Star cannister

[hillbillyreefer]

Last week I fired a canister shell made from a toilet tissue roll. Construction consisted of the roll, cardboard bulkheads hot glued in place for the stars, a bottom compartment with the time fuse and lift charge. When fired it went up about 10 feet came back down and burst on the ground. It still got lots of ohhs and ahhs from the kids. Everyone was at a safe distance, a rule that has been reinforced in my mind. I'm pretty sure I know what happened, it wasn't tight enough in the mortar for the lift, the roll isn't strong enough for a good burst (which in this instance was a good thing). Now for today's next try at it. The top and bottom of the star compartment will have double cardboard, and glue. The tube will have several wraps of either gum tape, pasted newspaper, or pasted craft paper. The question is which would be the best, and how many layers should be added? Building it up will have a two fold effect, both strength and making a better seal in the mortar.  The time fuse will be the same as used before, it worked well according to the video.

 

Is there a good ratio for BP coated rice hulls? I've seen 5:1 but can't seem to find the 5:1 what, I assume 5 rice hulls to 1 bp, but assumptions are dangerous. Instead of rice hulls I will be giving rolled oats a try, using what is available locally.

 

Any advice is appreciated. Thanks in advance.

 

On another note, Saturday we fired some commercial and homemade starmines. The commercial stuff, while more colorful than mine, paled in comparison.  The homemade effect was greeted with lots of cheering from the 9 kids and 6 adults. It was very gratifying. Even the wife is starting to think this is a pretty cool hobby!!!

Edited December 6, 2010 by hillbillyreefer

[50AE]

Last week I fired a canister shell made from a toilet tissue roll. Construction consisted of the roll, cardboard bulkheads hot glued in place for the stars, a bottom compartment with the time fuse and lift charge. When fired it went up about 10 feet came back down and burst on the ground. It still got lots of ohhs and ahhs from the kids. Everyone was at a safe distance, a rule that has been reinforced in my mind. I'm pretty sure I know what happened, it wasn't tight enough in the mortar for the lift, the roll isn't strong enough for a good burst (which in this instance was a good thing). Now for today's next try at it. The top and bottom of the star compartment will have double cardboard, and glue. The tube will have several wraps of either gum tape, pasted newspaper, or pasted craft paper. The question is which would be the best, and how many layers should be added? Building it up will have a two fold effect, both strength and making a better seal in the mortar.  The time fuse will be the same as used before, it worked well according to the video.

 

Is there a good ratio for BP coated rice hulls? I've seen 5:1 but can't seem to find the 5:1 what, I assume 5 rice hulls to 1 bp, but assumptions are dangerous. Instead of rice hulls I will be giving rolled oats a try, using what is available locally.

 

Any advice is appreciated. Thanks in advance.

 

On another note, Saturday we fired some commercial and homemade starmines. The commercial stuff, while more colorful than mine, paled in comparison.  The homemade effect was greeted with lots of cheering from the 9 kids and 6 adults. It was very gratifying. Even the wife is starting to think this is a pretty cool hobby!!!

 

1. What is the clearance between the shell and the mortar? And are you sure your lift charge is ok?

2. I don't trust toilet paper rolls. They are spiral wounded and I'm sure if they have a good strength. I like to make traditional cylinder shells, so I roll my casings, with the grain long.

3. I assume a paper roll has a size of 1,75 or 2". So 2-3 layers of 30-40lbs kraft will do.

5. 5:1 by mass means BP to hulls, not hulls to BP. BP is heavier and much denser than the filler.

6. BP to hulls is a very weak burst charge for a 2" shell. I would use H3 or KP. Or maybe a flash bag too.

[hillbillyreefer]

1. What is the clearance between the shell and the mortar? And are you sure your lift charge is ok?

2. I don't trust toilet paper rolls. They are spiral wounded and I'm sure if they have a good strength. I like to make traditional cylinder shells, so I roll my casings, with the grain long.

