Black Powder burning speed x charcoal

[SeaMonkey]

Did aluminum powder sped up your BP?

 

 

jimjones,

 

It didn't speed up open air burn for speed test but worked well

in Salutes. I tried some in a Rocket and it exploded in mid-air

shortly after lift-off. The small amount of Aluminum Powder

does seem to enhance certain aspects of its use in various

devices, especially where it is confined.

[j3cub]

I am in the Central Valley of California and we have an abundance of Cottonwood trees here that make for excellent BP charcoal.

[SharkWhisperer]

I am in the Central Valley of California and we have an abundance of Cottonwood trees here that make for excellent BP charcoal.

How is the no-burn/no-fire regulation enforcement these days in central Cali...still a tinderbox or moistened up for winter?

 

The OP is in Brazil, and I don't believe any cottonwood (or related aspen/poplar) species grow down his way.

[SharkWhisperer]

Most people test 10 grams of powder I do believe with the baseball using a 3” mortar. I personally use a Mighty-Might HDPE mortar 3” x 18” as that is what I have. The baseball is shot as straight up as possible in hopes of recovering it for another round.

 

Here’s a pretty descriptive article discussing testing with baseballs

 

http://www.pyrobin.com/files/A%20Basic%20Comparison%20of%20Milling%20Media%20and%20Preparation%20Methods%20for%20Black%20Powder.doc

 

 

I’ve never thought to ask if anyone has ever noticed a difference with a taller mortar. As some of the commercial mortars I use occasionally vary in height.

 

On average mortars are 6 times the height as diameter.

Anybody else routinely use 10 g BP for a 3" baseball test? Doesn't seem like much lift for a 5 ounce (uh, somewhere around 150 grams for our Euro/Aussie friends) baseball.

 

I usually play around with 15 gm to start, and sometimes up it towards 20 gm if I'm feeling sassy. The article by DF also used 2FA grains, which I consider a little large for a 3" mortar; sheesh, maybe he had like 2% clearance to the mortar walls...? I usually use 4FA (2Fg) or similar (either 8-20 or 10-20 mesh-screened) for anything 3" and under, and my 3-inchers are 18" long HDPE. Like Boo said, mortar length is typically 6x inside diameter. This length can be somewhat variable, just like a rifle/shotgun/muzzleloader barrel length. Selection might depend on desired altitude and lift powder strength/burn speed, just like any cartridge or a muzzleloader. For example, in a pistol you typically want a fast burning powder to accelerate the bullet down a short barrel. Similarly, in a shotgun, you reload with a fast burning powder so it completely burns under lower expansion pressures while the projectile(s) accelerates down the barrel. In rifles with a longer barrel, especially magnums with a heavy projectile, you might use a slower powder to accelerate the bullet down a longer barrel at high velocity but lower pressures. So, if I had 15 gm of good BP and 15 gm of shit BP and were launching two baseballs side-by-side and wanted to get them to a similar altitude, I might select my usual 3" x 18" mortar for my good BP and take advantage of a longer 3" x 21" mortar to use with my shit BP, to allow more time (barrel length) for gas expansion during a slower BP deflagration. And then there's the mass of the projectile to consider...

 

I aim for approximately 5% shell-diameter total clearance distance to the mortar's inner wall. Please don't use PVC--shrapnel is a real possibility. Use HDPE or fiberglass (or cardboard). Some folks use steel but that's pretty heavy, especially with bigger tubes, and ya gotta bury it. Although HDPE isn't prone to shatter it can warp if it gets hot and change tube shape from perfectly round, especially if firing repeatedly. Check this. If the tube isn't perfectly round, you can bend/push it back to "true" round with your (gloved) hands if it's hot. You don't want to have a shell of any size getting trapped in an off-round mortar or have excessive friction with the walls. It'll generally come out about as smoothly as it went in.

