AdmiralDonSnider Posted December 28, 2011 Share Posted December 28, 2011 Yesterday I had my first ever shell malfunction. The accused (now deceased) is a 3" shell with a 1 1/8" diameter, about 18mm long rising tail kyoku-do attached (as the right one seen below). It exploded in the mortar without any delay - flowerpot or mid-explosion, don´t know exactly. http://img515.imageshack.us/img515/7516/3asc.jpg As the only variable I´ve changed is the attached comet star I wonder if it´s possible that it caused the malfunction. I used hot melt to fasten it to the shell (as it is difficult to securely attach a flat surface to a curved surface), and then also pasted some kraft. I know that holt melt joints are basically indestructable (the cardboard tends to fail before the joint does), so could the turning shell (on lift) have ripped itself open by violently pushing the comet against the mortar wall? Strange theory - I know. Much rather it´s a simple weakness around the fuse. Maybe I did not hot melt the fuse enough this time. What do you think? (Not willing to spend my last finished NYE kyoku shell on testing...). But the issue of the shell turning on firing caught my attention. When you watch shells ascending they basically do always rotate like hell. Against this background I wonder why comets or other garnitures aren´t simply ripped off when the shell turns while still in the mortar. Or is this prevented by the lift gases, keeping the shell in minimum-drag position? Link to comment Share on other sites More sharing options...
Potassiumchlorate Posted December 28, 2011 Share Posted December 28, 2011 I think the lift gasses keep it in minimum-drag position. Otherwise the delay fuse would always hit the inside of the mortar, making the shell explode. Link to comment Share on other sites More sharing options...
Mumbles Posted December 28, 2011 Share Posted December 28, 2011 I always try to keep the comets well over the body of the shell. It's hard to tell from the image, but it looks like the comet on your shell is approaching the exterior limit of the shell body. It's viable I suppose that being so close to the edge it could have knocked into the wall, or got hung up or something, and caused some sort of violent tumbling within the mortar resulting in the premature explosion. I really don't think that the hot glue joint has enough strength to tear through the entire wall. If it did come off it may take a few layers with it, but not literally rip it apart. It could however send it around and knock into the fuse which could allow entry. You occasionally see rising comets shatter or come off from the mortar, which I always chalked up to knocking into the wall, but haven't ever really heard of a flower pot resulting from it. I guess the only thing to do is make a few more and see if it happens again, making sure to have the fuse well secured. Link to comment Share on other sites More sharing options...
nater Posted December 28, 2011 Share Posted December 28, 2011 is the mortar in tact? It could hide clues to show when the shell burst, so you know if it is flowerpot ot if it burst in mid-launch Link to comment Share on other sites More sharing options...
50AE Posted December 28, 2011 Share Posted December 28, 2011 I doubt the comet is blame. The edge would break easily if it hits the mortar's wall. But this is only my opinion. How do you glue the time fuse? How many shells have you fired without issue? Link to comment Share on other sites More sharing options...
TheArchitect23 Posted December 28, 2011 Share Posted December 28, 2011 I can not attest to the science of what could have gone wrong, however i can chime in that my first rising comets i attached to a 3'' shell also did the same thing.i came to the conclusion that i had put the comets to close to the sides of the shell and it may have gotten stuck. they were 3X 0.50'' gold glitter. i removed the comets from my other shells and they fired fine. now i only use one and try to center it towards the middle of the top of the shell. ( i do not use a string hook on top ) i vote for keeping them more towards the center of the shell. Link to comment Share on other sites More sharing options...
AdmiralDonSnider Posted December 29, 2011 Author Share Posted December 29, 2011 It's hard to tell from the image, but it looks like the comet on your shell is approaching the exterior limit of the shell body. I guess the only thing to do is make a few more and see if it happens again, making sure to have the fuse well secured. The comet is pretty much in line with the outermost point of the shell. The one on the failed shell was even a bit more on the outside. I have strenghtened the remaining shells´ fuses just to make sure. Will see how the remaining one with the comet works. Just wondering how even larger kyoku-do such as separating stars work if the shells tends to rip them off by rotation? is the mortar in tact? Yes it is. How do you glue the time fuse? How many shells have you fired without issue? I hot glue it on both sides. About 20 at least. Link to comment Share on other sites More sharing options...
pyrojig Posted December 29, 2011 Share Posted December 29, 2011 I can not attest to the science of what could have gone wrong, however i can chime in that my first rising comets i attached to a 3'' shell also did the same thing.i came to the conclusion that i had put the comets to close to the sides of the shell and it may have gotten stuck. they were 3X 0.50'' gold glitter. i removed the comets from my other shells and they fired fine. now i only use one and try to center it towards the middle of the top of the shell. ( i do not use a string hook on top ) i vote for keeping them more towards the center of the shell. Keeping the comet closer to the( center) top is a good idea for the larger comets. @ Admiral :I believe that it was just a fluke that you had a flowerpot. Try making sure that the time fuse is securely glued and sealed, then redo the same shell again. I believe the lift gasses create no friction on lift, meaning that the shell doesnt even hit the walls for the most part . Link to comment Share on other sites More sharing options...
AdmiralDonSnider Posted December 29, 2011 Author Share Posted December 29, 2011 Yes. We´ll see how the other one goes. Thanks for your advice everyone! Link to comment Share on other sites More sharing options...
AdmiralDonSnider Posted January 1, 2012 Author Share Posted January 1, 2012 Both shells seen above worked like a charm! I´m really glad they did. While I believe that the reason for the failure of the first trial was some weakness around the fuse, Mumbles could still be correct with the theory of the hung-up comet or tumbling shell. Placing the comet in a way not making its edge the outermost point of a shell is certainly a good idea. Thanks again for the help! And a happy new year everyone... Link to comment Share on other sites More sharing options...
Mortartube Posted January 1, 2012 Share Posted January 1, 2012 I would suggest that the time fuse is the most likely failure point. A tiny bubble hole in the glue could pass fire or if you lift the shell fairly hard the time fuse may have been driven into the shell by the force of the lift if the glue joint was weak. Link to comment Share on other sites More sharing options...
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