Aerial Shells

[justanotherpyro]

The reason for putting them on the top is to prevent the lift charge from shattering them or squishing them during loading. So it would only work with a very sturdy comet. I remember Frozentech's 4" ball shell that had a rising comet, and they may all spin awkwardly, but still are able to reach a good altitude. Perhaps the weight of the shell is enough to keep it from doing that.

 

I remember reading somewhere that in order to properly orient a shell that you glue, tie etc.. the rope to the shell. For instance to get a star or heart shape break look right you use this method to make sure the shell doesn't explode in a random direction. Does anyone have any experience with this?

[dragonman586]

This sounds familiar to what i used to do with my cumbustion cannon ammo. Basically you attach the long piece of string to the side of the projectile you want faciing the launch tube or in this case the ground and fire. The string is there to create drag or something on the side you want to be the bottom.

[justanotherpyro]

There was some discussion as I recall on the old APC. I can't find it because the old forum sucks, good call moving to this place .Were there are specifics to each spuds size and/or weight? Type of rope would be important as well I imagine.

[dragonman586]

They weren't spuds it was a pill bottle cannon that used these paper slugs. I believe it took me 3x the length of the projectile to create an efficient amount of drag to make it go straight. I never really weighed the ammo nor do I have any left to weigh.

[_DB_]

I'm wanting to coat some granulated corn cob with BP soon, but I'm a little confused. On United Nuclear they say use 375 grams of BP to coat one cup of corn cob. To me this seems like way too much BP just to coat one cup of cob. But in the pictures they show on that page the cup they use looks way larger than your standard 8oz cup. Is there a definate ratio for coating things with BP? Like so many grams of BP to what you are wanting to coat?

 

Also, what is KP?

[ApocalypsePlease]

Also, what is KP?

I have also wondered what KP is, but I figured from the context that it is some sort of break. So I went to W. Vissers compositions site and this is what I found:

 

Potassium perchlorate bursting charge #1

Source: Shimizu[1]. Page 208. Listed as ‘KP burst charge’

Comments: This energetic burst charge can be used for small shells, but is unsuitable for the smallest diameters (2...3 inch). It is much safer to handle than the H3 bursting charge since it contains no chlorates.

Preparation:

 

Potassium perchlorate.............................70

Hemp coal (or Paulownia coal).....................18

Sulfur............................................12

Glutinous rice starch.............................+2%

[Mumbles]

As far as ratio, most of the ones I have are for rice hulls or puffed rice. If you don't have corn cob handy, I could weigh a cup out for you if you wanted.

[_DB_]

I have a gallon bag of it in my room, I shall go get it now.

 

A cup of it came out to be 85.8 grams.

[matell]

hello

 

I am planning to make a 30mm canister shell.i have a question : how i am going to make it long the tube?(when it is not closed)

 

thanks

[Mephistos Minion]

I would make the casing an extra 20mm long, that will give an extra 10mm on each end to fold over the top of the end disks, with good white glue this will hold nicely. Also I would add a wrapping of heavily pasted paper to these shells to keep the fire out on launch.

[keepkool79]

I am making shells 4,5, and 6 inch USING PLASTIC ROUND SHELLS. So, what should I use to get a good break. I do not want to use bp because I have a little rock tumbler that takes a long time to mill enough bp for this many shells. I am thinking about using kp but I heard that I will not get enough pressure when using plastic. I made some 5 inch shells using whistle on rice halls but the stars where blown blind. Please, anyone that build 4-6 inch plastic shells, let me know what to use. I have 1 week to build this stuff.

Thanks

[Mumbles]

There is always Lloyd S.' flash base break of a shell. I hear it works wonderfully. I've been using standard BP coated hulls with a whistle booster mixed in. I get fairly symetrical breaks. Not quite the same can be said of 3". I want to use H3, but I enjoy sulfur containing stars. I think I am going to try KP in shells this 4th. Perhaps a bit of whistle for 4", but my 5" should be fine. Strapping tape and actual pasting of the shells will keep them closed longer before the casing finally fails.

[justanotherpyro]

For my 4" shells I use BP coated puffed rice with a 3-4g flash bag in the center. I reinforce with 8 vertical strips of 3/4" fiberglass reinforced tape, and then one strip of 2 3/4" fiberglass reinforced tape going horizontally around the seam.

 

Sealing them with PVC primer, and then a heavy layer of PVC glue around the seam increases the shells integrity substantially as well.

