BP core burner rocket CATO

[fieldworker]

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 September 25, 2022 by fieldworker

[fieldworker]

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 September 25, 2022 by fieldworker

[cmjlab]

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

[justvisiting]

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.

[Richtee]

 

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

 

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

[fieldworker]

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

[fieldworker]

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

[Arthur]

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

[fieldworker]

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

you are absolutely correct

[abhivishw]

Hey Guys, just want to express my gratitude for suggestions made in this post. I have had the same problem with motor CATO's during tests. Thanks to this post, i made some changes and it seems to be working now. I did 2 tests so far and they both have same results. Please let know your suggestions.

 

Edited February 25, 2023 by abhivishw

[justvisiting]

Just one suggestion: Fly one I bet it would look good

[utmustang05]

Rather then try to weaken your BP enlarge the nozzle. Also I would stay away from dampening your BP very much as it can crack when drying and you'll have an instant CATO.

I have been making BP rocket motors for years and I have never had the bulk head blow out. Finding the right nozzle opening will do wonders for the rockets ability to lift weight. As mentioned previously not knowing what size motors your making makes it difficult to know what size nozzle you need, however in my experience you will need to tweak the size because there are so many factors that can change the dynamic of the burning motor.

[tld6008]

I have a similar problem

I am attempting to making 3 lb motors using 75/15/10 BP which I milled, the charcoal was airflot. I did not moisten the BP

I use core burner tooling purchased from Skylighter, my 1"ID tubes were purchase from Skylighter also

I hand rammed the motors based on N. Gorskys video demonstrations.

First one CATOd

I read some and it seemed the consensus was if the tube was waxed the hot BP would be fine

I waxed my tubes and used 20G of kitty litter for the nozzle and upper bulkhead and 7 G for each BP increment

2nd one CATOd also

Originally I had thought that I need to add some charcoal to slow the mix which I guess I will do although I see above that possibly increasing the nozzle diameter might also work

Both CATOs resulted in nozzle and bulkhead blowing out as well as the tube splitting

Looking for some experienced advice

[SharkWhisperer]

I have a similar problem

I am attempting to making 3 lb motors using 75/15/10 BP which I milled, the charcoal was airflot. I did not moisten the BP

I use core burner tooling purchased from Skylighter, my 1"ID tubes were purchase from Skylighter also

I hand rammed the motors based on N. Gorskys video demonstrations.

First one CATOd

I read some and it seemed the consensus was if the tube was waxed the hot BP would be fine

I waxed my tubes and used 20G of kitty litter for the nozzle and upper bulkhead and 7 G for each BP increment

2nd one CATOd also

Originally I had thought that I need to add some charcoal to slow the mix which I guess I will do although I see above that possibly increasing the nozzle diameter might also work

Both CATOs resulted in nozzle and bulkhead blowing out as well as the tube splitting

Looking for some experienced advice

I'll hand-ram 3/4" motors all day, but my rammed 1"ers are a coin toss if they'll cato. For me, that size and larger is only or pressing. I strongly recommend you start with smaller motors. Get those right and then move on.

 

If your BP is decent, 75/15/10 would be expected to blow nozzles/bulkheads/tubes in coreburner configuration. That's basic. Either try nozzleless with that comp or slow it down (60/30/10)).

 

And please stop buying your supplies from SkyRobber unless you just have too much money to donate, ffs. They are pretty much double the price of other vendors, for everything!

[Arthur]

If you read Fireworks, principles and practise by Ron Lancaster, he gives a chart of the appropriate composition for rockets of different sizes. Definitely bigger rockets need a slower composition..

 

There is much to be gained from having a real hard copy of the classic modern texts. Even £/$ 100 for a book is far cheaper than losing a body part to an accident.

 

Look for Abebooks.com in your country.

[cmjlab]

Are you using milled/hot B.P. in your cored/nozzled motors? I'm no rocket expert, but most B.P. motors I see from others are using hot/milled B.P. without the nozzle but with a core (cored nozzle-less) OR nozzled but not cored B.P. motors (I.e. Endburner).

