Black Powder Rockets

[moonshot]

So I had this brilliant flash of inspiration to build a skyrocket with a cannister display header and I came up with this one.

http://i107.photobucket.com/albums/m314/di.../Picture127.jpg

It uses my latest successfully tested 130mm long 15mm ID rocket motor, described above, as a booster. The header is a basic cannister shell design with cut TT stars and pieces of white leaf fuse with a BP break charge. weight all up is 147 grams. Overall length is 39" (A little over 1 meter).

http://i107.photobucket.com/albums/m314/di.../Picture128.jpg

I figured out a great way to build the header onto the motor and have pics of the build process so if I get time I'll post It in the tutorial forum. It's just amazing what you can do with some brown paper bag, wood glue, twine, a hot glue gun, BP chems and a stick. . I'll post a vid of the launch.

[_DB_]

It's just amazing what you can do with some brown paper bag, wood glue, twine, a hot glue gun, BP chems and a stick.  . I'll post a vid of the launch.

 

Oh isn't it!

Looking forward to the video.

[superspike23]

3 try of BP rocket:

http://rapidshare.com/files/36950041/essaifusee.divx.html

[Mumbles]

Here is a pic of my latest rocket.

http://i107.photobucket.com/albums/m314/di.../Picture088.jpg

Specs are 130mm long tube hand rolled, 15mm ID and 4mm wall thickness. Rammed on homemade tooling 70mm long core, 4mm core ID. I reamed the nozzle ID out from 4mm to 6mm with a drill bit. The first one of these that I made blew out the nozzle and end plug hence the larger nozzle ID. 71/24/5 BP mix for propellant. I just fired one of these from my backyard and it flew great. Nice loud whoosh on ignition and great spark tail. Must have hit 250 to 300 feet. The header has enough volume for a good size break. This is probably the largest size BP motor that I will build. Now it is time to make some colored stars! happy pyro everybody and have a good July 4th if your in the USA.

Do you think if you wet the fuel with the PBR, the metallic taste would make a nice tail?

[moonshot]

touche'. Mumbles. You know ramming rocket motors is hard work and it takes a true blue collar working class beer to wash down all that excess air float comp . I have heard that if you drink enough PBR while ramming rockets your body will actually spontaneously combust. Hasn't happened to me yet but i'm still testing the theory . And seriouly the can is just there to give a scale to the size of the rocket . Anyway have a great July 4th

[Pretty green flame]

A simple question. When making short core burners, and keeping the tooling ratios the same, do I need a hotter fuel to get more or less the same power as a conventional core burner.

 

My rocket dimensions are as follows

 

ID -> 20mm

Length -> 130mm

Nozzle diameter -> 10mm

Spindle length -> 90mm

 

 

Basicly this modification took place because this is about the max i can comfortably make on my hobby lathe, basicly everything over 16mm is a bitch to make

 

Cheers

[Aquarius]

I might have misunderstood your question, but are you trying to make a core burner or a semi endburner?

 

If you taper down your spindle, you will get a smaller nozzle. This will generate more thrust. Or you can use a hotter fuel, it will give you the same result.

You could also try to make a endburner with say 3 to 4 mm nozzle, depending on your fuel.

 

 

I will expect a few CATO's...

[Pretty green flame]

I might have misunderstood your question, but are you trying to make a core burner or a semi endburner?

 

If you taper down your spindle, you will get a smaller nozzle. This will generate more thrust. Or you can use a hotter fuel, it will give you the same result.

You could also try to make a endburner with say 3 to 4 mm nozzle, depending on your fuel.

 

 

I will expect a few CATO's...

I am trying to make a short core burner, keeping the all the ratios the same. Basicly everthing is the same, the only thing that is changed is the lenght of the casing, from 20cm to 13cm, everything else is in ratio, so 1/2 ID for the nozzle, 7/10 ID spindle lenght and so on. From this i need to get similar power as a proper core burner of the same ID.

 

Cheers

[moonshot]

If the only thing that you are changing is the length of your tube and your tooling dimensions stay the same the only way to get more thrust is to go with a faster propellant. The volume of the tube has nothing to do with thrust. What does is 1. The speed of the propellant 2. The volume of the core and 3. The ID and to some extent the shape of the nozzle. I learned this by going on the NASA web site and playing with their animated rocket nozzle simulator. It's a neat program where you can change the parameters of a simulated rocket motor and see the affect on thrust on real time data readouts. Changing the volume above the nozzle doesn't affect thrust. If you increase core volume you will get a higher initial thrust on ignition due to a larger surface area of propellant burning, generating a higher pressure in the tube but this would mean changing your spindle size. On my 130mm long 15mm ID motors I had to decrease the core volume by shortening my spindle and increase my nozzle ID to lower the pressure on ignition so the nozzle and end plug wouldn't blow out. I just made a batch of fairly hot propellant and don't want to change it so I modified my tooling instead. I'm toying with the idea of making a stepped spindle rather than a fully tapered one so I can change my core volume without changing my nozzle ID. Well that got a bit long winded and I'm out of beer so I'll stop boring you guys to death and find my way to the local market. . Have fun!!

