Comets

[qwezxc12]

There used to be a nice comet thread on the old forum site (Old Thread) and I've seen some videos posted and some competition submittals, but I thought a dedicated thread for comet construction, compositions, and tests would be appropriate.

 

I've made a bunch of 2" comets (1.5" dia tooling) and am currently experimenting building a 2" comet fan rack, ala Passfire (only 2" instead of 1") using PVC tubing and drilled brake line for fuse tubing. I'm also planning to make larger comets...3" and 4", I hope.

 

I pretty much am sticking with 2-part resin glue for a binder, as it requires only ramming pressure, as opposed to pressing with a hydraulic jack, and a 2" comet that weighs 50-60g will cure fully overnight...near instant gratification After they cure, I use 1/2 oz. condiment cups for lift. A couple wraps of masking tape and you're done:

http://www.apcforum.net/files/Comets1.jpg

http://www.apcforum.net/files/Comets2.jpg

http://www.apcforum.net/files/Comets3.jpg

 

I tried a red composition from rec.pyrotechnics that was heavy on the perc (43%) and used 15% Strontium Carbonate for coloring, plus Saran, and MgAl and some other stuff. It looked nice enough that I made some more using Calcium & Barium Carbonates, Copper Oxide, and Cryolite for other colors. So far blue sucks...gotta keep working on it: (these are older videos)

 

Red

Orange

Yellow

Violet

 

I've also made some variations on BP + metal comets. These are nothing more than greenmix plus various grade of MgAl, Al flitters and Mg turnings. Cheap and easy, for sure and I bet they'll look kick ass in a wave from a fan rack:

 

BP + Mg turnings

BP + MgAl

BP + MgAl and Al flitters

BP + MgAl and Mg turnings

 

I'm going to try some Perc + Al "white mag" type comps, next...just a little curious about mixing up what's basically flash into a comet, though.

 

Please post your comets!

[pudidotdk]

I like those comets. I also like the cheap BP+Metals. BP+Magnesium turnings looks interesting, I might try it out since I'm looking for a bright comp. for my crossettes in a 3" (I.D) shell I'm planning. What size was the turnings?

[Pretty green flame]

Very cool comets, especially the Meal + Mg. Could you explain a bit on the use of resin glue in comet formulas. I am not familiar with anything similar that is sold where live. Is is polyester resin + hardener?

[qwezxc12]

pudidotdk,

 

The Mg is random curls, slivers and turnings. I have several lbs. because to avoid shipping restrictions, some companies here in the US ship fine Mg or MgAl powders 50/50 with coarse turnings. I would estimate the size of the slivers to be anywhere from 1mm - 5mm.

 

pgf,

 

The resin is a two part glue called Resorcinol - it's phenolic based, I believe, and is catalyzed with powdered paraformaldehyde. In the US, there are several different brands - DAP or Weldwood is one major one:

http://www.dap.com/images/products/002272.jpg

A better source is Aircraft Spruce - they have global reps in Italy, Spain and the UK, too, so international shipping shouldn't be a problem. I got the idea from a poster on rec.pyrotechnics, who wrote of commercial comet production using the resin as a binder...I figured if a professional display company used it, it probably would work on a smaller scale, too.

 

I use 8% (additional) resin thinned with 4% alcohol and 1% hardener as a starting point to a composition before I add any metal...the dry catalyst is added, the components are screened, then I add the thinned resin and screen the dampened mix again to distribute the binder. Because most of the metals are too coarse for my screens, they get added last. As you can see in some of the videos, I didn't get enough into some comets that partially fragmented during lift. The resin also acts as a fuel; I found I could cut down or eliminate redgum where it's called for fuel in the colored comets.

 

I tried Polyester resin and epoxy both...I personally never got the comps to burn properly. Besides releasing lots of nasties when it combusts, they also need acetone for thinning and cleaning...Resorcinol washes up with water before it cures.

