Pyrogeezer Posted February 3 Posted February 3 (edited) A few years ago one of our technicians at the shop came up with this simple, reliable way to make a small shell time fuse for (C) class materials. Get some ¼” Id bottle rocket tubes and cut one to the required length for the item you are making. The picture is for a 1.5” tube item, (color shell). It is not a finished fuse but shows how nicely the Safety fuse fits snugly into the rocket tube. The opposite end hasn’t been trimmed of yet. The tube is normally ¾” long and the American Visco Safety Fuse is 1” long, leaving about 1/8” of the fuse protruding out of each end of the cardboard tube. Insert the 3 pieces of Visco just slightly into the tube on one end and then cover all 3 of the safety fuses with plenty of full strength Sodium Silicate solution, PVC cement, Gorilla glue etc. so it fills in all the small gaps between the fuses and the inner tube wall. Let it dry completely and then insert the finished fuse into your shell. Prime both ends of the fuse with an appropriate powder, wetted with some Nitrocellulose lacquer. Let it dry well and it’s ready to go. Make sure that no glue has gotten on the ends of the Safety fuse to blind it. Edited February 3 by Pyrogeezer
Zumber Posted February 4 Posted February 4 The same way we prepare mini sky shot tubes we use two visco fuse and we insert it in same tube which later goes and expoldes in sky. We ram clay and visco together at one side of tube (half inch ID) Then we fill remaining tube with microstars and and nitrate flash about 5 grams flash. Other end is just filled with clay. This way sky shot finishes. But this method is only used just for half inch shot for shells we directly use spolette. Can numbers of visco affects burn rate? I mean if we use 4 to 5 visco than two visco fuse is there any difference in burn rate and timing?
Pyrogeezer Posted February 4 Author Posted February 4 Hi Zumber: Thanks for the information on how you make your 1/2" shots. We have tested more than 3 pieces of Visco and it doesn't appear to affect the burn time of the fuse but I don't see where more than 3 pieces is really required. If you have good, reliable Visco and they are all from the same batch of fuse, the flame front will only progress as fast as the first piece of Visco that is ignited. If primed well, and all air spaces are filled within the paper tube and fuse so no fire can advance within the tube there should be very little difference in the time of lift to the time of burst from shell to shell. It is very important that the tube be totally solid on the inside as you well know.
Zumber Posted February 4 Posted February 4 Thank you @Pyrogeezer..!! Is it reliable for bigger shells say 5 or 6 inch.? Another thing is sodium silicate takes too long to dry. We must switch anothe cool glue or dry clay powder as we do for multishots. Thank you.
Pyrogeezer Posted February 4 Author Posted February 4 Thank you for your recommendations Zumber. Yes, sodium silicate does take long to dry. We don't really use it much any more, but when we did, we would thicken it with clay to a paste and then use it that way. When finished, we would put many of the fuses on drying screens in our drying room for a few days, this worked well. Now we use a slow setting 2 part epoxy or like you mentioned , clay. The epoxy is more expensive but a little bit goes a long way. I would not recommend using this method on larger shells. We have never tried it, but after putting all the work into building a beautiful shell, you want a proven system to ignite it. I go with 1/4" time fuse in 3" single break and maroon shells, and spolette fuse in the larger sizes shells. Thank You
Zumber Posted February 5 Posted February 5 @Pyrogeezer. Thank you for discussing on this topic this can be very useful information for me and other members. 1
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