Display candle delay units

[AdmiralDonSnider]

Display size roman candles are items I am frequently using in commercial displays. I have done some autopsies recently, dissecting a 30mm silver candle and found what I expected.

 

The delay units are basically compact felt plugs with a central time fuse. They are a bit larger in OD than the candle ID and require some force to be pushed in the tube.

 

Has anyone ever experimented with such candle delay techniques, or developed similar units at home?

 

I personally dislike the traditional approach using candle composition for the delay. I have an AFN video by Mike Mara, but this technique obviously requires a lot of feel and burns away the tubes.

 

Another thought that comes to my mind is using reloadable metal tubes such as aluminum.

 

The dissected comets were primed all over the surface. I wonder if this not only serves igniting the lift charge more quickly, but also has beneficial effects for the burn duration and appearance of the comet, burning more composition per second. Many compositions I tested lacked the burn speed, which could be overcome this way I assume.

[Mumbles]

I frequently look for the right felt to make these, but have never really gotten around to trying them. I've only seen them in person or in images a few times. It seems that paper, metal, or plastic tubes all work just fine for the felt wads. I did include some information I've collected about them over the years. The majority of information I have is from candles between 1.75" (45mm) to 2" (50mm). This almost entirely comes from talking with a former manufacturer and from bits and pieces I've picked up from Mike Swisher and others on passfire and rec.pyro.

 

My only practical experience is with using a long piece of visco and rammed sawdust for the delay. I can go into that if you're interested.

 

The right type of felt seems to be about 1" (25mm) thick F-7 or F-12 felt. I generally see F7 being mentioned a bit more. The felt disk really only needs to be about 1/8" (2-3mm) or so wider in bore than the tube itself. The disk of the appropriate size is punched out, and a snug fitting hole for the time fuse/spolette/delay comp is also punched out. The delay element is covered with glue and slid into the hole. After drying it'll be pretty much airtight, and the additional compression from inserting it into the tube will seal everything up.

 

Comets are primed all over, or some blackmatch is wrapped around the comet lengthwise to act as a passfire. Short pieces of blackmatch or quickmatch serve an identical purpose for insert shells or other effects. I've also observed comets prepared with a hole down the center to act as both a passfire for blackmatch, and to increase the burn rate as you described.

 

 

I also have some instructions I found from a post from Michael Fales on passfire 5 years or so ago.

 

Use a hole saw (with the arbor bit) to create six 1.5 inch disks of 1/8'' thick masonite. drill out the center of 2 of the disks to 1/2 inch. Use scissors, knife or what ever means you find easiest and cut five 1.875 inch diamter 1/8'' thick felt pieces. Punch 1/4'' holes in the center of each felt piece. Stack the pieces in this order. felt, felt, disk, disk, felt, disk, disk, felt, felt. measure the stack and cut a piece of 1/4'' time fuse 1/8'' longer than the stack. apply glue to the time fuse and slip on a piece of felt leaving 1/16'' of the fuse exposed. Continue by glueing another piece of felt then 2 disks, another felt, 2 disks, and 2 felts. be sure to apply glue to the faces of the disks and felt as you go. The 2 disks with 1/2'' holes at the center go on the top and bottom protecting the 1/16'' of time fuse projecting from the felt. Clamp the stack until the glue dries. Prime both ends of the fuse with a hot meal slurry and dip or pour fine grain powder into the slurry.

This is what Lidu does for delays on their large bore candles and it works very well with consistant timing. It may seem like a lot of work but it goes quickly once you are set up for it.

With comets it will work as is. with shells a section of quickmatch must run from the top of the shell (directly under the time fuse)to the bottom where the lift is.

 

http://www.pyrobin.com/files/candle%20delay.jpg

 

From Michael Fales from passfire on 11/7/07

[AdmiralDonSnider]

I just wanted to say that I appreciate your input, Mumbles. This is one of the threads I start out of serious interest in the topic, but my limited participation not only reveals my limited knowledge in the field but also my current lack of time for pyro and testing new setups.

[Pyroboy]

I have done a little work on that kind of roman candle. I used heavy cardboard disks, hot glue an timefuse. Since I have no access to that thick pyroclock like timefuses, I used chinese timefuse and it worked.

The only problem with that method is, that you have to use two cardboard plugs. Otherwise the first shot may ignite the next at the same time. So the timefuse must be around 4cm = 4s or a bit longer.

I will see if I can take some pictures of that.