56 replies to this topic

[Peret]

No, we're not mad at you. A steel pipe would make a suitable mortar, especially if you find a cold-drawn pipe and not welded. A stout extruded aluminum tube would do nicely also, or HDPE plumbing pipe. Never use PVC, it tends to shatter into razor sharp flechettes that don't show up on X-rays after they penetrate your soft wobbly bits.

I didn't realize you lived in Canada, sorry.

[dagabu]

Bob,

You are cool with us here, you just have unrealistic expectations for a test that is ill timed partly due to the 4th celebration. As Peret says, Aluminum tubing is made to a standard ID and OD, it is not very expensive for a long lasting solution.

HDPE DR 9 is 1.81" ID but is really hard to find because of the minimum amount you have to purchase up front.

-dag

[Potassiumchlorate]

I think it's pretty ill timed for most European members as well, as it isn't "season" for anything pyro related here during spring and summer. I like the idea, though. I remember shooting my first dummies filled with coarse salt from 2.5" mortars.

[Potassiumchlorate]

Speaking of improving the BP. I got this idea: make BP as usual by milling all chemicals for three hours. Press pucks to a density of 1.7g/cc. Crush the pucks to granules. Take the meal B that you have sieved off, spray on a boiling solution of alcohol and water 25/75. Make polverone and let dry. Then mill the polverone for one hour. This will probably be extremely well integrated and can then be coated on rice hulls.

By the way: I'd like to ask one of my frequent questions again. What grain size does 5:1 BP on rice hulls equal compared with grained BP with a density of 1.7g/cc? The size is more towards FA than 2FA, but since it's hollow in the middle and a bit oblong in shape, one might not compare it that way? Suggestions?

Edited by Potassiumchlorate, 22 May 2012 - 12:10 PM.

[Algenco]

I would guess it' close to FA

We shot 6&8" shells this past weekend using 8% 5/1 coated hulls (made with Paulownia) , the lift was more than adequate
Using coated hulls seems to be more effecient than granulated or corned BP

[Potassiumchlorate]

Interesting. I have used 7-10% of the shell weight with a mix of FA and 2FA with a density of 1.7g/cc, but they seem too weak for lifting the smaller shells, although the BP itself is pretty "hot". I recently made 4FA grains instead, but they might on the other hand be too fine for 5" and 6", right?

I just must test 5/1 on rice hulls.

[Mumbles]

2FA in my experience is too coarse for small shells. I use 4FA on shells 3" and smaller, and most mines. I'd probably use it on 4" ball shells too just to be safe, but that is kind of a toss up. Much larger than that and you start really launching shells. I fired a 6" shell once with a normal amount of lift using commercial 4FA, and it was still well on it's way up when it broke. I thought I busted the gun it lifted so hard. You can use 4FA to lift larger shells, but you need to use less of it. a 6" shell probably weighs between 1100 and 1300g depending on what's inside. This would require somewhere around 75g of lift. Using 4FA will shoot it into orbit at that amount if you truly have hot powder. You could probably dial it back to around 60g or less. There may be some tables in some of the Best of AFN books.

The product I use for lift from my homemade powder is 2+3FA. I use a wider range than is normally used commercially. My meal is plenty hot on it's own, but inclusion of some of the finer stuff helps to break my shells a little better. I lift all of my shells as normal and they still work fine without lifting too overly hard.

[Potassiumchlorate]

So 5% of the shell weight of 4FA would lift a 6"? That's about what I thought, though I was uncertain if it was possible or not without breaking the shell.

[bob]

if using grass seed in a 5 to 1 ratio each seed should have .05 grains of black powder coated on to it
bob

[Potassiumchlorate]

How small mortars can BP on rice hulls be used in? It didn't work in a 16mm stargun. Just said "pooff!" and the star went one meter or so.

[californiapyro]

i've used it with a 12 mm stargun... i guess it depends on the amount of BP on your hulls

[Potassiumchlorate]

Hm, but now I have 5:1 on rice hulls. Weird. Must test some more.

[Potassiumchlorate]

*Sighs*

I tried again. Very long muzzle flame, but still "whoof" and not "bang". But maybe it should be that way with so small amounts (1.5g)? The star didn't seem to ignite this time, or, if it did, it burned too fast for me to notice. It's daytime here, so it's hard to decide.

[Peret]

Describing powders by FA grades is as traditional and pointless as describing rockets by weight - the more so since only a handful of people have access to FA grades anyway, and the sizes of FG grades are entirely different. Why not keep it in mesh sizes? I lift with 10-20 mesh mostly.

While the quality of a particular powder is important, I found it was more important to keep the lift charge confined, especially for small shells. It does take some finite time for the fire to propagate from grain to grain, and anything that doesn't ignite in the first milliseconds is wasted in a short mortar. 10 grams twisted tightly in a baggie will give a far better performance than 10g spread over the bottom of a mortar tube. My objection to using coated hulls would be that they're very bulky and can't be so well confined.

[Mumbles]

Another concern I'd have with using rice hulls to lift shells would be club shoots. At the clubs I generally attend, we have shared guns that are used repeatedly. If I were to bring half a dozen 6" shells with 90g of 7:1 as lift, by the time I fired them, there would already be more than an inch of rice hulls remaining on the bottom. I've ran into problems before with people using paper or plastic cups as lift cups and other things that are left behind. When there gets to be a little padding on the bottom of the gun I've started to experience lower breaks.

[mikeee]

Everyone,

Another good way to test black powder is to "shoot anvils".
You need (2) high quality forged steel anvils.
One anvil has a hole drilled into the center of the flat top.
A measured amount of black powder is loaded into the drill hole.
A playing card is placed over the black powder and a small diameter fuse ran to the outside edge of the anvil.
The other anvil is turned upside down on top of the other anvil.
Fuse is lit and powder ignites and propels anvil into the air.
Total energy of black powder is measured by the total distance anvil travels up in the air.
An old time military guy told me this was how they tested black powder in the civil war era.
Back in those days quality of black powder was an issue for the artillery groups.
If you wanted to hit your target you needed to know how "hot" the black powder was.

[Peret]

I've seen anvil shooting at Winter Blast. They go straight up a couple hundred feet and land next to where they took off. I wouldn't care to hand-light one in case I tripped running away.

[Potassiumchlorate]

Haha, anvil shooting is so American. Shooting something in the air that was never intended to be airborne.

[Potassiumchlorate]

Now I've tested BP on rice hulls as lift for a 2" dummy. Quite different performance. About as good as my corned BP.

[Potassiumchlorate]

Hm, now I have tested "baseball shooting" or what you call it in America. A tennisball, weighing 52 grams, was shot from my 3" mortar with 5 grams of my new BP. No liftcup, just BP on the bottom of the mortar. Ignition by visco+quickmatch. The ball was shot about 30 meters up in the air (I compared with a tree nearby) and reached its apogeum after about 3 seconds. How would you "rank" this?