Rocket pressing questions

[FieryCreations]

Finally got my tube supports from Woody’s. Have a couple questions.
 

The force gauge I bought is 1:1. It came with pressing calculations, but I can’t find anything listed about the desired pressing force for a 1 pound rocket. From what I found searching it seems to be 6500 psi? Are 2 teaspoons too much for an increment? Can I use more than that if pressing?

 

Also searched around  trying to figure out which type of BP to press with. It seemed like there wasn’t anything critical about using meal versus different grain sizes other than being dusty. I tried using meal and man, the dusters not manageable half of it squirts out.
 

What’s the easiest remedy? Wet it a little before pressing and then let it dry for a few days? Or go through the trouble of granulating and screening it?

 

also, curious if most people use the regular 75/15/10 ratio for rocket motors. I remember someone mentioning altering it for motors, but I can’t remember anything else. 

Edited January 9 by FieryCreations

[ThrownBiscuit]

I would say that 2 teaspoons is way too much for an increment  for a 1lb rocket. If I use more than 3/4 of a teaspoon a lot of the meal squirts out. So for that I'd say the easiest remedy is reduce the size of increments.

[FieryCreations]

37 minutes ago, ThrownBiscuit said:

I would say that 2 teaspoons is way too much for an increment  for a 1lb rocket. If I use more than 3/4 of a teaspoon a lot of the meal squirts out. So for that I'd say the easiest remedy is reduce the size of increments.

Dang. Even using two tsp it took forever to fill. I can’t imagine over double the time. 
 

If I granulate or wet the meal can I use that much?

[cmjlab]

Too big of an increment and you run the risk of crumpling the tube, getting your drift stuck (especially with meal, and not consolidating your rocket adequately (potentially leaving voids and causing CATO).

The B.P. you use depends on your tooling and the type of rocket you are making... (Nozzled / Nozzleless, Core burner, End-burner, etc.) for Nozzleless B.P. rocket you want your hottest B.P..  For a nozzled core burner, you probably want to start with screen mixed or lightly milled B.P., but not at 75-15-10.  You'll have to do some homework on rocket propellant formulas.  It's also probably where you recall discussions of how to tune your B.P. for nozzled core burners, and typically adding charcoal in small proportions to get the power right, etc.  (again more homework).

I'll m confused as to what you're asking for pressing - you have Woody's 1# tooling, a 1:1 PtoF gauge and a pressing sleeve with calculations provided.  Are you asking what most people press 1# motors at?  Some people, like Gorski, recommend 7500 psi for 1# tooling, which is all I have.

[FieryCreations]

33 minutes ago, cmjlab said:

Too big of an increment and you run the risk of crumpling the tube, getting your drift stuck (especially with meal, and not consolidating your rocket adequately (potentially leaving voids and causing CATO).

The B.P. you use depends on your tooling and the type of rocket you are making... (Nozzled / Nozzleless, Core burner, End-burner, etc.) for Nozzleless B.P. rocket you want your hottest B.P..  For a nozzled core burner, you probably want to start with screen mixed or lightly milled B.P., but not at 75-15-10.  You'll have to do some homework on rocket propellant formulas.  It's also probably where you recall discussions of how to tune your B.P. for nozzled core burners, and typically adding charcoal in small proportions to get the power right, etc.  (again more homework).

I'll m confused as to what you're asking for pressing - you have Woody's 1# tooling, a 1:1 PtoF gauge and a pressing sleeve with calculations provided.  Are you asking what most people press 1# motors at?  Some people, like Gorski, recommend 7500 psi for 1# tooling, which is all I have.

Ahh yeah that’s exactly what I was asking, thanks. I pressed at 6-6500. 75/15/10 with my first quality homemade charcoal. It flew fast and didn’t Cato this time. Seems to fly good but the dust… 

so 3/4 tsp per? I can’t even imagine how many times that would take to fill a tube having to remove it each time and reset  

 

 

Edited January 10 by FieryCreations

[ThrownBiscuit]

Slight damping will help consolidation but even with 6# motors I don't use 2 teaspoons of bp as an increment. As cmjlab stated too big of increment will get your drift stuck (especially with pressing) and it will be very annoying to pull out. Pressing will make things be a bit more consistent at least in my experience. I have one of Woody's PToF guages and it has improved my consistency.

