Pyros block

[NeighborJ]

For the past three days I've been working on a broomstick rocket. It seems like a petty problem but I'm just not sure if I like the shell arrangement and can't seem to bring myself to seal up the shell and spike it.

This is my biggest project yet, with three 4# nozzleless bp motors w/ titanium delay, lifting a 6" double pestle can shell. My plan is to use my 7/8" pumped w39j comets for the outer pestle and I was planning to use baclo3 stars w dragon egg cores for the inner. However upon testing the clorate stars I think they burn way too fast for this shell, they may go almost unnoticed compared to the long lasting w39. This rocket has been a lot of work and I just want it to be as nice as I can possibly make it.

I'm considering using a longer burning nitrate green but I like the clorate brilliance. I just can't decide on which direction to go due to my lack of experience.

The last 6" shell I made was a hemi with 5/8" rolled TT. It was awesome but I ended up with fallout and was saved by the fact that it had rained earlier that day. So this one I want to be way up there when it breaks so don't have a repeat. These stars will need to be very bright. I also have questions about the shell construction. I've been building my headers as if they are multi break shells. Can I leave the spiking uncovered on a header or does it need to be covered with Kraft?

[dagabu]

Yes, the center pistil can easily be lost in shells with large glittery tails BUT this also looks very nice and full because of the color followed by the glitter. This shell has a lime green inner pistil that is all but lost on a time lapse but made the shell when you saw it live.

 

Also, your shells on a rocket do not have to be flame proof (but it helps) or covered and a simple hole in the end disk can serve as a passfire from the rocket to the shell via a few strands of black match.

 

http://www.pyrobin.com/files/DSC_3420-001.JPG

[Mumbles]

The pasted paper does add to the confinement to some degree. I got the pleasure of meeting Tom R at PGI this year. He typically does not paste his shell headers, unless he is using a comet on top. Even then it's just to fireproof. One thing I did notice however is that he used a larger than normal number of spiking passes. I didn't have a chance to ask, but I wonder now if that helps to add confinement to counteract the lack of pasted paper. Rinfrasciature is a pasteless method, but also has additional spiking (in a way) which also increases confinement.

 

To answer your main question though, you can always make a mine of your comets and stars. I often do this to judge relative burn rates and test combinations.

[NeighborJ]

Mumbles and Dag, I've been experimenting with different amounts of spiking and passfire for these shells on 3+ 3-1/2" headers but have not had a chance to test them so I really didn't have any idea which direction would work best. I believe some of these are over spiked and will cause a bowtie break but I really won't know until I try it.

I love that shell Dag posted and I'd like to try to make something similar someday. I've never heard of the word Rinfrasciature but I guess that is what I'm trying. I've used a single strand and extra passes to compensate but I really don't know what I'm doing. I figured that if I try enough methods then when I test it I can decide which I like best.

The star mine is what I used to test the green stars but it was under lifted because it wasn't primed yet and it still burned out at 30'. I believe a thick priming may buy me a little time before the green lights so they are seen just a bit later in the burst. My problem is too many ideas and not enough experience and this is why I can't seem to pull everything together for a one shell deal.

[dagabu]

Just a couple things to note from your pictures: You don't need to use so many fuses from the rocket to the shell, one is plenty, two if paranoia takes over.

 

The spiking all the way up the sides around the shell may in fact lead to a bow-tie break, if the verticals were the same, it may break hard but would open otherwise normally.

 

Did you use past or glue on the shells after pasting? If not, you can get very poor breaks with dry spiking due to it unraveling upon break and making a hose break, ugly stuff.

 

The paste wrap will add slightly to the break but it on the outside and when walking the fields, I see TONS of paste wrap laying around in huge pieces but the shells are obliterated except for the end disks which are almost always intact with very little string attached.

 

http://www.pyrobin.com/files/P1050589.JPG

[NeighborJ]

Ha I only used one fuse, the other 6 are just folded in half and shoved in the tube to hold it in place. Tissue paper would have worked also.

The spiking pattern cross wrap is done in a manner to make squares, should this be OK? That close wrap is 3.5" shell with veline red so I want a harder break. I was going to lather them up real good before covering with the outer paste so I didn't bother covering the string with glue except around the spolette and end cap. These shells are not complete and one doesn't even have a fuse at all yet. I see you use gussets on your headers, I don't think I will need them for a 6" broom stick but should i use them for my single motors? My end disks are strong, made from 1/8" hi density particle board, it is stronger than textbook covers. The last question was about drying time for these shells. I was thinking about lining the inside of the can with a plastic shopping bag just to ensure the stars and burst won't absorb moisture from the pasting.

