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16CommentsJoined January 2nd, 2013

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  • harderm commented on randofo's instructable Turn Nearly Anything Into a Speaker1 week ago
    Turn Nearly Anything Into a Speaker

    Aaaah. But what does grating parmesan sound like? Cheddar? Carrots? By that, I mean to ask, how do things sound to an amplified cheese grater or whatever. Like ordinary speakers, piezoelectric elements can serve as microphones. Connect one to the input of an amplifier to hear the sound. I'm not sure if an impedance-matching transformer is necessary in this case. (No, I haven't actually built one.)

    Forrest Mims describes experiments with piezos in his books, in case any of you want to explore some more.

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  • harderm commented on mikeasaurus's instructable Unusual Uses for Vaseline2 weeks ago
    Unusual Uses for Vaseline

    At the risk of being a bit pedantic, solvation is chemical as well as physical. In certain solvents, water esp., weak solvent-solute bonds of partial covalent an ionic character can form. These can depend on temperature. Their formation generally decreases the entropy of solution. For example, the precipitation of magnesium carbonate solid from water is entropically driven, despite the high degree of order in the MgCO3 crystalline products. The ions form aquo complexes in water which are more 'ordered' than in the solid (and therefore crystalline) product. Of course, no electrons are exchanged in the process, which might disqualify solvation as a chemical process. Nevertheless, the chemistry text from which I teach contains chapters on coordination chemistry and 'weak' forces of...see more »At the risk of being a bit pedantic, solvation is chemical as well as physical. In certain solvents, water esp., weak solvent-solute bonds of partial covalent an ionic character can form. These can depend on temperature. Their formation generally decreases the entropy of solution. For example, the precipitation of magnesium carbonate solid from water is entropically driven, despite the high degree of order in the MgCO3 crystalline products. The ions form aquo complexes in water which are more 'ordered' than in the solid (and therefore crystalline) product. Of course, no electrons are exchanged in the process, which might disqualify solvation as a chemical process. Nevertheless, the chemistry text from which I teach contains chapters on coordination chemistry and 'weak' forces of cohesion (van der Waals, for example). These weak forces stabilize condensed hydrocarbon phases, so there too electronic structure is responsible for solubility.

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  • harderm commented on mikeasaurus's instructable Unusual Uses for Vaseline2 weeks ago
    Unusual Uses for Vaseline

    Interesting. I'll have to experiment with that.

    Have you tried paraffin wax instead of Vaseline? Just curious. Might make an interesting experiment. The advantage over the greasy stuff is that paraffin should be less messy when you're trying to squeeze everything into the pack at the start of a hike.

    Have you tried igniting these with sparks from steel, flint or magnesium fire starters? It might be nice to have an alternative to matches/butane lighters on a trip.

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  • Multi-Function Walking Stick - Converts to a Chair

    Yes, bamboo is hollow over the longer sections of its length. There are nodes containing short, solid cross-bridges. I don't know how strong it is; probably weaker than solid oak, but is that enough? That's why I mentioned the scaffolding. As for the tips, you might have to glue the in place with epoxy. Best way to find out, of course, is to build one and test it.

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  • harderm commented on SpecificLove's instructable 10 Life Hacks with Carabiners1 year ago
    10 Life Hacks with Carabiners

    True for the ones shown here, but many outdoor sports outlets sell 'biners for climbing/caving in larger sizes with a variety of safety features.

    Lose weight? Easier to buy larger 'biners, the kind used for climbing/caving. Or there are steel links available at better hardware stores. They're intended to be used as replaceable links in chains, so they screw and unscrew. I've trusted my live to these, they're bombproof.

    There are also "locking" carabiners in a larger size than those shown here. A sleeve around the gate-latch must be twisted and pulled down. Other varieties of 'biner require that you unscrew the guard before the gate can be opened. Useful for larger hacks.

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  • Multi-Function Walking Stick - Converts to a Chair

    What does this staff (Oak, 6' high) weigh? Has anyone tried using bamboo? Bamboo's lightweight, surprisingly strong, and used in temporary scaffolding for building construction in Asia. You'd have to pick through a bunch to match fittings. thediameter with the copper

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