 

BlueSquib,

 

Eastern Germany or Czech Republic, maybe?

If you have success using polyester resins, please share your experiences.

 

Some Perc / Al (wiith and without Ti) and BP with embedded color microstar comets are curing right now I'll post results as soon as they get launched.

 

Cheers.

[itwasntme]

Wow, those are amazing! The thing is, I have some coarse Mg, and I want to get some KNO3, I will defiantly try to order the KNO3 now.

[Pretty green flame]

In those mixes, BP + metal, does Green mix fair better than the milled stuff, having a longer duration burning and producing hot slag?

 

 

Thanks

[qwezxc12]

(snip)...does Green mix fair better than the milled stuff, having a longer duration burning and producing hot slag?

I think it does; actual BP meal or corning dust would, I think, burn far too fast to get the necessary hang-time for a comet. The 2" comets have a burn time of 3-4 seconds...meal would probably burn up in a second or two. I used Greenmix as a formula base because it is simple, cheap, and takes no time in preparation.

 

I'm finally home from work in Oregon and a business trip to Istanbul and Antalya, Turkey, so I'm going to try to get out and light some things. I have the 3" Comet tooling materials and several 2" comets pumped from Perc/Al and Greenmix w/colored micro-stars waiting to be shot. Maybe I can press up a 2" puck of milled BP meal and shoot it just to see how it fairs vs. Greenmix...perhaps we'll be surprised. I bet if I tape up the sides and top so that it ignites from the bottom only, it will self-propel

 

I want to try straight metal fueled comets, something like:

 

55 KNO3 or KCLO4

40 18-30 MgAl (coarse grinder run)

5 S

 

I finally got some fine mesh FeTi to make Blond Streamer and 5lbs. of coated Iron Filings...I need to make some more shells. I'm thinking along the lines of a 4" Blond Streamer Palm shell similar to this one, Yellow Palm, and a 6" D1 Glitter with colored pistil. Hopefully I'll have some more videos up soon...I haven't shot or posted anything in over a month

[qwezxc12]

Hooray! My Makeshift 3in comet tooling came in and I trimmed it up with a bandsaw at work:

http://www.apcforum.net/files/3inCometPump1.jpg

The sleeve is 2.5" SS schedule 10 pipe with an ID of around 2.63 and the rammer is 2.5" OD UHMWPE. The sleeve is 5.5" long and the rammer is 6".

 

I wasted no time in pumping up three 3in comets:

http://www.apcforum.net/files/3inComets.jpg

All weigh ~ 300g and are made from Greenmix made with a mix of airfloat and -30 mesh Charcoal:

 

1st one has 90g Mg curls

2nd one is a matrix of 80g of 3/8" Shimizu violet and blue and Luce Forte stars, plus 15g of 16-30 mesh coarse MgAl

3rd one has 40g -18-30 FeTi and 15g of 100-350 mesh MgAl and a surprise...a 15g salute pressed into it (that's why it's so much taller than the others) The one with the Mg curls is a bit taller due to the extra volume of the metal.

 

I also pressed up 16 2in Mg comets:

http://www.apcforum.net/files/2inMgComets.jpg

 

These will be for either a 6in shell or a fan rack comet salvo...or maybe I should pump up some more and do both...I hope to do a shoot in the next week or two. I'll post vids as soon as I do.

 

Mumbles, Are you still interested in the comet pump set?...I made two. PM me if you are.

[Pretty green flame]

Nice comets, although the 3" seem a little loose, especially the Mg fueled one. Are they also bound with resorcinol resin?

 

Other than that all i can say is that i'm look forward to seeing them in action

[qwezxc12]

Yes, they're bound with the same, 12% EtOH thinned resin & catalyzed with 1% paraformaldehyde. As far as how loose they are, we'll see...I pressed them with my 6-ton bottle jack press 'till it groaned...I could barely get the comets out of the sleeve afterward. My 2in Mg comets are just hand rammed and they hold together ok with no end-cap or pasting. Hopefully it'll be enough.

