Ventsi Posted July 23, 2009 Share Posted July 23, 2009 That depends on the comp you are using. I usually use a few 1/2" TT stars.For glitters , the same.Silver streamers, one fat, plumpy 3/4 comet on top.Pretty much unless its a fast burning comp 1-3 1/2'' stars on top wil make a nice tail that won't show up when your shell breaks. What comp are you using? Link to comment Share on other sites More sharing options...
KruseMissile Posted July 23, 2009 Share Posted July 23, 2009 Im not using any particular comp yet but i was thinking TT and D1. i want to get a comet pump so i was trying to find out a size i should use. Link to comment Share on other sites More sharing options...
Seymour Posted July 23, 2009 Share Posted July 23, 2009 For such small comets I see no need for a comet pump. Instead of splashing out on a (beautiful and shiny) comet pump, I suggest cutting off a bit of PVC pipe and topping a broom stick. While we are on the comet topic, I'm curious to see where people draw the line between a star and a comet. This is of course completely subject to ones opinions - there is no set boundary. I personally call a 1" chunk of composition a star, and a 2" chunk a comet. I guess a one and a half inch comet would be in a candle, while a one and a half inch star would be in a sixteen inch shell. So use plays a big part. What is your opinion? Link to comment Share on other sites More sharing options...
Miech Posted July 23, 2009 Share Posted July 23, 2009 I think its the usage which determines the name as well. Size probably matters as well, I've never heard of a 1/4" comet. Link to comment Share on other sites More sharing options...
KruseMissile Posted July 23, 2009 Share Posted July 23, 2009 I was thinking of like a 1.5" comet... i remember seeing someone who had a 2" ball shell and the comet was the size of the shell. I'll see if i have a piece of PVC and a dowel or piece of wood that will fit. thanks Link to comment Share on other sites More sharing options...
Mumbles Posted July 23, 2009 Share Posted July 23, 2009 Thats probably a bit large. A 2" ball shell is normally only 1 5/8" to 1 3/4" OD. I'd go no bigger than about 1/2 to 2/3 the nominal OD. 1 to 1.25" in this case. Otherwise the required curvature on the comet gets to be too great to get good compression in the corners. The same problem exists when pressing up Delaval nozzles. The 60 degree outer taper often doesn't compress very well at all. There are two ways to attach large comets to shells. #1 You press a curved recess into one side that matches the curvature of the shell.#2 You use a standoff ring of thick cardboard tube to set a flat bottomed comet on. Pasted paper is used to adhere it in both cases, sometime hot glue. Link to comment Share on other sites More sharing options...
KruseMissile Posted July 24, 2009 Share Posted July 24, 2009 ahh that makes sense... thanks for the help : ) Link to comment Share on other sites More sharing options...
Mumbles Posted July 24, 2009 Share Posted July 24, 2009 Luckily 1" and 1.25" are both common sizes of PVC and wooden dowels at hardware stores. Link to comment Share on other sites More sharing options...
pyrogeorge Posted July 31, 2009 Share Posted July 31, 2009 Some pressed comets.C6+8%Ti sponge and some Matrix comets with Lancaster red stars. http://img76.imageshack.us/img76/3603/comets.jpg http://img398.imageshack.us/img398/8250/matrixcomet.jpg Link to comment Share on other sites More sharing options...
TheSidewinder Posted July 31, 2009 Share Posted July 31, 2009 Those look good. Hope you can post some pics/video of them in use! Link to comment Share on other sites More sharing options...
Weasel Posted July 31, 2009 Share Posted July 31, 2009 Those do look very nice. And I can see a rocket in the background . Link to comment Share on other sites More sharing options...
pyrogeorge Posted July 31, 2009 Share Posted July 31, 2009 Those look good. Hope you can post some pics/video of them in use!Yes sure But first i must make a rack. Those do look very nice. And I can see a rocket in the background .Yes my rocket,but i made the nozzle too big and did't take off Link to comment Share on other sites More sharing options...
lodcomm Posted July 31, 2009 Share Posted July 31, 2009 There are two ways to attach large comets to shells. #1 You press a curved recess into one side that matches the curvature of the shell.#2 You use a standoff ring of thick cardboard tube to set a flat bottomed comet on. Pasted paper is used to adhere it in both cases, sometime hot glue. It appears that the common practice is to attach the comet to the top of the shell. I have a couple questions. 1) Assuming the application of an adequate prime, is the detonation of the lift charge adequate to ensure ignition of the comet reliably? if not, is it advisable to run a match leader to the comet? 2) Attaching using hot glue - if you have done this - Have you noticed any decomposition of the hardened glue (due to the heat of the burning comet) and have the comet detach? Thanks Link to comment Share on other sites More sharing options...
Seymour Posted July 31, 2009 Share Posted July 31, 2009 If the shell dos not fit too tightly in the mortar, ignition via the lift charge (which does not detonate by the way, it just burns - "deflagrates" ), then ignition of the comet should be reliable. This is how it i done commercially. I however slit the quickmatch near the comet just for peace of mind. With canister shells there is often a 'cushion' of cardboard or paper between the lift and the shell. If that is there, ignition of the comet without using the leader to do it is much less likely. It depends on the shell. If the comet is attached well with glue, this will not happen. Comets on shells are often pasted around the sides so they burn from one end to the other. In this situation the glue will only be exposed to the burning when the comet burns out. No problem. If the comet is not pasted on the sides, I suggest inhibiting part of the way up using hot glue, as this will stop the flame front getting between the comet and shell, which is the most likely way it will burn off. Often comets are not properly put on, and I have seen more than a few fall off. Pyrogeorge, what was the matrix composition for your lancaster red matrix comets? C6 again? Link to comment Share on other sites More sharing options...
