4 replies to this topic

[Flashy]

Hi there everyone, I'm thinking about making a large roman candle. 1 Inch diameter, is that too big. Has anyone had any success or experience making large bore candles. I've only ever seen people talking about half inch maximum. I've made myself a 1 inch star pump with two settings, either 1 inch long or half inch long.

Cheers for any advice,


Dave

[Creepin_pyro]

1" is not too big for a roman candle. I've never seen commercial candle this size made using the fuse/sawdust, or delay composition method. I think candles of this caliber are usually constructed using the felt wad/timefuse method. I have never attempted making a proper high-performance candle, but it is possible. Imagine each lift charge in the tube passing fire to a short piece of time fuse, which burns through a felt wad, and onto the next star, which wrapped in a few circles of kraft. I would suggest Passfire for more details...

[phildunford]

Ron Lancaster's book has some details about large bore candles if you can get a look at that.

The main problem with using delay comp in a big candle is that you need alot of it (expensive!) an it makes a lot of smoke. Those are two of the reasons that people use the felt wad technique.

he talks about candles with stars as large as 60mm!

[Phoenix]

The delay comp method may be a little impracticle on this scale, however, I recently made a 3 shot, 25mm candle with the sawdust and fuse method, and that worked just fine. I used black match for the fuse. I also made an 8 shot, 15mm candle in the same way, which gave perfect results. The fuse and sawdust method is my personal preferance.

PS, I'd have thought that 1/2" would be a bit short for a 1" star. It's usually good to keep them at least as long as they are wide, or they tend to rotate in the tube.

[pyrotechnist]

In a Roman candle the lift charge in the top star under it is thicker than the bottom e.g.

|-------|
|_____| -> thick layer of lift for star top lift charge
|++++|
|-------| -> medium layer of lift charge
|-------|
|++++| -> stars
|====|
|++++|
|-------| -> smallest lift charge

So the top one is thicker (the gunpowder charge to lift the star into the air) the one under it is a bit smaller and the one under that is a bit more smaller ect ect. This is because the top star needs more acceleration to lift of because it has no tube hardly to lift from so it needs more of a push to get it up there. The second one is more into the tube but still not yet far enough into it for the best thrust so it uses less gunpowder but still more than the others under it. The last one in the tube has the most least gunpowder because of the tubes mass in height, the more the lift charge is in the tube the more thrust it has to lift of. Hope this helps.


Michael

Edited by pyrotechnist, 22 July 2004 - 09:59 PM.