warthog Posted March 6, 2012 Posted March 6, 2012 The comets I am now making are 2"-4" for reference. If I understand things correctly, once pressed, they are wrapped with kraft and primed on just the open end. Lift is put into the tube directly and bottom fused. I will use my press to make these, what sort of pressure and dwell? How does one make a hollow comet? Do you make a regular comet then drill a hole in it? Does it take a different type of pump, like a cavity pump that goes all the way through rather than just make a little divot? Do you still wrap a hollow comet with Kraft paper? As I get into larger comets, I wanted to know how this is done. Since I realize this is one way to make them burn faster other than just making them shorter (I would think that would work too). I know this is a basic line of questioning so forgive my asking, I am still learning things. I get basic ideas from the books I have so what I ask of from you is the experienced view of what works. Thank You!
dagabu Posted March 6, 2012 Posted March 6, 2012 If you are just shooting these form a mortar, you don't have to wrap them but you will need to use a piston most of the time so they don't break up on lift. Comets inside of a shell are pasted and primed, single comets are left bare and are primed all over. When getting into slow comps or very large comets, a doughnut pump is needed to make the hole but even in 4" comets, this is seldom needed. Yes, a divot will help speed up the burn time so I recommend that you fire one and time the burn time and then modify the comet or lessen the comp to shorten the burn time or add comp to add to the burn time. -dag
warthog Posted March 6, 2012 Author Posted March 6, 2012 (edited) These are just plain. out of the mortar alone, comets. That is why I am sort of confused by them. Never tried this before except with little ones (if those are considered comets) like 1/2"-1.5" out of the tube before. Edited March 8, 2012 by warthog
dagabu Posted March 6, 2012 Posted March 6, 2012 These are just plain. out of the mortar alone, comets. That is why I am sort of confused by them. Never tried this before except with little ones (if those are considered comets) like 1/2"-1.5" out of the tube before. Good point, I am not sure where they stop being pumped stars and become comets. -dag
Givat Posted March 6, 2012 Posted March 6, 2012 I started playing with small comets an got into a problem myself.after some testings I found out my green comp burn in a rate of 0.57 sec/m"m. so if I make even small comet (1") it will burn for 7 seconds if lighted all around. I looked in hear and in passfire and found people use to make a hole in the comets only in 2" and bigger.So how do you deal with this problem in the small comets? I'm guessing my green comp is not so different in burn rate than other. (its BaNitrate + MgAl) BTW worthdog, In this 1" conets I started to drill a 12 m"m hole to make sure they don't burn to the ground. but I think this is not common.
busspuppy Posted March 6, 2012 Posted March 6, 2012 A comet can be as small as 1/2" or as large as 10" if you wanted the size doesn't matter. As well as a star can be 4". The size doesn't not make it a comet or a star. If you fire a 1/2" "star" by itself it is considered a comet. If you fire a bunch of "comets" in a shell is is considered a star.
californiapyro Posted March 7, 2012 Posted March 7, 2012 here is a 2.5" comet that I shot, the base comp is c6, and it almost burned to the ground http://www.youtube.com/watch?v=3IF9jpq1bbU now this is 70/30 c6/BP. the burn rate difference is about half. if you're making streamer comets then this method would work well I think http://www.youtube.com/watch?v=hhOQQMqSJv4
Mumbles Posted March 7, 2012 Posted March 7, 2012 You also don't need to make comets as tall as they are wide. It's not uncommon to just vary the height of a comet until it burns out when you want it to, especially in larger sizes. A guy I build with on occasion shoots 2.5" OD comets that are sometimes 1"-1.5" tall. You may see the term hockey puck or pancake comets floating around from time to time in reference to things like things
warthog Posted March 7, 2012 Author Posted March 7, 2012 (edited) Thanks everyone! Busspuppy, that was sort of what I thought the difference was but then I hear people say that a shell has this and that effect with X type comets and the question returns... I guess they are comets when you say they are and stars likewise. I guess what I nee to do is start lobbing these things and see what happens. I really like the way certain comps look all alone, streaming across the sky. They look sort of like meteors (unless they burn too long then they look like meteorites LOL). Edited March 8, 2012 by warthog
MikeB Posted March 7, 2012 Posted March 7, 2012 I really don't know if I want to get into this discussion, a lot has been answered yet much has not. Most consider a star as a component of a shell while comets are typically stand alone effects. Yet in larger sizes they are also used in shells. At what point does it become a comet? That is open to interpretation. There are as many ways of making them as there are builders. Using the same formula everyone will have different results depending on the purity and particle size of the chemicals, how they were mixed, and how they were made. It was asked whether they should be wrapped or bare, if a core should be incorporated or not. That depends on the effect you want and how your device performs. Wrapping a comet will add to its strength but slow the burn time. You can paste a band around the periphery or cover an end as in a crosette. Doing so will slow it down significantly. A special pump can be used to create a core of varying sizes and depths or they can be drilled. All will have different results. I don't think there is any one answer as to what is best. It depends on what you want to produce.
