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BP Speed Test

Swede

Entry posted by 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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4 Comments

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hobie

hobie 0

Posted

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

Swede

Swede 21

Posted

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.

rickyd

rickyd 0

Posted

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.
Swede

Swede 21

Posted

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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