don't have to control both the inside and outside dimensions of each cup. The outside of the small cup has to match the inside of the large cup. A round pin-shaped form will give good control over the INSIDE diameter, so a round pin should be used to form the OUTSIDE cups. A cup shaped indentation allows control over the OUTSIDE diameter, so it should be used to form the INSIDE cup. The outside diameter of the pin should match the inside diameter of the indentation. Matching the two parts is easy if you have access to a machine shop. With a lathe and some decent measuring tools, you can cut the indentation out of a block of metal and turn the round head over a piece of metal bar stock. Machinable plastic will work fine too, but it's just not as nice, and stinks when you machine it. Iron or steel will rust, changing the carefully machined dimensions and anyway, they're too much of a hassle to cut. Avoid them. Wood of any kind will warp, swell, and otherwise deform itself. It won't work. Aluminum won't rust and is easy to machine. This is best if your machining experience is limited. Brass is really NICE, though. Being able to machine your own parts is also nice if you plan to make a dozen or so of each part so that you can make more than one set of cups at the same time. Okay, so what do you do if you don't have access to a machine shop? Well, a little walk through a hardware store will give you the right materials, and you can even make multiple sets of matched pins and cups, even if they are really hokey looking. The indentations can be found in the plumbing section, under plastic pipe. Get the end caps, either in the 1/2 or 3/4 inch size. Note that the size of pipe is the inside diameter of the pipe, not the outside, so a 1/2 inch end cap will make decent sized cups. The 3/4 inch cap will make really hefty sized ones. There's a little problem with these end caps. Their insides are more cylindrical than they are cup shaped, and the cups they make won't be hemispherical. The bottom edges can be filled in a bit with some epoxy glue. Start with a little, so it doesn't run. When it hardens, add another layer. Keep adding layers until the inside is rounded. The pin portion can be hammered from a piece of copper pipe about 3 inches or so long. If you got a 1/2 inch pipe cap, get a piece of 1/2 inch pipe. Clamp a 1/2 inch steel bar into a vise, slide the pipe down over it. The bar should leave enough empty pipe above it so that you can hammer the copper into a curved top. If you can get a ball bearing that will fit into the pipe, so much the better. Hammer the pipe gently, turning it around the bar as you hammer it. Don't try to form the pipe too fast, or you'll crack the pipe, and you'll have to cut the end off and start over. Since it's possible to knock fragments loose, you should wear safety glasses while you do this. Hammer inward, rather than downward, as much as you can. The downward hammering will smoosh the copper downward and outward, causing the outside diameter to increase. We don't want this. You don't have to hammer the pipe until the top is completely closed. You can leave a hole about 1/4 inch wide and it won't hurt anything. Practice this out with 1/2 inch pipe. It's much harder to form 3/4 inch pipe without cracking it, but it can be done. Once you've got the end formed properly, the pipe will have expanded enough that it will no longer fit into the pipe cap. Take the bar out of the vise, set it and the pipe flat on an anvil, or the anvil-end of the vise, and roll it while hammering it. Keep checking the fit of the pipe into the cap until it fits easily. Congratulations! You've just made a forming pin. Now to make some cherry bomb cups. Cut out three 3 inch squares of kraft paper and soak them in water. Form one tightly over the forming pin and drop a glob of white glue over the top. Put the second wet sheet on top, smear it all around to cover the one side with glue, and form it tightly over the first. Repeat this with another drop of glue and the third sheet. Now, take some heavy cord and wrap it around the paper to hold it in place. Set it aside to dry overnight. If you were careful enough not to get any glue on the outside, you should be able to unwrap the string when its dry. Then, trim the cup with a small pair of scissors. You now have one completed outside cup. The inside cup is a little trickier. Here, you also start with three soaking wet sheets of kraft paper. Stuff the first into the indentation. Wipe some glue over one side of the second wet sheet and stuff it in on top of the first. Then do the same glue-and-stuff caper with the third sheet. Press all three sheets in tightly again, and set it overnight to dry. When dry, trim this cup as well. Exactly how much to trim will be obvious when you have one of each. The two cups should fit together snugly to form a crude ball. Smash paper over Stuff paper into the forming pin the forming cup \ / \ / ________ _____ _____ <-- ---> / \ \ / | <-- fuse / ____ \ ____ \_/ ____ | / / \ \ | | | | _|_ | | | | | | / | \ <-- inner cup | | | \___/ | | | | | | | | ||..