dynomike1 Posted July 22, 2017 Posted July 22, 2017 I just recently noticed this on a SOS i shot, my inserts broke a second early. Now the question is after the powder lights, how long does it take for the shell to actually break? It's either that or i got some bad time fuse. The reason i asked is i have never noticed this before.
Mumbles Posted July 23, 2017 Posted July 23, 2017 Well, the first thing to do would be to test your time fuse. There is some on the market that burns at around 3 sec/in, and some that burns closer to 2 sec/in or so. If you recently switched suppliers or started a new roll, this might be the cause. That said, the time between when the fuse or spolette lights the burst and when the shell opens is low, but not always insignificant. The larger the shell, the more burst has to light and the more pressure the casing needs to burst and thus the longer it takes. I've been told that you need to take this into account as you progress to larger and larger shells. Stars burn faster under pressure as well. I've been told for something like a 16" shell the amount of star/prime consumed inside the shell is actually pretty noticeable. Some people basically put a sacraficial layer of something over the top. Not only does the amount of star consumed inside the shell need to be taken into account, you also need to take into account the comp that is burning while the stars are traveling at a high rate of speed in order to not blow out more delicate stars like colors.
dynomike1 Posted July 23, 2017 Author Posted July 23, 2017 Where i came up with this is i shot a 8" SOS and my 2sec. inserts broke @ 1sec. Seems like all the time fuse that i have bought in the last 2 yrs. has been 2sec. Pyrocreations asked me to do a review on some 3sec. time fuse, and i told them that it timed out @ 2sec. So i guess when i build my 10" SOS this year i guess it wouldn't hurt to add another sec. from the 8 to10".
Mumbles Posted July 24, 2017 Posted July 24, 2017 If you have enough, I'd burn a 3 or 4" piece. It should give you a good idea of the timing. I doubt it's a factor, but it would also allow you to see if there is any burn through which would also cause quick timings. That'd probably be more random from insert to insert though.
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