11 replies to this topic

[Techohead]

hello again to all.
just a few weeks back i made my first ever 2/3" aerial report, using homemade black match for time delay fusing. they were reliable, so i took it a step further and made my first 1" aerial shell, with the same fusing in it, however they were starting to prove less reliable... so i thought about what to do next, when i came up with the concept of the spolette, without knowing it was already a widely used concept. i made a random formula to try, and found that it gave me a 1.5 second delay when 1" long, so thats what i used. it's been 100% reliable now, and i've made atleast 8 of these shells. now i want to make 1.5" shells, but the spolettes are starting to get fiddly, because they just aren't long enough.

so i started experimenting again, using different powder trying to get a 2" long spolette to burn in 1.5 seconds. i just cannot achieve it. with air float BP milled for 40 hours, it burns for 3 seconds, with corned BP it burns in 0.5 seconds. i cannot find anything to pack in my spolette, that burns 2" in 1.5 seconds. throw your formula's and ideas at me.

[marble]

Whats wrong with primed visco?

spolettes are only used on larger shells (3"+)

[cooperman435]

why do yo need it to be 2"?

my spolettes are all housed in identicle 4" tubes with a specific depth of composition to give the burn rate I desire. I used (a while ago before I had time fuse!) about 20% extra charcoal in my bp batch to give a nice rising effect and just rammed say 1cm for 1second of delay 3cm for 3 seconds etc.

The spoolette was put into the shell with the hollow end of the tube outermost which when putting on the leader I exposed 2" of blackmatch about 9" up from the end I folded it over and inserted it into the tube and tied the nosing off then used the 9" peice to go down the side to the lift bag and the long peice as the leader.

The powder length doesnt matter just the timing it gives!

[paul]

Anyway it should be +1cm, else a blow through is very possible. But when I use spolettes, i add a cardbord disc to them with a hole for a piece of good blackmatch. Blow though is not possible then, anymore.

[cooperman435]

I doubt you will get a blowthrough with top fusing?

[BigG]

I doubt you will get a blowthrough with top fusing?

let's summries:

1. Spolettes can be of different lengths, however, it is right to say that using one length is more common – simply because it allows companies and amateurs to order one type of tube from a supplier – which result in cheaper price.

2. You control the speed of the spollete in two ways. Put different amount of composition in it or changing the speed your composition burn. The first solution is simple. Measure how long a spoonful of composition burns when it is compacted into the tube, and multiply/divide that figure to get your delay. So – if one spoon gets you 1-second delay, you will probably need two spoons to get a two second delay.

The second method requires you to get a composition that burn slower. Adding charcoal to your BP composition will slow it down. So it your regular composition is 75g of KNO3, 15g Charcoal and 10g Sulfur, just increase the quantity of charcoal. For example 25g charcoal instead of 15g. It takes trail and error to get the timing right, but you will. It important to keep a log of your actions, so repeatable performance can be obtained.

3. To prevent blow through, make sure that the depth of the composition in your tube is larger then your tube diameter. So – for ½ inch spolette make sure you have at least ½ inch of compacted composition. I would recommend using small ID spolettes. 1/3’’ – ¼ ‘’ are good sizes.

4. Spolettes can be used in very small shells. It’s fine – however, if you intend to use shells bigger then 3’’, then you should not bottom fuse them. Please don’t ask what bottom fusing is – search. If you can’t find, get a specific new thread going. The reason you should not bottom fuse is because bigger shells require bigger lift, which as a result put more pressure on the bottom fuse. This can cause the areas around the fuse (even if well pasted) to give away, and a blow through is also more likely. Now, don’t get me wrong – I’ve seen 4/5/6 inch shells bottom fuse – it can hold, but industrial output shows a large increase in the number of failure of such shells. It’s not going to happed very often to us – because we make very few shells, but on large numbers the differences are obvious.


I hope that helps.
BigG

[Pretty green flames]

I personally wouldn't change the formula for the powder charge. Corning dust is what i use and it gives me 1s/cm delay, so if I want a for example 3.5s I charge the tube to a depth of 3.5cm. Why don't you just alter the dpeth of the dealy charge, beats the hell out of testing new compositions. And 2" is plenty long for shells up to 4", atleast for me it is. So go with BigG's advice and measure how much a certain ammount of powder takes to burn and work yourself forward from this point on.

