Star mines.

[TritonPyro]

I have used a small bag of BP with a load of star bits and off cuts and was pleasantly surprised in a 3 inch tube. I see some pyro's use a perforated disc on top of the lift bag and I wonder if this is a better way of doing it. I have been using wrapped Kraft paper with a length of quick match tipped with visco.

[Mumbles]

A bag method, such as you're using, gives a different result than a method with a piston. Typically a bag mine gives a lower, but wider spray of stars. A mine containing a piston of sorts tends to give a taller column of stars. Both are effective for their purposes. It's all up to personal preferences. I don't think tailed stars look as good in lower, wider sprays personally, but color can work with both.

 

Here's an example of mine of a more columnated mine:

 

 

 

And here's an example of a spray type mine

 

 

They were actually all piston type mines, but the purple one didn't have quite enough lift.

[TritonPyro]

Thanks mumbles, I really like the first one with the inserts. Would you think a piece of card, perforated over the lift? I am looking for an addition to my stars with a short crackle ( with no fallout ). Thanks for the reply.

[vegasdude]

I actually made some mines over the weekend using chipboard with holes in it for my piston and they worked very well. Normally I just drop 1/4 cup of stars on the lift and I would get the spray effect. This time with the chipboard I got nice tall mine effect.

[AdmiralDonSnider]

As with bombettes the perforated disk drastically improves the efficiency of the powder and thus the lift height. I have made 45mm mines with just 2,5 grams of 4FA lift. 30mm with 1gram.

All you need is a disk with a central hole fitting the ID of the mortar. It must not fall down without being forced/pushed down with a dowel. Another disk on top of the garnitures will not only further improve the lift, but also prevents premature ignition by neighbour mortars/fallout.

[Mumbles]

There are three main ways to build star mines in my mind. These would be bag mines, mines with a lifting disk, and mines with a lifting piston or sabot. They're listed in order of increasing height.

 

Bag mines are essentially what they sound like. A bag full of stars and lift. The lift, generally being smaller, migrates to the bottom and provides the lift. Alternatively, some people will segregate the stars and lift with a tissue paper or plastic bag of some sort. I prefer segregation, just to ensure all the lift is under the stars/inserts.

 

Disk mines is a step up in terms of lifting ability. Generally a perforated chipboard disk is placed between the lift and the stars. I still prefer to have the lift contained in something to prevent it from migrating up through the holes. I typically make all of my mines stand alone, so they can just be dropped into a mortar and fired, so I just use end disks for cylinder shells with several 1/4" holes drilled into them, with one 3/8 to 1/2" hole drilled into the center for the quickmatch. If you're building a single fire mine where the lift is loaded directly into the bottom of a mortar, you can use a wad of perforated paper or a few pieces of perforated thin chipboard, and press this down directly onto the lift. It's important to block the entire bore in this case. I also recommend another solid layer of paper or chipboard on top of the stars for confinement.

 

Sabot or piston mines are my personal favorite. They shoot the highest, most columnated mine. They were originally described or popularized by Skip Meinhart in the 1980's. I thought it was in one of the pyrotechnica journals, but I can't seem to find the information. Anyway, the construction is similar to what I just described for the disk mines, but using a piston instead of just one disk. Some people use a slice of a thick walled tube, often a bottom shot tube, sandwiched between two chipboard disks. Others use a series of smaller tubes between the two disks, like a series of columns on a building. I've used things as simple as a wad of coiled paper. For mines larger than 3", I also like to have a tube in the center of the disks, lining where the quickmatch goes through. I like the extra support in the center.

 

You can see an example of a bag mine and a piston mine here on skylighter.

http://www.skylighter.com/fireworks/how-to-make/1.75-Inch-mines.asp

[AirCowPeacock]

I actually like the wide spread bag mines give, but I use disk mines because it saves me lift and only adds a little work.