[dagabu]

Good golly! Lots of ground to cover here...

 

No gussets, just field expedient strapping tape attachment, works well, its an optical illusion.

 

Spiking in squares is good with hemp, single strand but with cotton, I use two strands side by side and follow the standard 16/2 verticals with 4" shells.

 

While I see the desire to use a robust end disk, they are also quite fragile and break with a robust break. A good end disk should deform along with the paper and spiking to form a "ball" shape when the burst is burning, allowing for as spherical break as possible. With inserts, elongate the horizontal squares allowing the break to propel the inserts out and away from the shell with minimal containment on the horizontal plane while maintaining the end disk containment.

[NeighborJ]

OK Dag I've finished the shell with the baclo3 inner pestle. I put an extra thick layer of prime on them, the funny thing is it doubled the burn time and it is still green thru the entire flight. I couldn't change the particle board discs so they are still in and I'm happy with the construction. I still need to make and attach the motors but I'm going to wait till labor day. I took pictures at each stage so the forum can suggest changes for next time.

[dagabu]

WHOOT! Great stars and shells, VERY nice construction! That is exactly what an Italian shell should look like in that size. Certainly NOT a criticism but I bet you could have packed another star into the ring if you left the cardboard out. More stars = fuller burst.

[NeighborJ]

Oh damn!!! I just screwed myself on this shell. I'm trying to finish up a number of smaller can shells for memorial day. I've got enough bp for these shells but I won't have enough bp for the three 4# motors. I made some more but it got screwed up, I used a very old can of naphtha to add paraffin to it but something went wrong and it won't even lift a motor, just sits there with a huge orange flame bellowing from it. I really don't know what went wrong so I've changed my lift plan to use five 1# whistle motors. I've not used this arrangement before so I am winging the delay timing. The shell is a whopping 2450grams and I'm nervous something will go wrong. I may add a sixth motor just in case.

I'll be launching this on the river so there will be nothing to damage unless it takes off sideways.

[dagabu]

20:1 ratio is more than enough lift, just watch the delay time, that can kill ya real fast. Consider delaying 1/2 the motors start to boost the lift.

[NeighborJ]

When you say delay half the motor do you mean delayed ignition or use only half for boosters? I have 3 motors with only a thrust phase then a clay plug on top. The others I've made have a thrust phase then a 39j delay, or I can choose the full whistle delay. I made a bunch of many types but have not attached them to the shells yet. I haven't decided which gets what.

From my calculations four 1# whistles should lift the shell fine but I added the fifth for good measure, I just don't know what delay time to use, I've made 3,5,&7 only one motor will set the fuse.

[dagabu]

You want your delay between the first Motors and second batch of Motors to be no more than a quarter of a second, as much as one half second but certainly no longer. You want your second batch of Motors to kick in just as the thrust is tapering off of your first set.

 

Black powder rockets are relatively easy to cluster and delay, whistle, no so much. Probably the easiest way to time this is to drill a hole for a strand of quick match in the side of one of the main motors right at the spindle top or just after.

 

The passfire will light the QM and when piped to the second cluster, will light them just as the first cluster drops thrust.

 

6 motors work very well with two or three clusters. With three clusters, the first cluster of two can be hybrid or whistle.

[NeighborJ]

OK Dag I trust your advice. I used the second stage for a 1/4 second delay. I've completed all 14 rockets for labor day and can sit back and relax a little. Those rockets took a whole week to complete. I think it will get much quicker when I get used to these headers. I also had to make a bunch of stars but that's OK I have a little stockpile now.

[dagabu]

MAN! I hope that fuse works OK. The pink stuff scares me.

[NeighborJ]

I chickened out. I launched all other rockets and they all flew great. Every one of them burss.t at apogee with exception of a 100g ti salute powered by a whistle motor which sat in the pyro shed for 6 weeks. It was a huge Cato.

These whistle motors lifted 600g+ headers to a nice display height but it was the glitter fallout which deterred me from launching the broomstick. It is packed with 7/8" D1 comets. The stars will burn out in time but this glitter hangs a long time. I think I should use 3# whistles.

[ExplosiveCoek]

Nice collection you got there!