Aerial Shells

[50AE]

We fired some of the shells on Friday night. Here's the video.

 

http://www.youtube.com/watch?v=bJWwjVweKRw

[PoorBoy]

I have been searching because I think I saw this question or a similar one answered a long time ago but I can't find it, or at least couldn't in the last half hour I have been looking.

 

I use a table for lift while building spherical shells, and want to test my hand at canister shells but dont know the lift ratio. I know multi break shells require more lift and a longer delay but for sake of argument lets say we are talking about a single break canister shell and its heavy.

 

Is there a lift:weight ratio you guys use, because I saw videos of 5" can shells like 3' long, I think nighthawkinlight made them. how is the lift calculated? I get the gist of everything else and with much practice i'll figure it out.

 

I figured there has to be some formula to give you an idea of where to start with the lift and then i can fine tune it for my specific bp later.

[Weirdo]

I hope I did get your question right. For all my shells, spherical of cannister I use 10% of the weight of the shell. So If I have a 5 inch cannister thats wheighs 900 grams I use 90 grams lift. You can calculate it to, for the people that dont like thinking . (Shellweight/100)X10=Ammount of lift.

[Pretty green flame]

*SNIP* (Shellweight/100)X10=Ammount of lift.

 

Or Shellweight / 10 = Ammount of lift. Same thing

[Mumbles]

Actually multibreaks need less lift, and shorter delays.

 

The rule of thumb is an ounce of 2FA per pound up to 10lbs, and then half an ounce for every additional pound after that. Obviously this is a very Imperial system rule of thumb. Under 10lbs it works out to

 

shell weight/16 = lift

 

Over 10lbs it works out to:

 

(Shell weight-10)/32 + 10oz = lift

 

Thus it works out that a 4lb shell uses 4oz lift, an shell uses 8oz of lift, a 20lb shell uses 15oz lift, etc. More often than not, just to be on the safe side, I round up everything to the next half pound. So a 300g 3" shell is lifted with a full oz of 2FA. A 400g 4" shell might be lifted with 1.5oz, and so on.

[PoorBoy]

Yup, you guys hit the nail on the head that is exactly what I was asking. what started this is I wanted to make an 8" ball shell for 4th of july and saw the expensive cost of the larger mortar tubes on pyro direct and decided it would be more cost effective to do a longer 4" can shell to get a similar amount of stars in the sky. I'm still growing in terms of chemical inventory and would rather increase variety than to spend the money on bigger mortar tubes right now.

 

I found tables for canule size and such and i found tables for lift on ball shells, but you guys filled in the blank on canister lift. Thank you.

 

Mumbles Partial Quote:

Actually multibreaks need less lift, and shorter delays.

 

I figured on shorter delays between breaks, but I thought you would want a longer delay on initial burst and extra lift to get it up higher.

My thinking was that it needs to be higher due the 2nd 3rd 4th etc breaks would be falling the entire time. I'll attempt to explain my thought process so you know what i mean.

 

EX: Initial break 4 second delay and extra lift and the following breaks @ 1 second delay each. So that a 3 break shell would rise for 4 seconds and for the 2 seconds following you have the last break falling towards the ground so that when it bursts it is 2 seconds from the ground.

 

I obviosly didn't do any calculations of physics and gravity to figure initial velocity versus constant pull of gravity, but assuming the shell burst at apex I thought that made sense. How would you calculate lift on a 3 break 4" shell? I'm just curious cause Mumbles never posts bad info so that means I need to get a better understanding of how lift and timing works on multi break shells.

 

Thanks guys.

[Mumbles]

I see what you meant now. I was talking between breaks. It is normal to start breaking multi break shells on the way up, at least with several breaks. With only 2 or 3, I generally shoot for just before the apex so that all of them are around the top, but that is more personal preference than anything.

 

As far as lift, just weight it and use the appropriate amount. It will probably weigh on the order of 3lbs, so 90g of lift.

