56 replies to this topic

[Jerronimo]

Hi everybody,

This is my first post on this forum, I have to say that alot of good advise is given here.

At the moment I'm mostly making rockets with payload, they work fine but I just can't get an nice symetrical burst.

I use "pulverone" as an burst charge and toiletpapertubes as shellcasings.

I was wondering, should the burstcharge be seperated from the stars?
I mean by an innercasing surrounding the burstcharge.
Any good site's about this subject would also be helpfull.

I hope somebody can help me,

By the way sorry about the bad english.

Greetz,

Jerronimo

[BigG]

Okay, first I have to note that rockets are not my cup of cocoa, so you will get better advice from others. However, You do need to give us more information. What is the size of the rocket? What payload does it take? What are the dimensions of your shell? What is the weight of your burst charge?

As a rule of thumb, toilet paper tubes will be too strong for very small shells. You will need to use kraft instead. For 2-inch internal diameter, 4 round of thin kraft should get you going.

In small shells, there is no point in separating the stars from the burst charge, but consider getting a larger precentage of burst charge to insure that the shell open.

BigG

[Matt]

Symetrical as in nice and round? or symetrical as in not blowing out of one side, If thats the case then I think that using a toilet roll is the reason they are blowing out one side. They never seemed to be that great for shell casings to me.

-Matt

[BigG]

I must say it is quite a challenge to get symmetrical break from ANY shell that is less the 4 inch ID. I have seen it done on 3 inch but never on less. I read somewhere explanation about why bigger shells are easier to work with, but I can’t remember where.

BigG

[maxman]

I thought the idea WAS to have a thick tube for a good break while using bp! and to spike the thing! am I getting confused somewhere??

[BigG]

I thought the idea WAS to have a thick tube for a good break while using bp! and to spike the thing! am I getting confused somewhere??

Maxman, you are not getting confused. Spiking allow you to get a good and even break by spacing the place that the shells breaks on. However, BP is used as breaking charge mainly in LARGE shells. In small shells, BP is not energetic enough to break the shell strongly. Therefor, thick walls might surrender only marginally to the BP gases (which are produced slowly) and allow enough gas to escape before the shell break completely. This will produce a rather weak break.

Shmizu did a lot of research on the subject. He suggest to break 3 inch shells with chlorate charge, 4-7 inch with perchlorate charge and only 8 inch and above with BP.

In practice, many industrial manufacturers uses BP even for four inch, but they keep the walls reasonably thin to allow the BP gases to break the shell. Pyrotechnica IX state that for canister shells 3 inch ID you should use a mare 3 turns of the thinnest kraft. Any more, and the shell will break slower, not faster.


BigG

[maxman]

Well I learn something everyday! So does this mean when you make a break this way with bp there is no bang that goes with it?

[BigG]

Well I learn something everyday! So does this mean when you make a break this way with bp there is no bang that goes with it?

Well, it’s not exact science I heard a few good booms that BP produced. Don’t forget that smaller shell break in much lower altitude, so they are closer to the listener ears. One of my multi-tube fountains, (ID 1 inch, 20 centimetres high with BP based composition) went wrong and exploded while I was 20 yards away. The ringing in my ears lasted for two days.

BigG

[Stuart]

Could break the shell with a HE

[adamw]

Now dont get carried away...

How about a 5/5 or even a 7/3 flash. If you take a bog-standard Chinese rocket as an example, the tubes they use for headers are about equivalent to a toilet roll, sometimes a bit stronger. A rocket header propery plugged should give a nice break with 7/3 flash. It wont be perfectly symmetrical, but it wont be a 'mine' either. I have got perfect breaks using 20mm pumped stars and a gram of flash in a 2" dia x 4" tube (basically the same size as a bog roll). If you find that too strong, then try corning the flash like you do for pulverone (carefully). You could also try using both pulverone and flash (make sure it is KClO4 based as to avoid any nastyness with the sulphur). Whatever, make sure the top of the tube is well disked (2 pasteboard / strawboard discs should do fine) and well glued.

[Jerronimo]

Thanks for all the replies .

I normally make charcoal stars diameter: +-7mm the salute/star chamber about 4 cm wide and 6 cm long the problem is that it only breaks at one side.
I think the starchamber,rocket connection is the weakness
I examined an rocket that I could find and saw that the chamber only had a
gash, it dit not blow appart as intended.

Lately I'm experimenting with KCIO3 based stars,due to limited chem's I made some rockets with the following starcomp.
(strontiumcarbonate,KCIO3,sucrose,)as an bursting charge I use H3.

Tonight I will fire them and tell you the results(hope it works).

Greetz,

Jerronimo.

[Jerronimo]

Wow they worked awsome!!! but I think I have to downtune on the H3 burstcharge
some of the stars wouldn't ignite.

Greetz,

Jerronimo.

[BigG]

Wow they worked awsome!!! but I think I have to downtune on the H3 burstcharge
some of the stars wouldn't ignite.

Greetz,

Jerronimo.

This is because chlorate based stars do not ignite as easily as you might think. Dust them with outer layer of sulphurless BP.

What do you use as fuse for those lovelies?

BigG

Edited by BigG, 30 September 2003 - 04:03 PM.

[Jerronimo]

Hey thanks for the tip BigG!

I just use normal visco about 1 1/2 mm diameter for the rocket itself.
For the rocket/starchamber connection I use some homemade BP fuse.

some extra information:

As an rocketfuel I use KNO3/sucrose 65/35, casings I make from 18 mm PVC pipe
95 mm long, 16 mm ID
front nozzle: 13mm (Nozzles I make from ground up kittylitter)
core diameter: 4.5 mm
core lengt: 70 mm
end nozzle: 12mm ( I use hot melt glue for that)
total weight about 38 gram's

These babies can take a pretty large shell, in total my rockets weight about 160/180 gram's!!!not bad for a sucrose fuelled 38 gram rocket

Tonight I will try some again but with BP burstcharge and ''normal" charcoal stars

Greetz,

Jerronimo.

[adamw]

Sounds like you got a good plan. You sure cant beat rockets - cheap, cheerful and they work suprisingly well. The only problem is getting enough sticks!