warthog Posted March 8, 2012 Author Posted March 8, 2012 (edited) Thanks Mike. I appreciate your insight and I hope I get it more often. Here is what I have decided to go with, at least to start. I will be ordering, as money allows, combo pumps & extraction sleeves for the following sizes: 1.75", 2.5" & 3.5" which will give me the 2", 3" and 4" comets I want to start experimenting with now. Combo pumps will have the following "tips", square hole crossette, regular type cavity and a full face so I can make a basic comet. I also will mess around with cavities and making them shorter etc. If I find I want to make hollow comets, I will take a piece of copper tube and, while the comp is still moist and in the pump, press the tube through the middle to make the hole. Once the hole is there, I will press the hollow comet out into the extraction sleeve and allow it to dry as usual. Of all the methods I have been sent or have been posted here and on Passfire (I posted this both places so I could get the broadest base of answers), this seems to be the easiest and best way to handle things for me. Remember, I said for me here, YMMV. Now on to launching. I plan on trying them bare first. Should they fall apart, I will add a piston or maybe just a disk to the bottom of the comets to help them resist the lift hit. If the disk/piston isn't enough, then I will paper them. And finally if this doesn't work I will try to add some sort of fibers to the comp while it is moist to help it with more physical strength by inner reinforcement. The downside of this is the fiber will also be burnt and may have an adverse effect on the performance of the comet. That is why it is the last resort. Crossette comets will be made the way crossettes are usually made, except I really never have good luck with the fins, the round shots I haven't tried and they don't look, from a physics standpoint, to be a good idea either. After looking into the "Olde" ways, I find that square holes are the way it was done before the fins so I will give those a try. Now all it will take is some time to do some of this stuff. Edited March 8, 2012 by warthog
dagabu Posted March 8, 2012 Posted March 8, 2012 If I find I want to make hollow comets, I will take a piece of coper tube and, while the comp is still moist and in the pump, press the tube through the middle to make the hole. Once the hole is there, I will press the hollow comet out into the extraction sleeve and allow it to dry as usual. After the comet is pumped? -dag
warthog Posted March 8, 2012 Author Posted March 8, 2012 Once it is pressed and while it is still in the pump, remove the piston part of the pump and place the copper tube centered on the pressed, still damp, comet then using the press again, push the tube through the comp. Once this is done, press the comet out of the sleeve with the pump's piston into the extraction sleeve. Set this aside to dry as usual.This was how it was described to me by Ben when I asked him how to make hollow comets. Seems like a good way too, at least until I try it and then we will see if it works in prcticve. He says he does it this way so it must work for him at least. I will se later on, if I do need to make them at all, if I can make it work for me too. If not, then I try something else.
dagabu Posted March 8, 2012 Posted March 8, 2012 Dang, never thought of doing it that way before. -dag
MikeB Posted March 8, 2012 Posted March 8, 2012 Once it is pressed and while it is still in the pump, remove the piston part of the pump and place the copper tube centered on the pressed, still damp, comet then using the press again, push the tube through the comp. This was how it was described to me by Ben when I asked him how to make hollow comets. I will bet you get a crumbled mess. But then I don't bet because I always lose. There is not enough water in the comp to make it plastic. Once it is pressed they can be quite dense and hard. Trying to force a tube through it just does not sit right somehow. Then you have to extract the tube without damaging the comet, another big if. Drilling them out is no big deal. Personally I prefer a base with a spindle, sort of like a cored rocket.
