Black Powder Information

[shockie]

A series of samples of rough Black Powder

were prepared and burned to measure their burn

rates. Each sample was a loose 1 gram pile of –

100 mesh material, ignited about half way up on

one side of the pile using a hot wire igniter.

Sample A was dry mixed by passing several times through a 60

mesh screen.

Sample B was dry mixed for several

minutes using a mortar and pestle.

Sample C was wet ball milled for 4 hours, dried and crushed to –

100 mesh with a mortar and pestle.

The charcoal and sulfur for sample D was dry ball milled for 4

hours; then with the potassium nitrate added, and

wet ball milled for 8 hours; then dried and crushed

to –100 mesh with a mortar and pestle.

The average mass burn rates for three measurements of

each sample of rough Black Powder are shown in

Black Powder Burn Rate.

Also attached is BP Ballistic performance

Also attached burn rate of BP with sodium bicarbonate

Also attached compaction pressure on BP

Edited November 30, 2020 by shockie

[justvisiting]

That's interesting stuff Shockie, thanks! The last chart makes me wonder about some stuff. I hope you don't mind if I add some observations about it. Since they say black powder "fuel", I assume they are making rockets. They don't say whether they are pressing dry or damp. In my experience, you are not going to press dry black powder to 1.8g/cc in a rocket. 1.8g/cc. will only be achievable if the 'fuel' is dampened with water. It will also only be achievable if we are talking about black powder (75-15-10), and not your typical rocket propellant (60-30-10, for instance). According to one of the charts posted from Ronald Sasse's work, there is a huge change in burning rate of black powder between densities of 1.7 and 1.8. If I'm reading it correctly, the burn time of BP at 1.8 is 4 times that of BP at 1.7.

 

When I was pressing nozzleless and end burn rockets to compare my powders, I was only able to achieve a grain density of about 1.4 with dry powder, even pressing at 9000psi. With 2% water, the density went to 1.8, easily. Then I lowered the pressing force by more than half.

 

I thought maybe I could make good baby pucks with damp BP on a 1 ton arbor press. I was only able to achieve a density of 1.5 at the rated capacity of 2000lbs, which is around 2550psi on the comp. I'm sure that's fine for a nozzleless core burner, but for making actual BP pucks, not so much. At 1.5, the grains were a bit crumbly and corning made a lot of fines. It certainly wasn't worth the trouble, but now I know One thing the experiment taught me is that I could make a 3lb rocket on a 1 ton arbor press if I really had to, and a 1lb rocket any day of the week.

 

One little tidbit that got passed to me by Ed was to gauge the porosity/density of my BP by wetting a puck with straight isopropyl alcohol. At a density over 1.7, the puck can be wiped dry, and there is no absorption. Below that, it absorbs.

 

I'd be most interested in any comments about the extreme change in burn rate between d.1.7 and d.1.8, if anybody has experience with that.

[shockie]

Yes this is about Rockets. I would assume they are talking about wet vs dry. That's some intersting information you provided. Thanks. Where can I see that Sasse Chart. I have numerous reports by him. Got an URL? TIA

[justvisiting]

https://www.amateurpyro.com/forums/topic/12899-how-to-make-hot-bp-indoor-safely-lab-intensive/?view=findpost&p=178839&hl=%2Bthe+%2Binfluence+%2Bphysical+%2Bproperties+%2Bblack+%2Bpowder+%2Bcombustion+%2Bproperties

 

The chart I'm referring to is in this thread. Somewhere there is a link to the full article 'The Influence of Physical Properties on Black Powder Combustion.' I think I posted it, but I can't find it now. I'll try to unearth it later.

[shockie]

Thanks! I have both of those. But your info on real life experience on reaching a plateau when pressing is very interesting to know.. every little bit of info helps us all.