Chrysanthemum Shell (3")
From PyroGuide
 A chrysanthemum shell is a type of aerial shell with a spherical break of stars, similar to a peony, but with stars that leave a visible trail of sparks behind. A black powder propelling charge (lift charge) is used to project the aerial shell into the air and are fired from a mortar tube. Upon firing, the lift charge is consumed and the shell is projected from the mortar. The pyrotechnic effect is produced near the highest point of flight (apogee) when a burst charge within the shell explodes, dispersing the stars. | |||||||||
[edit] MaterialsShell hemispheres  Star composition
Burst charge Meal coated rice hulls are used to help break the shell apart without shattering the stars to dust at effect time. A booster can optionally be added, such as whistle mix or a perchlorate-based Flash powder. Flash powder can disturb colour perception if the flash is too bright.  Time fuse Pasting Lift charge Ignition Other | |||||||||
[edit] Shell Construction Start by drilling a hole in the pole of one of the shell hemispheres. The diameter of the hole must be the same as the diameter of the time fuse or spolette. Insert the time fuse or spolette about half way in the hole, and hot glue it on both sides. Make absolutely sure that there are no air holes, this will likely result in a flower pot. | |||||||||
 Place each hemisphere on a stand, which can simply be made out of an empty toilet roll cut in half. This will prevent the hemispheres from rolling around when they are filled. | |||||||||
 Arrange the stars around the wall of the hemispheres to the rim. The stars should be sticking a bit over the rim. If the shell is underfilled it will result in a visible area of no stars when the shell is fired. Next cut two pieces of tissue paper, one of them with a hole to go over the time fuse or spolette. Put the pieces in each hemispheres against the stars and fill tighly with burst charge to the rim. A bit of booster, such as whistle mix or flash powder is added in the center of each hemisphere and spread loosely in the burst charge with fingers. Not much should be used, if using too much booster, the stars may shatter or blow blind. | |||||||||
 Quickly snap the two shell hemispheres together. This is not as hard as it sounds like, but if done too slowly, the stars or burst charge might rearrange or fall out, and the previous steps will need to be repeated. If each paper hemisphere touch eachother at this point, the shell is underfilled. However if done correctly there should be a small gap of around 1 cm at equator. Place the shell on the stand fuse-side down, and use a wooden dowel to gently hit the upper hemisphere on different places. The stars will then arrange inside the shell and hopefully the two hemispheres will reach eachother. Seal up around the equator with masking tape to close the shell temporarily. Also put a piece of masking tape around the end of the time fuse or spolette to protect it from being damaged during the next steps. | |||||||||
 The next step is pasting the shell, which is the hardest and most time-consuming part of spherical shells. The pasting method descriped here is the socalled 3-strip pasting method. Unlike the "normal" pasting method (pasting strips with a length of half the equator around the shell) the 3-strip pasting method does not "build up" near poles. To make your pasting strips sticky before you paste you will need to add a glue to each 70x15 mm paste strip on one side. This can be done quickly by arranging some strips on a wide wooden board. Next apply a thin, even layer of wheat paste with a brush. These strips are now ready for pasting, but you will need to repeat this step many times, since you will need a lot of strips to complete your shell. | |||||||||
 The shell is pasted as showed on the picture. A strip is pasted from the "northpole" pointing towards the "southpole". Then a strip beside is pasted from the "southpole" pointing towards the "northpole". A strip is then pasted between these two strip. This pattern is continuously pasted around the shell. Press out the airbubbles under the strips, this will result in a nice-looking shell. Everytime you finish a way around the shell (layer) make sure to write on the shell how many layers you have pasted so far, you might forget it. When finished pasting the shell, multiply the layer-number by two, since each layer with this pasting method counts for two actual layers. | |||||||||
 While pasting the shell, cut a ~8 cm piece of cotton twine and make a loop on it. Hot glue it to the top of the shell (the opposite hemispheres of the one with the time fuse in it) and paste like before, just making the strip covering the twine. This shell needed 10 layers of pasting (=20 effective layers) to complete. The diameter of the finished shell should be y=x*3/pi, where y is the diameter of the finished shell and x is the size of the mortar. So for this shell it should be 3*3/pi=2,86". Making it this diameter might take a lot of time for beginners, however it is not as problematic with small shells like this one. Making shells like the size of 6" or bigger will take a lot more of work. After the layers of pasting, let the shell dry completely. | |||||||||
 Peel of the making tape that protected the time fuse. Cut two lengths of black match and bend them over the exposed end of the time fuse. Wrap a line of string numerous of time around the black match to secure them to the time fuse. Then either secure the string with a dot of hot glue or tie a knot. The black match will be a prime for the time fuse and make it easier to ignite. Without it the time fuse might fail to ignite and make it a dud shell. | |||||||||
 The next step is the lift. Take your desired lifting cup and poke a hole in the bottom, big enough to put the quick match or shooting wire through. The quick match or shooting wire should be long enough, so that when the shell is loaded in the mortar, there will stick a bit out of the mortar. If you use quick match insert a piece of visco fuse it. This will be the delay between when the shell is ignited, till it shoots out of the mortar. Next put the quick match (not the visco fuse end) or shooting wire through the hole punched in the lifting cup. If using quick match, tear a bit of the paper off the end, so that the black match will be exposed. If using shooting wire, attatch your e-match. Next slide the quick match or shooting wire back, so it centres in the middle of the lifting cup. Secure the hole with a bit of hot glue or gummed paper. | |||||||||
 Add you lift charge in the lifting cup, in this example 15.3 grams of pulverone was used. The amount used all depends on the quality of your black powder. The rule of thumb is to use approximately 1/10 lift of the shells weight. The shell's final weight (everything included) was around 150 grams. | |||||||||
 Attach the lifting cup to the shell. The time fuse should be pointed directly down the lifting cup and the quick match or shooting wire should be put inside the loop on the top of the shell. Add a line of hot glue around to secure the lifting cup. | |||||||||
 Cut either a strip of gummed paper or kraft paper. The strip should be long enough to fit all the way around the lifting cup plus a little more. Cut the strip halfway all the way down with a distance of ~1" as shown on the picture. If you're using gummed paper activate it with water, if using kraft paper, brush with layer of wheat paste. | |||||||||
 Wrap the uncut part around the lifting cup and the cut part around the shell as shown on the picture. Again, make everything as tight as possible. | |||||||||
 If you want to add a rising comet to your shell, attach it the same way as the lifting cup was attached: Cutted-up strip with glue and hot glue. About 2 mm of the comet should be exposed to ensure ignition. | |||||||||
 The shell is now finished. It is a good idea to attach label in case you keep the shell over a longer time, so you will know what type of shell it is, which stars, amount of lift etc. When firing, you can either use a mortar stand to hold your mortar tube if you have one, or you can bury the mortar tube in the ground about 2/3. Next the shell is loaded to the tube with the quick match or shooting wire sticking out - the shell should fall freely, without any help to make it reach the bottom. | |||||||||
[edit] Video
3" Chrysanthemum shell - 1.6 meg - The shell made in this tutorial, fired from a fibreglass mortar half burried in sand. Fired in front of a small audience.
- Pudi Amateur Pyrotechnics - http://www.pudi.dk
