Tuning Tests - Bottle Rockets with Star Payloads
Date: 2005-03-11
Description
I recently got Rich Wolter's bottle rocket tooling set, it is a very nice piece of kit to use. I asked him to make me a funnel and wire set to match the pyrotube.com 1/4" tubes in addition to the $48 bottle rocket tooling, I was really blown away when I first used it, makes building these bottle rockets quick and easy.
The nozzle and core geometry is a bit different than my usual hand-drilled bottle rockets, as such milled 6:1:1 black powder is perhaps a little too fast. Most survived, but one or two exploded violently. I have a quantity of slower 15:3:2 meal that was made with contaminated KNO3 (remember the lazy stingers), using that is just about perfect, as is greenmix that has been milled for about 20 minutes followed by a dampening and drying cycle. The granulation of the later makes it quite nice to work with.
Quite a few motors were tested until I was happy that I had everything worked out. Then a few were flown with small payloads, a BaSO4/MgAl strobe star (that didn't work, damn it!) and an increasing number of dense Zn fuel stars in a twisted-shut nose extension made from a few turns of recycled kraft. This crude payload actually functions *very* well and is more fun than stargun shots.
Anyway, the result of the propellant tuning is a rocket than can lift at least 4 Zinc stars to an excellent height.
The motor used wax treated clay and was 2/3rds charged with slow meal, no clay bulkhead just bare meal on top of which was placed a few grains of benzolift. The shell bottom was friction-fitted into the motor tube ID and the four stars and pinches of benzolift squeezed in. As this was my first go lifting that much weight with this motor I didn't glue the hemispheres with Xylene, if the motor catoed or failed to get up there I didn't want to be wearing a hot Zn star down the back of my kneck.
The stick was a bamboo BBQ kebab skewer (full length/thickness, no splitting) hot-melt glued in place. The fuse was a short length of Zinc match held in place with a small ball of paper wadding.
All rockets were launched from a beer bottle.
Comments
Unfortunately I didn't have my usual camera girl on hand, and in the excitement I only videoed one test. I am no where near as good as Tanya with the camera, so please excuse the video quality.
Rich said he uses commercial BP in his rockets, not quite sure how! But his description of the performance is about right, they just keep going and going hundreds of feet up. Too high really, any effect is greatly diminished. A flash salute is quite nice, the 2/3rds charged case has plenty of space for a good bang.
The primitive payloads are great if you want an uncomplicated device that just dumps out some stars at apogee. The 7/8" shells are kinda cute though, finally a use for them! The rockets don't go quite as high with that big bulb thing on the front, but they still go plenty high. Some AP microstars in one could make a pretty good little break, a bottle rocket scale sky rocket? Some whistle and coarse Ti would make a very respectible salute rocket (even without the ball shell).
I used Zinc match because it was the first length I pulled out. It is slower than blackmatch so it can implement a good delay in a fairly short length but produces lots more light which perhaps isn't ideal. Rich's tooling appears to be designed to mate well with commercial visco. I throughly recommend the tooling, $48 isn't much for the pleasure you'll get out of using it.
Attachments
| title | type | size |
|---|---|---|
| bottle rocket with 7/8" ball shell | video/x-msvideo | 651.168 kbytes |
| rocket as fired in video | image/jpeg | 35.570 kbytes |
| other rockets too | image/jpeg | 62.140 kbytes |
| tooling | image/jpeg | 66.805 kbytes |