|..|| <-- outer cup | | |_______________| | ..|.. | \_____/ powder is inside Outer Cup Fixture Inner Cup Fixture Assembled Cups If all of this seems an awful lot of work, remember, I did say that it was easier and worthwhile to buy the ready made cups. But all of this does work, so if you want to increase your experience in pyrotechnic fabrications, give it a try. To tell the truth, there's nothing that these cherry bombs can do that a tube salute cannot, and with lots less work. But cherry bombs seem to have some mystique that give them everlasting popularity. Oriental Salutes There's another way to make very effective salutes, one that's totally different from the standard tube salute we see in The States. The cost of the materials is lower than what we've discussed, but they take a lot of time. This makes them the choice in poor countries, where labor is cheap. Since salutes are banned in the United States, these oriental items aren't imported. The usual salutes are the quickly made tube type that are made in clandestine factories right here in the good ol' U S of A, and most people have never seen these hard little pear-shaped oddities. Unlike tube salutes, which must have mostly empty space and use a supercharged flash powder, these items are packed solid and contain low grade flash powder and ordinary gunpowder. Here is a crude cross section. ---- /----\- Oriental Salute //++++\-\- //+ -- +\\-\- +++ = flash powder ||++/**\-\\\\\\ *** = gunpowder ||++|================== === = fuse || +\**/-////// Paper is represented by all of the following: \\+ -- +//-/- // -- || \\ \\++++/-/- \----/- ---- As you can see (??) the salute is made of a central ball of gunpowder surrounded by an outer shell of flash powder. The gunpowder is enclosed in a tissue shell to keep it from mixing with the flash powder. The fuse is coated heavily with paper so that it will burn through the layer of flash powder ***WITHOUT*** igniting it. The fuse only ignites the gunpowder in the center. This produces a burst of hot gas that quickly ignites all the flash powder. While the American salutes rely on extra fine aluminum dust and a considerable air space inside the salute to get the powder to flash all at once, the oriental device uses a gunpowder ball, almost like a primer, to rapidly ignite the flash powder that uses much coarser powdered aluminum. While this takes effort to make, it can be used by those who don't have access to aluminum dust, but can file down an aluminum block with a fine file. Start with a 3 inch length of green fuse. Last time we discussed the higher degree of side spit produced by red fuse, and that has a greater chance of igniting the flash powder on its way to igniting the gunpowder. This gives a salute with less reliability. Use green fuse if you have it. Place a pinch of FFFF grain plack powder in the center of a 3/4" square of tissue paper. Use wrapping tissue, as opposed to the flimsier facial tissue. Dip the fuse into the powder and fold the tissue up into a ball at the end of the fuse. Twist the tissue ends and apply a little glue to attatch it to the fuse. When dry, wrap 2 or 3 layers of masking tape around the fuse where it meets the ball. This will shield the flash powder from the burning fuse. Now that we've attatched a tiny ball on the fuse, we'll do it again with a larger one. The dimensions can vary as we have some choice as to how large a bang we want to make. Lets start with a tissue square about 4 inches square. Into this we dump about 3 grams of flash powder made of Potassium Perchlorate - 4 parts Sulfir - 1 part Bright Aluminum Powder - 1 part The bright aluminum powder is much easier to find in chemical supply catalogs and can also be made by filing an aluminum block with a fine file. There's no need for aluminum dust here. Fold the tissue up around the gunpowder ball, bringing the corners of the tissue up onto the fuse, wrapping it around the fuse and securing it with a drop of glue. You should now have a ball of flash powder with a tiny gunpowder ball inside, to which the fuse extends. This ball has to be wrapped with two or three layers of dry newspaper strips, about 1/2 inch wide. Wrap them around the bottom and attatch them to the fuse with a twist and a drop of glue. The dry paper is to keep the flash powder dry when we wrap it all with similar strips of kraft paper soaked in paste. Once again, wrap it around the bottom and twist it around the fuse. The paper should really be dripping wet with paste. While attatching the dry paper is tricky, doing it with the wet stuff is downright frustrating, until you've had some practice. It would be a good idea to try this first with