Vast numbers of things you have to learn names and part specs for, in multiple competing standards. Electrical connectors alone would fill a history book.
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It’s both horrifying and fascinating. And there’s no way to learn except by shopping. Bugs = buying the wrong thing.
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I spent an hour this morning with calipers first figuring out, then buying... nuts and bolts. And there’s a chance I got it wrong.
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The polarity of build vs buy decision-making has flipped in the last 30 years. There’s really no such thing as pure building anymore. It’s all degrees of buying. A “from-scratch” design really means “from commodity COTS” — the baseline is not unrefined raw materials but China.
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I didn’t realize how utterly bad I was at this part till I tried doing non-trivial amounts of shopping in the last few months.
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Example: a typical early mechanical engineering class is called kinematics of machinery. It’s applied geometry. You work a lot of problems about how one thing will move if another moves. The things are connected by pins, sliders etc. In the textbook, the pin is just a point.
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In practice... buying a pin is a whole production. Took me hours of googling and Twitter questions to even shortlist the types of pins to choose from, and finding a cheap source of a sufficiently varied assortment box so I have room to experiment.
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And now my whole initial design is junk because I thought pin selection would be trivial. Now it is the driving constraint around which the rest of my design is developing.
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In fact I suspect “purchasing inertia” drives a lot of design. Selecting, characterizing, calibrating, and testing a catalog part is so much work that you will reuse that part in future designs until you’ve amortized the purchasing decision overhead.
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I suspect, if you’re a part supplier, making it brain-dead easy to choose your part for a large, cheap, low-end application class buys you very loyal future customers for higher-end versions.
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Oh yeah forgot a big aspect. One reason they don’t teach shopping is that actual shopping is expensive. Window shopping doesn’t cut it, since the learning is in the trial-and-error build-buy loop. You can fill up shopping carts as exercises but that’s like 25% of the learning.
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Engineering competitions are a great way to get to do this twitter.com/vgr/status/137…
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Exhausting afternoon of technical shopping. Spent around $270 on Amazon on 27 items. Some of the hardest thinking ever. Mostly electronics/electrical parts and tools.
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heh you got me thinking how speculative part buys are kinda analogous to renovating your kitchen or bathroom or something—you don't know up front how much it's really going to cost but you are pretty sure it's going to cost way more than any ordinary, even big, retail purchase
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The RadioShack Shopping experience is a lost memory and sacred to some.
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