 

If you are using hot/milled B.P. with a core and a nozzle, I'd have to assume that you would need to press a 3lb motor to have a chance if it working routinely.

 

Just an outside observation....

Edited August 1, 2023 by cmjlab

[tld6008]

I'll hand-ram 3/4" motors all day, but my rammed 1"ers are a coin toss if they'll cato. For me, that size and larger is only or pressing. I strongly recommend you start with smaller motors. Get those right and then move on.

 

If your BP is decent, 75/15/10 would be expected to blow nozzles/bulkheads/tubes in coreburner configuration. That's basic. Either try nozzleless with that comp or slow it down (60/30/10)).

 

And please stop buying your supplies from SkyRobber unless you just have too much money to donate, ffs. They are pretty much double the price of other vendors, for everything!

Thanks for the info, Skylighter was the first place I stumbled across when getting interested in this craft, any suggestion regarding an alternative?

I will get some smaller ID tubes, after searching for reasonably priced tooling, it's amazing the price of these sets.

Your suggestion to try nozzleless , would that require an additional tooling set or is there a workaround to use what I have now? I will make 2 more 3 lb attempts using a 60/30/10 mix

[tld6008]

If you read Fireworks, principles and practise by Ron Lancaster, he gives a chart of the appropriate composition for rockets of different sizes. Definitely bigger rockets need a slower composition..

 

There is much to be gained from having a real hard copy of the classic modern texts. Even £/$ 100 for a book is far cheaper than losing a body part to an accident.

 

Look for Abebooks.com in your country.

Thanks for the advice , happens that I buy books frequently from Abebooks and Thriftbooks. The latter had an acceptable copy for $28 which I will have in about a week!

[tld6008]

Are you using milled/hot B.P. in your cored/nozzled motors? I'm no rocket expert, but most B.P. motors I see from others are using hot/milled B.P. without the nozzle but with a core (cored nozzle-less) OR nozzled but not cored B.P. motors (I.e. Endburner).

 

If you are using hot/milled B.P. with a core and a nozzle, I'd have to assume that you would need to press a 3lb motor to have a chance if it working routinely.

 

Just an outside observation....

Yes my BP was milled and at the time of making it I did not realize that the larger motors were susceptible to CATOing if hand rammed. I need to look into the other designs i.e. nozzleless and endburner. I have quite a bit of the 1" tubes so want to utilize this stock if possible before retooling for a more reliable hand rammed motor.

[Arthur]

For rocket motors for fireworks;

Start with BP, sometimes meal powder, try changes in the usual ingredient ratios, also people have used milled powder with added unmilled ingredients.

 

Just get used to the reality that a fuel for a half inch bore rocket and a inch bore rocket can be very different. The bigger the tube the slower the powder needs to be to resist the ever close cato

[SharkWhisperer]

Thanks for the info, Skylighter was the first place I stumbled across when getting interested in this craft, any suggestion regarding an alternative?

I will get some smaller ID tubes, after searching for reasonably priced tooling, it's amazing the price of these sets.

Your suggestion to try nozzleless , would that require an additional tooling set or is there a workaround to use what I have now? I will make 2 more 3 lb attempts using a 60/30/10 mix

In the US, Fireworkscookbook and Pyrochemsource come to mind first. Both are legit and have comparable prices--each has some unique chems that the other doesn't carry. I'd need to be in quite a bind to ever pay the ridiculously inflated retail prices at Skyrobber (never have, never plan to).

 

For hot commercial charcoal (if you don't make your own--you should learn how at least--it's a useful and rewarding skill), fireworkcharcoal.com is great and reasonably priced.

 

Many roll their own tubes--I don't and there's many vendors with reasonable pricing that are easy to find online. My favorite would be the one that sells what I want at the best price including shipping.