tissue, sand, and wire until you get the technique down. You'll probably want to attatch 3 to 5 layers of the glue soaked paper. If you choose to use a larger tissue square and more flashpowder, you'll get better results by adding additional layers. If you want to get decorative, you can get colored model airplane tissue from a good sized hobby shop. Wrap this on as a final layer. The layers of paper wrapped around the fuse will change the shape of the salute from a cherry to more like a pear. This is to be expected. Leave the finished salute in a dry, warm (not hot!) place for a couple of days. After drying, if made properly, the casing will be hard and sound like a piece of wood when knocked on a hard surface. Whistles These little curiosities are fun to make, but tend to be tricky. Unless they're made just right they'll just make a lot of fire and smoke. The chemicals must be very well mixed, the tube has to have the proper dimensions, and even the smoothness of the inside of the tube will make a difference. Sound is simply the result of rapid back and forth changes in air pressure. Burning pyrotechnic mixtures certainly create pressure. If we can produce a device whose burning rate changes rapidly, it will produce sound. The trick is not only to get it to change, but to change at speeds that will produce tones that we can hear. If a mixture burns deep down inside a tube, and the gas can't escape as fast as it's produced, the pressure inside will increase. If the mixture's burning rate is very sensitive to the pressure it's under, we might have the makings of a whistle composition. Since we might not expect that such properties are common, we won't be surprised if we need some rather unusual chemicals to make whistles. It turns out that many aromatic compounds (molecules with benzene rings in them, for you chemistry nuts) will work. Unfortunately, many such compounds are liquid at room temperature, and even the solids tend to evaporate. Many that do work have other problems. If you have access to some of the outdated pyrotechnic texts, you'll see whistle mixtures that use Potassium Picrate. This stuff is extremely sensitive to shock and should never be used. The fact that it has to be homemade from the even more sensitive Picric Acid is thoroughly scary. Even the old texts mention the danger of Picrate whistles, and suggest a "safer" composition of Potassium Chlorate and Gallic Acid. Last time we discussed how a Chlorate can ignite spontaneously in the presence of an acid, and we won't use this either. We won't even mention the proper proportions needed, though we will say that old texts seem to have gotten copied from other old texts and somewhere along the line, someone accidentally reversed the proportions. As a result, many, but not all of the old texts have the proportions swapped. It's just as well. Fewer people will have gotten hurt from this mixture if they tried it, it didn't whistle, and they gave up making it. The modern whistle formulation consists of Potassium Perchlorate - 7 parts Sodium Salicylate - 3 parts This is far safer than any of the other formulations, and happens to be cheaper, too. For once, everything worked out in our favor! Whistles need some special care. While some variation is allowed, it's suggested that you follow these instructions to the letter. There are so many different little things that can be done wrong that it can be hard to find the problem if you're not familiar with what's required. It's best to exactly follow a set of instructions that work, and once you've got that down you can make small changes, one at a time. The inside of the tube should be as smooth as possible. In fact, commercial whistle tubes are often made of plastic to get the smoothness. In the orient, they use bamboo tubes, which work best. But even if we lack a consistent bamboo supply, and don't have some special plastic that resists softening while containing a flaming mass of chemicals, we can still make do with carefully rolled paper tubes. Shopping bag kraft paper tends to be fairly rough. See if you can find a supply of kraft paper on a roll. Commercial rolls come 3 or 4 feet long and quite thick. It's often used for wrapping packages and the like. You won't want to buy it by the roll, but you may be able to find a business that uses it for wrapping that may be talked into selling you a dozen or so feet of it. If you can get some, roll it carefully, and try to keep it from getting any bends that would mar its surface. Alternately, some stores use paper bags made of a very thin, very smooth kraft paper. These aren't supermarket-style bags, though. Check various clothing stores and others that use the type of bag that opens by bulging out at the middle, rather than unfolding into a box shape. If the paper has been bleached and dyed pink or blue, the whistle won't mind. Papermaking machines operate by