For 1 lb rockets I press to approximately 7500 psi which using [(pi/4)*D^2]*P which is [(3.14/4)*(0.75 in.)^2]*7500 psi = approximately 3313 lbs of force. So, I try to press pretty close to where the gauge shows 3300 lbs, allow for a bit of settling, press it back up to close to 3300 lbs, release and then add the next increment.

As far as the ratio to use with your black powder, trial and error on the strength of your powder. That being said nozzled core burners are a lot more forgiving of weak BP I have had pretty good luck with 69-21-10 with them. I also like to mix in 5 % pine charcoal to the hardwood for a nice sparky tail but that's just a personal preferance.

[FieryCreations]

All right, thanks. Maybe they won’t be so slow to fill once my powder is in squirting out.
 

 

So is the goal to have slower burning powder in rocket motors? Is that why the different ratio? Wondering if I should be packing my motors with the couple pounds of slow BP I have instead of my harder to make good stuff. 
 

is that 5% pine charcoal something you add to completed BP, or are you just substituting 5% in the 15% charcoal ratio when you make it?

Edited January 10 by FieryCreations

[DavidF]

This might help with your powder issue. I would never load a rocket with straight mill dust that has not been either moistened or granulated in some way. It's messy, and it's a waste of time. I don't make rockets the way most folks do, but I use 12 increments to load a 1lb BP motor. The choice of funnel is important too. 

If you add 2 - 2 1/2% water to your mill dust and screen it in well there will be little to no dust and you can press the rocket with less force and get better consolidation. It's not popular among the old school rocket crowd (especially the nozzleites), but the folks that make the most reliable commercial rocket motors use water- and nozzles. I use water in nozzled BP rockets too, at 3%. There are a lot of techniques that work to make reliable rockets. Ned Gorski and Woody both have videos showing how they do theirs.

When I press with moistened BP I use around 3500psi loading pressure. The propellant grain is as hard as stone. Dry powder pressed at twice the loading pressure is not as dense. There's no need to dry the motors either. They fly fine as soon as they are made. Just try one, one time. See for yourself what's what.

[FieryCreations]

34 minutes ago, DavidF said:

This might help with your powder issue. I would never load a rocket with straight mill dust that has not been either moistened or granulated in some way. It's messy, and it's a waste of time. I don't make rockets the way most folks do, but I use 12 increments to load a 1lb BP motor. The choice of funnel is important too. 

If you add 2 - 2 1/2% water to your mill dust and screen it in well there will be little to no dust and you can press the rocket with less force and get better consolidation. It's not popular among the old school rocket crowd (especially the nozzleites), but the folks that make the most reliable commercial rocket motors use water- and nozzles. I use water in nozzled BP rockets too, at 3%. There are a lot of techniques that work to make reliable rockets. Ned Gorski and Woody both have videos showing how they do theirs.

When I press with moistened BP I use around 3500psi loading pressure. The propellant grain is as hard as stone. Dry powder pressed at twice the loading pressure is not as dense. There's no need to dry the motors either. They fly fine as soon as they are made. Just try one, one time. See for yourself what's what.

Ooooo that's smooth flowing. 

[ThrownBiscuit]

Yes, the 5% pine charcoal is substituted into the normal charcoal ratio. Slow burning black powder is fine for core burner rockets but does not work for end burner rockets.

I would definitely listen to anything DavidF says about rockets, he has been doing rockets for a while now as you can see if you read up on some of the old topics like I am prone to do.

[FieryCreations]

On 1/10/2024 at 9:05 PM, DavidF said:

This might help with your powder issue. I would never load a rocket with straight mill dust that has not been either moistened or granulated in some way. It's messy, and it's a waste of time. I don't make rockets the way most folks do, but I use 12 increments to load a 1lb BP motor. The choice of funnel is important too. 

If you add 2 - 2 1/2% water to your mill dust and screen it in well there will be little to no dust and you can press the rocket with less force and get better consolidation. It's not popular among the old school rocket crowd (especially the nozzleites), but the folks that make the most reliable commercial rocket motors use water- and nozzles. I use water in nozzled BP rockets too, at 3%. There are a lot of techniques that work to make reliable rockets. Ned Gorski and Woody both have videos showing how they do theirs.

When I press with moistened BP I use around 3500psi loading pressure. The propellant grain is as hard as stone. Dry powder pressed at twice the loading pressure is not as dense. There's no need to dry the motors either. They fly fine as soon as they are made. Just try one, one time. See for yourself what's what.

David-

I tried your method with water and pressed a rocket with a lot more ease. It CATO'd about 15' up but I'm guessing that was due to my spindle being bent a bit in a few directions. 

