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BP Speed Test

Swede

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Based upon a thread that discusses BP in general and the "CIA" BP precipitation method in particular, I decided to check the various speeds of BP, including a CIA batch carefully prepared according to the directions in Tom Perigrin's book, "Introductory Practical Pyrotechnics."

 

All of the homemade powders were 75:15:10. The CIA powder used Skylighter commercial airfloat charcoal, which is going to slow it down. The remainder used willow charcoal from the Custom Charcoal guy.

 

Each sample was a carefully measured 5 grams, which fills the aluminum channel to an acceptable level. The timer is good to 1/1000 second. The start and end switches are not nearly as sensitive or consistent, consisting of sewing thread holding two micro-switches closed. The BP burns through the thread, starting and stopping the timing. While crude, previous tests have shown it to work well and be reasonably consistent, probably to within 4% to 5%.

 

http://www.5bears.com/firew/speedt06.jpg

 

The greatest variation, aside from the manufacturing technique, is the grain size. I attempted to keep as consistent as possible in that regard, and also included a finer sample that was closer to the CIA powder in consistency.

 

Here are all the samples, in order. You can get an idea of the appearance and grain size.:

 

 

1) Milled, pressed, corned, sieved willow: 20-40 Mesh

http://www.5bears.com/firew/speedt01.jpg

 

2) Milled, pressed, corned, sieved willow: 10-20 Mesh

http://www.5bears.com/firew/speedt02.jpg

 

3) Milled, riced willow: fairly heavy mesh, used for lift on 3" and smaller shells:

http://www.5bears.com/firew/speedt03.jpg

 

4) CIA precipitation method powder, screened and riced... a bit fine:

http://www.5bears.com/firew/speedt04.jpg

 

5) Goex 2FG:

http://www.5bears.com/firew/speedt05.jpg

 

 

And the Results! In seconds to burn the length of the channel...

 

1) Milled, pressed, corned, sieved willow: 20-40 Mesh

0.692 s

 

2) Milled, pressed, corned, sieved willow: 10-20 Mesh

0.472 s

 

3) Milled, riced willow: fairly large mesh:

0.643 s

 

4) CIA precipitation method powder, riced:

1.352 s

 

5) Goex 2FG:

0.408 s

 

So in order, from slowest to fastest:

 

CIA precipitation method powder, riced

Milled, pressed, corned, sieved willow: 20-40 Mesh

Milled, riced willow: fairly large mesh

Milled, pressed, corned, sieved willow: 10-20 Mesh

Goex 2FG

 

Interestingly, the grain size had more impact on speed with my own powder than pressing, with the large-grained riced lift powder being faster than 20-40 mesh pressed BP. My best powder was close, but did not surpass Goex, which was a bit disappointing, but the BP is still quick and serviceable. I do tend to use a lot of binder like red gum, which is going to slow things down a bit.

 

The results are a curiosity only. There are HUGE variations in technique that are going to alter these results for others. Definitely take it with a grain of salt. But it was fun to burn an ounce or so of BP in the name of science.

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hobie

I am new to this forum. This topic is of interest to me. I have a homemade BP mortar. This is unlike anything I have seen on the internet. It is a steel tube 5' long of which about 4' is buried in the ground and anchored to a concrete pad. The diameter is about the size of a basketball. It was built to shoot pumpkins. I have seen photos of it in action so I know it works. My question is what type of BP should I use and how much to create a lift charge? Could i also build an aerial shell that will explode once the lift charge has launched the projectile? Any help would be appreciated.

 

Hobie

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Swede

Hobie, the best place to ask this question is in the beginner section on APC. I can recommend a homemade riced BP that would work, with the big issue being a very large grain size commensurate with the large bore of your mortar. You'll possibly want a cardboard disk wadding (or maybe newspaper) to create a decent seal between the pumpkin and the bore.

 

The big things will be grain size and quantity, along with how the powder was prepared. Good luck and please stay safe.

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rickyd
Want to see super fast BP? Try using balsa wood charcoal. It is very tough to work with, super light, but it makes very fast BP.
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Swede
I do have a couple of pounds of both balsa and alder. One of these days, I will try and create a powder that beats these times and surpasses commercial. The pursuit of super-fast BP can be fun, a hobby all by itself, but for functionality (lift and burst), the riced BP I used for this test is fully up to the job. :)
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