[BigBang]

I use a much simpler method for timing my shells (works fine for shells up to 2.5", wouldnt recommend it for bigger ones). I use silver falling leaf fuse ('silver' as opposed to any other colour because it burns the hottest and most consistant). I simply wrap the fuse, tightly in craft paper, and just cut to length, to give the required delay. A 1/2" length gives approx 1sec. delay. Ive had a very high success rate using these. Very simple to make and dont even need priming!

You can use different types of visco to give longer length/delay or use time-fuse which is more accurate and doesnt need to be wrapped, but is a lot more expensive.

I know you asked for formulas, but these are just a couple more options for you to consider.

[Techohead]

i appreciate the quick responses from all.
firstly, i do not have visco, i live in australia and cannot obtain any.
secondly, i know that i can get the correct timing from a 1/2" spolette (1.5 seconds) but that spolette is barely long enough to penetrate my firewall and external spiking.

it has been suggested that i have a 1" spolette, with 1/2" of packed black powder, and teh other 1/2" filled with granulated BP. this would work, but i wouldn't be able to get an exact quantity of each every time i make them, so timing will vary by up to 1/2 a second or more. it seems most people are used to using spolettes that are barely long enough, as if almost standard practice, so i guess i will have to find the best way i can to keep the short spolettes reliable.

[Pretty green flames]

Oh come on, spolettes are much more simple than you think.

Roll a 6mm ID and 5cm long tube (~1/4" ID and 2" Long) and ram a column of powder that gives you a sufficient delay, in your case 1/2" which gives you 1-1/2" of free tube left, to fill the remaining space up, just stick a couple pieces of black match in it and you're set.

[BigG]

i appreciate the quick responses from all.
firstly, i do not have visco, i live in australia and cannot obtain any.
secondly, i know that i can get the correct timing from a 1/2" spolette (1.5 seconds) but that spolette is barely long enough to penetrate my firewall and external spiking.

it has been suggested that i have a 1" spolette, with 1/2" of packed black powder, and teh other 1/2" filled with granulated BP. this would work, but i wouldn't be able to get an exact quantity of each every time i make them, so timing will vary by up to 1/2 a second or more. it seems most people are used to using spolettes that are barely long enough, as if almost standard practice, so i guess i will have to find the best way i can to keep the short spolettes reliable.

All you need to get right is a consistent black powder. the length of the spolette really does not matter. As long as you compact the same amount of black powder into it., and it burns the same amount of time, the spollete will give consistent timing. Here is a simple picture of how this done:




The blackmatch can be held in gluing one end of it to the end of the wall or simple by gluing the open end using a thin tissue paper - you can in most cases just push enough folded match for it to pressure fit. When you fill the shell, some of the burst charge and the stars get into it anyway and they help with the fire transfer.

The transfer is instantaneous. The thin tube does not allow the gases to escape and it ignites the black match the same way a quickmatch does. If you don't know how a quickmatch works, then search the forums, or send me a PM. Do not start a new thread on the subject. I don't want to judge in any way, but I feel you might want to learn some more basic elements first.

[Frozentech]

i appreciate the quick responses from all.
firstly, i do not have visco, i live in australia and cannot obtain any.
secondly, i know that i can get the correct timing from a 1/2" spolette (1.5 seconds) but that spolette is barely long enough to penetrate my firewall and external spiking.

it has been suggested that i have a 1" spolette, with 1/2" of packed black powder, and teh other 1/2" filled with granulated BP. this would work, but i wouldn't be able to get an exact quantity of each every time i make them, so timing will vary by up to 1/2 a second or more. it seems most people are used to using spolettes that are barely long enough, as if almost standard practice, so i guess i will have to find the best way i can to keep the short spolettes reliable.

What matters is the length of the powder charge in the spolette, not the length of tube. I use the same 3" long x 3/8" I.D. tubes for all my spolettes. Generally you want to ram or press more than the amount of powder you need for your timing, then drill back to the exact powder train length for the timing you need, for instance ~ 1 3/8" of rammed powder for a 4 second delay. Mike Swisher on rec.pyrotechnics, Passfire, and Pyrotechnica IX and XI ( the "Fulcanelli articles" ) are all excellent resources for building spolette timed shells.

What the others have mentioned about fire transfer is correct. There is almost NO chance of fail to fire with a properly rammed spolette. Here is a video of a timing test I did on a spolette. Imagine something basically like a small BP rocket exhaust shooting down the center of your shell. You can further ensure good fire transfer by putting in several short sticks of black match, held in place with some nosing paper, on the "open" end of the spolette that passes fire to the burst charge.

http://www.pyroguide...llette_test.wmv