Why granulate?

[ollie366]

I'm interested in using BP for rockets, not fireworks. I've had good success with KNSB fuel but want to explore other options, including BP and the 50:50 mix of BP and KNSB as described by USAPYRO.

Whenever I read about making hot BP, granulating is almost always mentioned, but it seems to be in the context of fireworks, not rockets. I will be using a ball mill with 1/2" lead balls to mill the BP. I plan to ram as well as press the fuel, both 1/2" and 3/4" ID tubes. With and without cores. So my question, as basic as it may be, is - do I need to granulate the BP from the ball mill or can I use it as is for rocket fuel?

- if I need to granulate, why?

- If I granulate, do I need a binder? Again, why and what's recommended?

I look forward to learning more about this and appreciate getting responses to this basic question.

 

 

[Mumbles]

Granulating shouldn't affect the strength. For your applications it shouldn't matter much if you granulate or not. The one advantage of granulating is that it helps to cut down on dust and mess. It might be a little more consistent if you're measuring increments by volume.

 

If you decide to granulate, or at least try it out, I would not add a binder. You essentially just want to use water or alcohol to adhere the grains together, but still be easily crushed during ramming or pressing.

[justvisiting]

Granulating helps the propellant flow into place when making rockets. Otherwise, you have to tap the funnel and tubes to coax the powder down into place. It's a PITA. I made this little clip that shows the improvement granulating makes.

https://youtu.be/cUpRJqOnj-o

[ollie366]

Thanks for the quick and helpful replies. The video was quite interesting- the granulation does help with handling, which is a real plus.

[Arthur]

Moisture granulated powder is much cleaner and easier to put into the tubes and when you press or ram it the granules just crumble. Powder granulated with binder is used for fireworks burst and lift and doesn't pack well into rockets.

[BetICouldMake1]

You can also just add .5-1% water to your mill dust before ramming/pressing. Cuts the dust and saves the trouble of granulating.

[justvisiting]

BetIcouldMake1, yes- you are right. But are you saying that your moistened mill dust will flow easily as my granulated powder does? With many increments per rocket, the rate of flow through the funnel seems to be a big deal, if efficiency is desired. I have found damp powder to stick in the funnel as my video shows- but maybe worse. Does your dampened powder flow like the granulated powder I've shown, or like the mill dust I've shown- or somewhere in between? Do you think that running the dampened powder through a screen and drying is excessive? Just trying to see where we differ is all.

[BetICouldMake1]

Just to be clear I wasn't advocating one method over another, just throwing out an option that wasn't mentioned. But, to answer your questions, the half to one percent moisture isn't enough to make the powder sticky. It definitely plops more than it pours, but that's not an issue for me because I use a funnel with a much wider opening than the one you show in your video, so the powder just falls through. The spout on most funnels is a narrow tunnel that creates a choke point. Lop that off and life gets easier. Often I don't even bother with a funnel and just use a tall narrow scoop made from spent rifle brass. Fewer moving parts=more efficiency.

 

I've made rockets using granulated fuel, meal left over from grading lift and burst, and I do like the way it pours. If you're making smaller rockets, under .75in ID, then I'd use granulated. What I like about using the dampened mill dust is that I can keep a bucket of straight 75-15-10 dust on hand and if I want to press rockets just amend that based on whatever I'm building, that same dust can be used as base mix for stars, turned into slurry for blackmatch, etc. I don't think granulating is excessive, but it is an extra step that requires time and space to dry. I can take a jar off the mill, spray in my water, run it through a screen and be ready to go. Just what works for me.

 

BetIcouldMake1, yes- you are right. But are you saying that your moistened mill dust will flow easily as my granulated powder does? With many increments per rocket, the rate of flow through the funnel seems to be a big deal, if efficiency is desired. I have found damp powder to stick in the funnel as my video shows- but maybe worse. Does your dampened powder flow like the granulated powder I've shown, or like the mill dust I've shown- or somewhere in between? Do you think that running the dampened powder through a screen and drying is excessive? Just trying to see where we differ is all.

[Bkristensen]

Following

[justvisiting]

BetIcouldMake1, yes, using dampened BP works well too. I've used waxed BP that was granulated using wax dissolved in naphtha and dried. It gives extreme reliability and ease of use. Using dampened BP (I used 2% water), I was able to press a grain that was as dense as an Estes grain (1.8g/cc.). The water really helps consolidation and slows the burn down (if well pressed), giving a motor with excellent performance too.

Myself, I'm partial to using granulated propellants. They are the fastest to use, but not necessarily the 'best'. Got a bigger funnel now too

[dagabu]

Among the reasons to consider granulation your BP for rockets is not just better flow and less mess due to lack of dust but also MUCH better control of increment size. If you weigh it out, you will have the same size increments but if you use a scoop, this will give you better results.

