Black Powder not fast enough for lift

[PyroSim]

Hello,

 

I've read alot about the topic but couldn't really get to a solution.

 

My BP (75/15/10) granulated with 3% dextrin is not fast enough to use as lift.

I put the KNO3 in the oven to dry out, the charcoal is pine.

I have a ball mill with a rubber drum (cheap one), filled 50% with 9-11MM ceramic milling media, and 25% BP mix.

The RPM'S are about right, with a filled drum I can hear the balls hitting each other but i've also ordered an RPM counter to be 100% sure it's at the optimal speed.

I let the mix (minus the dextrin) mill for about 8 hours, multiple batches, all with too slow of a result.

When I open it up most of it is clumped up to the sides with the balls stuck in it but breaks apart easy. I still hear the balls right before I turn the mill off. I have tried tapping the drum regularly while its milling.

I now have a drum rolling with only KNO3 to get it as fine as possible and then when it's done i'll milling it with C & S to see if it's better that way.

I've been looking for lead fishing media but it's too expensive to fill half a jar, and my mill would not be strong enough to turn it.

[FrankRizzo]

Rock tumblers don't turn fast enough to get good grinding action unless you've increased the drive roller size.

To get an RPM count, put a piece of tape on the end of the jar near the edge. Use your camera to record a few seconds of video at 30fps while it turns. Count the number of frames it takes to make a full revolution and do the math.

A 4"(101mm) jar with 10mm media needs turn about 91 RPM to be efficient.

[Guernica]

In addition to dialing in your mill setup, it sounds like you should be drying out your charcoal in an oven, too, since you're getting some clumping. Even if it seems dry you might be surprised how much moisture it can hold- I find I lose more water weight with it than I do when I dry my KNO3. Also, probably don't use pine for this application- save it for charcoal stars. Try to find some alder or willow or cedar or any of the hotter species from which to make your charcoal. 

[PyroSim]

I've calculated that it needed to be at around 97RPM. The tip with the camera is a good way to tell the RPM, thanks.

I thought pine was good, is oak a better option? I'll try drying the charcoal aswell.

 

---

Edit: I currently only have pine & oak, i'll use the pine for stars. Is oak a good charcoal for BP or is it also best used for stars?
Which ones of the following, if you had to choose, is the BEST for fast BP: vine, chestnut or juniper?

Edited September 24 by PyroSim

[Guernica]

I'd save the oak for stars as well, and you're right that pine would probably be better than it for lift, but maybe you can find some bags of cedar pet shavings in your area that would be better than either. Cedar shingles are good sources too, but expensive unless you know (or are) a builder and have access to scrap.

If by vine you mean grape vine, I think I've read here that it can work very well, but I have no personal experience. I have no idea about the chestnut, nor do I know about the juniper, although like the grape vine, I think I've read here on the forum that it can be good. 

So I guess I'd try the vine next, then maybe the juniper, then as an experiment the chestnut- in any case you'll have plenty of charcoal for stars which isn't a bad thing. 

Oh and until your mill is dialed you'll probably get better results milling for much longer than 8 hours- also pre-mill your (oven dried) charcoal first just as you have been with the KNO3.

 

Edited September 25 by Guernica

[DavidF]

Eastern red cedar (pet bedding) is a juniper.

[Guernica]

Interesting! Western red cedar is itself in the cypress family, so apparently the Western & eastern red cedars aren't as closely allied as their names would suggest. I've never made charcoal from a true cedar (as in Cedrus genus), but am curious to should some fall into my hands. 

[Arthur]

For the typical cheap rock tumbler try one day as a starting time for powder. If the powder is OK at one day then great, if not increase the time. Rock tumblers turn too slowly for quick milling. 

OR Build your own mill with a 300+watt motor capable of turning much faster. 

[PyroSim]

My charcoal is 100μm, do you think it's necessary to mill it on it's own before milling it with the rest?

[cmjlab]

+1 Juniper charcoal makes excellent black powder. 