 

I will be preparing these like Passfire's 5" Matrix Comet tutorial: with a hot-glued chipboard end-cap, and 3-4 turns of pasted in light craft. The end-cap will be on the bottom to support against the force of the lift. I'm going to slice a section of the quickmatch and tape it to the exposed top of the comet as insurance for ignition, though the hot lift gases should do the trick.

 

I hope they work.

[jlmemt]

What is a good, preferably cheap, material to make these rammers out of?

I didn't recognize the letters, UHMWPE, posted above.

 

 

Thanks.

 

 

Jason

[qwezxc12]

Ultra High Molecular Weight Polyethylene...cheaper than brass (at least at this diameter) and far more durable than wood.

[jlmemt]

Thanks. I had never heard of it. I just did a quick search and learned a little, but didn't see where I could really get it, only a manufacturer. Do you know of a decent source for this?

 

 

Jason

[qwezxc12]

Try www.mcmaster.com/

 

or www.onlinemetals.com/

[qwezxc12]

Well, work continues to conspire against me preventing any shoots (I only have access to the site now and then), so I have been passing the time making more stuff to light...including my first 4in canister shells. Imagine that, someone who's piled high with RAP shells is actually pasting and spiking...gods forfend!

 

Anyway, here's a picture of a 2in comet: Shimizu's Silver Wave, a 50:50 mix of perc and Al. I used a blend of three grades of flitters & shards ranging from +20 up to 350mesh or so. The formula is notoriously hard to light, so I pressed a step primed comet: a layer of greenmix +10% MgAl, 1/2 & 1/2 greenmix and Silver Wave, then finally 100% Silver Wave. All were bound with 5-7% dextrin this time. I made six of these. If the first one works, I banged together a 5-shot fan rack so the rest will go up in a salvo.

http://www.apcforum.net/files/2inSilverWaveComet.jpg

[qwezxc12]

Well I shot the comets and I liked the 5-shot fan of 2in Silver Wave ones so much, I put them into the competition

Comet Competition Submittal

 

I'll post more on the 3in ones when I convert the DV.

[psyco_1322]

How do you set up a comet to be shot? As far as do you use a lift cup, hows it attached?

[qwezxc12]

How do you set up a comet to be shot?  As far as do you use a lift cup, hows it attached?

For the 2in ones, it's all in the text and pictures of my first post: Make quickmatch and attach to comet with a strip of tape, lea ving the fuse ends protruding below the comet. put the lift in a condiment cup and attach to comet with a few wraps of masking tape.

 

The 3in comets were finished differently. Due to their weight, I attached an end-disk and paste wrapped them so they wouldn't shatter while being shot:

http://www.apcforum.net/files/3incometsPasted.jpg

 

With the end-disk attached, the comets have to be top fused, just like a canister shell. The lift charge (~35g) was contained in a 2 oz. condiment cup. Lift gasses probably would ignite the comet, but for extra reliability, I slit the QM leader and taped it into a big glop of prime slurry on the top of the comet, then taped it in place:

http://www.apcforum.net/files/3inCometsFinished.jpg

 

Here are a few framegrabs from the videos:

Mg Curl Comet:

http://www.apcforum.net/files/3inMgComet.jpg

 

Salute Comet (broke on the way back down):

http://www.apcforum.net/files/3inMgAlFeTiSaluteComet.jpg

 

MgAl and Imbedded star Comet:

http://www.apcforum.net/files/3inImbeddedStarComet.jpg

 

I'll post the videos when I convert them.

[psyco_1322]

Is that quick match leader made of paper fuse? How does that fire jump down that stuff? And why not just bottom fuse the 3"? Is there really that much pressure to break your stars. I would think that the binder you use would make them very hard and immune to shattering. Can you buy that Resorcinol at walmart/ace or someplace of the like? One last question>How much clearance do your comets have with mortar? I used a lift "tube" for my shells, like consumer ones, becasue I tryed a paper bag/cup and it didnt even get the shell 20ft up. I think the tube acts as a explosion chamber and helps to shoot the shell. I figure that the paper cup just went poof and the gasses escaped around the shell.