pressing a slush of wood pulp between two surfaces. One is a felt-like material, and the other is a fine wire mesh. The difference between the surfaces gives paper two different surface finishes from side to side. Sometimes this is more obvious than others. On some kraft paper, one side will be smoother. If so, just keep the smoother side pointed to the inside surface of the tube. Since you want smoothness, wrap the paper around a 1/2 inch diameter metal or plastic rod, rather than a wooden dowel. Don't glue it yet. Wrap at least 4 or 5 layers around the rod and then twist the rod so that the paper is wound as tightly as possible. Now, set it on a flat smooth surface and unroll it as far as you can go without letting the end on the inside come unravelled. Apply a line of glue along the juncture where the flat portion of the paper meets the rolled part, and start rolling it up again, pressing the roll into the flat surface. Keep adding glue where it becomes thin and keep rolling. Make sure that none of the glue runs out the ends of the roll, or it will make it difficult or impossible to remove the tube. If your supply of the smooth paper is small, stop after applying 4 or 5 layers and build it up the rest of the way with the cruder grade of kraft paper. The tube should be rolled until the wall is at least 1/8 inch thick. If you're just learning, it would be better to roll it up to 1/4 inch thick. The reasons will become clear later. When the tube is rolled to the proper thickness, cut off the ends that don't have sufficient glue, remove it from the rod, and let it dry thoroughly. The paper should have been of sufficient size that when the scrap ends are cut off, the tube is 4 or 5 inches long. We haven't discussed chemical mixing much yet, except for the motorized milling for gunpowder, and that's a special case. Many pyrotechnic mixtures have to be thoroughly mixed to work well, and it's not possible to tell the difference by looking at the mixed powder. In his book "Pyrotechnics", George Weingart discusses the use of fine screens for mixing chemicals. This isn't talking about window screens; they just won't do. Many metal dealers offer metal meshes that almost might be considered coarse metal cloth. Finely powdered chemicals can be mixed by slowly swirling them in a soft plastic container and then repeatedly pressing them through these mesh screens. These screens can mix the chemicals exceptionally well. One thing Weingart mentions is that one should avoid letting their fingernails strike the screen, as that can create a spark and cause a fire or explosion. While it seems amazing that anyone would want to push flammable or explosive chemicals through a screen with their bare hands, it does bring up another concern. While we avoid metal tools wherever possible, there might be a circumstance where a metal tool might accidentally fall on a screen, causing a spark. In these modern times, it's possible to get brass mesh screens, and brass doesn't spark when it's struck. Now, back to mixing chemicals. Powder each ingredient separately until it resembles flour or confectioner's sugar. Combine the ingredients in a soft plastic container and swirl it slowly to crudely mix them. Then press them at least 5 or 6 times through a 100 mesh screen. Brass is the material of choice, for reasons already mentioned. Once mixed, it's time to load the tube. There's a problem when loading the tube. We've made all sorts of efforts to keep the inside of the tube smooth, and now we're going to go dumping in chemicals and scraping it with a ramrod. We can't eliminate this problem, but we can minimize it. We know that we need a long empty space in front of the whistle tube. It's possible to fill the front end of the tube with a dowel and load it from the back end. This will at least keep one end clean. Get a block of wood and drill a 1/2 inch hole into it. The hole needs to be at a good, right angle, so drill the hole with a drill press, not a hand drill. Glue a 1/2 inch dowel pin into the hole so that it sticks out about one and a half inches. With the glue dried and the dowel extending squarely from the block, you can slide a whistle tube down on the dowel and proceed to load the tube. The block and tube is loaded from behind a heavy barrier, to protect you from an explosion, in case the whistle explodes while loading. This is not a frivolous extra. While an explosion of this material is unlikely, you can never completely trust chemical mixtures. Every now and then, you can get surprised, and the trick is to make sure that the surprises aren't harmful. A good barrier is made from two pieces of steel plate welded or bolted firmly together at right angles. This is another tool that the pyrotechnic practitioner uses a great deal. The steel barrier is attatched firmly to a workbench in such a way that you will stand inside the "V" area that it