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BP core burner rocket CATO

BP core burner rocket cato

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#1 fieldworker

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Posted 25 September 2022 - 09:20 AM

Hello I have been making core burner rockets with 60-30-10 comp with finest airfloat charcoal and I have followed approx dimensions from rocket sketcher tool and I am using a homemade rocket tooling, the rocket motor is not able to contain the pressure and the clay bulkead is pushed out every time, even though I have made longer tube to put more clay at the top still no luck, the tubes are fine, the bottom nozzle is fine, only the top bulkhead is pushed out, How can I prevent the CATO?

1)I'm using raw ball milled BP without any percentage of moisture, is that an issue?

2)should I remove the bottom nozzle and try ?

3)how can I weaken the reactivity of BP to lower the pressure in the rocket motor? I mean what should I add with the 60-30-10 comp to lower the reactivity


Edited by fieldworker, 25 September 2022 - 09:26 AM.


#2 fieldworker

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Posted 25 September 2022 - 10:57 AM

Update: Tried after removing clay nozzle and seesh it flew like nasa rocket, I'm so happy that at least the nozzle less version works like charm and it was so much powerful that it can easily lift upto 5 inch shell easily I guess. So my questions reduced to:

1)how can I weaken the reactivity of BP to lower the pressure in the rocket motor? I mean what should I add with the 60-30-10 comp to lower the reactivity or burn rate


Edited by fieldworker, 25 September 2022 - 10:58 AM.


#3 cmjlab

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Posted 26 September 2022 - 06:46 AM

Until someone with more rocket experience chimes in, it's generally accepted (Weingart I believe) that if there's too much power - add charcoal (5% increments is the recommended starting point), if not enough power add more oxidizer (KNO3).

Charles
Until someone with more rocket experience chimes in, it's generally accepted (Weingart I believe) that if there's too much power - add charcoal (5% increments is the recommended starting point), if not enough power add more oxidizer (KNO3).

Charles

#4 justvisiting

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Posted 26 September 2022 - 11:26 AM

Interesting problem! You don't mention the rocket size, or whether you hand ram or press. That would be helpful to know. Also, what kind of clay bulkhead did you use, and how thick was it? What did the top surface of it look like? Pics? Do you use a tube support?

 

You say you are using raw ball-milled BP, and also mention using the finest airfloat. I'm assuming that means you are ball-milling the complete 60-30-10 mixture. That's not typically done. 'Standard' BP rockets use finely powdered or milled ingredients, but not milled together like BP. A typical nozzled BP coreburner would use half of the 30 parts of charcoal as airfloat, and the other half would be coarser, like 36 mesh or 80 mesh. The charcoal would be made from slower burning hardwoods, not hot BP charcoals. That's what I do, and I have no problem at all with blowthroughs. You mention using the powder with no moisture in it. I use a couple of percent of water, spritzed and screened in. This helps greatly with consolidation. The clay is never moistened. Most folks don't use water in the propellant, but it's becoming more popular in my mind.

 

The way to "weaken the reactivity" of the BP won't be needed if you do as I mentioned above. These aren't my ideas, they are generally accepted by most.

 

Since we don't know the size of rocket, we can't be sure that your hope to lift a 5 inch shell is possible, but it's doubtful (in my opinion). A 1lb nozzleless rocket with hot 75-15-10 will lift a 4 inch ball shell to proper height every day of the week. 5 inch, not so much. My guess is that your 60-30-10 ball-milled propellant in a nozzleless configuration won't be enough for a 4 inch- in the 1lb size. If you were to use 60 milled potassium nitrate, 15 fine charcoal, 15 coarser charcoal, and 10 sulfur with a nozzle you should be able to comfortably lift a 3 inch shell, maybe a 4 inch. Some of us use a hot BP charcoal for the 15 parts of fine charcoal instead of commercial airfloat to get more zip. 

 

You should try lifting dummy shells with kitty litter and burst before you take a chance with a live shell. 