Couple of questions for you. I did press it at 7000 PSI (didn't realize you said only 3500 PSI with this method).

 

It seemed to take a lot more than 12 tsp increments. Is that probably because I doubled the pressure you use, or do you use increments larger than 1 tsp?
 

Is it possible my CATO was due to my BP being to hot? I'm still unclear with this. I made the best BP I could. It seems hot, and is still 75/15/10. Should I be ok with this or am I very likely to keep running into CATOs if I don't tone it down?


Thanks. 

Edited January 15 by FieryCreations

[cmjlab]

Until Dave responds, are you making end burner (with a nozzle) or core burners (with a nozzle)?

If you have one made up already, you could maybe try opening up the throat a hair, with a drill bit (by hand).  Or as ThrownBiscuit said in the post before yours, add an extra 5% charcoal to slow your fuel.  

I'm sure Dave or others who have more rocket experience will chime in, but I've learned that the general rule if you're going to tune your fuel is to add charcoal to decrease strength, and add more KNO3 to increase, in 5%. Increments.

[DavidF]

When I made my first 3 rockets, I 3lb made black powder rockets with hot 75-15-10 and a nozzle. Of course, 3 CATO's. Then I realized that although they are called black powder rockets, they are not made with black powder! Oh its black alright- but not 75-15-10. More like 60-15-15-10 or similar. Anyhow, for nozzleless rockets or end burners, folks use hot BP of some sort.

When I press a nozzleless rocket with 75-15-10 + 2% moisture screened in, I press it to 3500psi. This makes sense when you consider that commercial black powder is pressed to 3000-3500psi when it's being made. As a friend once said to me, "You're just pressing pucks in a tube. How much harder do they need to be?" But still, on a psychological level it's hard to just reduce pressure when the whole community are mostly 6500psi folks.

If I'm pressing a 'traditional' rocket with a nozzle, I'll add 3% water screened in well. I'll use a nozzle and 60 parts fine potassium nitrate, 15 part airfloat charcoal and 15 parts coarser charcoal like 40-80 mesh, and 10 parts sulfur.

I was saying 12 increments because my increments are well-rounded teaspoons for 1lb motors and well-rounded tablespoons for 3lb rockets. Waxing the tubes makes the tubes more forgiving to larger increments is my guess. And the water makes each increment compress more. I did notice that loading larger increments of dampened BP tended to pull a dry tube down, where that did not happen with the waxed tube. I'm not saying this to try to change any minds on waxing. I'm simply reporting that I do it because I think my results might be different if I didn't do it, and I don't want to mis-represent. If you get compression wrinkles on the outside of the tube, time to back off on 'something'.

[FieryCreations]

1 hour ago, DavidF said:

When I made my first 3 rockets, I 3lb made black powder rockets with hot 75-15-10 and a nozzle. Of course, 3 CATO's. Then I realized that although they are called black powder rockets, they are not made with black powder! Oh its black alright- but not 75-15-10. More like 60-15-15-10 or similar. Anyhow, for nozzleless rockets or end burners, folks use hot BP of some sort.

When I press a nozzleless rocket with 75-15-10 + 2% moisture screened in, I press it to 3500psi. This makes sense when you consider that commercial black powder is pressed to 3000-3500psi when it's being made. As a friend once said to me, "You're just pressing pucks in a tube. How much harder do they need to be?" But still, on a psychological level it's hard to just reduce pressure when the whole community are mostly 6500psi folks.

If I'm pressing a 'traditional' rocket with a nozzle, I'll add 3% water screened in well. I'll use a nozzle and 60 parts fine potassium nitrate, 15 part airfloat charcoal and 15 parts coarser charcoal like 40-80 mesh, and 10 parts sulfur.

I was saying 12 increments because my increments are well-rounded teaspoons for 1lb motors and well-rounded tablespoons for 3lb rockets. Waxing the tubes makes the tubes more forgiving to larger increments is my guess. And the water makes each increment compress more. I did notice that loading larger increments of dampened BP tended to pull a dry tube down, where that did not happen with the waxed tube. I'm not saying this to try to change any minds on waxing. I'm simply reporting that I do it because I think my results might be different if I didn't do it, and I don't want to mis-represent. If you get compression wrinkles on the outside of the tube, time to back off on 'something'.

I'm making nozzled coreburners. 

So it sounds like I'm best off starting over with new comp if I don't want to continue wasting them all. 