 

If you're only competing with yourself, and especially if you're living in the city, take care with what you're launching. A baseball's going to go a hundred meters upwards and come down at high speed; and probably not exactly straight up and down! If you need to tone it down a bit and are just comparing your BP methods & batches, maybe start conservatively and play some pyrogolf or use a weighted plastic film canister or similar. In his charcoal comparisons, http://wichitabuggywhip.com/fireworks/charcoal_tests.html launched 35-mm film canisters loaded with 35 g sand, lifted with 2 grams of BP. That's about 1.4" in diameter for Muricans and Brits, which is even smaller than typical consumer 1.91" aerial shells. I probably would've used 3 or 3.5 grams BP for first test shots. But you don't use as much powder for simple testing with smaller mortars, you won't wake up too many neighborhood dogs, and you are less likely to have an errant missile (baseball) strike property or meat when it returns from the stratosphere. You really do need a decently large open area to launch baseballs from a 3" mortar...

 

But OP/JJ, glad to hear your new BP is even better ! Maybe use the older (but still good) BP to make yourself some blackmatch--you're going to be using a lot of it, hah ha!

Edited February 20, 2020 by SharkWhisperer

[Mumbles]

2 grams under a film canister and 10g under a baseball is basically the same ratio.

 

I agree that smaller grains are better for smaller shells or projectiles. I always use 4FA. I had really mixed results with 2FA.

[SharkWhisperer]

2 grams under a film canister and 10g under a baseball is basically the same ratio.

 

I agree that smaller grains are better for smaller shells or projectiles. I always use 4FA. I had really mixed results with 2FA.

Yuppers, both are approximately 6-7% of projectile mass. That seems kinda low-powered, even for a cautious test. Then again, those film canisters were launching out of Schedule 80 PVC, so probably wisest to start on the low end. Surprised me that he got 6-8 seconds of flight time with the charcoals we usually consider standard for decent lift BP, and for commercial Elephant BP, too, with just 6% shell mass--just seems like a wimpy lift load for those flight times. Maybe I just count a little faster than his stopwatch :+}

 

Double yuppers, in 2FA the ratio of absolute diameter between largest/smallest granules is around 2.8 (biggest are nearly 3x larger diameter than smallest); with 4FA the ratio is right around 2. But get this, I did the math--no I didn't, I let the computer do it: https://www.gigacalculator.com/calculators/volume-of-sphere-calculator.php . Anyways, assuming perfectly spherical granules, with 2FA the ratio of grain volume between largest/smallest particles is 23x !! Approximately 450 mm³ versus 20 mm³. That's huge! In smaller 4FA, the ratio of grain volume between largest/smallest is only 8x.

 

Couple that with variability in batch to batch amounts of large vs small grain (I pool batches, but don't make 5 gallons at a time...) and it seems like there's more variability in how the bigger-grained powders burn vs smaller-grained, unless you screen super-stringently. All of my lift for 3" and below is pretty religiously 10-20 mesh, a tight 8-10 mesh for 4", 20-40 mesh for toy mines/starguns under an inch, and anything less than 40 mesh is either prime or gets hammered into rockets & gerbs. So my ranges don't precisely match up to the FA or Fg size ranges. I guess my 3" lift would be more appropriately called 3.5FA !! To each their own, so long as it's working well.

 

Off Topic: Nitrocellulose lacquer. I keep reading about folks having difficulty getting smokeless powder into solution....shake, stir, wait, do it again in 30 minutes...blah, blah. Nonsense! Get over to Bass Pro or Cabella's and get a pound of Hodgdon's International shotshell powder. This thin round wafer (high-velocity) double-base make a 10% beige-colored solution in acetone with 2 minutes of lazy shaking in a bottle! No hassle. No residue. No precipitate. Stores well warm or cold. Dynamite Dragon Eggs!

Edited February 20, 2020 by SharkWhisperer

[Maserface]

Everyone I know, including me, uses 10 grams when baseball testing.

[BetICouldMake1]

6-7% lift is fairly standard, at least for cylinder shells. I know ball shells are different animals but lift amounts are usually pretty close if were talking weight ratio. As you mention, shell fit and mortar length will play a role, but those tend to be fairly standardized as well. The goal of baseball testing, to me at least, is to determine how well your powder measures up to know standards/dialing in lift amounts based on how hot (or not) your powder is. Hence the standard 10g amount.

 

If it takes more than 10g to get that baseball up there you gotta work on making better powder

[Carbon796]

Or know to use more. So, your not dropping bottom shots on the ground, or spraying people with lit stars . . . Edited February 22, 2020 by Carbon796