taiwanluthiers Posted November 29, 2013 Posted November 29, 2013 I notice on mythbusters when they light a stick of dynamite by fuse, they look like time fuse. Does anyone know what is time fuse originally intended for, is it for blasting or was it really for time fuse for firework shells? Any reason why visco, or at least the thicker cannon fuse aren't used for dynamites?
Nessalco Posted November 29, 2013 Posted November 29, 2013 What we refer to as time fuse was originally called Bickford Fuse. http://en.wikipedia.org/wiki/Safety_fuse KO 1
Mortartube Posted November 29, 2013 Posted November 29, 2013 Bickford fuse was designed to make the detonation of nitro glycerine safer in mining and quarrying operations. Prior to safety fuse, glass jars of nitro glycrine were often hung from ropes at the required height over cliff face and shot at with rifles. Safety fuse allowed nitro glycerine and later dynamite to be detonated at a particular known time.
mike_au Posted November 30, 2013 Posted November 30, 2013 I suspect that spoolettes were probably the standard for fireworks before the invention of time fuse, and since they work quite well I doubt there was much pressure to develop a replacement. Time fuse is preferred over things like visco for blasting because it is much less likely to skip. If the flame from the fuse ignites some grass that could easily ignite visco further along and thereby shorten the delay before the blast goes off. With time fuse the flame is much more contained and less likely to ignite things around it in the first place but even if it did, it is extremely difficult to light timefuse other than on the end so there is much less risk of a small fire or stray spark messing up the timing.
taiwanluthiers Posted November 30, 2013 Author Posted November 30, 2013 Time fuse seems difficult to light even from the end, the tar would melt and prevent the fuse from lighting. Seems the only way to reliably light time fuse is to cross match it. I've seen in videos people attach some kind of a device at the end of a fuse, where they pull something to light it, I suspect because it's hard to light time fuse with a lighter?
Ferret Posted November 30, 2013 Posted November 30, 2013 I just got some time fuse, having never used it before. It actually lights fairly easily at the end with a lighter, and even easier when you simply slit it down the middle a little to expose the (rather thick) blackpowder core. It's quite a vigorous burn, and you can actually hold the paper casing while it's burning for a little without it getting to hot, it's that thick. I'm not sure how to prepare it for shells yet though, I'm having trouble making reliable blackmatch so I don't want to crossmatch, but i'm thinking just slitting the fuse a little will be all I need to do. and wet prime it. That wiki page was an good read. I thought it was rather interesting that they used to set off nitroglycerin by shooting it
taiwanluthiers Posted November 30, 2013 Author Posted November 30, 2013 Would have been better if they just made tannerite, but I guess back then it wasn't invented and they probably didn't have a fast enough rifle to set off tannerite. You have to cross match time fuse. I find simply slurry priming the ends do not guarantee reliable ignition... had several duds as a result. This goes for cutting a slant, etc.. I think the issue is the tar actually melts, or at least cutting the time fuse causes the tar to cover the bp core and hampering ignition. Cross matching just ensures that the fire gets to where it needs to go, and black match takes fire very easily. To make reliable black match, instead of just pulling the string through bp slurry, put the string inside and knead and massage the string before pulling them out. This causes the string to be completely impregnated with bp slurry, making it more reliable. The black match will burn through instantly lighting the time fuse instantly so delay isn't an issue. If you have commercial quick match you can dismantle some of them and use the black match inside as crossmatch. Chinese paper fuse also works as cross match.
