34 replies to this topic

[Stuart]

Couldnt find a topic on comets so I thought I would start one.

How are they made? I would like to try making some because they look good and I dont think they would be to difficult to make.


Stuart

Edited by Stuart, 21 October 2003 - 06:31 AM.

[Matt]

Big star pump... The 1 inch comets on my site arent even 1 inch, they ar 20mm so you cant even really call em' comets. Anyways im guessing you would start that size? if so I did have a star pump but one day i chopped the end off a plastic hobby suringe (sp?) and i make a batch of star mix (generaly chrysanthemum 6 for my comets) and pull the plunger out a bit then pack it with mix and hand press it then pop it out. does the job nicely.

-Matt

[BigG]

1 inch are small - but not a bad size to start with. For my 4 inch Comets (I want my tools too big to bring into the uk, and not very useful when you do not do pyro in the uk...) I had to use 5 ton press.

To do a proper Comet you will need a good press. 2 ton press might do for 1 inch, but generally speaking, you will need 5+. Get yourself a press first - best hydrulic, but a large Arbor press can be useful as well.

BigG

[Stuart]

Ok, thanks. Might try Matts little comets first until I have be 'broken in' and then move onto the big boys toys

Stuart

[Pazza]

<brag mode>
well i'll be ok, since i have a *20 ton* press, MUHUHAHAHAHA, i fart on your ludicrously small little presses!
</brag mode>

yeah ... anyway ...

[phildunford]

I'm sure all these mega-presses are great stuff, but so as not to discorage beginners I can tell you that I've made some great comets using a star pump made from 22mm plumbling tube and a wooden plunger.

I fired these from 28 mm plumbing tube using 10 grams of coarse grain powder and got a pretty good effect...

[paul]

A few days ago, I made my first about 2" by 2" "tigertail"comet.

It used the following mixture:

55 KNO3
25 mixed charcoal (charcoal directly from the blender)
15 Sulfur
and 5 Dextrin

I first had doubts if such a big device will dry throughly at all, but it does! The composition was manufactured the CIA method, I added much alcohol in the end. After squeezing it out I hammered it into the former-case, which I removed after one day. It is rock hard by now and loses only about 1 gram moisture per day anymore.

From 190g in the beginning to 150,9g atm.

In rec,pyrotechnics they all recommend to put a feld wad under it to stop it fragmenting. Has anyone experience with this "large" comets?! How much lift should I use. In rec.pyrotechnics most people seem to use the 1/6th of comet weight rule of thumb.

with best regards,

paul

[italteen3]

I have only done half that size and have not had that problem. I believe if you press right and with proper wetting you should be fine. When I first started making them I under wet them having no hands on experience with it only what I have read. So what some people Ive talked to and articles I have read say to put aside 10% of the comet composition just incase.

1/6th of the comet weight for lift? Sounds like a bit much. I cant recall the thread but someones nice comet was fragmented into a mine. Not sure if it was 1" or 2" but 1/6th weight may be a bit to much. I have not had much experience with larger comets yet.

How hard has your comet set? When mine have rolled off my bench onto cement I have had no breaks or cracks when fully dried.

[LadyKate]

1/6th of the comet weight for lift? Sounds like a bit much.

Sounds heavy to me, too. (Complete guess coming up): I think this and perhaps some other 'rules of thumb' are weird offspring of the Pyrotechnica tables - which are shown on Passfire, and in the back of several AFN books. Those tables are based on 2FA and can result in overloads - and they worry me a bit.

When we talk about commercial equivalent BP, we almost always are comparing our homemade stuff to 2FG. Many hobbyists have never seen 2FA. This could get hobby pyros into a bit of trouble. For instance, I showed a hybrid mortar shell/comet on another post that weighed 48 grams without lift. I used 4 grams of lift (commercial 2FG equivalent). See it take off (again) here: http://www.wichitabu...orks/comet3.wmv As you can see, it had a good strong take off. The shell was the normal loosely fitting shell for a 1.4g mortar.

Using the 1/6th idea, it would take 8 grams of lift for that shot - which would really be an overload that might damage the tube. An even larger overload would be to put 8 grams in a tight fitting mortar - I think that would result in a lot of cardboard shrapnel.

Edited by LadyKate, 03 October 2005 - 01:55 PM.

[BrightStar]

Whenever I cook dinner for friends, they usually have to survive a pyrotechnic test or two with their coffee... This week's attempt was a simple comet:



Video here: (3gp format - Quicktime):

Chrysanthemum 6 comet test

It was just a 1" * 1.5" chrys6 pumped comet, 16g mass, with 1.6g riced BP lift, with a sticky match leader and placed in a 1.25" PVC mortar (yes... I know the risks ... long fuse...)

It seemed OK. The next step is to figure out how to bond a Veline comp header to the comet as I'm planning a rainbow cake of these things...

[Pretty green flames]

It seemed OK. The next step is to figure out how to bond a Veline comp header to the comet as I'm planning a rainbow cake of these things...

Press one composition on top of the other then paste the comet so not all of it ignites from the lift. The lift will ignite only the first layer of comp this will then ignite the next and so on.
Is this what you were looking for?

[JamesH]

If you want a coloured comet with a charcoal tail, you could try a cavity comet. Ideally, you will need a comet pump that will form a cylindrical cavity in one end of the comet. The coloured comp is pressed into this cavity once the main comet body has dried. The finished comet can be wrapped if desired, but only on its circumference, leaving the ends exposed.
You would need to experiment with these a bit to get both comps burning out simultaneously. Obviously, both comps would have to be compatible.

[karlfoxman]

I have made some 1" Silver tailed comets using the formula:

Potassium perchlorate 58
Bright flake aluminium 42
Redgum 8

They are drying at the moment, I will make them in to single shot candles and do a comet chase left to right.

Here is a picture, I have primed them with slurry at one end (Not in the picture)

[BrightStar]

Karl - should have known you would be working on something Look forward to seeing them fired. I'm paying over ?60/kg for bright flake aluminium in the UK (there's an opportunity for Inoxia here... hint hint...).

I hope to create a Chrys 6 comet with a bright Veline header for use in a rainbow cake. Both comps should ignite at at once and burn out together - I might add a few dragons eggs to finish. So far the suggestions on how to do this (thanks guys) have been to paste 2 layers together with an outer Kraft wrapper, bond a 3mm * 1" disc of Veline to the 1" Chrys 6 comet with NC laquer, and to embed a smaller veline star (say 10mm * 10mm pumped) into the top of the comet. I'm aware that my Chrys6 burns at about 15mm/s , whereas the Veline header will burn at approx 1.5mm/s and the whole comet should only burn for 3s or so.

I guess I will just have to do a few experiments now, but the rainbow cake will be something to see when it works

[karlfoxman]

60 Quid, ouch!!!! For making cavity comets I use my Wolter cavity pump as seen in the picture. I have made Glitter w/ blue comets using my larger 1 1/4" cavity pump. They worked well when I test fired one of them. I will video the silver comets as and when I do a test fire.