makes. | | /<--- Edge of workbench You |/ stand | here /| / | / | _________|<--- Steel Barrier / / O <-- Casing being loaded The barrier should be made such that another plate can be attatched horizontally on top. We won't need it for these tiny whistles, but it's important for some larger casings that get loaded by ramming, like skyrockets. The horizontal plate will have a hole through which you load the fuel and insert the rammer. These whistles are small enough that you can position yourself where the "V" portion alone can protect you. But don't try to load the casing without it. Remember, if you're standing at a workbench, the casing being loaded will be mere inches from your balls. If that won't persuade you to be careful, nothing will, and maybe the removal of your "stupid genes" from the gene pool will be a benefit to humanity. You'll want to wear a heavy face shield and protective gloves while ramming. Ear protection, the things that look like large earphones, aren't a bad idea, either. As a ramrod, you'll want another 1/2 inch dowel, 1 foot long, but this one should be sanded a bit so that it fits loosely down the tube. This will keep the smooth insides from getting rubbed and scraped as you load the whistle composition. Load the composition, moistened just slightly with alcohol, about 1/2 teaspoon at a time, and ram it by hand. The safety rules that come with these files caution you from ramming any mixture. This is good general advice and it should be followed. However, there are a few cases where it can be gotten around. The mixtures must be moistened and relatively insensitive to shock. They must also be loaded from behind the aforementioned barrier, so that even if anything does go wrong, you'll just end up with ringing ears and a desire to go out and get yourself sloshed. Now that we've discussed the barrier and the rules of ramming, we can ammend our safety rule, but only very slightly. Don't hit the rammer with anything and don't ram it really hard. While you ram the casing, you should be standing back so that you can't actually see it, your view blocked by the barrier. The only part of you that will be exposed to a possible explosion will be your heavily gloved hands, and they'll be at the end of a foot long dowel. If you don't ram straight into the tube, or you ram too hard, the tube will be cocked sideways, and the whistle will probably be ruined. Since you won't be looking directly at it, this will take some practice. For this reason, you might want to make your first whistle casings twice as thick, so that they will be a bit more forgiving of your errors as you learn. If you're going to make a lot of these, you might consider building a wooden fixture that will guide the rammer straight into the tube. Note that if there is an explosion, the dowel may be fired from the tube like a bullet from a gun, so hold it in such a way that it will not be driven into your hand. Also, make sure that it's not "aimed" at anything that you don't want trashed. Guiding in the ramrod will be nearly impossible for the last inch or so, so stop there. Cut a 1/2 inch plug off of a 1/2 inch dowel and slide it down the tube until it rests gently against the powder. Then drip a bit of glue into the tube, turning it so that it glues the casing to the dowel all the way around, and set it aside to dry. Don't set it on its side. Keep it pointing straight up so that the glue doesn't run. Now, to get the proper performance out of this thing, the alcohol must dry completely. This means setting it aside for a week or two before proceeding further. Now we have to hook a fuse onto this thing. It's easier said than done. Once again, we'll want to use green fuse instead of red, because of its reduced side spit. Since side spit will gunk up the smooth inside surface of the tube with residue, green fuse will be more likely to produce a working whistle. The need for an open tube keeps us from having any good solid surface to attatch the fuse to, and so if we had somehow imbedded it in the powder, any wiggling of the fuse would have broken up the nicely packed powder. Any pressing of the fuse into the powder can cause cracks and keep the whistle from working. There are two ways of attatching a fuse. Neither is very good. The easy way, which might be best for beginners, is to bend a length of fuse over double, and stick one end in the tube, contacting the powder, and the other end outside the tube, held in place with a ring of tape wrapped around the tube and the fuse. The advantages are that its easy to do, and any external bumping on the fuse will be absorbed by the tape, and little shock will be transmitted into the powder, where it might shake some loose. The disadvantages are, it burns in direct contact with the inside surface of the tube, roughing up the surface, once it burns past the tape, the fuse is no longer held against the