[Aquarius]

I must slightly disagree with Moonshot on this one (or I might have misunderstood his post) BUT:

 

A smaller nozzle creates a higher internal pressure in the combustion chamber. Very simplified, this is why thrust is lower with a bigger nozzle opening than with a smaller one if the other ratios are kept the same. But is is not said that the smallest possible nozzle is the optimal, as it will also effect the gas flow.

 

 

The higher internal pressure also acts on the propellant (BP), making it burn faster, creating more pressure and the cycle repeats itself untill the all propellant is used or the internal pressure is greater than the shearing strength (CATO).

 

The ID of the driver will affect the overall thrust. This is because when a coreburner starts burning, it will burn from the inside and out.

And since the surface grows as the propellant burns, the pressure is at it's peak just before burnout (not including delay). Thrust will grow with ID, as a bigger burning surface (bigger ID) will create more pressure. This is called a progressive burn.

 

So, back to your project: If the only thing you change is the length of your casing, making the delay ABOVE the spindle shorter, it will not affect thrust as the delay contributes little to thrust. Then you have three opions, eighter propellant, nozzle or both.

 

The propellant can be made hotter, making the propellant burn faster and create more pressure (or thrust). This also give a shorter thrust period.

Or the nozzle can be made smaller, and this will in the same manner increase internal pressure (thrust).

 

Or a combination of the two above.

 

Did this make any sense?

 

By the way, does anyone have a quick and easy comp for a slowburning delay mix, maybe a smokemix?

[hst45]

By the way, does anyone have a quick and easy comp for a slowburning delay mix, maybe a smokemix?

Try your standard BP rocket mix cut with 15% sodium bicarbonate. This works very well for me.

[willowmp]

Well i just set off what I consider to be my first bp rocket. Now i knew this mix would be a little strange because instead of adding corse charcol for the tiger tail i added very fine charcol. Instead i used ground up charcloth which becomes airfloat and extremely fine with minimal grinding. I knew the mix wasn't working for my purpose when my very thin walled rocket blew up and i got the fountain clay to the face and eyes(one hell of an experience that was ). I thought that if I put it in a much thicker tube it would work good.

 

The ID of the tube was a little smaller then 1/2 inch. Taking a guess the drilled hole was 1~2 milimeters i would guess maybe a lil bigger then that.If the length matters just ask and i can mesure the tube remains. Its also an end burner with no corring.

 

 

Heres the video i made of it.

 

http://www.youtube.com/watch?v=jcvROU3Tt94&mode=user&search=

 

 

 

It was also extremely loud, didn't sound like just a bp salute maybe a cross between bp and flash.

[rocket]

To me it looks like you taped the fuse to the side of the rocket which wouldn’t help at all, the tube seemed to have blow at the point where you had the fuse so I think it may have weakened it. Next time tape it to the stick.

[frogy]

Try rolling a tube with at least a 1/16" wall out of 60 lb. kraft or something...

 

If you made any core or to small of a nozzle that could cause catos...

 

You never want to add coarse charcoal to rocket propellant or it will clog up the nozzle... Most people add 80 mesh charcoal... 80 mesh is basically Talcum powder... Practically airfloat

 

75:15:10 end burners shouldn't really CATO unless you have a bad nozzle or extremely junky tube...

[hst45]

willowmp, while it's never a great idea to change multiple variables at once, there is really no down-side to making stronger tubes as frogy said. If I were you I'd then try to add charcoal to the mix, 3% to 5% at a time, to slown down the fuel. Also make sure that you ram or press the fuel grain solidly as voids in the fuel will result in CATO.

 

Oh, and just in case, you might want to lengthen the fuse too . Good luck.

[willowmp]

Thanks for the info guys. Originally i taped the fuse to the side but it burned a milimeter then hit the tape and stopped so i cut along the tape and freed the fuse. It is possible the fuse may have blown as it wasnt the best fuse, had a few creases. Im going to go look at the walls because I was pretty sure that tube could and would have stood to it. I could press really hard and not feel the tube give way.

 

I was surprised that i heard you say corse is the worst. I mean i was talking reasonablly course and i remember reading on the forum many times its course but it would make sense with what you say.

 

Personally i think that it was the nozzel, im almost positive now because it was a small nozzel and we found the rocket had flown about 20 feet away and the explosion isn't likely to be this. I think it burned for a short period of time then the pressure blew the casing outand consumed all the fuel.

 

Oh and frogy i don't use craft paper so i don't have 60 pound, i use the paper bags it works quite well, espically if you can get a cato like this one.

 

 

Edit* Here are the stats of the tube:

 

OD=1 5/8"

ID=1/2"

Length=Aprox. 2 3/8"

 

The top of the tube is not damaged due to the clay plug blowing out and releiving pressure. It is hard to the touch, I am unable to pinch it and have any flex. The damage stops half way up the tube.

