Shell Size vs Mortar size

[bobkeyes]

Being a newbie I am confused about what size spherical shell goes into what size mortar tube. I want to start making some 2" shells. What size mortar should I buy??

 

Thanks for the info.

[mfstraydog1]

well the shell should be a little smaller than the morter. for example if the motor is a true 2" ID. then a spherical shell would be around 1 5/8 " this allows for pasting and such. for a 2 1/2' moter a 2 1/4' shell would work.

 

i hope this helps

 

 

[jwitt]

You want a mortar with a 2" inside diameter. Several pyro supply stores sell HDPE mortars that are already plugged at the bottom.

 

If you are making paper shells, 2" hemispheres are what you need. They do not actually measure 2" - pasting the shell brings its dimensions up to spec. You want a sliding fit in the mortar with a bit of clearance- shell diameter should be 90% of mortar ID.

 

Plastic shells are made a bit differently, but once again, you would buy 2" shell hemispheres.

[bobkeyes]

Thanks Guys. On the sites I have looked at, most don't give the actual size. I was worried that after taping etc. a 2" shell wouldn't fit a 2" mortar.

[jwitt]

Just to be 100% clear- when ordering stuff, mortars and shell hemispheres are listed as 2", 3" etc to make it simple. A 2" shell hemi is designed to be pasted up to the size that fires from a 2" mortar.

 

 

It gets more complicated when you talk about "festival balls" or consumer shells because there are a few different sizes on the market. This means that you have to be careful of dimensions if you make a mortar rack to fire consumer shells!!! You would need to take calipers to the fireworks store or otherwise make sure of the shell diameter, or else you risk low breaks or flowerpots from too-loose or too-tight fit, respectively.

 

 

Are you doing paper or plastic? Many folks recommend paper. It takes some work to paste 'em, but they work wonderfully and don't leave plastic debris everywhere around your shoot site.

[mfstraydog1]

jwitt is right i did not mention that when you buy shell they are specified by the inside dieameter of the mortar. the numbers i gave you are the ruff dementions of plastic shells, paper shells might be a little diffrent in dia.

[bobkeyes]

Well, I still have a problem. If I go here http://www.americanp...R_HEMI_S_2.html and buy the 2" paper hemis it says they are actually 1 7/8". Then I go here, http://www.americanp...AR_TUBES_2.html and buy a 2" mortar it says it is 1.917 ID typical. That's not a lot of room for pasting??

 

See my problem? If I want to shoot a 2" shell I can't seem to find the right combination.

 

Looks like I may have to go to a 3" to get a good combination. What do you all think??

Edited August 13, 2010 by bobkeyes

[Cookieman]

Well, I still have a problem. If I go here http://www.americanp...R_HEMI_S_2.html and buy the 2" paper hemis it says they are actually 1 7/8". Then I go here, http://www.americanp...AR_TUBES_2.html and buy a 2" mortar it says it is 1.917 ID typical. That's not a lot of room for pasting??

 

See my problem? If I want to shoot a 2" shell I can't seem to find the right combination.

 

Looks like I may have to go to a 3" to get a good combination. What do you all think??

 

 

Go for it! go for a 3" inch or you could always look for other suppliers.link

[bobkeyes]

Thanks a lot. I'll be working on the 3" then.

 

You've been a big help.

[jwitt]

I think you'll be happier in the end with 3" anyway. OK I haven't shot 2"...but folks say that 3" is easier to build and easier to get symmetrical breaks with. And they're WAY noticeably bigger than consumer stuff

 

I imagine that people build smaller shells so they can shoot at home as opposed to running out to their shoot site. There's advantage in that, as well as star testing. If I'd ever want to do those sorts of things, I'd make film canister shells.