 

Weingart's advice was good, but: he suggests using "mixed coal" in his propellant, not a ball-milled complete mixture.



#5 Richtee

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Posted 26 September 2022 - 02:07 PM

 

Weingart's advice was good, but: he suggests using "mixed coal" in his propellant, not a ball-milled complete mixture.

Oooh!  I love rocket science :D

 

I have hit some snags myself. The answers are here tho.


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#6 fieldworker

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Posted 27 September 2022 - 11:54 AM

Until someone with more rocket experience chimes in, it's generally accepted (Weingart I believe) that if there's too much power - add charcoal (5% increments is the recommended starting point), if not enough power add more oxidizer (KNO3).

Charles
Until someone with more rocket experience chimes in, it's generally accepted (Weingart I believe) that if there's too much power - add charcoal (5% increments is the recommended starting point), if not enough power add more oxidizer (KNO3).

Charles

Thanks for the suggestion will try altering the charcoal ratio to reduce the bp burn rate



#7 fieldworker

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Posted 27 September 2022 - 12:06 PM

Interesting problem! You don't mention the rocket size, or whether you hand ram or press. That would be helpful to know. Also, what kind of clay bulkhead did you use, and how thick was it? What did the top surface of it look like? Pics? Do you use a tube support?

 

You say you are using raw ball-milled BP, and also mention using the finest airfloat. I'm assuming that means you are ball-milling the complete 60-30-10 mixture. That's not typically done. 'Standard' BP rockets use finely powdered or milled ingredients, but not milled together like BP. A typical nozzled BP coreburner would use half of the 30 parts of charcoal as airfloat, and the other half would be coarser, like 36 mesh or 80 mesh. The charcoal would be made from slower burning hardwoods, not hot BP charcoals. That's what I do, and I have no problem at all with blowthroughs. You mention using the powder with no moisture in it. I use a couple of percent of water, spritzed and screened in. This helps greatly with consolidation. The clay is never moistened. Most folks don't use water in the propellant, but it's becoming more popular in my mind.

 

The way to "weaken the reactivity" of the BP won't be needed if you do as I mentioned above. These aren't my ideas, they are generally accepted by most.

 

Since we don't know the size of rocket, we can't be sure that your hope to lift a 5 inch shell is possible, but it's doubtful (in my opinion). A 1lb nozzleless rocket with hot 75-15-10 will lift a 4 inch ball shell to proper height every day of the week. 5 inch, not so much. My guess is that your 60-30-10 ball-milled propellant in a nozzleless configuration won't be enough for a 4 inch- in the 1lb size. If you were to use 60 milled potassium nitrate, 15 fine charcoal, 15 coarser charcoal, and 10 sulfur with a nozzle you should be able to comfortably lift a 3 inch shell, maybe a 4 inch. Some of us use a hot BP charcoal for the 15 parts of fine charcoal instead of commercial airfloat to get more zip. 

 

You should try lifting dummy shells with kitty litter and burst before you take a chance with a live shell. 

 

Weingart's advice was good, but: he suggests using "mixed coal" in his propellant, not a ball-milled complete mixture.

I am using a hand ram and yes I use small mechanical rings for tube support, and thanks for the suggestion. Also, I figured out the issue, the issue was my bottom clay nozzle hole was too small, so the hot air was not able to escape as it should be and one more thing that I was doing wrong was ball milling together all the ingredients, which we should mill them separately and then mix them with hands as you mentioned. Coming to my rocket dimension, mine is 1lb and thanks everyone for the suggestions :)



#8 Arthur

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Posted 29 September 2022 - 04:13 AM

My understanding is that milled incorporated fuels are for nozzleless motors and milled separate ingredients are for nozzled motors. 



#9 fieldworker

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Posted 30 September 2022 - 09:00 AM

My understanding is that milled incorporated fuels are for nozzleless motors and milled separate ingredients are for nozzled motors. 

you are absolutely correct






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