jakespeed Posted March 30, 2016 Posted March 30, 2016 the majority of the mortar launch howto's show visco attached to the end of quickmatch i get the use of the slow visco, but why use quickmatch why not use all visco fusing to light a mortar shell ??
OldMarine Posted March 30, 2016 Posted March 30, 2016 The visco burns slower and spits flame which will damage the hdpe and fiberglass tubes. QM and the lift burn off too fast to melt the tube.
braddsn Posted March 30, 2016 Posted March 30, 2016 Jakespeed, there are a few reasons for this. 'Most' visco burns at about 30 seconds per foot. In a 36" mortar, that would be 90 seconds... that's a LONG time to stand and wait. Instead, a small 3" piece of visco attached to the QM makes a lot more sense. The 3" piece of visco gives you 6-8 seconds to get safely away, then the shell fires. It gives you more control over ignition of shells. If I am firing a show and I want to fire a certain shell at a certain time, 90 seconds won't cut it. I need the shell to fire within seconds. Another reason, and to me the most important one, is safety. If you were just shooting 1 shell for the night, visco would be fine for the whole fuse.. (although it would still be a long wait for the fuse to burn). You could stand there, wait for the fuse to burn, and the shell to fire. Easy and safe. However, if you are shooting a show, you are firing many shells with 6-10 seconds between shells. In order to make that work with all visco, there would be multiple shells lit at the same time, as the visco was burning down. You could quickly forget which shells had fired, and which ones were still in the tubes with visco burning, and it could get dangerous. Ideally, when you light a shell, you want it to fire a couple seconds after you light it, that way you can know if there is a possible hangfire, misfire, etc. Hopefully that makes sense.
Seymour Posted April 1, 2016 Posted April 1, 2016 Also, often the Visco is not used and an electric igniter is used. Sure this could be put straight in the lift, but since Ematches are more sensitive than the pyro in shells, it is safest to have quick match coming all the way out of the mortar so an match can be put in the QM without placing your body parts over the mortar.
schroedinger Posted April 1, 2016 Posted April 1, 2016 One thing to mark down is that there is also 10 cm/s Visco, witch can be used as replacement for qm ( like on festival balls). But then it doesn't allow for timed ematching.
Zumber Posted April 1, 2016 Posted April 1, 2016 Cheap than visco...once bare end finishes it burns pretty fast. 1
lloyd Posted April 1, 2016 Posted April 1, 2016 Well, if you're doing pyromusicals fired by computer, even the length of a QM leader is too variable to be accepted. In those situations, some practicioners cut the QM to only an inch-or-so out of the lift bag, and apply the match there, tightly tying the juncture shut, so pressure will develop more-or-less instantly. The more fastidious operators remove the QM entirely, and match "directly" into the lift. Because US law permits only a small handful of companies (who are part of a 'special group') to transport shells so-matched, it must be done "in the field", as it were. On really large shows, we'd send a two or three person crew ahead by a couple of days to begin matching. When the rest of the crew arrived, the matchers had a head-start, plus at least two more days before shells were needed, since the first two or three days (minimum) on such a show is racking. We did a few (still do two, annually) that required six or seven days of racking before the first shell was 'dropped'. LLoyd
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