1569 replies to this topic

[al93535]

I used BP coated onto rice crispies, with one gram of flash loose in the center.

Edited by al93535, 13 March 2006 - 12:45 PM.

[karlfoxman]

thanks for the info, i have made 3 inch shells with 7 layers and they shatter because i found parts of them all over the field. so maybe i should try 8-13 layers and see at what point the shells perform best. after seeing heinz's second 4 inch shell movie i think i will be getting some titanium. where is the best place to get it? i.e what uses will the spherical Ti 250-500?m have except pyro?

[paul]

I finished my new 3" shell, too. The break will be very weak, so I hope to get the desired effect of falling stars more than a perfect flower.

?Used 7layers of craft paper for pasting. It?ll be a crysamthemum peony shell.




The pasting isn?t too smooth, because I used homemade shell halves like these
http://www.kkpaul.rp...alb_zuender.jpg

So I have to improve my pasting skills alot...

Greets, paul

Edited by paul, 01 March 2005 - 06:05 PM.

[karlfoxman]

they looked quite smooth to me, when you paste the shell with strips try cutting them so the top part is a triangle. this will stop the top getting a bump and i know pro ones use this method as i have found fragments of thm before. a good place to get shell formers is an art shop, they sell polystyene balls different sizes. i still think i will paste 13 layers on my 4 inch shells i have lined up. my 4 inch mortars arrived today and to my pleasent supprise they already had the wooden plug in the bottom!! i am hoping to video them so as soon as i do i will post

karl

[aapua]

Hi everyone!
Here I'm gonna describe my "weird" way of making spherical shells. Important - I don't use any paper at all, and still I have very-very-very strong shells.
First I need a base on what I will make my shell. A simple rubber ball is OK. I cover it with plastic foil, then with a sheet of paper (sorry, the only time the paper is needed...), after that I tape it tightly. This step I need to get my base (a rubber ball) back in one piece so I can use it many times. If the base goes up to the sky as well, go stight to the step two.
Step 2. For making a shell I need 3 components: dextrin, wood or paper dust (fine sawdust is OK) and glue PVA (polyvinylacetate).
Making a shell is actually like growing your round stars. Wet the star and shake/roll it in a mixture, let it dry and repeat until the desired size. Same here. I make a solution of PVA and water. Drop the ball into it. Let it wet.
Mix 1 part of dextrin with 2-3 parts of sawdust. Put the wet ball into that mixture, shake, let it dry. Then drop it into the PVA solution, then shake it with the dextrin/sawdust mixture, let it dry. And so on. After 3-5 covering the shell is ready to cut into half. (Only thing is that I have to cut it very carefully for not cutting my inner rubber base). Fill these two halfs with your stars etc, put together with the tape and continue with step 2 until the size you need.
For the extra strenght I use pure PVA instead of solution in the very first and the very last layer.

And that's it. I found this method be more quick than classical "cabbage", and even more important - it gives in my opinion super quality. For 3'' shell I cover 'bout 7 times. Mostly I use silyndrycal shells, but all my spherical ones made with this method worked exellent!
Right now I'm working with my first 6'' shell. I guess covering some say 15 times would be OK. Effect I hope would be not bad as well - this shell will be filled with many-many small, 1'' shells. I'm gonna shoot it hopefully next week.

Any comments, suggestions, remarks and what ever are very welcome!

Edited by aapua, 02 March 2005 - 01:04 PM.

[paul]

For me this sounds more time-consuming than the other methods although you repudiated it (have to try that!) .But it sounds very very interesting, because I could imagine, these shells get very very smooth.

Do you use the finest sawdust available?! And how often do you set these shells aside to dry. After every additional step?!


greets,

kkpaul

EDIT: I forgot to ask about the "problem" with the timefuse. When do you glue it in?! I imagine rolling the shell - with the timefuse allready glued in - in dextrine/sawdust is a bit difficult first?!

Edited by paul, 02 March 2005 - 01:20 PM.

[aapua]

Do you use the finest sawdust available?!  And how often do you set these shells aside to dry. After every additional step?!
greets,

kkpaul

EDIT: I forgot to ask about the "problem" with the timefuse. When do you glue it in?! I imagine rolling the shell - with the timefuse allready glued in - in dextrine/sawdust is a bit difficult first?!