Also agree with everyone else that rock tumblers (not modified) needs more time to make better B.P.

Also agree that charcoal holds a lot of moisture even when it feels dry.

Ceramic media probably needs extra milling time (this is pure speculatuon, ive never used it) ecen if you had an efficient mill, since it doesn't have the same weight / density as lead or stainless.

Good luck, you will feel great once you figure this out though. 

[Arthur]

Good woods for charcoal include willow and red alder historically, you may have to look up their Latin names and translate that into your language. Balsa is highly regarded for very fast BP but it's low density means you need a big retort. Binders can slow powder greatly If you are trying 3% do a test at 2% see whether there is improvement, original BP was pressed and corned and sieved to mesh sizes without any binder.

[Soloserly]

If you're in Belgium you can probably easily find some Black Alder, which makes great fast charcoal. 

It may seem obvious but the purity of your KNO3 matters.  Depending on your source, it could be contaminated with other salts that are slowing it down. 

[kingkama]

Toilet paper It is the best improvised alternative to replace vine or willow, obviously the central part of the roll must be eliminated.

[Richtee]

7 hours ago, kingkama said:

Toilet paper It is the best improvised alternative to replace vine or willow, obviously the central part of the roll must be eliminated.

As I have posted before...newspaper. Try it.

[Mumbles]

I would still mill the charcoal at 100 microns.

Pine charcoal kind of falls into the "it depends" category.  It depends on what type of pine it is.  Something that doesn't have a lot of relative sap and is fairly fast growing, like white pine, tends to make decent BP.  Something slower growing with more sap, like yellow pine, tends to make relatively poor BP.  That said, it's great for spark trails though.

If you're making your own charcoal, some of the characteristics you'll want to look for are fast growing, relatively clean or devoid of sap, and lighter weight. People talk a lot of about willow, eastern red pine, paulownia, staghorn sumac, balsa, etc. These all tend to fit those characteristics.  There are any number of other varieties that will work just fine.  On the whole, I've also found homemade charcoal to be hotter than more commercially produced stuff.  It's probably just the closer control we have over it and smaller relative batch sizes give a more even pyrolysis.

[Arthur]

ONE of the historic guidelines for charcoal for powder was "young branches of fast growing trees that grow by water from the size of a mans wrist to the size of his forearm". If your home area has water then this might offer some leads among your local trees. Suitable wood should be cut and stacked to dry for a year or two before being charcoaled.

Some pines are better for effect sparks than power powder, most hard furniture woods make poor powder.

Some people swear by charcoal made from toilet tissue or kitchen paper towels.

With modern material availability there will be lots of sources to try for anyone inclined to make lots of test batches of whatever takes their fancy then do lots of testing of the finished powders, this would of course cost the whole defence budget of a small nation state so we will have to rely on people's suggestions from whatever they can find locally to them.

Remember that commercially made BP is made to a standard speed, sometimes by mixing faster and slower batches, commercially and militarily reliability and uniformity from batch to batch is the critical factor. Amateur wise usually faster is better with slower powders being sidelined for rockets and fountains.

[johnnypyro]

I use a rock tumbler with ceramic media for BP with good results.  I have it on the slowest speed of 88rpm which just about matches what it should from the formula:

idea rpm = 0.65*265.45/sqrt(Container Inside Diameter - Media Diameter) 

All measurements in cm.

I use willow charcoal which is already powdered. Sieve this with 40mesh and into the tumbler for 6 hours. KNO3 and S get 2 minutes each in the coffee grinder. Combine for BP and then mill for 12 hours. After that, I didn't get any noticeable improvement. Dextrin at 2% makes the grains easier to re-sieve after drying.

[Mumbles]

Just an FYI, that formula is designed to work in inches.  The critical speed formula (without the 0.65 factor) is essentially just a rearranged equation balancing acceleration due to gravity and centripetal force. The 265.45 value in it is a collection of constants, one of which is derived from the acceleration due to gravity. Using the metric gravitational acceleration would be required for an equivalent formula in cm.