[Arthur]

It's should be a design feature not accident that chooses whether the separate breaks in a multi, break on the rise, at the apex, or over the top.

[Weirdo]

Or Shellweight / 10 = Ammount of lift. Same thing

 

 

 

Haha, your right xD never thought about it .

 

 

[PoorBoy]

I never thought of multi breaks breaking on the way up, glad i asked that question. It would be pretty neat to design a shell with a lot of breaks, that is fired on an angle breaking on the way up and down making a glittered arch like a rainbow in the sky. That gives me a cool idea for something down the road after I learn the art of canister building.

[Arthur]

Big arches are often big, fast, thick tailed comets. Over lift them and they burn out in the straight portion of their flight, under lift them and they curve over at the apex and come back down too far. Chose the lift carefully!

 

A big shell can have a 5 second fuse and that's a long while to wait and things go too high if you over lift them then the effect is lost.

[Mumbles]

I actually have a pastel rainbow 3" or 4" multibreak planned. I'm looking at 6 breaks and a bottom shot. When you get to really big and heavy shells, there is actually a different way to lift them that allows you to use less and lower quality lift powder. I think it starts becoming economical around 10lbs or so. I mean it doesn't take anymore lift below this, but you don't save any for all the extra work.

[PoorBoy]

Arthur: Yea, I figured it would be a little tricky. The lift ammounts would vary from shell to shell depending on the exact weight and the quality of the batch of BP I bet. I know from past experiences I one batch might vary slightly depending on the type of charcoal used or time it was milled or how wet it got when it was granulated. I know thats a bit of over thinking it, but I imagine due to changing variables in this project it would be tough to design one that works every time just the same as the last. It's definately a (way in the) future project lol.

 

Mumbles: You will have to post a video when you launch that shell, I am interested, I have never seen that effect before. What do you mean by a different way to lift shells? You really got my attention there, I have never heard more than one way. Has this already been explained in a different topic or maybe in this one? I would search, but I don't know what this method is called or what keywords to type in that won't bring up most of forum as a result. How can a shell be lifted differently than bp under a shell inside a mortar?

 

 

( I put inside a mortar on purpose so that no one replies, "with a rocket" lol.)

 

 

[Mumbles]

It's generally called the "Maltese method" or "sabot method". It's along the same lines as normally lifting shells, but adds a little extra work, but allows you to use less and lower quality lift.

 

How this works is you take your BP, and granulate it and all that like normal. No need to press and corn or anything like that. You fill your lift into a paper canister, just like you'd make for a canister shell. You spike it, just like a canister shell. This is what allows you to use somewhat lower quality lift. Between the shell and this lift maroon, a plywood disk and a thick wad of rolled up news paper are placed in. This in theory makes somewhat of a seal for the lift gasses, which is partly what allows you to use less lift. Passfire has an excellent tutorial on this kind of stuff.

 

One downside is that the lift amounts have to be experimentally determined, as it doesn't follow any linear pattern.

[PoorBoy]

Ok, I see. Its basically allowing the bp to produce the gasses, which are all released at once instead of at the speed the bp burns. Is this what people are talking about when they say they are going to build a maltese shell or is that something different too?

 

Cool info, I'll keep this in mind for when I start getting into bigger shells. I believe the heaviest shell I have made was around 2 pounds or so. I didn't weigh it at the time, it was a 4" filled with 3/8 granite stars, packed with bp rice hulls, and mill dust to fill voids. Maybe I'll test this method out on one of those just for fun. if I would normally use 2 oz, would you start the testing of maltese method with 1 oz lift? I realize I'll have to figure out the exacts on my own due to all the variables. This sounds like a cool build though, I bet the noise sounds alot cooler than the traditional bp under shell lifting. Probably a much better BANG.

[Mumbles]

Honestly, the lift is quieter than you would expect. Quieter than a normal shell lift in my experience. It may just be that I am generally farther away from these shells when they're being fired. Maltese shells are a style, technique, and a variety of shell. It can apply to a lot of things. Generally, they refer to multi-break canister shells made with special techniques to take advantage of cheaper materials. They often contain numerous salutes. The lift method is just one aspect of the shells that allow them to take advantage of cheaper materials.

