Making shell hemis

[PyroCube]

Hi all

 

Is there a simple and reliable way to make shell hemispheres myself?

I know I could just buy them, but my pasted shells are always a bit too small and I have to make them

bigger by applying some masking tape so the shell fits tight enough into the mortar.

 

 

Greets

[ollie1016]

I believe NighHawk has a good YouTube tutorial on hemis's, if not have a look on YouTube. Your shell doesn't need to be tight in the mortar tube! It doesn't need to be fitted like a bullet. You can leave 1/4"/5mm around the shell and it'll be fine.

I'm sure more experienced guys will add to this topic. Ollie

[LambentPyro]

I believe NighHawk has a good YouTube tutorial on hemis's, if not have a look on YouTube. Your shell doesn't need to be tight in the mortar tube! It doesn't need to be fitted like a bullet. You can leave 1/4"/5mm around the shell and it'll be fine.

I'm sure more experienced guys will add to this topic. Ollie

 

I'll second this, but it takes a while and I can't really find a good sized former.

[schroedinger]

Look at the tutorial section, there are some quite god way shown to make them.

 

They start from the Japanese method by pasting Strips on to a core, over to making formers for pressing hemis.

[Mumbles]

This is one of the better ones we have here: http://www.amateurpyro.com/forums/topic/5505-newspaper-hemispheres/

[Seymour]

While this only helps for 3" shells, which are not exactly the best shell to make (fours are much better for beginners) a tennis ball is ghetto fabulous for 3" hemmies. Paste a dozen layers of newspaper over it and cut through the pasted paper - but not right through the tennis ball - and you have hemmies. Obviously you can do the same with other sized balls.

[PyroCube]

Thank you all. The tutorial really convinced me, I`ll give it a try.

@ Seymour I really want clean and good looking hemis, maybe even better than the comercial ones. I dont

think I can achieve this with the tennis ball method...

 

Greets

[Bonny]

I used to make 3" hemis with ~2.5" wood balls. To start I'd wrap the balls with a layer of saran wrap. Then paste on strips of kraft paper, don't remember how many layers I did though. To smooth, simply roll the ball around on a table or whatever. Once dried I'd slit in half. To do this I made a slitter using a pizza knife blade and a 1/4" bolt. I'd chuck the slitter in my drill press and set the table height for centre (yes centre... Canadian spelling) of the hemi. Rotate the ball to slit in half, pop off the hemis and you're good to go. If you could find bigger wood or plastic balls I'm sure it work just fine.

[Arthur]

IMO most hemis are a good size for proper firework mortars if they are used with sufficient pasting wraps. Before you redesign the hemi check that your pasting meets the usual standard. Often the pasting helps the burst and igniting the stars.

[schroedinger]

Found a good descryption of the method on the UK Forums, interesting how you made your former mumbles.

 

But i still have on question, the vacuum, how strong does it need to be?

Just some normal vacuum e.g. 850 mbar or stronger?

Edited August 20, 2013 by schroedinger