With the new electronic firing system there will be much less need for traditional fusing. Historically we had to connect several elements with various speeds of fuse to “time” the ignition of each element.
“Visco” fuse is a higher-quality fuse used for consumer fireworks. It is most commonly colored green, red, or pink (plus white, orange, dark red, etc) and is found as a twisted, coated strand. Visco is a 3/32 – 1/8 inch (2–3 mm)-diameter cord with a black powder core. There are three external layers to visco fuse. First, a layer of string is wound around the core, then a second, less tight, layer of string is wound in the opposite direction to prevent unraveling. The last layer is a low-nitrate nitrocellulose lacquer that keeps the fuse from falling apart. The last layer helps to make the visco fuse water resistant and to prevent moisture from degrading the black powder core.
The different colors signify different burn rates measured in secs per foot. The fastest fuse we can buy burns at less than a second per foot (called violent burn rate, as the fuse tends to shoot around like a tiny rocket if not secured). The slowest we have takes 45 secs to burn a foot. We would use different fuses of various lengths to try to “time” when one element would fire in relation to the others. It was never very accurate, and sometimes didn’t work at all.
We won’t be timing most elements with visco fuse now, but there is one area we will still use it: chain firing the mortar shells. With 324 shells to fire, we will chain them together in groups of 6 so they only require 54 of our 216 channels in the ignition system. In previous years (with 144 shells) this has taken two or three hours under a tent in the heat to get everything ready. We have tried tape, zip ties, zip ties and tape, and three different brands of clips. They all “work”, but they are time consuming and difficult. No more.
I was getting ready to order more fuse one day when I came across a new product. Fuse Lynx.
It’s a piece of Visco fuse (either 12 sec/ft or 25 sec/ft) with 6 small paper tubes attached every 2.5″ with shrink tubing. To use, you insert the fuse from each aerial shell into the tube associated with that tube location. When the end is lit, the fire moves up the chain and lights each firework in time.
They claim Fuse Lynx makes fusing a rack about 10x faster than over traditional connectors. I believe them. However, we decided to make our own, both because we like making things, and so we could have more control over the timing. With the fuses we have available we can achieve several different timing sequences:
I found that 6mm paper straws are the perfect tube. Marine grade adhesive lined heat shrink tubing in 1/4″ D is the perfect thing to secure the tubes onto the fuse. Finally, for our purposes, 18″ of fuse with the tubes spaced 2.625″ works for our racks. With the fuse we have we can ignite 6 shells in 1, 15, 25, 30, 35, 45, or 60 secs. In the case where we want two sets of 6 to ignite together we can add some length to one fuse and another tube to ignite the beginning of a second set.