 

I would honestly start with the same amount of lift as you would use anyway. 2oz of lift. As I said before it doesn't really become a viable lift saving technique under 10lbs from what I've heard. Maybe a little less, around 1.5oz since it's only a single break. Passfire has some experimental details for 5 or 6 shells of different weights. For what it's worth, the 6lb shell they list uses exactly 1oz per pound (180g). A 20lb shell is listed as only 200g. Once you get sufficiently heavy, around 10g per pound seems about average. It conveniently works out to around half of the required amount by the rule of thumb I posted above once you get to 15 to 20lbs. You wanting to only use half of the required amount on a 2lb shell may not work out all that well.

 

One other thing I should mention is to NEVER fire a shell lifted like this from an HDPE or cardboard gun. The lift plugs can't survive the lift. Steel is greatly preferred for it's strength. Fiberglass may be able to stand the lift in smaller shells, but not over a few pounds. I wont use them for canister shells over 8 or 9lbs period, and would never dream of using this lift method in fiberglass period. Then again I'd never use this lift method unless the shell weighed at least that much anyway.

[50AE]

By the way, I blew my cardboard mortar from lifting a long 4" can shell. I shared this fact with a professionnal pyro and he told me that recommend the using of steel mortars, not cardboard. What has happened is normal. The same cardboard mortars are successfuly used to fire spherical shells.

[Seymour]

I've used very similar processes to lift shells from 3" to 6", canisters and spheres, from both HDPE and paper tubes, though I guess a 6" ball will not stress the HDPE tube as much as a 6" four break canister.

 

Usually I am too lazy to go all out and spike the lift charge, but I always confine it at least as well as a 'polumna' style lift charge. It allows a small quantity of crap lift to shoot a shell quite high, very reliably.

[pudidotdk]

It's not often I get the opportunity to fire stuff, but yesterday I went to a birthday held on a farm.

Lot's of space, perfect for a few shells.

 

I was testing for 10% different metals mixed with TT (400# spherical alu, german dark, MgAl, Ti)

Granite shell blew blind, I suspect it was because I used some flash. The others I used whistle as booster.

Burst was 7:1 KP:Rice Hulls and 4:1 BP:Rice Hulls, mixed 50:50 by volume. Worked pretty good.

Shells were taped with some fiberglass tape: (4" not fired yet)

 

http://i.imgur.com/mSsOm.jpg

 

Pasted with 5 layers of kraft paper, 3 strip method.

12 grams of lift.

 

http://pyrobin.com/files/dsc00713.jpg

http://pyrobin.com/files/dsc00718.jpg

 

Unfortunately there is no video, but they were nice and round in the breaks and the best part was people was cheering

Edited April 21, 2010 by pudidotdk

[Bonny]

Unfortunately there is no video, but they were nice and round in the breaks and the best part was people was cheering

 

For me, that's always the best part!!

[Weirdo]

That looks really nice But damn, you use KP, flash whistle fibertape and 5 layers of 3 strip? That must have been some really loud breaks . Did you prime your granite stars? And did al the stars survived? It's a pity you didn't film those shells, I really wanted to see them .

[pudidotdk]

I have two left, MgAl and German Dark wasn't fired.

But KP does require a lot of pasting.

I'll see if I can record it next time.

Edited April 22, 2010 by pudidotdk

[PyroMan LTU]

Hello,

 

Last evening fired three 3" shells:

 

http://www.youtube.com/watch?v=W0P9LwDfIGs

 

PyroMan

[50AE]

Very good looking shells!

 

We fired my first 3" with salute inserts a week ago, but I didn't film it. It was very beautiful though. It had 4 small 3g flash salutes and a big one 15g for finale.

[Cookieman]

Those shells were beautifull!!! great job Pyroman!