Making a Ring of Stars with a Small Payload
The inspiration for this came from a discussion on the UK Rocketry forum. Essentially, it is hard to get a shaped break when using small payloads. This is an attempt to do just that. Apparently, Black Cat has a small rocket that will break to a nice ring but I haven't seen it - I've just read the descriptions.
Get a cheap hole cutter and cut three pieces of fiberboard. The above pieces were made with a 1 3/4" and a 1" hole cutter. Note that there are three pieces of fiberboard. Two 1 3/4" pieces and one 1" piece. The 1" piece was glued to the middle of one of the 1 3/4" pieces. The actual sizes are smaller since the saw blades cut off material and we are using the plugs. Gummed paper tape was wrapped around the two piece section and moistened slightly to get it to stick. Getting it fairly tight and straight (so the other piece can fit into it) is important. The left-over 1 3/4" piece has a bit of tubing pasted on it as a mounting device for the rocket. Hole cutters make pilot holes in the center of the blank they cut. We will use one of those as a pass-fire from the rocket to the shell.
The Middle Part
Pack 1/4" stars along the outside ring. Plug the top hole with something (in this case hot glue).
The Penultimate Part
Put a thin layer of hot BP (or, in this case, a gram or two of Benzolift) into the shell so that the comp just comes to the top of the stars. Make sure the stars have comp around them.
The End Part
Glue things together, trim, and mount on a 3/8" rocket motor (see rockets.html). The base fiberboard will hold the 1/4" stars and ignition material in place. I smeared wood glue over everything. The tape will be stiff anyway and the wood glue makes it even more brittle. The idea is to have a small break that is fairly directed.
Well, with all this build up, I bet you thought you were going to see a perfect ring, no? Guess again. It didn't work. Click on the image above to play the video. Experienced pyros will probably tell me that I needed to make the break a lot harder. However, the stars seemed to be fooling with me, too. Take a look at the video and watch the break a couple of times. One star gets legs and does a spin around the break.
Once More, Back to the Moulin Rouge
Ok.. Let's do that again. Since the autopsy of the first shell showed that the top separated leaving the bottom virtually spotless, I thought a better plan would be to cinch the top onto the bottom a bit more. To do that, a piece of 1/4" tube was used as a column to pass fire and to hold the top to the bottom a bit better. I drilled a 1/8" hole through the side of the tube. It passes fire to the break charge.
Let's make the sides a bit sturdier while we're at it
The sides were given two windings of paper and were overlapped on the top and bottom. In addition, a gram of flash was added to a gram of Benzolift (oops - this is a clue about what happens in the video below). Finally, I replaced the stars from the first test (robbed from a Roman Candle) with my own Bleser #1 with +10 PVC (see compositions.html)
The Big Bang
This was fun. It almost worked. Not quite --- but almost. The stars came out lickety split and the break was almost circular .. except for the parts that weren't. ;-} The Bleser Reds ignited nicely and behaved. Click on the above link and watch the video. The idea of a gram of Benzolift and a gram of flash seemed really good at the time I did it. Improvements for the next time I try this might be:
1. Back off on the strength of the break just a bit - somewhere between the first try and this one would seem like a start.
2. I need to set the delay on the rocket to about 1/2 of the current delay - the rocket arced over and was on the way down. However, it got plenty high enough so it is just an ignition delay issue.
Here is yet another design (and one that comes closer than the others)
However, this one got me a warning from the local law - Not supposed to shoot rockets, even small ones, in the city. The cop was nice but firm about it. Which is a shame - my test site was very remote but still inside the city limits. Ah, well. I'll have to move my test ground.
Easter Egg Bottom with 5/8" spacer
Might as well use the top of the Egg
Terrible shot but you can see the ring (barely). It is laying left to right and rotated away from us a bit.
But wait! Guess what I found!
Ok.. I finally found the rocket I was trying to imitate. This should help a bit, eh?
Here it is with its cover stripped off. Looks like a festival ball shell to me!
Fuse to shell is a paper fuse with a BP coating.
Inside, you can see a sawdust top covered with paper and the ring of stars around the outside of the bottom half.
The stars were packed with rice hulls (KP or BP?) and some smaller microstars
Click on the image above and watch the commercial version work!