53 replies to this topic

[Jerronimo]

I don't worry to much about the shrapnel caused by plastic shells, and don't think
that the shrapnel caused by a 3'' plastic shell break will be hasardous to animals.

The mass of the shell fragments is low and the irregular shape of the falling pieces will aid in a high windresistance, so the velocity of these falling fragments will be to low to cause any damage.

[pyrotechnist]

Is there anyone ho needs paper star shells made from straw bound paper from 3" going upwards to 12" I think.

[tajmiester]

The plastic shell tutorial was on dexters site too:

http://www.redhouse....ge/myshells.htm

Tris

[BigG]

I've seen the magnalium article before, but this shell-making thing is kinda cute.

[The_Djinn]

You know what it is like, you can do something over and over then only realise something else much later.
I was making tennis ball size paper hemi's today and it was only when I had them off the former that I noticed I had slightly crimped one edge of a hemi. Sitting on my desk was an old light bulb which I decided to use to roll the crimp out of the edge to neaten it up.. lo and behold after years of doing this I suddenly find that the OD of a light bulb is the same as the OD of a de-fuzzed tennis ball.

Going to use some nice red stars in these shells and for once, I have taken pic's along the way to put a page together on round shell's for those interested.
Looking back at what was said earlier about thickness of shells or better burst charge required and thickness of shells, there are many different techniques that can be used. I have seen people apply a varnish to the inside of the hemi and outside which hardens the shell and I have seen people .. hmm, I hesitate to use the term "spike" as there is no spaces, more like wrap the entire shell with string prior to applying final layer/s of Kraft.
In Shimizu's literature, he talks of wall thickness of around 2 - 3mm on the smaller shells, currently my hemi's are around .5mm and that is 3 layers of kraft so I should end up around 10 - 12 layers. At this point, the hemi's are already pretty strong, I can balance a brick (+/- 2.5kg) on an upturned hemi and it holds the weight.

On another note, when busy on projects take pic's and notes to use not only on your own web sites but when Honcho has time to do more to the site it will be great to see a build / technical area with great documentation and pic's similar to that seen on Passfire.

Mark

[Jerronimo]

Hi all,

I succesfully launched my first shells today!!!

No more endless rocketmotor ramming!

I use a cardboard tube with 13mm wallthickness and a length of about 60 cm as mortarmaterial.
The shells that I use are plastic 3'' hemmi's from pyroplastics.
Currently I use 15 grams of H3 to lift the shell, I know it's not the safest way but will have to do untill I finish my ballmill,I use paper drinking cups as liftbags.

I have had some duds because of poor spolette priming, now I just attach the leaderfuse directly to the spolette, a length of tape to secure it.
This has two advantages:
1: the spolette will allways light
2: the sulfercontaining blackmatch will not come in contact with the H3 liftcharge

I also tested my new lampblack formula, very long hangtime, to long I might say because some of the stars burned all the way to the ground .

[Phoenix]

Cool! Did you have any shells other than the lampblack chrysanthemums? I made (and launched) my first large (70mm - large by my standards) can shell a couple of months ago (a charcoal chrysanthemum). I like the increased safety and reduced BP consumption of shells and the simplicity compared to rockets aswell.

I cover my larger shells in an outer layer of horrible bright pink paper, so that I can find them easily the next day if the spolette fails. Hasn't happened yet though.

[Jerronimo]

Yes I also tried some aluminium based stars,a formula of my own.
I was surprised with the endresult, glitter!allthough they wearnt supposed to do that, strange.

[Phoenix]

What was the formula? (I suppose you should put it in one of the star formulas or glitter topics).

Edited by Phoenix, 25 January 2004 - 08:04 PM.

[BurlHorse]

Welp,

Was perusing the past posts and here are my thoughts on plastic shells, I use them up to 8". I have seen lots and lots of differing opinions on thier use, burst, fallout etc. My first (Miserable) attemps had lots of problems; Uneven breaks, flowerpots, etc. Of course, all is Usually well now, but I have a few tips. If these are redundant to any other posts, sorry.

1: Small shells, 1.75 to 4 inch, need a harder/faster break to disintegrate the shell and force a more even break. My approximate burst charges follow:

1A: 1.75" Festival balls, pointless to try any real configuration with these, they are just too too small. I mix up a bunch of small stars about 1 to 1 ratio with BP Coated hulls with whistle mix coating on BP Hulls, (Pottasium Perchlorate 70, Potassium Benzoate 30% for whistle mix) 6 parts bp hulls to 1 part whistle mix by weight. After fusing and priming Visco on both ends( I'll leave the timings up to you as it's obvious obtaining standard visco is a problem over there, A dab of N/C laquer and dusted with some 4Fa or meal, let that dry for a day. These little shells ( and I guess all other sizes too (duh), silly 'Ol Bear) need a good bond on the seam, I use my own styrene glue ( 1 Quart jar, cut up two six inch shell halves into little pieces, add just enough xylene to cover them, close jar tightly, swirl around a bit a few times a day, in a day or two they will disolve and you will have a great glue for bonding shell halves up to 8") fill both halves level with star and hull mix, pop em together and then use a cotton tip swab to liberally apply glue to the seam, now, tap shell halves with a dowle rod or screwdriver handle to consolidate the contents until shell halves are fully closed. After it's fuly closed, run another bead of glue around to clean it up. I apply one strip of thin strapping tape going from fuse, over top of shell and back down to fuse on other side of shell to hold them together. Let the solvent/glue dry for at least a day or three is best. I don't generally find any fallout at all with this method.

