25 replies to this topic

[Potassium chlorate]

I guess it depends on the size of the shell to the % of lift.

The bigger the shell the less lift is required as a percentage of the weight (also as shell size increases the powder speed needs to decreased).

Ultimately there is not an exact answer, as the amount used will depend on the grain size. A bigger grain size will require more powder than a smaller grain size.

So go and shoot some dummy shells in a nice wide open space and time the flight time for different powder grades and amounts. This will allow you to optimise the break height for your shells.

I was thinking about this. My BP is excellent, but the coarse grains are pretty big, up to 10 mm or even more in a few cases.

For up to 3", I use powder that goes through a spaghetti strainer of metal but not a fine tea strainer, i.e. 1-2 mm or so. I only need 6% of the shell weight to lift it about 50 meters, which I think is pretty high for a 3".

However, when I fired 5", I had the coarser BP, and then I needed to increase the amount of BP to 10%. Ergo: the coarse BP is somewhat too coarse, but how much? 6% of the finer BP would probably be too powerful and even cause a flowerpot.

Some rule of thumb for how fine BP I can use for 5" and upwards without risking a flowerpot? I also prefer a "soft" lift if possible, so that the lift isn't louder than the break.

What about the maximum grain size in mm being the same as the shell diametre in inches? Does that sound reasonable?

[BrightStar]

I was thinking about this. My BP is excellent, but the coarse grains are pretty big, up to 10 mm or even more in a few cases.

I'd say 10mm was very big! It's bigger than the coarsest 1FA blasting powder (4 - 8mm) and twice the diameter of Canon Grade BP (1.6 to 4.7mm)...

What about the maximum grain size in mm being the same as the shell diametre in inches? Does that sound reasonable?

It sounds a bit complex. You might be better off just making two grades of lift powder consistently and tuning the quantites to the applications.

The common grades for lift use seem to be:

2FA - 4 to 12 mesh (4.76mm to 1.68mm)
3FA - 10 to 16 mesh

2FA is used to lift larger shells, 3FA smaller shells. Having said that, I've seen a 5" ball lifted with reasonable quality 3FA at 16:1 by weight, though it certainly got some height on it...

Edited by BrightStar, 20 September 2010 - 09:54 PM.

[Potassium chlorate]

But 4-5 mm would be OK even for the biggest ones, then?

[Vic]

But 4-5 mm would be OK even for the biggest ones, then?

Making your lift with a spaghetti and tea strainer isn't ideal and it will be a matter of you dialling it in due to the non-standard sizing. You can try some dummy shells with comets on so you get a better idea. It's time consuming I know, but worth it in the end. However, if you go to that trouble you might as well invest in some screens; If you push it through an eight mesh you won't go far wrong.

Oh and a word of warning (I'm getting good at these) if you do fire dummy shells, keep well clear of the fall out area as I didn't and had a very close call .

[Potassium chlorate]

I do fire dummies, but I avoid it as much as possible, since the only "acceptable" time shooting fireworks where I live is for New Year's Eve and Easter, and I don't want to annoy people, of course.

8 mesh is about 2.5 mm. That's actually a little bigger than the spaghetti strainer. I have 10-20 mesh for the finer BP. For the bigger ones I think 4 mesh would be acceptably big considering the quality of my BP.

[BrightStar]

But 4-5 mm would be OK even for the biggest ones, then?

I've never seen anything coarser than 2FA specified in shell making tutorials, even for large canister shells. Never say never though...

The mesh range given defines the limits, not the 'ideal size', so all of your 2FA once dried should pass through a 4-mesh screen and it should all be held on a 12-mesh screen.

The majority of granules will be somewhere in the middle between the two limits and you will have to experiment to find the actual screen mesh and method to make it. As I mentioned, consistency here is important.

[c.brad]

quick question wat is easiest to make 3inch or 2inch because i have seen topics about 3inch shells being easier is this true

[dr thrust]

two inch may be slightly easier to make, but they both involve the same advanced skill level , heres a link to a shell tutorial 3" shell this will give you an idea of whats involved

[drtoivowillmann]

hi i have some three inch shells ready for nov 5th but last year i did one and it bascially rolled out of the morter and went over the fence ( into a woods) and exploded there, litterally scimmed over the fence, this is my upmost fear ever since then i have put into the shells more than enough lift powder, but im just wondering - how much is too much? like what willl fllwerpot theshell#/ also i dont want to to bee too loud (naouboes probbley wont of herd that many cat4shells going off yards from there windows hahah) i know that the avg percentage ammount of bp to shell ratio is usally arround 10 - 12.5 percent but i have loaded up the shells with like 30 - 38 percent of the shells weight! ov corse safty is paramount but could my fearof putting too littlelift in a shell is a hazzord? i dont want a flour pot but nor do i want anouther innsadent of last year, i could do a dummy shell , with say - 15percent of the shell weight and just use a tenniss ball full with the respective weight in dirt?

please tell me your thoughts on this matter, and sorry if im making anouther post on what has alredddy been coverd, but i couldent find any!

Dear Friend:

For Your orientation, her's a list, using commun Black Powder:

Shell Powder Charge
2" 8 g
3" 20 g
4" 30 g
5" 45 g
6" 60 g

Note: the lifting charge is NEVER proportional to the weight of the shell. Who says so, tells you nonsense.

Greetings from Brazil:

Toivo

[PyroCreationZ]

I always use 10% of the shell's total weight and this has worked good for me.
If I make a 2" and the total weight is around 50gr then I use 5gr lift. However I do tend to add just a few grains more up to 5.5gr.

Recently I launced a 4" half full of scrap BP and half full of kitty litter (dummy shell and my first 4" btw ).
I used the same powder and again 10%. The height seemed about right.

I have a (short) list of Shogun shell specs and make my shells based on that.
Especially for the timefuse e.g. 2" = 2sec, 2.5" = 2.2sec, etc. Although I haven't made a lot of shells, each one of them worked perfect based on that list.

Reading the comment above that would mean either my BP is better then common (= commercial?) BP or my shells don't go high enough? Lol
Imo 8gr for a 2" sounds too much ... atleast for commercial BP.

Edited by PyroCreationZ, 03 December 2010 - 05:14 PM.

[Mumbles]

I've never seen anything coarser than 2FA specified in shell making tutorials, even for large canister shells. Never say never though...The mesh range given defines the limits, not the 'ideal size', so all of your 2FA once dried should pass through a 4-mesh screen and it should all be held on a 12-mesh screen.The majority of granules will be somewhere in the middle between the two limits and you will have to experiment to find the actual screen mesh and method to make it. As I mentioned, consistency here is important.

I've never seen larger than 2FA specified, but then again I've never seen a tutorial for a 12" 3 break shells either. In reading through passfire, the large shell builders who use traditional italian-american techniques mention that 1FA is used if available for a little gentler lift. They also state that 2FA can work just fine too. I believe there is a mention in Fulcanelli about grading 2FA, and using the 4-8 mesh for lifting larger shells, and 8-12 for smaller.

I generally use 4FA to lift smaller shells. It's both more available than 3FA, and is a very logical choice when making your own lift.