casting techniques while soldering
Monday, December 1 2014
For the past few weeks, the drain on the upstairs bathtub has become increasingly clogged, detracting significantly from the experience of showering there. Gretchen takes all her showers there and I take nearly all of mine there as well (though I always take baths in the basement), and so it was Gretchen who eventually decided to do something about it, though I leaped in soon after Gretchen began twisting the phillips screwdriver to remove the debris mesh above the drain. (For someone like me who uses tools on a regular basis, it's painful to watch dilettantes attempting household maintenance. I'm sure Gretchen feels the same way when she sees me attempting to chop vegetables.) The drain screw came out with a huge knot of slimy semi-decomposed human hair hanging off it. I tried to pick the knot apart, but that was impossible. The solution to extract the screw from the knot was to clamp it tightly in a vise and then use my trusty Hitachi hammer drill to unscrew the bolt out of it.
I also dumped some Liquid Plumr (leftover from the last time I had to unclog my urinal system; I'll be having to that again soon) down the drain to attack any hair further down. Celeste the kitten was fascinated by all of this (as she is by anything I do involving the use of small hand tools), and she jumped down into the tub and began to roll around on top of the drain, the worst possible thing she could have done. She did so until the tips of her hair were all damp with a mixture of water and traces of Liquid Plumr. That's just the way Celeste is; more than a month ago, she did something similar with vines of Poison Ivy I'd just removed from pieces of salvaged White Ash. But I didn't think much about the dilute Liquid Plumr on her fur until I saw her beginning to lick herself. At that point, Gretchen and I grabbed her, put her in the sink, and gave her a complete bath, something she took surprising well. Gretchen later reported that the bathtub was again draining like a champ.
I've been researching methods for measuring wind speed and wind direction that do not involve carefully-balanced moving parts. Ideally, such a system would utilize sensors in some sort of array and work out these two important weather parameters mathematically. I was impressed and delighted by the sensor using ultrasonic transducers to measure the speed of sound in air in two dimensions and then work out speed and direction from that. Then I read something in the Wikipedia entry for anemometer about a windspeed sensor that simply measures the pressure in a vertical tube. The difference between that pressure and ambient pressure is proportional to wind speed. This got me to thinking: what if I set up an array of barometric sensors in tubes oriented in the four cardinal directions (as well as one pointing straight down)? Wouldn't the pressure differences in those horizontal tubes provide a way to determine wind direction as well? Of course, the tubes wouldn't actually be horizontal; I'd have them slope slightly downward to keep water out.
Today I ordered five cheap I2C barometric sensors from China (since they all have the same I2C address, I'll have to multiplex one of the two digital inputs on each). Then I set to work building a hub wherein the sensors will reside and where the tubes will attach. The best material for something that will be out in the rain and sun is copper, so I made the core of the hub out of a one-to-half-inch sweat copper fitting. I drilled four small holes at the four cardinal positions where the fitting necks down from big to small and then, using superglue, temporarily attached half-inch-to-half-inch straight copper fittings centered over each of these holes. I would have machined these fittings to make them fit the two-dimensionally convex surface of the center fitting, but I thought doing so would make them attach less consistently (different angles and different depths). Instead, I cut pieces of copper foil and used it to fill the gaps between the central fitting and each "arm fitting." Eventually, I'll solder it all together, but since the superglue is likely to break down in the heat of soldering, I will have to place the whole thing in sand before hitting it with a torch. Doing so will combine a technique from basic metal casting and apply it to the task of soldering together components that weren't machined to fit together (and have no inclination to do so). Unfortunately, the copper foil I have is a bit on the thick side (0.003 inches, or 3 mils), and so didn't want to crumple tightly against the fittings. I was forced to use bits of thin copper wire (ultimately from Cat-5 cable) to hold the foil down tight. Miraculously, none of the superglued joints broke as I did this stuff.
The copper hub I made today, after gluing (but before filling in gaps with copper foil).
As I worked, I watched the movie Her, which was possibly given that name in order to make it harder to find on thePirateBay.se (though it didn't stop me). It's the story of the romantic implications of computers reaching human-levels of cognition. Since most of what happens is related in verbal conversations, it's a good movie to "watch" while doing something crafty with one's hands (in that way, it was sort of like a podcast). When I looked up, though, I delighted in the subtle ways that the not-so-distant future was depicted. Men are now sporting mustaches again. And low-cut trousers are nowhere to be seen. This story takes places at a critical inflection point in machine intelligence, and I was pleasantly surprised how a number of different issues were handled, particularly the possibilities available to intelligences not trapped in any single corporeal body and what they might do once they outgrew the humans who had brought them into existence.
Later, as part of my ongoing fascination with movies about drunks, I watched Leaving Las Vegas, which I'd seen parts of in the past. I remember it being a big favorite of my housemate Matthew H.'s back in Charlottesville when he decided that he wanted to become a recalcitrant drunk. (The line "You can never ever ask me to stop drinking," really stuck with me.) I was hoping to see a full-bore depiction of delirium tremens, but there really isn't one.
Tonight while Gretchen and I watched the Kids' Tournament on Jeopardy, the dullness of the easy questions was compensated for somewhat by an insanely gutsy risk taken by one of the contestants, an adorable skinny white boy (evidently with three mommies) named Cerulean. He had $11,000, made it a true daily double, thought he didn't know the answer, displayed a lingering moment of incredible pain and regret, but then got it right! (And his answer was, "What is a barometer?" — how topical for me!)
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