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Methods of Priming Spolettes


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Posted
Hi, I was just curious what different ways you can prime spolettes and how effective they are at ensuring ignition. I have only tried the method where you scratch the powder core, then bend over and tie on a few strands of black match.
Posted
I scratch the powder core,use a drop of BP slurry on half the spolette core and bend a piece of black match over the core and folded up again like ears. It is the way I was shown by a very skilled builder and has not failed yet.
Posted

I prefer priming the end of spolette with black powder slurry and then adding coarse bp over it.It never fails.

Attached Image is of my friend.

post-10498-0-81787300-1421227741_thumb.jpg

Posted
Alright, thanks for all the suggestions guys! So it seems that BP slurry with granules on one side with black match on the other is the preferred method for ensuring ignition. One last thing, does this method still apply for small spolettes for small shells (2-3 inch)? Because it seems like it would be a bit tricky...
Posted
Yes It can be applied for small shells,The picture attached is of a 3" shells.
Posted

I'm with Bangkok and Nater on this. Using just BP slurry and granules will not guarantee ignition, unlike what our friend from India seems to be claiming. It's certainly not 100% foolproof. The blackmatch tied over the top really gives it that "belt and suspenders" approach, and really doesn't take much time. Bangkokpyro took his time to carefully show and explain all the steps and reasoning for them. In practice it doesn't take much time at all you get the hang of it.

  • Like 1
Posted

I'm with Bangkok and Nater on this. Using just BP slurry and granules will not guarantee ignition, unlike what our friend from India seems to be claiming. It's certainly not 100% foolproof. The blackmatch tied over the top really gives it that "belt and suspenders" approach, and really doesn't take much time. Bangkokpyro took his time to carefully show and explain all the steps and reasoning for them. In practice it doesn't take much time at all you get the hang of it.

 

+1

Posted

I never had problems with small spolettes and just scratching the surface, but since i learned about the tying with black match way i just do it to be sure.

To easen that process i got a gum expander for attaching pellets to hooks from the carp section of a fishing store. The bands cost less then 1 cent each and with this device the match is fixed in just a couple seconds

Posted
Ok, good to know. Can the end of the spolette be primed with BP slurry and granules on the whole surface then have a piece of black match tied over it? Or would this not be as effective? Thanks
Posted
I believe the idea behind only priming half the surface with a BP slurry and fine BP before attaching the black match is to prevent the possibility of a delay caused by the burn time of the slurry. I use a jig to drill back spolettes and the timing can be precise. If one needed identical timing for inserts, even a slight delay would ruin the effect.
Posted
Ahhhh I see. Thanks for the clarification.
Posted

The scratching is also important for what it's worth. It'll knock off any paste of glue that gets on there, and provide a nice rough surface to take fire.

Posted
Yeah, that's what I figured. It increases the surface area and exposes "fresh" BP.
Posted

One last thing I just thought of, what is the most commonly used or 'standard' tube I.D. of a spolette used in a 3 inch shell? I'm thinking 3/16" or 1/4", maybe even 5/16". Does it even matter?

  • Like 1
Posted

5/16" ID X 1/2" OD

 

The same holds true, down to 1-3/4" inserts.

Posted

That's the size sold by Hobby Horse at least. Precocious Pyrotechnics stocks other sizes. http://pyro-pro.com/files/2014%20Precocious%20Pyrotechnics%20Wholesale%20Catalog.pdf The sizes mentioned in Fulcanelli tends are 5/16"-3/8" ID x 0.55-11/16" OD.

 

As long as the tube is sturdy enough, the actual dimensions don't really matter a great deal. Most tooling is sized for one of the above commercial sources though. Typically the tube is held against a flat surface and rammed/pressed without the use of a support. Supports can be used however. They're more to stabilize the tube than actually provide structural support.

 

One of the above sources is the most convenient source of tubes, or you can roll your own if you'd like. I'd go with 1/8" walls on whatever ID you decide. The hobby horse ones are slightly under 1/8" walls, but more than strong enough. I'd also recommend at least a 1/4" if not standard 5/16" ID. The thicker the powder column, the more area you have to light.

Posted
I was just coming back to correct my above stated OD dimension to .550" but Mumbles was faster : )
Posted

Thanks guys! I was going to make a 3/16" I.D. spolette as I had a tube that size lying around and I'm glad I did'nt, as that would be incredibly annoying to tie blackmatch onto and prime... Now off to make some tubes!

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