The rocket motor was one of my standard 8 mm ID, 50 mm long units, rammed with RP. (The case was actually 70 mm long to facilitate mating of the shell) The motor core was drilled out using a 2.5 mm drill and an off-centre 2.5 mm passfire hole in bulkhead.
The canister shell was rolled from 2 turns of chipboard with an over-wrap of A4 80 gsm paper. One end was sealed off with a disk and the A4 split, folded down and pasted well.
A 15 mm core tube was inserted as a temp loading jig. The Winokur #24 cut stars packed around it, and some -40 mesh pulverone shook into the cracks. The inner tube was filled with -20+40 mesh pulverone as a break charge and the core tube carefully removed. Any slack space was filled with -40 mesh pulverone.
The top-disk was pierced in the middle with a 3 mm ID lance tube, cut and glued in place with hot melt, sized so as to terminate in the dead centre of the break charge. The disk was placed and the paper cut and pasted over it. Two sticks of blackmatch were inserted later as a passfire.
Spiking was vertical only, with 3-ply cotton thread, the same as I make my thin blackmatch with. The spiking thread was tied off to the 'spoulette' and bent around it each pass.
A final pasting of kraft was used to dress the shell, weighing in at 28 g once complete.
The motor casing bulkhead end was filled with a little -20+40 mesh pulverone, the shell blackmatch folded out and over the tube, then liberally painted with meal-NC paste, and finally plunged into the top of the motor case. A large bead of hot-melt glue fixed the shell to the motor.
Completed with stick and fusing, the device weighed 42 g.
Spectacular CATO!
The motor exploded out of the bulkhead shortly after ignition, igniting the shell passfire and lifting it a few metres. The shell burst shortly afterwards in a very symmetrical and impressive manner.
The w24 stars worked great, beautiful goldern glitter filling the air. The payload was definately worth the effort, the damn rocket motor just let it down. :-(
It wasn't a total loss. The effect was great, although I wished it would have been higher. I was actually fairly concerned during construction that the poor 8 mm motor wouldn't be able to lift the shell to a good height, but I elected to use it rather than an untested 12 mm motor. I definately didn't want a major malfunction of the motor itself especially with a fairly powerful shell as a payload.
I didn't recover any shell parts, it was likely shreaded by the break. The motor was recovered just alongside the launch pipe. The stick was torn off, and was found later inside the launch pipe with a sizable gouge out of it from the edge of the pipe. The CATO was rather violent and probably wrenched the case off the stick.
The motor bulkhead was missing, perhaps I made it too thin, perhaps drilling out the core caused problems, or maybe this batch of propellant is especially hot. More tests will be needed before I risk another major payload.
| title | type | size |
|---|---|---|
| Test Video | video/x-msvideo | 1.018 Mbytes |
| Pre-Test Picture #1 | image/jpeg | 43.367 kbytes |
| Pre-Test Picture #2 | image/jpeg | 41.136 kbytes |
| Post-Mortem Picture | image/jpeg | 102.403 kbytes |