1B: 2" and 2.5 inch, Same method as described above, trust me, you can make dozen of these quickly and will notice no appreciable difference in the break Symetry than if you you go through all the hassle of trying to layer the stars on the outside of the shell halves and burst in middle.....Again, they are just too Small.

1C: 3" and 4" okay, heres where things change a bit and of course bigger is better haha. I'm assuming here that you guys use 1/4" or jap or chi time fuse, ( Is it Known as Bickford Over there?) save yourself some time by cutting with a (NEW Single edge sharp) razor blade, a bunch of these, 1.5 " long and crossmatch 1/4 inch from one end. Hot glue in the crossmatched side inside the shell half, leaving about 3/8" on the outside of the shell half. Layer stars on the outside of the shell halves, and change the burst to same bp hulls, but 8 to 1 whistle mix. Fill remaining space in center of shell half until level with top, GENTLY tap both shell halves to get the hulls to fill all the little nooks and crannies, top up the shell half(s), for good breaks, make sure your stars (3/8" for 3's, 1/2" for 4's is a good starting point.) stay on the very outer edge of shell halves, if you have a couple fall in to the burst, don't sweat it, just leave the fallen ones and add where needed.(You can tell anyone watching that those are the inner petal stars hanging there haha) If alot of your stars fall into the burst, dump it, seperate the burst and stars and start over.
Okay here's where there will be a HUGE bone of contention with everyone, however, I will tell you that my fours break like commercial six's so, do what you feel safest doing, I will.
Before flipping shell haves together, add 1/4 teaspoon flash to each half in the center of the burst (1/2 teaspoon total)( Just 70/30 perc/dark/black aluminum, nuthing fancy or more sensitive) for either 3's or 4's. Flip shell halve together, apply glue as mentioned above, and follow same procedure for closing, except this time use two strips of strapping tape, from fuse over top back down to fuse, add second strip 90 degrees over, so when you look down on top of shell tape should look like crosshairs or a + sign. I've found the trick to be filling them as full as possible and tap, tap, tap away to close them so there is no movement or rustling noises inside of shell when done, don't spare the solvent/glue and let them set up until you can't dent the seam with your fingernail, if your patient, they will break as big as commercial 6" shells, but the seam HAS to be rock hard before firing. Cross match 1/8th " from fuse end for 4's and 1/4" from fuse end for 3's. Lift is shell Weight in pounds or ounces, divided by 16, generally accepted rule however your results may vary, test, test, test. I use 1 F G for 3's and 3 F A for 4".........Geez, look at the time, ok, on to 6's and 8's and bigger when time allows.

My point to this post is that the methods described above leaves virtually no appreciable fallout, gives great breaks and up to four inch, reqire NO pasting in. So Have fun, and I can't wait to hear the "fallout" from my putting flash in with them to beef up the break....haha. To date I've had no mishaps, however, safety is a relative term when working with all energetic materials, Have fun, stay safe/green and stay tuned........

Regards,

Bear

[Sparkler]

Sorry to bring up an old topic but, I have a few questions before I attempt to make my own plastic shells. Question 1;By strapping tape do you mean the polyester backed tape with fiberglass strands? Question 2; How wide should the strapping tape be? Question 3; How big should the stars be for 2 inch shells? Question 4; I have commercial FFg Black powder, would this be okay to use for lift?

I have also found this tutorial by United Nuclear(surprise) for making plastic shells.
http://unitednuclear.com/shell.htm

P.S.- Would like to see those tutorial for 6 and 8 inchers.

Edited by Sparkler, 02 June 2004 - 03:48 AM.

[BurlHorse]

1)Yes, the Strapping Tape is as you described,

2) 1/2" wide will do nicely.

3) 1/4" rolled stars are probably the biggest you'd want for 2" shells, but for very fast burners, 3/8" will be fine. Test them and find out, Light one and count it out, one m-i-s-s-i-s-i-p-p-i, etc.

4)2ffg Is Great for Festival ball Size shells and up to 4" shells, but again, test them and time them, it's you best repeatable method and it gives you an excuse to GO LIGHT SOMETHING....hehehe

Regards,

Be Safe,

Stay green,

Bear

[Jerronimo]

Hey thanks for all the info Burlhorse!

I normaly use methelyne choloride for bonding the shellhalves together, won't make that much of a difference I think.

The tape you mean is also sold under the name ''ducttape'' I think
or have I got the wrong kind in mind. I use the same method U discribe.

With chlorate starcompositions I use H3 to break the shells, Bp based stars I break with BP and a centre ''booster'' of wistle.

Sadly I don't have any vid's of these shells doing their thing .
My cameraskills are still rather poor.

Edited by Jerronimo, 02 June 2004 - 06:02 PM.

[sasman]

Im just got back from my holiday and the first thing i wanna do is Fire my 4" plastic ball shell

...I have just glued the hemis together using Cellulose thinnners as Adam Mentioned in another post. I'm not to sure about the strength of the joint so i think ill make some styrene glue as burlhorse mentions..But im stuck on the strapping tape?.. Is it duct tape? if its not were can i get some?...It might not be needed for a ball shell but i would like to use some...What kind of store would sell it? and what is it actually used for?

Cheers