[Pretty green flame]

Question

 

I fired 2 of my own 20mm rockets (core burner type). Top plug blew out on both tests. What course of action should I take

 

1. Add 5 more percent of airfloat charcoal to the mix.

Right now i am using

70:20:10 BP made from commercial hardwood charcoal and ball milled for 25 minutes. Then 5% airfloat charcoal is screened in. Should I add additional 5% to the mix to slow it down a bit?

 

2. Stronger end plug made from unmilled kitty litter keeping the formula the same as in todays test? For these two tests i used commercial bentonite clay, no aditives.

 

3. Make 4 rockets, 2 for each test and see which works better?

 

Thanks

[Aquarius]

Try strenghtening the top plug, make it thicker and test again.

If it now works, thats fine.

If it blow the tube, add 10 % C and try again.

If it works, try adding only 5 % C in the next one.

You have now used three of your four rockets and can try the last rocket with the working config. And that's it.

[Mumbles]

I have to disagree with frogy on this one.

 

80 mesh charcoal is still reasonably granular. You can feel the individual particles, and is no where in the realm of talcum powder. It doesn't clog up any nozzles or anything like that. IMO it makes a prettier effect, and also slows the propellant down a bit.

 

Anyway, I am fairly certain your failure was a result of your nozzle size. It is far too small. Try something more on the order of 1/3ID, so about 4mm instead of 1 or 2.

 

 

PGF, I would probably take action number two.

[frogy]

He said coarse... 80 mesh really is no where near talcum powder... (Talcum powder is more like 600 mesh), but 80 mesh is more in the range of Flour than granular like sugar when I sift it through my screens... I have 80 x 80 w\ .0055" wire diameter SS Wire Mesh and the charcoal comes out more of a powder than a granule for me...

[moonshot]

Hey willowmp I had to smile after seeing that rocket CATO. It reminded me of the first few motors I made that blew up. Looking at your prefire pic it does seem your tube wall thickness is a bit thin I would go at least 1/8" or even 3/16". I also agree with mumbles that your nozzle diameter is too small at 2mm. I would try opening your nozzle up first to 4-5mm and see if that works. If not and you still get CATO's try slowing down your propellant by adding that extra charcoal. Sorry to hear you took some shrapnel from the explosion. We seem to underestimate the power of BP when its confined . The tube length looks about right for a small end burner. Glad to see your using the paper bag for tubes. It's true it may not be as strong as virgin kraft but I have used it very successfully. Anyway next time light the fuse and GET AWAY!

 

PS. I bet that scared the hell out of your neighbors!

[frogy]

I've used 1/2" by 4" end burners with a 1/16" wall that were make from paper bags and they did not CATO...

 

Can you give us some better Specs on your BP? like ratios

 

I used 60 lb. recycled kraft for my tubes (at least I think it's recycled... It was only $3 for 30" by 40'...

 

Normally you try to make the rocket 10 times in length as it is in diameter... But this doesn't really matter in end burners...

 

But always try to make the nozzle 1/3" of the ID of the tube...

[willowmp]

Yes i agree mumbles the nozzle was much to small .

 

Oh and i didnt get hit by shrapnel from this rocket, i was talking about a test fountain of the comp i used. It blew up and shot the clay into my face like buckshot. I also wasnt using a fuse on it as the fuse had failed and a tab of it was left in the fountain core so i just used bp down the hole and on the top of the hole. The blackpowder was slow to ignite so i looked over it and it lit and catoed right as my face was over it. sorry for the confusion.

 

 

I do not know the comp. mixture, it was bp and charcloth ground down.

 

Its amazing how fine the charcloth was, i would say it was a good 600+ mesh as it was extremely fine. It was airfloat and it would fly around the room.

 

 

 

Im pretty sure it was just my nozzle id, it was way to small.

[hst45]

The blackpowder was slow to ignite so i looked over it and it lit and catoed right as my face was over it.

I'm not trying to be bitchy, just helpful, but that's rookie mistake #1; DON'T get anything in front of the muzzle of a gun or in front of a pyo device ever, especially your head. I'm an old guy who's been doing half-assed amateur pyro for almost 20 years and I can still count to ten on my fingers because I've been careful and I've been lucky. This summer, for example a few basic safety procedured kept a fountain from going off directly in my face, in spite of some basic mistake that I made. I singed a few hairs on my eyebrows, but I was laughing about it later rather than explaining to the plastic surgeon where my nose used to be. Please be careful.

[willowmp]

Yes i am aware it was a rookie mistake and im not going to do anything stupid like that again.

 

I certainly learned my lesson from getting clay shot into my eyes.

 

 

off topic:

 

i might do rockets as my science fair since its required this year.

Curently im trying to figure out a way to have data results from them, i might find a way to measure thrust and compair thrust curves and length of burn time with addition of certain pyromaterials such as Ti and alum.