The only real change after the first trial flight was to make a pair of Delrin bushings because the edges of the brass tube tended to dig into the kite string, even after some pretty vigorous deburring.
The body of Droppy is made out of some K&S brass tubing I picked up from a hobby shop years ago in Texas. Most model shops carry the stuff, and even some hardware stores. I picked some convenient sizes. Nothing special.
The brass tubes were lined up, bound with iron wire (a twist-tie is iron wire with paper backing), and Sta-Brite flux, solder, and a butane torch were used to fuse everything together. The contrast on this image was bumped to emphasize the soldering job. It's a lot more subtle when you look at it under normal lighting. But the soldering job made for a very sturdy bit of construction. Normal use shouldn't tear it up much at all.
You can also see from this angle that the outside diameter of the Delrin bushing was more or less left unfinished. I was in a hurry, and wanted to finish it before my ride showed up. I'll admit: I rushed it. But the inside has a nice 30-degree taper on the inside edges and a 45 degree taper on the outside. It should be pretty gentle to the kite string.
A string's-eye-view of Droppy more or less shows how it works. The string passes down the main tube, and the whole thing is free to slide up and down the string. The music wire clip is on the up-hill side of the kite line. When Droppy reaches the kite, the clip strikes the bridle ring and slides backward. This is what opens up the lock and lets the poor cute fuzzy stuffed animal drop.
In the closed position the clip spans both the short tubes. Anything with a loop or a small eyebolt can be held in the lock. For the parachute I use on the stuffed animals, I just put a safety pin at the apex of the parachute. The loop at the back of the safety pin goes inside the lock. Slide the clip forward and the parachute is held in place.
When Droppy strikes the kite's bridle ring, the clip slides back (never mind the fingers in the picture) and the lock opens. The parachute is released, the fuzzy critter falls safely to earth, and the kids chase after it, getting tired in the process.
So here's the real genius of this plan: I've already showed them all how to operate Droppy. They already know how to work the line messenger I got from Into the Wind, and they're all good at chasing down parachuting kittens. So we hit the flying field, I put the line messenger and Droppy on the line, hook up to the Flowform (the Rokkaku has far too steep a line angle for this exercise), get it a good hundred or two hundred feet out, and anchor it. At that point the kids can attach the parachute, send it (and its stuffed critter!) aloft, release, chase madly after it, and by the time they come running back the line messenger and Droppy are already back at the ground, ready to be re-loaded.
And while they're running around getting exhausted, I get to read my book! Or take pictures of them from the air using the Rokkaku. I haven't decided which is better...
Tom
P.S. Yes, I finally figured out I could post multiple pictures in the same blog entry. Even I can learn new tricks. What's the world coming to?
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