3. I assume a paper roll has a size of 1,75 or 2". So 2-3 layers of 30-40lbs kraft will do.

5. 5:1 by mass means BP to hulls, not hulls to BP. BP is heavier and much denser than the filler.

6. BP to hulls is a very weak burst charge for a 2" shell. I would use H3 or KP. Or maybe a flash bag too.

 

1. 1/4-3/8 all the way around. So most of the lift charge would blow by, kind of like firing a 6.5mm bullet in a 7.62mm barrel. I'm using commercial 2fg for lift. I can buy all the BP I can afford,

but kno3 is strongly regulated in my country. It doesn't have to make sense, it's the government!!

2. All the stuff to roll my own casings has been purchased, just need to find the time to do it.

3. Thanks

5. Thanks, my assumption was totally wrong!

6. My biggest need at the moment is a perchlorate cell, but it will probably have to wait until spring, due to the crappy winter temps. The temp here at the present time is around -38C

with the wind. My thinking is I can probably get an acceptable burst, if I strengthen my canister enough to build decent pressure with the BP.

 

Thank you for your help, it is much appreciated.

[ChrisNZ]

I haven't tried making one, but I believe you want the shell to be tighter in the mortor tube.

 

Any gaps around the side of the shell will let the gases out, which would be wasted as they wouldn't be forcing the shell out of the tube. I'd suggest if you haven't yet.. Spike the shell with string, as seen in many photos in the member galleries, and pasting/wrapping kraft paper around the outside until it's a snug fit in your tube.

 

If it helps I think a finished shell should look like this more than this.

 

Edit: (No offence to anyone whos pics I linked to, just my opinion.)

Edited December 6, 2010 by ChrisNZ

[Algenco]

5/1 ratio for BP coated hulls works if you have very,very hot BP, typical ratios are 7/1

[Mumbles]

I have to agree that spiking could solve a lot of your problems. It increases outside diameter, and strengthens the case. On this size of shell, I use 8 vertical strings, and however make horizontals to make roughly square shaped patterns. After this is done, paste with 3 layers of thin kraft paper. I use 30lb kraft, but I bet the paper from paper lunch sacks would work well too.

 

For the burst I just fill all the spaces between the stars with granular BP. It packs an appropriate punch without resorting to H3 or KP. I only boost the breaks when making spider inserts.

 

There really isn't anything special required to roll your own casings besides an appropriate sized former. I still use an old contact solution bottle to roll casings of this size. The only specialty item I have is purchased end disks, but you can just as easily cut them by hand. Besides that it's just paper, and I do use some manilla file folder paper as a liner.

[Updup]

I haven't tried making one, but I believe you want the shell to be tighter in the mortor tube.

 

Any gaps around the side of the shell will let the gases out, which would be wasted as they wouldn't be forcing the shell out of the tube. I'd suggest if you haven't yet.. Spike the shell with string, as seen in many photos in the member galleries, and pasting/wrapping kraft paper around the outside until it's a snug fit in your tube.

 

If it helps I think a finished shell should look like this more than this.

 

Edit: (No offence to anyone whos pics I linked to, just my opinion.)

 

In my defence that shell wasn't finished in the picture, just loaded with a firecracker beraq ring, no stars or break in it yet.

 

How much lift did you use? It's possible that it was a combanation of not having enough lift and the shell not fitting properly in the mortar.

[hillbillyreefer]

Thanks to all of you for the advice. Didn't get around to the new shell today, busy cleaning fish tanks and parenting.

 

Updup, I'm pretty sure the poor lift was due to a loose fit in the mortar. The charge may have been a bit lite but should have been much better than it was, if everything else was setup correctly. The shell was 53g and the lift was 5.3g.

[ChrisNZ]

In my defence that shell wasn't finished in the picture, just loaded with a firecracker beraq ring, no stars or break in it yet.

 

Didn't mean to offend Updup, just using your pic as a visual example.