 

It is SO simple to do, just make your BP mill dust, add small amounts of 90% water and 10% alcohol (trust me on this, you will get that water into the BP much faster) until you have a ball that will stick together when packed like a snowball. No, it will not stick as well as when you use a little dextrin in it but it will work.

 

Push the ball through a screen (I use an 8 mesh screen) by scraping it across and pushing it through with your fingers onto a sheet of clean kraft paper. Let it dry for a couple hours and run through the screen again. I put it through a 20 mesh screen after it is dry and run that over a 100 mesh screen to de-dust it.

 

It flows like dry sand, you will never go back to dry BP or moistened "clog my funnel, please!" BP ever again.

Expensive and wax retards the burn rate. What is the benefit?

 

BetIcouldMake1, yes, using dampened BP works well too. I've used waxed BP that was granulated using wax dissolved in naphtha and dried. It gives extreme reliability and ease of use. Using dampened BP (I used 2% water), I was able to press a grain that was as dense as an Estes grain (1.8g/cc.). The water really helps consolidation and slows the burn down (if well pressed), giving a motor with excellent performance too.

Myself, I'm partial to using granulated propellants. They are the fastest to use, but not necessarily the 'best'. Got a bigger funnel now too

[justvisiting]

Dagabu, yes, using waxed granulated propellant is more expensive and slows the burn rate somewhat. I used that method for making nozzleless rockets with hot BP. The comp presses like a dream, and I've stored such motors in baggies in a damp shed for up to 5 years with no change in performance. Just another way to get to the same place

[dlking59]

It is SO simple to do, just make your BP mill dust, add small amounts of 90% water and 10% alcohol

 

If my IPA states on the bottle that it is 91% alcohol do I use this as is with the 91% alcohol and the other 9% water or do I use the IPA plus add 10% water.

 

 

 

[dagabu]

Dagabu, yes, using waxed granulated propellant is more expensive and slows the burn rate somewhat. I used that method for making nozzleless rockets with hot BP. The comp presses like a dream, and I've stored such motors in baggies in a damp shed for up to 5 years with no change in performance. Just another way to get to the same place

[dagabu]

Black powder is stable even if no wax is included. I have ESTES motors over 50 years old that work as well as the day my dad fist used them.

 

On your side, 1% of wax will help the BP consolidate and not wrinkle the tube, well worth the cost vs CATO.

[dagabu]

 

It is SO simple to do, just make your BP mill dust, add small amounts of 90% water and 10% alcohol

 

If my IPA states on the bottle that it is 91% alcohol do I use this as is with the 91% alcohol and the other 9% water or do I use the IPA plus add 10% water.

 

 

 

Just use 80 parts of water to 20 parts of your 91% rubbing alchohol. Close enough.

[justvisiting]

Black powder is stable even if no wax is included. I have ESTES motors over 50 years old that work as well as the day my dad fist used them.

 

On your side, 1% of wax will help the BP consolidate and not wrinkle the tube, well worth the cost vs CATO.

Yes, I have fired Estes motors over 20 years old, no problemo. Of course, those were end burners, and I'm talking about coreburners. When I pressed a couple of coreburners on BP tooling with 2% water in the 75-15-10, I got tube compression big time. Having a spindle up the middle of the motor changes the dynamic a bit I think The same mix in a waxed tube core burner gave a motor with perfect appearance (no compression). I did cut one motor open and verify the density of the grain as +1.8, just as Estes grains are. With water-dampened BP, the increments are cemented together. The potassium nitrate is the binder

[dlking59]

Just use 80 parts of water to 20 parts of your 91% rubbing alchohol. Close enough.

Ok Thanks alot

[dagabu]

Keep in mind that ESTES may dampen their black powder slightly before pressing. I can't get Ed to confirm that (he was a builder of "Mable") but he alludes to that. The major difference is that the powder they use is all granulated and moistened. It still flows like dry sand but binds better so I do think you have a good point, thank you.

 

The point for those trying to copy this for their rockets is to weigh your water bottle, zero it and add the very same amount of water to your BP every time for repeatable results.

 

I like using the Febreze ONE spray bottle, I have never seen such a fine mist from a commercial sprayer, you can put an extremely fine layer of mist on a large surface quickly.

 

Yes, I have fired Estes motors over 20 years old, no problemo. Of course, those were end burners, and I'm talking about coreburners. When I pressed a couple of coreburners on BP tooling with 2% water in the 75-15-10, I got tube compression big time. Having a spindle up the middle of the motor changes the dynamic a bit I think The same mix in a waxed tube core burner gave a motor with perfect appearance (no compression). I did cut one motor open and verify the density of the grain as +1.8, just as Estes grains are. With water-dampened BP, the increments are cemented together. The potassium nitrate is the binder