The other half of the cut 50 mm long, 9 mm ID tube was made into an additional hummer, but as an experiment I decided to try converting it into a stinger in much the same manner as I had in the past.
Propellant was again straight meal powder. An additional 1.8 mm hole was bored through one end plug, and all the way through the propellant grain, almost out the other end-plug.
Fused in the usual manner with blackmatch and meal-NC paste. Launch pin using a sparker wire twisted and glued onto a bamboo stick to match the rocket launch tube.
Worked Great!
First daytime launch of a flying device, the smoke trail clearly showing its path and apogee. Very straight flight for the high-wind conditions.
Rotation peaked out at an amazing 1150 Hz, or about 69 kRPM, before being doppler shifted and diminished with increasing distance from the launch point.
It is hard to estimate the apogee, but it was quite good for such a small stinger-style device.
The key to these devices is to make them as light as possible. Half of a TU1013 tube is about 2.2 g, you can make lighter tubes yourself if you are careful, especially if you fire-proof thinner walled tubes with waterglass. Hot-melt glue is less dense than clay, it will probably hold together for the bulkhead seal, but isn't really suitable for the lift nozzle. You can make the clay suprisingly thin before the motor explodes, this helps cram more propellant in the case and keeps the dead-weight down.
There is a 1" (long) version of the 3/8" ID tube available from Skylighter, which would save cutting the tubes by hand. I used the 2" because it is what I had. There is also a 3" version which is even better value as you can get 3 cases out of it, offering 300 micro stingers for about $17 USD compared to 100 for $10 or 200 for $14.
Small percentages (5-10%) of metals can be added for effect. It gives me chills to drill into Ti/meal or Fe/meal, but Al/meal is pretty safe in my experence. Just go slow and clear the drill often, the smaller diameter drills clog very easily.
Fully charged and fused the device is about 4.9 g, perhaps a little less. A hummer version (no lift vent and core) is about 5.4 g, so about 300-500 mg of material is drilled out of the core and wasted.
A large batch of exotic metal-tail micro stingers could be pressed at once on mandrels if you wanted to go to the trouble of making up the tooling. Pressing might improve their performance even more, as well as being less risky with Ti and less wasteful. The drill swarf is contaminated with clay and paper fibres, maybe you could pump a small comet with the sweepings from a huge batch.
Mass launching them might be very spectacular. They are too small to carry any real payload, I guess you could put a bunch of them into a shell as inserts, like go-getters with on steroids with a tooth ache. :-)
| title | type | size |
|---|---|---|
| Test Video | video/x-msvideo | 719.778 kbytes |
| Pre-Test Picture | image/jpeg | 21.857 kbytes |
| Spectrogram | image/jpeg | 125.632 kbytes |