Mumbles Posted July 31, 2009 Share Posted July 31, 2009 Unless the sides are inhibited from burning, I've had numerous comets melt the glue and fall off. If only burning from the end, by the time it heats the glue up enough to fall off, it's nearly burned out anyway. Even a few turns of masking tape (I prefer gummed tape) is enough. I wrap up the sides, prime the comet with NC and granular BP, and hot glue them on. A "shoulder" of glue around the comet keeps it on in all of my experiences. A side note. I've had comets melt the casing of plastic shells before. I found a full hemi, and it was significantly dented inward at the site of comet attachment. I haven't had a burn through though. If I'm worried about ignition I tape a few strands of blackmatch over the surface of the comet. Combined with the prime, I've never had a rising tail blow blind. Link to comment Share on other sites More sharing options...
lodcomm Posted July 31, 2009 Share Posted July 31, 2009 Thanks Both, Most of my shells have been of the canister type.. I utilize heavy kraft paper as a bag taped or pasted around the circumference to hold the lift charge, my (perhaps erroneous!) assumption being, that when the lift charge deflagrates (tnx Seymore) and blows the bottom of the kraft "bag", the remaining kraft paper edge under the tape will expand and help seal against the side of the mortar tube. ( I have noticed in my unscientific testing, that less lift charge is needed for a similar sized shell than if I were to bottom charge the mortar!). With this in mind I was fearful that there may not be enough hot gasses bypassing the shell to ignite the comet reliably. Perhaps my best bet is to simply test it out! thanks again -t Link to comment Share on other sites More sharing options...
Seymour Posted August 1, 2009 Share Posted August 1, 2009 You are not the only one who employs that technique of using paper to compress and "seal" the shell in. The Maltese do this as their normal lifting technique, and they are able to use much less lift than normal. Additionally they spike a lift charge, much like a canister shell, which allows them to use much lower quality powder to great effect due to the confinement. Back on topic, if you use the paper to seal the lift gasses below the shell, I strongly sggest you at the least split the QM beside the comet and timefuse, if not fully connecting it with BM. Link to comment Share on other sites More sharing options...
lodcomm Posted August 1, 2009 Share Posted August 1, 2009 Back on topic, if you use the paper to seal the lift gasses below the shell, I strongly sggest you at the least split the QM beside the comet and timefuse, if not fully connecting it with BM. Yep, I plan to do exactly that, I will "cast" some match right into the comet prime as Mumbles described, and tuck it right into the slit/split QM.. thanks again, my mind is at ease.. Link to comment Share on other sites More sharing options...
TrueBluePyro Posted August 1, 2009 Share Posted August 1, 2009 When I made my first few shells, I just glued a few "stars" onto, now for a 3" ball shell I use a 20mm "comet", that seems to be a good size for me. Link to comment Share on other sites More sharing options...
pyrogeorge Posted August 13, 2009 Share Posted August 13, 2009 Some comets ready for shoot..Also you can see it in my album. http://www.apcforum.net/forums/uploads/1250150951/tn_gallery_1952_31_29184.jpg http://www.apcforum.net/forums/uploads/1250150951/tn_gallery_1952_31_78398.jpg http://www.apcforum.net/forums/uploads/1250150951/tn_gallery_1952_31_91881.jpg http://www.apcforum.net/forums/uploads/1250150951/tn_gallery_1952_31_6796.jpg Link to comment Share on other sites More sharing options...
TrueBluePyro Posted August 13, 2009 Share Posted August 13, 2009 looking good george, what are they? about 4" (3.5"?) I guess. what comp? charcoal? you gunna video them? so many questions, lol Link to comment Share on other sites More sharing options...
pyrogeorge Posted August 13, 2009 Share Posted August 13, 2009 C6 + 7% Ti and Matrix comets with lancaster red stars.No,it is 2,5".I will upload the video when i shoot it,but not now because it is dangerous in summer time. Link to comment Share on other sites More sharing options...
TrueBluePyro Posted August 13, 2009 Share Posted August 13, 2009 oh, well that was a bad guess by my end, lol, matrix comets are the best, I want to make a colour comet and put the same colour micro stars and make it appear that the colour comet is leaveing a colour tail. Link to comment Share on other sites More sharing options...
pianomistro Posted August 23, 2009 Share Posted August 23, 2009 oh, well that was a bad guess by my end, lol, matrix comets are the best, I want to make a colour comet and put the same colour micro stars and make it appear that the colour comet is leaveing a colour tail. That would be quite difficult to accomplish. First thing is that the comet would have to be huge to accommodate the microstars. Getting the stars to fall away from the comet and not just burn in place would be another problem. Good luck though. Link to comment Share on other sites More sharing options...
TrueBluePyro Posted August 23, 2009 Share Posted August 23, 2009 maybe might try a 3" comet (2.5") it could work. Link to comment Share on other sites More sharing options...
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