[MisterSteve]

I'm pretty sure you have to put them in a mortar tube. I think the paper cup is just there to hold the lifting charge like on an aerial shell. But I haven't made these so IDK.

[qwezxc12]

Is that quick match leader made of paper fuse?  How does that fire jump down that stuff?

Yes. It's fast paper fuse from Skylighter...it's actually three strands of blackmatch wrapped in gampi tissue. I didn't have any blackmatch, so I used it instead. Every shell video posted by used it for the leader...so you can see it works.

 

And why not just bottom fuse the 3"?  Is there really that much pressure to break your stars.  I would think that the binder you use would make them very hard and immune to shattering.

Those comets weigh ~300g and are lifted with ~35g...given the cracks that formed in the comets while they cured, I doubt they'd survive the (fairly violent) lift. I posted a video a while ago of a 50g comet that shattered with only 5g of lift....more of a starmine than comet.

 

Can you buy that Resorcinol at walmart/ace or someplace of the like?

Try Ace or True Value

 

One last question>How much clearance do your comets have with mortar?  I used a lift "tube" for my shells, like consumer ones, becasue I tryed a paper bag/cup and it didnt even get the shell 20ft up.  I think the tube acts as a explosion chamber and helps to shoot the shell.  I figure that the paper cup just went poof and the gasses escaped around the shell.

 

The 2in mines are made with a 1.5" pump and hand rammed. The 3in mines are made with a 2.5" ID pipe and pressed in a 6-ton press. They are fired from 2" and 3" HDPE mortars. Lighting them unconfined would result in the powder popping the lift cup, not lifting the comet.

[qwezxc12]

Here are the videos of the 3in comets:

MgAl and Imbedded star Comet

 

Mg Curl Comet

 

Salute Comet

As you can see, they all burnt too long...so either less comp (~250g) and more lift (~40g maybe), or I'll need to make a set of cored tooling for the next batch. I'll probably paste them a little heavier for a snugger fit in the mortar as well.

 

Any recommendations from anyone who's done this already? Is cored the way to go on this size comet?

[pyro4life]

Why not just use more lift and a tighter fitting comet? and possibly mill the greenmix for 15-30 mins..

[psyco_1322]

I got my glue finally! It cost a bit. And im not sure how much to use. Im not to good with percentage things and thinning, it confuses me. Can you give me an ammount of resin and catalyst for some much comp? How you found any hazards with this stuff, like should i wear gloves & respirator when using it like they say? And what kind of alcohol you use to thin it?

[qwezxc12]

I got my glue finally! It cost a bit. And im not sure how much to use. Im not to good with percentage things and thinning, it confuses me. Can you give me an ammount of resin and catalyst for some much comp? How you found any hazards with this stuff, like should i wear gloves & respirator when using it like they say? And what kind of alcohol you use to thin it?

Ummm...sorry, but if you are "not to good with percentage things", you are in the wrong hobby. It's too easy to hurt yourself if you do not have a firm grasp of the math used to make compositions.

 

Anyway, the ratio I use is as follows. All amounts are by weight.

 

Make your composition as normal. Thoroughly screen in +1% dry catalyst.

 

Then wet the comp with a mix of:

+8% liquid resin glue

+4% alcohol - I use denatured methOH.

 

The alcohol is necessary as a wetting agent and to delay the setting of the glue to ~6-8 hours rather than minutes.

 

For a 300g batch, you'd screen in 3g dry catalyst, then wet with a mix of 24g resin and 12g methOH.

 

I always wear gloves, eye protection, and a respirator when I'm mixing comps...breathing aluminum dust, BaNO3, Potassium DiChromate, Red Lead, etc. is an excellant way to do yourself in.