warthog Posted March 8, 2012 Author Posted March 8, 2012 (edited) How does that work Mike? I asked about that too but the way it was described on Passfire wasn't clear to me. Do you just use a spindle along with a pump that has a pump with a hollow in it to accept the spindle?Can I afford to have these made? I asked Ben about doing them this way too but he then replied with the copper tube method. The tube is sharpened and the comet placed on a hard surface. Maybe I should let it stay in the collar with the tube in it until it dries? Then press it out of the collar and slowly remove the copper tube? Heck, I don't really know who to do it until I try. In fact I am not sure I will want to do it until I launch some. I think they only time I will want a hollow comet at all is if I can't find a way to keep the burning comet from coming back down in that state some other way. I am really open to all solutions here. Edited March 8, 2012 by warthog
dagabu Posted March 8, 2012 Posted March 8, 2012 I made a BP puck with 10% water just now (real quick like) and tried to press a hole in it when still moist. Even while still inside the sleeve, the comet cracked all the way to the edge of the sleeve but a spade drill made quick work of making a hole. I think I would make a spindle like Mike says, it sure sounds simple and I bet you could make an actual doughnut shape with curved middle and ends as well. -dag
warthog Posted March 8, 2012 Author Posted March 8, 2012 (edited) I can't make dookie. I suppose I will try things until one works and this is still only if I wind up with a need to do so. I will make comets of varying lengths at first and see how they fly and how they burn keeping notes on weights so I can reproduce them. If I am not able to find something for a comp I want to use that will fly right and burn fast/slow enough for it to look right, then and only then will I start looking for ways to go hollow. I suppose I will see what happens when I get a chance to make it start happening. Edited March 8, 2012 by warthog
MikeB Posted March 8, 2012 Posted March 8, 2012 You can make a base and spindle out of wood. Even without having a lathe you can chuck it up in a drill if you are creative. Or use a large knitting needle as a spindle. All sorts of ways to skin the cat. Before I got a metal lathe I made all sorts of functional tooling from whatever pipes and dowels I could lay my hands on. One of the advantages of a center hole in a comet is that the burn speed is increased, this may be considered a disadvantage by some, but you will get a much more impressive effect also.
Mumbles Posted March 8, 2012 Posted March 8, 2012 In the archives on Passfire under comets there is an article entitled 4" Matrix Comets and an article under Tools entitled 4" Comet Pump. These will give you one idea how to make the cored comet tooling. It doesn't need to be as advanced, but it will hopefully get the gears turning. One nice benefit of cored comets is that they get bushier as they burn out instead of fading away.
warthog Posted March 8, 2012 Author Posted March 8, 2012 (edited) Thanks Mike and Mumbles. I can make things on a wood lathe, at least I can try. I am still learning the ropes with it but I am starting to get the hang of the thing. I will check out the archives, I missed this the first time through when I went looking which doesn't surprise me. A hollow comet appeals to me because of what you are saying Mike. I would think that it would allow so much of the comet to be involved with the fire that it wold make, say a glitter type comet really glittery and super nice to see. Edited March 8, 2012 by warthog
dagabu Posted March 8, 2012 Posted March 8, 2012 Thanks Mike and Mumbles. I can make things on a wood lathe, at least I can try. I am still learning the ropes with it but I am starting to get the hang of the thing. I will check out the archives, I missed this the first time through when I went looking which doesn't surprise me. A hollow comet appeals to me because of what you are saying Mike. I would think that it would allow so much of the comet to be involved with the fire that it wold make, say a glitter type comet really glittery and super nice to see. And like Mum said, it will not peter out into a thin line like lots of smaller comets will do. It stays really bushy all the way through the burn. -dag
warthog Posted March 8, 2012 Author Posted March 8, 2012 One nice benefit of cored comets is that they get bushier as they burn out instead of fading away. IT'S BETTER TO BURN OUT THAN FADE AWAY! WOO WOO!
pyrogeorge Posted March 11, 2012 Posted March 11, 2012 I use my press to make comets.Also,i made a pump for making 2.5" comets. http://img11.imageshack.us/img11/5248/pressmv.jpghttp://img72.imageshack.us/img72/6250/cometpump25inch.jpghttp://img807.imageshack.us/img807/3603/comets.jpghttp://img542.imageshack.us/img542/8250/matrixcomet.jpg
pyrogeorge Posted March 11, 2012 Posted March 11, 2012 (edited) More videos in my channel Edited March 11, 2012 by pyrogeorge
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