[viziers]

Well i have a bit of a dilema (sp) here maybe not though. On a 3" shell can i get by with just using my BP corn cobb shells as a break? If not i'm screwed because i do not have any material to make a burst charge and i do not have time to order and wait for the chems go get here... I know this is gonna be very far fetched BUT if anyone that lives near me and wants to help me out and sell a little bit of chem i'd appreciate it very much, the burst charge id like to use is whistle mix cause i have no interest in flash. I am on the south east coast and if you are willing please PM me.

[ravaz]

For me, the key to getting a good break is being consistent. When I first started making shells using plastic hemis, I would use meal coated hulls, and flash or whistle as the initiator. I got hard breaks, but symmetry wasn't the most consistent. What I do now is I make a "strong" burst on rice hulls. This is for my 3” – 8” plastic shells. I can't give out the specifics of the formula. When your hulls are dry, put them on a 20 or 30 mesh screen and get the extra loose comp off. If you have any loose comp, it will effect the break. This goes for paper shells too. Also, it helps to "paste" the shell with a few layers of gummed tape.

 

Good luck.

[d4j0n]

What is the point of a flash bag? Would it do the same if the flash was just mixed in with the burst? I'm going to try 1" cup set shells tonight with granulated bp and flash (don't have any sulfur for kp ). Hope it works.

[Frozentech]

What is the point of a flash bag? Would it do the same if the flash was just mixed in with the burst? I'm going to try 1" cup set shells tonight with granulated bp and flash (don't have any sulfur for kp ). Hope it works.

A flash bag, or coupette keeps your break-boosting flash centered in the shell, improving symmetry. Loose flash can migrate around in your break charge and give lopsided breaks. I don't bother with the flash bag except in 4" or larger round shells. I still want to try the easy, neat method used by Tom Rebenklau, of just twisting up a 2 gram 'bubble' of flash in some saran wrap and centering that in the break charge of the shell.

[Pyrohawk]

Thats what I do....how else would you do it?? I gues I've never seen anyone elses flash bags before.....

 

I always use saran wrap and pour some poder in it and twist it up.

[_DB_]

I finally got around to making a mortar for my 2.5'' plastic hemis. So I did a test launch today with a dummy shell filled with 82 grams of cat litter. I used 15 grams of lift, which is a little too much but I did it anyway. When it launched an echoing boom was produced and the shell reached an altitude of about 275 or 300 feet I'm guessing. Now I just need to paint my mortar and strenghthen it at the base a bit with some epoxy. I'll post pictures when it's done. I'm very pleased with my lift now and can't wait to start cranking out shells!

[d4j0n]

Lol, I bought the 2.5" kraft ones from cannonfuse. They seem pretty sturdy...I dunno about those plastic bases though. Would you guys suggest plugging the mortar with plaster or something before putting it on the base or is that just being paranoid?

[_DB_]

I would since one time I made a mini mortar without pluging the tube and it came off the base first shot. On the mortar I just put together I plugged the tube with a very sturdy kraft endplug and woodglue.

 

EDIT: I just finished making my first batch of BP coated corn cob. I got the ratios from viziers and they are as follows: 3.5 cups of cob, 375g of BP and 75g of Dextrin. It was a messy procedure but it yielded a lot of burst. Thanks viziers!

 

Da Cob

[viziers]

No problem DB glad i could be of some help.

[_DB_]

I put some more epoxy on my mortar and gave it a cosmetic make over.

Ta-Da!

 

Thats one of the plastic hemispheres setting beside it that will be fired out of it. If you can't tell the original tube had a stripe spiraling up it. The mortar seems very durable and I hope it lasts awhile. I just wish I would have painted the inside of the tube first to make it more resistant to fire damage. Oh well.

[viziers]

I put some more epoxy on my mortar and gave it a cosmetic make over.

Ta-Da!

 

Thats one of the plastic hemispheres setting beside it that will be fired out of it. If you can't tell the original tube had a stripe spiraling up it. The mortar seems very durable and I hope it lasts awhile. I just wish I would have painted the inside of the tube first to make it more resistant to fire damage. Oh well.

DB is that tube a cardboard tube if so it will alst a while but no where as long as an HDPE tube will last. But however that tube looks very good. Congrats on your work.

[_DB_]

Yes it is only a cardboard tube, albeit a stout one at that. The walls are about .5'' thick. Here's the other piece of tube like it that I have -

Tube

Tube End

 

You can see that the end is all gnarly. That's only because I'm not too graceful with a reciprocating saw!