Double & double component ball milling - any results, comparisons?

[mabuse00]

I wonder if anybody here has ever compared BP made the traditional way and BP made via double and double component milling.

 

Is there any difference in performance?

Many people claim there is one, however I did not find any direct comparisons on the internet.

 

I'm about to make one myself, a simple comparison of burn rates in spoletta tubes, but with my current equipment it's hard to get repeatable pressure on the composition.

So the results are typically a little diffuse, especially if the difference is rather small.

 

 

Do you guys have an opinion on that matter (ideally one that you can bolster with proper scientific measurements )?

 

 

edit:

with the ratios suggested on Pyroguide (Nitrate & 1/3 of charcoal + 2/3 charcoal & sulphur) the nitrate run has about 2x the volume of the sulphur run.

 

My thought right now is something like doing 3 runs, 2 nitrate/charcoal runs and one doubled sulphur/charcoal run...

Edited November 14, 2015 by mabuse00

[Merlin]

You can measure small differences. Download a photo editor that allows freeze frame and records time (Avidemux 2.6.). Take a piece of typing paper and crease it diagonally. Weigh 3 grams of your meal and spread it neatly into the crease say for a distance of ten inches. Fuse it and put on a surface were you can see from the side. Flame and smoke will obscure from above. Light fuse and video with cell phone and email your video to your computer where you have the editor. Move video to editor and precisely measure time from first frame with fire to last frame. This sounds worse than it is. It is really fast and simple to precisely measure the speed of your BP. I use this after each milling to be sure milling is optimum.

[Andres1511]

I make my with the double and double milling method. I know, the nitrate run has a lot more volume, but I just let it run twice the time the sulphur runs.
My BP is good enough for lifting shells with the standard 10%, and good enough for everything you might need in pyro. I can't really compare, because I never made BP by just milling everything together.

[mabuse00]

@ Andres1511:

Thanks for sharing the experience.

 

@Merlin:

imho that is to uncertain. There are a lot of factors like jumping sparks that will add to the variance of results. Some kind of tube is a must.

 

 

But hasn't anybody here ever made a direct comparison with "normal" milled BP?

Edited November 22, 2015 by mabuse00

[DavidF]

I have done direct comparisons between separately milled and screen-mixed, double component+double component milled and screen-mixed, and milled BP (with the charcoal pre-milled). My tests were done with nozzleless rocket motors made on 1lb BP tooling. I was able to predict similar heights with different propellants. I was able to avoid milling complete BP with no real loss in performance. But, performance as a single propellant grain in a nozzleless rocket motor is different than burning without a core in a spolette tube, which is again different than using granulated or pucked and corned BP in a mortar tube.

 

I reported my results to one of the BP 'big boys' and he was not impressed at all. After licking my wounds and thinking about it for a bit, I lost interest. Not because of the 'slight' at all. It was because the amount of extra face time while screening the mixture was just a different danger than that of a mill explosion. I never posted my test results anywhere because I didn't know if it was wise to suggest anybody else go down the same path.

 

An important thing to note about my results is that a nozzleless motor made with lightning-fast BP actually lifts a shell to a lesser height than if the BP was a little slower. I don't think my data would be useful to predict BP performance in mortars.

[mabuse00]

Thank you for your report David.

 

 

An important thing to note about my results is that a nozzleless motor made with lightning-fast BP actually lifts a shell to a lesser height than if the BP was a little slower

Thats interesting.

Maybe your lightning BP had a lower density? Balsa charcoal ect.?

Or your rocket was very light -> accelerated to very high speeds and air drag became dominant over gravity drag?

 

 

 

It was because the amount of extra face time while screening the mixture was just a different danger than that of a mill explosion

I'd still prefer that over having the hazard during many hours of having the mill run.

 

And sieving - I wonder if sieving is even required, won't shaking the two batches together in one vessel suffice?

My feeling is that sieving is still less dangerous than dumping the mill barrel with the media crashing in between.

[Mumbles]

I just wanted to start out by saying that I've been very interested in methods to eliminate live milling. Even more so after my accident. I've seen some tests of black powder made by this method before: http://wpag.us/learn/How%20To%20Make%20Black%20Powder.pdf

 

I'd consider this pretty well inline with double component milling and screening, though a little different. I just figured I'd include the exact process for completeness. To address your previous comment Mabuse, I am under the impression that screening is advantageous to achieve the most intimate mixture possible. This is mostly anecdotal evidence though. In my hands, well screened green meal (40 mesh) is more vigorously burning and results in somewhat less dross than something simply hand mixed. It would stand to reason that a similar effect could be expected even when starting with well milled chemicals and a hotter charcoal (I was using neither). I suppose the only way to know for sure is to take some samples along the process. I'd be interested in the results if someone did this.

 

Anyway, I saw some lift tests done with the above method and a few different varieties of BP. The author claimed that it's every bit as hot as milled BP. I don't entirely agree, but it definitely works. Like all things BP, there are a ton of variables and factors at play. For the 3" comets that were tested, I'd estimate that an extra 20-25% lift would be required to get it back in line with commercial BP. That may just be because he's using different mesh sizes (-4+8 for 2FA, and -8+12 for 4FA) than what is considered standard.

 

Reading this thread makes me realize that we probably need to test separately in all the applications we use black powder for. Rockets might be different than shell lift which might be different from blackmatch and spolettes. Pressure plays a big role in the performance of BP, and very likely will lead to different results for different applications.

[taiwanluthiers]

I have been doing double milling the whole time simply because I couldn't afford to have a mill explosion at all. I got the idea from pyroguide when they were around.

 

I would say mill time is important because there were a few times where I milled one component too short and the resulting bp was too slow. I test the batch by burning a very small sample on a piece of paper. If the paper has a hole burned in it it's too slow.

[mabuse00]

 

To address your previous comment Mabuse, I am under the impression that screening is advantageous to achieve the most intimate mixture possible. This is mostly anecdotal evidence though. In my hands, well screened green meal (40 mesh) is more vigorously burning and results in somewhat less dross than something simply hand mixed

I agree.

 

BUT:

normally you have 3 seperate, uncontaminated powders, which tend to adhere to itself and clump.

Especially if your nitrate doesn't contain any anticake.

 

In this case the charcoal will act as anticake. I assume this to be a different situation - mixing two mixtures - than mixing the 3 individual components.

 

I have the hope that the typical lumps wont form themselfes. Mixing two powders that are really "airfloat" normally don't need no sieving. Mostly...

 

One could do a third test to confirm this. On my todo list for next year.

 

 

 

PS:

In my opinion, when talking about a comparision of methods, the mill time should be taken into account. The way I would compare would be to create two samples, who both got an identical amount of milling work per weight of BP.

 

The idea is not to compensate for an alledgedly suboptimal method with super long milling time or the use of better charcoal.

In later practical use I'd be willing to mill some time longer if necessary.

 

 

 

simply because I couldn't afford to have a mill explosion at all

That's my problem and i think many other guys' too.

Edited November 30, 2015 by mabuse00