 

For nozzleless coreburners you can use the same tooling; however instead of ramming a clay nozzle you ram BP in those increments (and all the rest...). Pretty easy.

 

If 60/30/10 turns out to be too slow for a nozzled coreburner, then step up the oxidizer in 5% increments (or so), so next try 65/25/10.

[tld6008]

SharkWisperer

I have read reference to a couple fusing methods i.e. Jhook and Top lit or something like that. I was lighting my nozzled rockets with a length of visco with the end folded over inserted in just past the clay nozzle, I assume this is the Jhook? I also assume that the top lit one would just be inserted all the way into he core but shielded except for the very end? Assuming I have this right what is the recommended method for the no-nozzle core burner?

[SharkWhisperer]

SharkWisperer

I have read reference to a couple fusing methods i.e. Jhook and Top lit or something like that. I was lighting my nozzled rockets with a length of visco with the end folded over inserted in just past the clay nozzle, I assume this is the Jhook? I also assume that the top lit one would just be inserted all the way into he core but shielded except for the very end? Assuming I have this right what is the recommended method for the no-nozzle core burner?

Folding over the fuse is J-hooking it. BP coreburners are often ignited with a length of blackmatch inserted up to the top of the core--the core boundary acts like the containment tube in quickmatch so once the flame enters the core it acts like quickmatch and almost instantaneously sends flame across the propellant grain to the top of the core and simultaneously ignite the whole core surface almost at once. Visco rammed all the way up a BP core is already tightly encased in the plastic/NC/fibers and won't increase burn rate along the core like containing a strand of blackmatch does--so sparks from the visco fuse only ignite the lower regions of the core and the flame then spreads progressively upwards along the core surface of the propellant (the still-burning visco will get spit out as thrust forms).

 

In composite rocket motors not typically used in fireworking, we use a hot electric igniter rammed all the way up the core. The APCP propellant is harder to ignite than BP and lighting at the bottom would give unpredictable results--by igniting at the top of the core, it's pretty assured that the initial flame will ignite the remaining core surface nearly all at once to generate max lift.

I'm just mentioning this because with APCP, failure to ignite properly often causes launch failures (rocket just sitting there sputtering unpredictably). BP can be a little more forgiving and is easier to ignite, so some folks fuse their coreburners with visco instead of blackmatch and still get predictably good launches because the progressive burning quickly reaches the top so max thrust is soon generated.

 

No-Nozzle coreburners are ignited like any other coreburner. Best with a piece of blackmatch that fires up the whole core surface almost simultaneously, but you'll usually get away with decent ignition by lighting the bottom of the grain with visco (if you stuff a long piece of visco up the core, the top will get lit by the propellant grain flamefront spreading along the core surface long before the flame of the visco would ever have a chance to reach the top...).

 

With BP endburners (like Estes model BP motors) the flamefront exists only at the back end of the propellant grain so igniter type and placement is not really that important.

[tld6008]

Update

I built 2 more 3lb. motors, first was nozzle-less coreburner with the 75/15/10 BP, second was nozzled with 75/15/10 BP altered w/ addition of 5% airflot charcoal screened in. Both had clay bulkheads on top, both J-hooked fused at bottom and both Cato'd.. I need to make a new batch of BP and get some smaller tubes and tooling. I would like to make the largest size motors that have good chances of success. Would .75" id be a safe step down with reliable success rate?

[Arthur]

Not knowing you, your powder, your supplies, tools or location, here are a few possibilities. Make good written notes so that you can do lots of tests and know what you did!

 

Get enough ingredients probably that fall through a 50 mesh but sit on a 100 mesh each separately. Press a 1" tube with a simple mix of this. Mill the rest of the power for one tenth of the time you consider normal for your powder and press a 3/4 tube and a 1" tube. Then try them in a safe place.

 

Some makers from history would take good BP and slow it by adding un-milled ingredients in the usual ratios, some would slow good BP by adding un-milled ingredients to purposely make an off-ratio powder