Arthur Posted November 30, 2013 Posted November 30, 2013 Prior to the invention of Bickford Safety Fuse delays were unreliable with skips and hangs likely -so people got hurt in the mines.Bickford was a train of composition inside paper tar and cloth layers which meant that the speed was certain and continuity of fire was assured too. The tar made it water resistant and the outside diameter was suited for crimping a detonator on. The modern firework time fuse is a reliable diameter and rate but the tar waterproofing made life difficult so it has been replaced by more paper or thread, the lack of waterproofing is not significant as the rest of the firework is not waterproof anyway. Modern blasting is unlikely to use fire fuse as time delay as the crimping action is hazardous and electric firing is now considered normal using nonel/shocktube as delay and distance pieces
Jwdrummer5 Posted January 20, 2014 Posted January 20, 2014 Would have been better if they just made tannerite, but I guess back then it wasn't invented and they probably didn't have a fast enough rifle to set off tannerite. You have to cross match time fuse. I find simply slurry priming the ends do not guarantee reliable ignition... had several duds as a result. This goes for cutting a slant, etc.. I think the issue is the tar actually melts, or at least cutting the time fuse causes the tar to cover the bp core and hampering ignition. Cross matching just ensures that the fire gets to where it needs to go, and black match takes fire very easily. To make reliable black match, instead of just pulling the string through bp slurry, put the string inside and knead and massage the string before pulling them out. This causes the string to be completely impregnated with bp slurry, making it more reliable. The black match will burn through instantly lighting the time fuse instantly so delay isn't an issue. If you have commercial quick match you can dismantle some of them and use the black match inside as crossmatch. Chinese paper fuse also works as cross match.I have been 100% successful with simply cutting the time fuse straight and then priming with NC/BP slurry then dabbed into 2Fg. I have done various tests from a quick flick of a torch, to using this in shells up to 6". I always use a new very sharp razor blade with a single straight down motion like an anvil cutter (I see a time fuse cutter in my future). Never sawing through it. I immediately dip about 1/8" into the often mixed NC/BP slurry, then directly into some 2Fg. And let dry. I usually do both ends his way. That being said, I still used the traditional cross matched time fuse (for one of the 2 time fuses) when building my 10" shell. Why on the 10" shell? Because my 40 or so shells is nothing in compairiasion to the millions of shells built using the cross matched technique, time tested and proven. I just want to be able to use my limited manufacturing time the best way possible. When did I start doing this?I saw someone at WWB doing it a few years ago and thought I'd give it a go. I really like being able to cut my time fuse exactly where I want it for the time needed. Only issue that I've dealt with is that I have less time fuse inside the pass-fire, but this allows for more black match, which I see as a plus.
Arthur Posted January 20, 2014 Posted January 20, 2014 Bickford was certainly the first fuse that had a reliable burn rate with no skips or stops, that previously plagued quills full of BP. The Tar layer isn't needed for fireworks so it isn't there in Chinese made fuse. The stiffness helps the powder core to remain intact, as distinct from cheap visco.
taiwanluthiers Posted January 21, 2014 Author Posted January 21, 2014 So that all white time fuse everyone complains about, you know the one that is difficult to take fire, I take it that's more for blasting than for fireworks?
Peret Posted January 24, 2014 Posted January 24, 2014 (edited) FYI, in mining and tunneling there isn't just one fuse. The face is drilled with a pattern of many holes, dynamite inserted, and each hole fuse cut to a specific length so they explode in sequence over a few seconds. First "relievers" blast a cone out of the center, then "breakers", a ring of outer shots, break the rock into the cavity so formed, then "lifters" at the bottom blow the broken rock away from the face into the tunnel so it can more easily be removed. The old time miner didn't have one fuse to light, he probably had 20 or more, and though he probably had fifteen minutes of fuse, they all had to be lit in a short time to go off in the right sequence. They always split the end of each fuse. Then a common technique was to cut another foot or two of fuse and notch it to the core 30 or 40 times, depending on how many fuses needed to light, and the spit from each notch was used to light a different fuse. Aside from making better timing, it avoided the problem where the spit from a fuse blew the candle out and left them to stumble away in the dark. This sequence firing is how it came to be known as "time fuse" and why a constant burn rate was important. It couldn't be done before the invention of Bickford fuse. Obviously it got much easier when electric firing was developed. I snapped a couple of relevant pages from the Good Book. Hope they're readable. Edited January 24, 2014 by Peret
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