To Press Or Not To Press....

[TheArchitect23]

To Press... Or Not To Press...

That Is The Question!

 

 

So, i have always used my best BP and a 2'' puck pump to press my lift charge. Break, screen, repeat.

Performance is good, however it is very time consuming and requires a good press.

 

I am since no longer able to use said press ( bent ). I know some only granulate, how does you're lift compare to pressed lift?

In terms of power , other than density, transportability.

Edited July 12, 2013 by TheArchitect23

[Seymour]

I almost exclusively use a kitchen grater nowadays. I find it takes less time than a screen. I grate it and dry it before screening it in to different grades. I guess i use 10-20 mesh and 20-40 mesh grains most. I add 2% Gum Arabic, though Dextrin and others will of course be excellent.

 

Due to the lower density and higher surface area, grated or granulated through a screen has a considerably higher burn speed - especially as the pressure rises.

 

This means you need to use less. I've broken mortars by substituting grater grain Paulownia for commercial 1:1. I'd hesitate to lift anything over 6" with this stuff for this reason.

 

Burst I see it having a significant benefit. If you are going to be using grain to burst a shell, having it have half the density and a habit of being consumed entirely in the explosion is, in my opinion, a good thing. Obviously burst coated on to a filler is less dense still, but there are times that I want a stronger burst than BP on hulls or other fillers, especially in shells under 6"

 

In some pyro where space is really tight (like mini cannons) grater grain significantly under performs pressed and corned. I bet this has a lot to do with the corned having twice the density, and getting twice as much in that tiny space.

[Mumbles]

There is another technique in granulation that will yield a product somewhere between pressed grains and using a kitchen grater. I never much cared for the ribbons of composition that a grater gives. If you press the wet comp through a little harder, and avoid just sanding the comp ball over the wires from a screen, you can get good granules out. Regranulating a few times as it dries helps to keep it free flowing, and really rounds out the granules rendering them more spherical and denser.

 

You can see a picture of the final product here: http://www.amateurpy...seup-2jpg/ The crystals of KNO3 you see are from using coarse material since this is polverone anyway. They're black and homogeneous when using milled powder.

 

It comes out solid as a rock. After grading the initial granulation into whatever sizes you want, it generally stays that size. The bottom of a bag or bucket will usually only have minimal powder. It works just fine for lift. I've used it in shells from 2" up through 8" so far with no issues (different grain sizes though). I'd have no qualms about putting it under a 12" ball shell or a large multibreak shell either.

[TheArchitect23]

thanks for the feedback, ill try that method on the next set of shells and see if it works for me. save alot of time.

[Seymour]

I'll agree that the ribbons are unideal, but you don't get them as a result of using a grater, they're a result of adding too much water to your BP. I've had them plenty of times with a screen too, just because it was too wet. Perhaps you need it to be a bit drier for a grater, but at the right moisture level they break off before they can extrude any significant length.

 

I'll definitely agree that re granulating during drying is a great idea. I'll typically granulate up a fair bit of BP in one go, and aim for a broad range of grain sizes for different uses. Perhaps I'll grate five kilos through the coarse side of the grater and five kilos through the finer side. When it's dry enough to handle , but still a bit soft I'll select the screen that represents the largest size I want the grains. For me this is something around the five to ten mesh mark.

 

I generally find that by this time the BP is loosely sticking together, and granulating it while its drying allows all of it to be broken up with less dust and effort, and as Mumbles said, you'll round off some of the edges. And its a good way to bond with your black powder while it's still not ready to burn.

 

As for the big shells, I think this is both a case of me being a bit paranoid. It's just that I've killed a few mortars using what I thought should be a normal lift charge.

 

That said, it's really a case of dialing it in. When I kill mortars it tends to be when I substitute particularly hot grains with say, Chinese lift 1:1. I need a lot less and maybe bigger grains.

 

After all the Maltese lift their multibreaks with rough powder do they not? I believe them to be using roughly one hour milled BP with heavy confinement, though it'd be nice to be backed up here. I did a very similar thing until a few years ago to get great results with shit grain.

 

I guess also, the mortar has got to be up to it. I've never busted steel, but yet again I don't use it. I've killed lots of paper, a good fraction of the fiberglass mortars I've touched and a few HDPE too. I guess the shell always surviving is evidence against the lift being necessarily excessive, but you've got to work with what you've got and mortars being weak is often a reality. I'm sure it'll work with big things, but I'd still hesitate a bit until I had that powder dialed in. Still do it though.

[TYRONEEZEKIEL]

I just recently started corning my BP. I will say that I do love the consistency and the durability of the grains. From my experience with granulating, it just turns to powder simply too quick for my liking. It is simply a matter of what works best for your situation.