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Quick and Easy Spolette Time Fuse


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I know, I know. Spolettes aren't anything new and most members here have been making them for a long time.


This is in response to a recent post asking about them and I've picked up a few tricks so I thought I'd share my technique. Of course I'm always open to suggestions for any improvements.


If you don't have access to commercial time fuse, spolettes are a great option. They are reliable, consistent and easy to make, they just take a bit more time to prepare.


I start with a piece of scrap A4 80gsm copy paper, fold it in half 4 times then slice down the fold lines to make 4 perfect strips.




For the former, I use my .25" stainless rammer with half wrapped thinly with tape. This gives the slightest bit of clearance between my rammer and the ID of the tube.




Start the roll by folding approximately one third of the strip over the former. This helps to get the alignment perfect but it still takes a bit of practice to get a nice neat roll. Once done, just tape to finish the tube. I don't use any glue.






Using the copy paper, my outer diameter is pretty consistently 9.3mm


I made a support sleeve from a piece of 19mm OD acetal rod with a 9.5mm drilled hole. Its not essential but it does prevent the tube from buckling if you hit the rammer a bit hard.




I use fast, finely granulated BP but meal can also be used, its just alot messier.


I've already run a series of tests to determine burn rates of my black powder and correlated it to a weight in grains so that I don't have to keep checking how long my BP charge is. You will have to determine this for your own BP, the burn rate should be somewhere between 2.5-3.5s per inch.


In this case, the spolette is for a 3" shell with a time delay of 2.8s which correlates to 16grains of my BP.


I ram approximately the first half of the powder followed by the remainder using the untaped end of my rammer (my rammer is closed on the ramming side, not tube)




You should be left with a nice smooth finish




To get perfect, reliable passfire, it's necessary to nose the spolette with black match. Before I started doing this, I would get the occasional failure to ignite the burst. Since I started nosing, I haven't had a single failure.




I do this by inserting three pieces of BM into the open end and lightly taping it closed


The spolette is now ready to put into a shell. To guarantee that the spolette takes fire from the lift (or quick match if you are top fusing) I prepare the spolette after assembling the shell as follows


Scratch the smooth surface of the spolette, dip in NC lacquer, dip in granulated BP and allow to dry. I have NEVER had a spolette fail to take fire from the lift using this method.


If I'm doing a batch, it is quite easy to finish a large number of spolettes in just one hour, just remember to only keep small quantities of BP in you workspace.


Another neat thing you can use spolettes for is delay fuse on your quickmatch shell leaders. If you don't have access to visco, just make slow hardwood BP and ram a delay charge of 10-15s then attach the nosed spolette to your shell leader. Its much safer and more consistent than using black match for this purpose.


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Great tutorial.

I'm a little suprised that dry rolled tubes are strong enough, but if you roll them neat & tidy I can agree it's possible.


One thing I didn't understand at first (but viva Google): you mentioned the weight in grains, as I European I was like "Whut, grains ? Grams ?" But for al the Europeans in here: 1 grain = 0,06479891 gram ;) .

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  • 2 weeks later...

Nice one Twiggy.



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  • 3 months later...

So you're getting good/predictable results just ramming two increments? I've avoided spolettes so far because when I got started a few months ago it was with rockets, and I'm getting tired already of the multiple ramming iterations. I was really dreading ramming a quarter-inch tube 8 to 10 times, but I'll have to try the twice-and-done method.


As an aside, an idea that's been tickling my brain but I haven't been brave enough to start a thread about: it seems to me that if you set up a vibrating table and then rammed rockets on that (hydraulic/mechanical ramming would probably be better than hand-ramming) then the vibrations would help the rocket fuel (or spolette BP) consolidate and maybe only need two or three slow rammings. Does anyone happen to know if that's been looked into at all?




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I've never tried 2 increments, but do regularly use approximately 1/4" increments. For a typical shell, this equates to 3-5 increments, and maybe a minute or so total time, if that. With an appropriately sized scoop, it doesn't take much time at all to ram or press them. If you're concerned about speed, you may want to look into an arbor press.


I'm not aware of anyone who has looked into a vibrating table for this application. There would likely be some issues of alignment to address to do it well however.

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Thanks for this info. I am working on multiple break round shells with a system where I fuse internally. i think this will solve some of my problems. I know spolettes are old, but so am I.

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  • 2 weeks later...

No real issues with two increments as it was still only 8-11mm per increment. The biggest inaccuracy was the scale but was still keeping it +-0.15s as calculated from frame grabs of a recording.


Deliberately ramming a bit more and then using a jig to drill back down to exact depth is a winner, very consistent.

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That definitely would have saved me some time. Whenever I make my spollettes or rockets I can't ever seem to get them to roll up nicely, but rolling 1/3 of the paper over the former would have worked nicely and quickly. Thanks. Edited by PyroNinjaah
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  • 3 weeks later...

I aim for 1 tube id per increment after its pressed, usually ends up being a bit less. For thickish walled tubes you could get away with dry rolled but not for thin walled. For a small amount of glue and a little extra time, you get belt and braces peace of mind.

Here`s some thin walled spolettes i use for small timed report inserts, pic was the dry fit test taken before priming them. I find spolettes are much easier to light than time fuse, less fiddly and dont take up much space.



Edited by Col
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