Is that coarse charcoal pretty mandatory?  I hate trying to screen chemicals like that. Can I just throw everything in my mill except the 15 parts coarse charcoal and mix that in later? It sounds like you don't use any binder on this right? 


I hate ball milling BP for safety reason but man I cannot seem to screen mix chems without making a huge mess, getting frustrated, and wasting a bunch of time for very little. 

Edited January 16 by FieryCreations

[DavidF]

Well, if you already have 75-15-10 made up, why not just leave out the nozzle and use it up? I don't know about making rockets with a spindle that's bent!

The coarse charcoal is to be used with nozzled rockets, mostly. I have used 5% coarse charcoal in nozzleless rockets to make a tail. Mostly I just use a pinch of FeTi in each increment above the spindle tip for tail on the nozzleless ones. That way I don't lose power. A typical 1lb nozzleless rocket should easily lift a 4" ball shell. A typical 1lb nozzled rocket should easily lift a 3" ball shell.

Nozzled rockets are the easiest from a prep point of view. If you don't have any coarse charcoal like 40 or 80 mesh, you can still make rockets, but the tail will be finer. 70 parts milled potassium nitrate, 20 parts commercial airfloat charcoal, and 10 parts sulfur should work fine. Maybe 65-25-10 if they CATO? I would screen the powder twice or thrice through a normal kitchen sieve, until the color looks even. If you decide to use 2 or 3% water, it would need to be screened again once you spritz it in. I like to leave the powder to 'temper' for a while before I use it. Damp propellant needs less pressure as mentioned before. If you decide to use 8% water spritzed in and screened in instead, then you'd dry it in a thin layer on some paper and press it dry later to 6500psi. I've seen people suggest using really fine screens like 100 mesh for rocket propellant. I would never do that. It takes way too much time and is not needed. A gravy strainer is fine for nozzled BP rocket propellant. I hope this helps.

[FieryCreations]

38 minutes ago, DavidF said:

Well, if you already have 75-15-10 made up, why not just leave out the nozzle and use it up? I don't know about making rockets with a spindle that's bent!

The coarse charcoal is to be used with nozzled rockets, mostly. I have used 5% coarse charcoal in nozzleless rockets to make a tail. Mostly I just use a pinch of FeTi in each increment above the spindle tip for tail on the nozzleless ones. That way I don't lose power. A typical 1lb nozzleless rocket should easily lift a 4" ball shell. A typical 1lb nozzled rocket should easily lift a 3" ball shell.

Nozzled rockets are the easiest from a prep point of view. If you don't have any coarse charcoal like 40 or 80 mesh, you can still make rockets, but the tail will be finer. 70 parts milled potassium nitrate, 20 parts commercial airfloat charcoal, and 10 parts sulfur should work fine. Maybe 65-25-10 if they CATO? I would screen the powder twice or thrice through a normal kitchen sieve, until the color looks even. If you decide to use 2 or 3% water, it would need to be screened again once you spritz it in. I like to leave the powder to 'temper' for a while before I use it. Damp propellant needs less pressure as mentioned before. If you decide to use 8% water spritzed in and screened in instead, then you'd dry it in a thin layer on some paper and press it dry later to 6500psi. I've seen people suggest using really fine screens like 100 mesh for rocket propellant. I would never do that. It takes way too much time and is not needed. A gravy strainer is fine for nozzled BP rocket propellant. I hope this helps.

Oh man, I think I was doing some things wrong and I really appreciate the replies.

 

Do I not need to use a 100 mesh to screen mix BP chems together? That's why I was having a rough time and hating it so much. My little coffee grinders would barely get anything to 100mesh. I'd continually be putting it back in and re grinding for a teaspon to make it through the 100 mesh. What's a gravy strainer, 20-50ish mesh? I bet that would be tolerable. 


As far as leaving the nozzle out- I thought my tooling dictated both nozzle/nozzleless and endburner/coreburner. At least where I bought mine on Woodys they seem to be separate tools. The 75-15-10 is a hot mix that took some time and dedication to make, and I had planned on making it my "standard" BP mix after I get the stuff to granulate it (SGRS).

It sounds like I really need to figure out screening. If ball milling isn't super critical I'd love to be able to avoid it. 

As far as the charcoal- I seriously am not worried about any effects at this point. I want to start with consistent rockets that actually WORK. My stars are just plate pressed BP with no other chems. I want to get the basics of functioning down before moving on. (Non CATO, consistent delay mix, passfire to header, star ignition etc.)

