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3" Shell Testing Recap

jwitt

Entry posted by jwitt

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SHELL X1:

 

Used Long Hangtime Willow Stars, white chinese time fuse, ~1g whistle boost, and crappy BP rice hulls. It was my first pasting job, and it was lumpy and bumpy. I used 28g glazed cannon powder given to me over a decade ago for lift, and it did not perform well enough, although shell diameter was not consistent and may have allowed too much gas to pass the shell in some spots. The shell was strong, however, and went off even though there were some time fuse issues.

 

SHELL X2:

 

Improved pasting skills made a smoother shell. Same stars were used, ~1.5-2g whistle boost, same crappy hulls. A 3 second spolette was used with good success. 35g homemade Red Alder 4FA sized BP lifted the shell to a respectable height. Burst was nice, but a little weak, probably due to the crappy BP hulls.

 

SHELL X3:

 

WOW! 40g homemade BP sent this thing up with a resounding bang. 5g whistle burst officially makes a "high profile" 3" shell that could be clearly heard from well over 1 km away. 2.8 second spolette performed exactly to spec. Once again, WOW. The whole sky was painted in slowly falling sparks of lampblack and charcoal...total time of effect was maybe 8-10 seconds!

 

 

Final Shell Specs for 2010:

  • 3" paper hemi loaded with BP rice hulls and 2-4g whistle boost, depending on desired effect.
  • 5 layers of 3-strip-method pasting, overlapping slightly more than halfway for a perfect fit in the mortar.
  • 2.7-2.9 second spolette for timing- .9 inches of powder in a 1/4" ID tube.
  • Passfire end of spolette armed with 6 1" long pieces of thin blackmatch, nosed with paper and vented.
  • Take-fire end of spolette scratched with X. 3 thin pieces of blackmatch hot glued and tied in a "U" over end of spolette.
  • My current requirement is 25% of shell weight in homemade 4FA lift...pending further lift testing and tweaking- I obviously have a long way to go in BP manufacture! No worries, the lift cup is the last thing to go on anyway.

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PyroBros
Thats all good info! Did you find a good tutorial on making Spolettes? I have been looking for one!
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jwitt

I don't think I found a spolette tutorial. I had 1/4" x 2" tubes on hand for my "timing & ignition assembly" using time fuse, so I began experimenting with spolettes out of frustration with making tine fuse work correctly.

 

Here's the way I do it. We'll see how reliable they are at the end of this month (4th of July party delayed until the 31st....ARGH...can't get everyone together until then!!!)

 

- Buy 1/4" hardwood dowel (oak)

- Notice that the fit into the tube is too tight

- Sand the dowel just enough for a tight sliding fit. Too loose is NO GOOD! What seems "a bit snug" is better. The dowel will bind in the tube if it's too loose.

- Set aside plenty of BP mill dust- you want to use the same batch for spolettes for consistency.

- On a hard, non-sparking surface, ram in your increments. I put in the first increment and ram the ever-loving heck out of it with my rubber-faced mallet. I figure this ensures a very hard "end" to the spolette.

- Continue ramming increments until 1 inch is filled.

- To test, grab stopwatch. Tape spolette to hard surface. Pile a bit of powder (meal D or the like) by the fire-taking end. Light powder and hit stopwatch. You'll know when to stop when the spolette hits the far end.

- Do some math to get your timing down.

- Mark your ramming dowel with the appropriate markings. I have a mark for loading the first increment from the "bottom"- that is, the dowel is in the tube, and about 3/8" of powder is added. This is flipped over and rammed. Then the dowel is removed and remaining increments are rammed.

- Test several spolettes until you are confident of timing.

- Insert blackmatch pieces into the open end of the spolette and attach nosing paper to hold 'em in through shell assembly.

- When completing shells, arm the spolette by gently scratching an "X" into the surface. Attach blackmatch to the spolette to take fire from the lift.

 

Hope this helps. Like I said, we'll see if I have any misfires or blown-through spolettes. With 1" of powder in a 1/4" tube, I think there's enough friction acting on the powder grain to prevent blow-through...but we shall see.

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angelluis

Sounds really promising good thing you are keeping records! How about a 3/8" ID x 1/2" OD X 2 " LG 1" gives me 2.75 burn time but I make cylinder shells .I also granulate my bp so it not so messy and it tends to stick better ! I also put about 5 starnds of black match and vent the spolette ! Good luck!

 

 

 

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