Need some help possibly!

[viziers]

Ok maybe im wrong but when i make my 3", 4" and the 6" shells my commercial 1f BP lift charges are as follows any correction is very appreciated.

 

3" shell weight is roughly 100g w/20g BP w/3 sec fuse

4" shell weight is roughly 300g w/50g BP w/4 sec fuse

6" shell weight is roughly ? w/? BP w/6 sec fuse

 

would you say these lift charge weights are good, Because ive noticed

that most make their own and use significantly less than what i use

and is commercial. Im thinking it right because of the time delay on my fuses. Any thoughts?

 

P.S. all shells are spheres.

[asilentbob]

I don't have any of my data on hand, but i think my 3" shells are around 100g too. I use commercial (GOEX) 1Fg too as lift. I use around 1/14 the weight of the shell usually because my shells aren't always a wrapped enough to be a better fit in the mortar.

[viziers]

I don't have any of my data on hand, but i think my 3" shells are around 100g too. I use commercial (GOEX) 1Fg too as lift. I use around 1/14 the weight of the shell usually because my shells aren't always a wrapped enough to be a better fit in the mortar.

Ok i dont feel too bad about using that much then atleast for the 3" shells

[psyco_1322]

I don't have any of my data on hand, but i think my 3" shells are around 100g too. I use commercial (GOEX) 1Fg too as lift. I use around 1/14 the weight of the shell usually because my shells aren't always a wrapped enough to be a better fit in the mortar.

Ok i dont feel too bad about using that much then atleast for the 3" shells

That would be about 7.14g of lift. Not 20g. Thats a bit over kill if the 7.14g works well. I use commercial fffg (3f) bp at 1/12th the shell weight. And it works exectionally well. Im not sure how you came up with your figures but for the 3" it was 1/5th the weight and the 4" was 1/6th the weight. And your 4" shell holds 200g more than a 3"? That dont sound right either. As far as timeing goes im not sure but 3sec. is about what I use for 3". I came across a few paper 4" tubes and im gonna fiberglass them to use as mortars since the are pretty flimsey and thin. I was wondering about how long should a 4" mortar be. My 3" is ~27" I think, but its a little on the big side in my opinion.

[Frozentech]

That would be about 7.14g of lift.  Not 20g.  Thats a bit over kill if the 7.14g works well.  I use commercial fffg (3f) bp at 1/12th the shell weight.  And it works exectionally well.  Im not sure how you came up with your figures but for the 3" it was 1/5th the weight and the 4" was 1/6th the weight.  And your 4" shell holds 200g more than a 3"?  That dont sound right either.  As far as timeing goes im not sure but 3sec. is about what I use for 3".  I came across a few paper 4" tubes and im gonna fiberglass them to use as mortars since the are pretty flimsey and thin.  I was wondering about how long should a 4" mortar be.  My 3" is ~27" I think, but its a little on the big side in my opinion.

From the Passfire chart for *single break* shells :

 

3 -- 15

4 -- 20

5 -- 24

6 -- 28

8 -- 34

10 -- 40

12 -- 46

 

The mortar length is measured from above the bottom plug. A rule of thumb is 5 times the mortar diameter for shells under 8 inches, and 4 times the mortar diameter for shells 8 inches and up.

 

Source: Illustrated Dictionary of Pyrotechnics

[psyco_1322]

Thanks for that frozentech. Im not a passfiremember but im hopeing to be soon. Ive been wanting to get one. Just got me a PGI membership and am planning on attending the convention this year for hte first time. Hoping to gain some more knowledge.

[viziers]

I don't have any of my data on hand, but i think my 3" shells are around 100g too. I use commercial (GOEX) 1Fg too as lift. I use around 1/14 the weight of the shell usually because my shells aren't always a wrapped enough to be a better fit in the mortar.

Ok i dont feel too bad about using that much then atleast for the 3" shells

That would be about 7.14g of lift. Not 20g. Thats a bit over kill if the 7.14g works well. I use commercial fffg (3f) bp at 1/12th the shell weight. And it works exectionally well. Im not sure how you came up with your figures but for the 3" it was 1/5th the weight and the 4" was 1/6th the weight. And your 4" shell holds 200g more than a 3"? That dont sound right either. As far as timeing goes im not sure but 3sec. is about what I use for 3". I came across a few paper 4" tubes and im gonna fiberglass them to use as mortars since the are pretty flimsey and thin. I was wondering about how long should a 4" mortar be. My 3" is ~27" I think, but its a little on the big side in my opinion.

I know im using about 20% of the shell weight in lift in my 3" shell and i can probabbly reduce the lift charge for the 4" shell by 10g to 20g and still

be ok with a 4 sec fuse time

 

And as far as the shell weight yes the 4" shell weighs 200g more than a 3" i know because i weigh all my shells on a digi scale and record ALL information as far as shell weight, lift charge used and type of stars in the shell and size of stars.

[psyco_1322]

Are you sure your 4" shell weights 300g when the 3" is only 100g?

[viziers]

Are you sure your 4" shell weights 300g when the 3" is only 100g?

Yes im POSITIVE without any dought (sp)...

[viziers]

Give me 5 minutes ill go check and report back ASAP...

 

 

EDIT: Yup those figures are correct.. My stars are pumped from a 3/8" piece of copper pipe.

 

P.S. I weigh just the finished shell minus lift charge and pouch and quickmatch.

[psyco_1322]

Strange. Are they the same type of stars? The shell isnt out of porportions with the other is it? Ah...nevermind. 3/8" stars in a 4" shell seems small. I use them in a 1 3/4". Unless they just burn really slow.

[viziers]

Strange. Are they the same type of stars? The shell isnt out of porportions with the other is it? Ah...nevermind. 3/8" stars in a 4" shell seems small. I use them in a 1 3/4". Unless they just burn really slow.

Nope i use the same size stars in both the 3" and 4" shells.

[psyco_1322]

OK then.

 

I need to make some 3" paper cylinder shell casings. Does anyone have an easy way to do this? Ive seen those wooden stick things but how the heck do you use them? I know you wrap paper around it but thats all.

[viziers]

Sorry ive never used paper hemis before ive only used the plastic ones.

[psyco_1322]

Im not wanting hemis though. Cylinder shells dont have hemispheres. Hemispheres are round hence the sphere in the name. A common mistake. No harsh feelings.

[Frozentech]

OK then. 

 

I need to make some 3" paper cylinder shell casings.  Does anyone have an easy way to do this?  Ive seen those wooden stick things but how the heck do you use them?  I know you wrap paper around it but that's all.

It's really well documented in Pyrotechnica IX and XI, the "Fulcanelli articles".

 

Basically, for a 3" cylindrical shell, you use a 2.5" diameter former ( "that wooden stick thing"), and 3 wraps of 70# kraft paper, just taped to hold together. An end disk is placed, and the "slack" paper pleated down and glued to seal one end, then a 2nd disk glued on. The shell is filled with your desired contents, then an end disk (with fuse unless you chose to build from the top down) is placed, the end paper pleated down, and a final end disk glued in place. The entire assembly is then spiked with strong twine, for a 3" shell, a 12 vertical pattern is traditional, with horizontals about 1 per cm. Then the entire assembly is pasted in with wheat paste, and dried. A final 2-3 wraps of ~30# can be pasted over that, with a final 2 wraps of 30# to hold the lift charge and form a bucket for the leader and passfire.

 

I highly recommend reading the Fulcanelli articles, or getting a Passfire account for more details.

 

Some pictures of the process can be seen at http://www.pyrotechs.org/content/view/18/44/

[psyco_1322]

OK thanks thats a great tut. It will help me bunches.