Sawdust should be as fine as possible. But, I've tried sawdust about 0,5 mm - maybe 2 mm size, the result is OK, although making is a bit complicated.

The drying depends on quality you need - same as with stars. The best way is one covering per 24 h. I usually do one covering in the morning, second in the evening.

Good you mentioned the time fuse. NO, IT IS NOT A PROBLEM, BELIEVE ME OR NOT. After I cut the shell into 2 pieces, I load it fully (it means time fuse as well). Then I cover the very end of fuse with lack or paint to prevent water and glue getting in. The shaking with or without the time fuse - I see no difference... I always make the time fuse about 1 cm longer than needed, after the shell has its desired or required size, I cut the extra piece off.

[Stuart]

That sounds like quite an easy way to make the shells. Do you have any pictures of the finished product?

This method could easily be adapted for very quick mass production. Sure you have to wait about 24 hours for each layer to dry, but you could do a good 100 shells in five minutes if they weren?t too big and let them dry.

[ProfHawking]

yeah i like the idea. Also, it wouldnt take any longer to make big shells, than small shells. All you do is dip roll dip roll etc.
could get a production line thing going and churn out a hundred in a batch if you set your mind to it.
I might have a go when/if i run out of plastic hemis

[aapua]

That sounds like quite an easy way to make the shells. Do you have any pictures of the finished product?

This method could easily be adapted for very quick mass production. Sure you have to wait about 24 hours for each layer to dry, but you could do a good 100 shells in five minutes if they weren?t too big and let them dry.

Tnx. It's a bit a problom with pictures. But I'm working on it, so hopefully in few days I can put something for others to see.

As a mass production, chinese shell-makers use pressing method. In this case they use almost dry mixture of dextrin or rice starch and cellulose which is put between two spherical plates and compressed to form half sphere. Before my method, I also started with cellulose. Simply take whole sheets and hold them in hot water, this will give you a "porridge" of cellulose. I tried to press it and did even more different things, until I decided to mill the dried remains. It gave me almost ideal powder. From that I worked out the method I described earlier.

[italteen3]

If you have problems getting a host, let me know I can help you out there. If it is getting digital pictures then thats a whole different story.....

[paul]

aapua, I have access to cellulose powder. The particlesize is 200?m (0,2mm). I think this should work, too?!

Because I can?t get my hands on wood dust and this powdered cellulose costs me 4.2? per Kg....


thanks in advance,

paul

[aapua]

aapua, I have access to cellulose powder. The particlesize is 200?m (0,2mm). I think this should work, too?!

Because I can?t get my hands on wood dust and this powdered cellulose costs me 4.2? per Kg....
thanks in advance,

paul

The particle size should be just exellent, all I can say is I truely hope it will work :-)
So, good luck for trying, and let know how it worked out when ready?

[aapua]

And one more question to all. What burst charge do you use, what is the shell size when burst should be in the centre and what's your construction for center charge?

So far I've made mostly 3'' shells, they don't need central charge. For the large ones I make extra, smaller inner shell for the burst charge, just it is not as hard as the main shell itself. I drill holes in it (since I use powder burst charge, I have to pack it into plastic first) - maybe some 20 or so holes. Any comments - are the holes necessary? And even more interesting, since I haven't made too many experiments yet, how hard / strong has to be the burst holder? Isn't there a danger that too hard / strong inner shell makes the ignition of stars worse or even breaks them instead of igniting?

Thanx,
aapua

[paul]

Today we shot 3 shells.

I?d like to share one of them with you It?s the 3" crysanthemum peony shell from the picture earlier in this thread.

http://www.kkpaul.rp...zoll_willow.wmv There it is.

The lift (15g of obviously relatively weak CIA blackpowder) wasn?t strong enough (don?t know why, worked great in the past...) so the shell lwas lifted to about 30m I think

But anyway the effect is great for such a small shell with 8layers pasted and only blackpowder as the breakcharge.

greets,

paul

ps: Here?s the video of my poor spiderweb shell. There were more sparks but anyway it looks weird

http://www.kkpaul.rp...derweb_poor.wmv

Edited by paul, 06 March 2005 - 09:43 PM.