powder, but can fall loose. On top of this, the end is open to the air, so all sorts of crud can settle inside if it sits around for a while. Glue a thin paper cover over the hole if you use this method. The second method is to glue a single layer tube of wrapping paper over the tube that extends about an inch and a half beyond the open mouth of the tube. When this is dry, insert a length of green fuse that's just long enough to reach the top of this new paper tube. The fuse should touch the powder at the line where it meets the wall of the casing. Bunch the wrapping paper tube up against the fuse, and apply a little glue where the paper touches the fuse. Now, pulling the paper foreward, twist it as tightly as is practical around the fuse without causing it to move and rub against the powder, and slip a lose knot of string over the twist and pull it tight. Apply a dab of glue on the string and let it dry. By pulling the paper foreward before attatching it tightly to the fuse, you cause it to pull the fuse inward against the powder. Even when the fuse burns through the paper, some tension will be retained. This gives a greater chance that the whistle will be ignited. It also covers over the open mouth of the tube and only touches the inside surface of the tube at the point where it touches off the powder. The disadvantages are that it takes longer to make, and that any bump into the fuse will cause it to crumble the powder. This second method is preferable if you are careful in handling your whistles. Since you presumably have complete control of your whistles from workbench to firing, you can store and move them with the needed care. As has been said, the powder has to burn from inside a tube to make an audible sound. As the powder burns deeper inside, the length of the open tube effectively increases. This increased length changes the speed with which the burning chemicals oscillate (it slows them down) causing the frequency to to start out high pitched gradually dropping down to a very low frequency. This is the reason for the distinctive sound of whistles and the reason you never hear one going in the other direction. It also sets a limit on how long a whistle can be, since they will tend to be uninteresting if they drop below the range of human hearing. Whistling Rockets The strict requirements on making a working whistle and the need for an open tube would seem to make it impossible to put it in a rocket engine and get a whistle. Yet whistling rockets are available. The larger skyrockets tend to have a whistle tube attatched to the outside of the rocket, and both the engine and whistle get ignited simultaneously by a branch in the fuse. The tiny whistling rockets use a clever way of getting a rocket-like action out of an open tube. /\ / \ /----\ |****| |****|<---Whistle tube with |****| nose cone and fins |****| /|===\|\ / |===\| \ / |===\| \ / |===\| \ |____|===\|____| ===\ ===\\ Solid plug--> === \\ <--Fuse attatched to === \ support base === ============= If we were to stuff a loose plug down the whistle tube with a hole just large enough to admit the fuse, then when the whistle composition ignited, the pressure would would fire the plug from the tube like cork is forced from a champagne bottle. If we take a whistle tube with only a limited amount of composition in it, attatch a nosecone and fins, and stuff a stationary plug up the whistle tube, then when the composition is ignited, the whistle tube would blow itself up off the plug into the air. The reason for the limited amount of whistle composition is for weight considerations. Only the initial burst of gas will fire the whistle tube into the air, and any extra composition will just weigh it down. The trick is for it to stay in the air while it's whistling. A whistling rocket that pops into the air and then lands on the ground while still whistling will be regarded by spectators as a "dud". Commercial whistling rockets tend to use plastic tubes, and use inside diameters only 1/4 to 3/8 inch. There's usually only about a 1/4 inch depth of fuel inside. Some of the tiny whistling rockets end with a report. Since a regular firecracker would add too much weight, the usual report is made by adding a chemical that detonates, exploding without a casing. If the nosecone end of the whistle tube has a small hole in it before its loaded, then a small amount of whistle composition will be visible through it. A small wad of Lead Azide can be placed into this hole so that it will be ignited and explode when the whistle composition is just burning out. The Lead Azide can be kept from crumbling off by hiding it under the nosecone. Preparation of Lead Azide is described in part 2 of this series. Stay tuned for part 6, where we'll talk more about fireworks that require special construction. Have fun but keep it safe! 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