[DavidF]

When I say 'milled potassium nitrate', I mean ballmilled. It's as fine as icing sugar. I did not realize you were using a coffee mill. In that case, you would need a super fine screen, and it would take forever. I'd hate that too. I don't know what potassium nitrate you are using. I buy greenhouse grade powder and mill it. Some guys buy it as finer powder. You really need a ball mill to go very far with this.

[FieryCreations]

32 minutes ago, DavidF said:

When I say 'milled potassium nitrate', I mean ballmilled. It's as fine as icing sugar. I did not realize you were using a coffee mill. In that case, you would need a super fine screen, and it would take forever. I'd hate that too. I don't know what potassium nitrate you are using. I buy greenhouse grade powder and mill it. Some guys buy it as finer powder. You really need a ball mill to go very far with this.

I have a treadmill I converted to a pretty good mill. See this is the part I don’t get. If you guys are needing to mill individual chemicals, how can it not be more efficient and practical to just measure and mill them all together?? Why even screen mix. I’m so confused. 
 

I can throw 500g to 1kg of BP mix in my mill, come back some hours later and I’m done. 
 

Micro granulate the meal with water as you suggested for rocket motors, and then use a binder to granulate the rest and sort by mesh size for lift/burst charge? Am I missing something?

Edited January 16 by FieryCreations

[cmjlab]

If you mill them together you assume more risk, and you mix the three ingredients much more intimately than you do milling independently.  You also must store it in a safe place to avoid accidents or mishaps leading to fire, and if you are trying to stay legal, need to store it in an explosives magazine.  Those are just some of the reasons people don't mill the 3 together.

[FieryCreations]

15 minutes ago, cmjlab said:

If you mill them together you assume more risk, and you mix the three ingredients much more intimately than you do milling independently.  You also must store it in a safe place to avoid accidents or mishaps leading to fire, and if you are trying to stay legal, need to store it in an explosives magazine.  Those are just some of the reasons people don't mill the 3 together.

Can you please show me where the "must store in an explosives magazines" comes from? I paid for legal consulting from an explosives company. They said if you have you FEL you must, otherwise the feds do not care if you store it next to you gas stove. State laws may be more strict. 

[cmjlab]

I'm not a lawyer and I won't be representing you if you ever need it, so take what I say with a grain of salt...

The ATF orange book is what I would use to discern legal storage requirements, if I could not afford a lawyer willing to interpret AND back up what they told me in court.

And you are right, I misspoke about B.P. storage, it is only commercially manufactured B.P. that is regulated (yes I realize there are exemptions).

I will say, that if something happens, and the ATF or local authorities realize that you are making fireworks, I would not want to show them that I had it stored anywhere other than in an explosives magazine, even if I didn't have a license and was relying on the federal interpretation of for my own use, on my own property....

Edited January 16 by cmjlab

[FieryCreations]

Off topic now but….

 

As I’ve mentioned I hate ball milling BP. It seems low risk but very high consequence. I’d much rather not with my proximity to neighbors. 
 

Provided my charcoal is decent, just how much worse will my powder be if I screen mix these individually milled components, use a binder such as SGRS and then rice it, as opposed to milling the 3 components together? 
 

Is the difference worth worrying about? I guess I can deal with more frustration and mess for safety as long as it’s not a massive difference. 

[CountZero]

You could ball mill your components speparatly and screen mix them...

[DavidF]

When you make standard nozzled black powder rockets, you use ball milled potassium nitrate, screen-mixed with the other ingredients. I described what I do above. When you make nozzleless rockets, you use ball milled black powder. Myself, I use 2% water, as I described. You can make screen-mixed black powder by milling the components separately, but it takes some effort to make it powerful enough for most uses. What I do is to mill the charcoal to a very fine powder with small SS media (not lead). Then I screen mix it with milled potassium nitrate and fine sulfur. Twice through a 40 mesh screen with hand mixing in between works for me. Most people opt to just mill the complete mixture.

Black powder has so many iterations and so many uses, it's hard to give concise information on it for all cases. When using black powder ingredients for rockets, there is no binder used. The grains need to be soft enough to be easily compressed. The soft 'micro-granulated' stuff I showed in the video clip is for pressing rockets dry, which most folks do. Different pyros have different techniques, and we don't all agree on the 'right' way of doing things. I described specific things that I do for specific situations. Black powder is a broad topic, and there are so many different ways it is used that it is a bit confusing in the beginning.