 

Before I knew what I've learnt in the last few weeks I would've looked at that and thought that was good to go, I think a lot of new people may not pick up on the spiking and pasting a good strong shell straight away. I saw pictures of people with string looping around things and thought that was a bit weird. But after a bit of reading and research I can fully understand and appreciate why it's done.

 

My mine point was though, the shell should be pretty snug in the tube, but I believe not so tight that it can't be lowered to the bottom under it's own weight.

[Xtreme Pyro]

My mine point was though, the shell should be pretty snug in the tube, but I believe not so tight that it can't be lowered to the bottom under it's own weight.

 

A good rule of thumb to follow by when starting out would be 5% of the shells diameter for the clearance. A shell doesn't necessarily need to be a snug fit in the mortar to properly fire. If he is using a toilet paper roll as the casing and shooting it out of a 2" mortar, 3mm of clearance all around is about right.

[Updup]

A good rule of thumb to follow by when starting out would be 5% of the shells diameter for the clearance. A shell doesn't necessarily need to be a snug fit in the mortar to properly fire. If he is using a toilet paper roll as the casing and shooting it out of a 2" mortar, 3mm of clearance all around is about right.

 

Interesting though, because unless my toilet paper rolls are bigger than yours, you should have a perfect fit, as the TP rolls that I have fit in a 2" mortar with about 3-4mm all round, almost too tight before spiking and pasting, What size mortar are you using?

 

Also Chris, you didn't offend me, I knew what you ment =)

[Mumbles]

If the TP tubes are almost too snug before spiking and pasting, you're probably using commercial class C mortars. They're not really 2" ID. For shells made this way you need a legitimate 2" ID mortar. Standard toilet paper tubes are around 1 5/8" in diameter. You could maybe get away with using a 1.91" ID mortar if you're careful. I start from a 1.75" Former, and the shells drop easily into a 2" gun, you'd have to be doing something far different than I am for a TP tube to ever be confused for being almost too snug.

[Updup]

If the TP tubes are almost too snug before spiking and pasting, you're probably using commercial class C mortars. They're not really 2" ID. For shells made this way you need a legitimate 2" ID mortar. Standard toilet paper tubes are around 1 5/8" in diameter. You could maybe get away with using a 1.91" ID mortar if you're careful. I start from a 1.75" Former, and the shells drop easily into a 2" gun, you'd have to be doing something far different than I am for a TP tube to ever be confused for being almost too snug.

 

My mortar is a 2" HDPE pyrodirect mortar, and TP tube measured out to 11/16", It works, but after spiking and pasting and running a fuse up the side its a little too tight for my liking.

[Arthur]

In my opinion, a shell should slide gently down the mortar under it's own weight, so yes less than 5% diameter difference. With small shells the fuse needs to be small to let the shell slide well. Also the break needs to be very good and fast on small shells.

[hillbillyreefer]

Thanks for all the advice. My mortars are indeed 1.91. This morning I made a bunch of tubes using a tutorial from Skylighter's newsletters (thanks for that). Basically butcher's paper wrapped around a former and warmed in the oven to melt the plastic and glue the tubes together. The 1.5" id tube I made should make a much better canister, and once they are pasted and spiked will hopefully provide the desire effect.

 

Now to research and build a bunch of spolettes.

[hillbillyreefer]

Finally success, using homemade canister tubes!! This is the first attempt since the first cato. I used a 1.5" id home rolled parallel tube. The ends were cut and pasted in over cardboard plugs. Time fuse was viscoe, stars were chrysanthemum #8. 30 grams of stars, 6 grams of 2f burst, with another gram of home made BP dusting the stars. The loaded canister weighed in at 86 grams, used 6 grams commercial 2f and 2 grams homemade BP for lift in a cup. Fused with 10 cm commercial viscoe and 18 inches of black match. This was my first attempt at black match and it seems to work well, good because I made 330' of it yesterday. I cheated a bit on the spiking, I used several wraps of fiberglass reinforced tape instead of pasting and twine.

