Spiking Ball Shells

[Nessalco]

Since I've learned to make rolled stars, I am, of course, going to make some ball shells. However I am too cheap to drop $2K on a WASP, much less the gummed tape required, but want to produce 200+ shells a year - so I've been looking around for 'easy' methods of pasting ball shells. I had seen a Russian video in which the individual was using disks of paper for pasting rather than strips, and wanted to give it a try. It also occurred to me that spiking a ball shell might be beneficial.

 

So, using APC's search engine, I located this thread http://www.amateurpyro.com/forums/topic/9042-spiking-ball-shells/?hl=%2Bspiking+%2Bball+%2Bshells

 

Spiking and disk pasting in one place! Eureka!

 

So I gave it a try. I made up some 3" shells using a variety of spiking patterns, and shot them. The results were very encouraging - nice big, symmetrical breaks without any booster. So I played with the spiking pattern until I came up with one that worked, was easy to apply, and didn't result in any serious twine buildup. These pics are of 4" shells that I have in process.

 

I then paste the shells using 12 layers of 50# kraft, applied as disks. The resulting shell is a little wrinkly, but I don't care - this isn't a beauty contest, and it's going to explode anyway.

Pasting with disks is fast and relatively easy. It takes a bit of practice to get the two disks to meet properly, but once I figured it out it was great. I can apply disks as fast as my spouse can apply paste and break the grain - though I let the disks soak in paste for about 10 minutes before I begin to apply them.

If the weather is favorable this weekend (meaning enough rain or snow there is no fire danger) I'll loft a few of the 4" shells and get video.

Kevin

 

[Nessalco]

PS> Those 12 layers are applied 3 at a time, with adequate drying time between applications.

 

KO

[OblivionFall]

I heard that spiking ball shells doesn't work, but in this case it just might. Looks cool too.

 

Test out the shell and if it breaks well, then spiking works

[schroedinger]

Isn't 12 layers a normal ammount of pasting?

[ExplosiveCoek]

Yes, it's already quite excessive in my opinion. With that many layers you for sure will get a decent break, you won't need the twine anymore.

[Nessalco]

Yes, it's already quite excessive in my opinion. With that many layers you for sure will get a decent break, you won't need the twine anymore.

 

<shrug>

 

I'll paste one up with all the same components but without the spiking and video the results.

 

My inspiration is the first couple minutes of this video

 

 

I suspect their reason for this approach is more than just keeping costs down.

 

Kevin

Edited November 20, 2015 by Nessalco

[Maserface]

Cool idea! Diet Cylinders

[zan89]

I can tell that most of Italian round shells are spiked, I was working in Vaccalluzzo production and they are all spiked!

[Col]

I dont spike ball shells but i couldnt resist wrapping a 3" in string just to see what it would look like. I didnt have the shell locked rock solid in the clamp so it did slip a bit and thats the reason the pattern isnt perfect.The unpasted thick cotton string didnt fall off the shell when i removed it from the clamp so it clings on pretty good. I reckon a single wrap of (glue soaked) 1mm hemp twine followed by a layer or two of gummed tape might be worth a go on a shell or two.

 

 

 

[Arthur]

What you need to watch is the finished size of the ball shell. The available hemis assume the usual method of paper pasting to produce a good fit in a tube. With an odd method you risk needing an odd size of tube or hemi to achieve a good fit and lift.

[Col]

The 1mm hemp will bite into the hemi and flatten out so i dont see it adding much. A 3" can shell doesnt have as much spiking as whats on that ball shell I doubt it`ll need many paper layers for confinement, just enough so it fits the gun and to protect the hemp from the lift.

[Nessalco]

What you need to watch is the finished size of the ball shell. The available hemis assume the usual method of paper pasting to produce a good fit in a tube. With an odd method you risk needing an odd size of tube or hemi to achieve a good fit and lift.

 

Agreed. My finished shells are as large in diameter as it's possible to be and still fit in the guns, with only 12 layers of paper.

 

Still waiting on the weather to do some tests. It's been unusually warm and dry, and the fire danger is just too high to risk it.

 

Kevin

[Mia]

The 1mm hemp will bite into the hemi and flatten out so i dont see it adding much. A 3" can shell doesnt have as much spiking as whats on that ball shell I doubt it`ll need many paper layers for confinement, just enough so it fits the gun and to protect the hemp from the lift.

 

 

I dont spike ball shells but i couldnt resist wrapping a 3" in string just to see what it would look like. I didnt have the shell locked rock solid in the clamp so it did slip a bit and thats the reason the pattern isnt perfect.The unpasted thick cotton string didnt fall off the shell when i removed it from the clamp so it clings on pretty good. I reckon a single wrap of (glue soaked) 1mm hemp twine followed by a layer or two of gummed tape might be worth a go on a shell or two.

 

spiking test.jpg

 

 

I do

[Col]

Looks like 25-30ft of hemp spiking plus 5 layers of pasting produces the same diameter as12 layers of pasting. If nothing else, i know the woody can handle string/twine as well as tape. The cotton string impregnated with sodium silicate might come in useful for pasting very small ball shells.

Edited November 25, 2015 by Col

[Nessalco]

After doing some testing and experimenting, I can report that spiking ball shells works well indeed. Spiking plus 4 layers of paper gives a better break than 12 layers of paper alone. Much quicker to paste in. I'm using disks of paper rather than strips, and have enjoyed 100% success so far. I taught my wife the technique and she finds it quick and easy - she tried helping me paste using the 3-strip method and couldn't follow the process.

 

I'm using an offset pattern, with 12 verticals on a 3-inch shell, and 16 verticals on a 4" shell. I'll be trying 5-inch shells in the spring - right now I've about run out of BP. I've been spiking the shells vertically only, as I showed in the original pics. I tried adding circumferential spiking and it distorted the break.

 

I tried video a couple of times but missed getting the shells in frame - I'm watching the shells, not the camera. Now it's back to bone dry and no snow on the ground, so further testing will have to wait. But the long and short of it is that using spiking + disk pasting gives an excellent break, is quick and easy, and can be taught to your minions. Also I can assemble, spike, and paste a shell in the morning and it will be dry by evening using my dehumidifier box.

 

Kevin O

Edited December 6, 2015 by Nessalco

[Nessalco]

Finally got to shoot some video of one of my tests. Of course, the shell performed poorly - at least half the (Sunrise Yellow) stars blew blind, and the ones that lit acted oddly. I'll have to suss out if this was because of oversized stars, inadequate drying, or some other factor. Many of the stars from the bottom half of the shell hit the ground hard, still alight. Lift charge and fuse timing were consistent with previous (successful) tests.

 

The 3" shell was spiked with 16 verticals of doubled flax twine and four layers of 50 pound kraft. Stars were rolled to 3/8", primed with BP over BP + 10% MgAl.

 

Edited December 21, 2015 by Nessalco