 

The shot was awesome, lift sounded good, I could see the time fuse burning as the canister rose, I'm guessing 200' or so. Burst was nice and symmetrical the last of the stars were out around 1/2 way down. WOOOOOHOOOO, the only problem was I standing there like a slack jawed yokle with the camera in my hand pointed at the ground, so no video.

 

Now onto new pretty colors!!!!!!!!

 

Thanks for all of your help getting me to this point, the kids and I really appreciate it!!

Edited December 14, 2010 by hillbillyreefer

[Algenco]

congrats!! the first sucess usually happens like that, too impressed to video

[Invogue]

Yes well done with the shell. Been shooting a few of these recently, great fun.

[hillbillyreefer]

Fired another successful canister tonight. The break was not as good as the first one. The bottom of this canister must have been the weak point as all the stars shot out the bottom. It did go about twice as high as the last one, a bit too high for the small effect it was carrying. This hobby is sure addictive!!

 

Now that I think about it, the shell wasn't spiked properly, that is why the break wasn't right.

Edited December 17, 2010 by hillbillyreefer

[hillbillyreefer]

One last try to post the video.

[Adrenaline]

I have similiar problems with my 3 " ball shells. If I put them in a mortar the clearence is 6,5mm, thus 3,25 mm on each side. If I use the 5 % rule the maximum clearance for 3"shells should be 3,75mm. So my shells are way too small. If I would add more lift would this compensate the clearance?

I don´t understand why my shells turn out so small, I allready pasted 14 layers (3 strip method) of kraft on them.

 

I just measured the diameter of my mortars, its 77mm. Maybe that is the problem?

Edited December 18, 2010 by Adrenaline

[Algenco]

Mortar could be slighly oversized, hemi's could be slightly undersized.

Have you test fired one?

You may need to add a little to the lift, but I would test as is first

[hillbillyreefer]

I have similiar problems with my 3 " ball shells. If I put them in a mortar the clearence is 6,5mm, thus 3,25 mm on each side. If I use the 5 % rule the maximum clearance for 3"shells should be 3,75mm. So my shells are way too small. If I would add more lift would this compensate the clearance?

I don´t understand why my shells turn out so small, I allready pasted 14 layers (3 strip method) of kraft on them.

 

I just measured the diameter of my mortars, its 77mm. Maybe that is the problem?

 

To tighten up the shell in the mortar you could wrap the shell in paper tape, (masking tape), much quicker than pasting. In my opinion, more lift would probably work, but at some point the added lift will probably damage the shell. Where that point is I don`t have a clue, we will need some more experienced guys to chime in on that one.

 

My last three successful shells were tight enough to rub on the mortar walls on the way in. A very, very gentle push was needed to move the canister down into the mortar. It wasn`t tight before I fused it. So once the fuse burnt off there shouldn`t have been much drag on the way back out. I have increased my lift charge slightly to about 12%. The canisters used are weakest on the ends, so my effects are blowing out the ends, they are far from perfect, but still pretty cool. When I get around to it, the kids and I are going to paste up some ball shells, in theory they should be easier to get a nice symmetrical break out of. Come on Christmas holidays!!

[Seymour]

In my opinion, more lift would probably work, but at some point the added lift will probably damage the shell. Where that point is I don`t have a clue, we will need some more experienced guys to chime in on that one.

 

A well made shell should be able to handle pressures far in excess of normal use. If a smallish shell (let's say less than 6") is damaged by using double the lift, my opinion would be that the shell is not built strongly enough.

 

With the very large shells, especially canisters, there may not be so much leniency, but at 3", I would be comfortable giving it even 100g lift. The mortar might explode if it's one of those (in my opinion dodgy) fibreglass ones, and the shell would be too high to look good, but I'd expect the shell to function.

[hillbillyreefer]

That is good information to know Seymour, thank you.