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Cake day: June 18th, 2023

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  • With the previous ELI12 under control, let’s ELI>12 overhead line catenary a little more. For instance, why do you need tension in the first place?

    Fact of the matter is that using a rigid conductor is problematic with high voltage AC (skin effect and such), plus it’s more visually intrusive than wires. Meanwhile, a wire will sag, regardless of how much tension you can practically apply. So you need a few devices to help keep the wire at height.

    For one, the wire is supported every few dozen metres. Secondly, there’s a second wire strung above the first one. And while both wires are pulled taut, there are dropper wires between the upper and lower wires, which vary in length. Longer near the poles, while at the shortest near the middle between two poles, which creates a structure similar to a suspension bridge to keep the contact wire within a tight margin of vertical space.


  • In case people don’t want to click a link, let me explain it here:

    If you want to use overhead line electrification, you need to suspend a wire over the rails. In theory, you could simply hang up a wire, but whichever amount of tension you choose, if it’s warmer outside, the wire will droop, potentially causing damage, while if it’s colder outside, the wire will pull taut and may snap. So you want a system to account for external temperature.

    Instead of picking a tension at a standard installation temperature, you pick an amount of desired tension and use weights to pull it taut. Now, if the wire heats up and extends, the weights drop, and if the wire cools down and contracts, the weights are pulled up.

    And to keep the amount of weight you need to add under control, you use a series of pulleys to control the tension in the wire.

    In NL, the mainline system looks a lot simpler: They have only one wheel, but that’s two pulleys: a larger one and a smaller one. The larger one holds the weight, while the smaller one holds the wires.





  • Iron Lynx@lemmy.worldtoScience Memes@mander.xyzMushrooms
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    1 month ago

    … it’s very hard experimenting when you’ve no idea of potency or dosages.

    This.

    Fun thing I bumped into a few weeks ago: the guy who’s credited with inventing LSD tried a bit to see how it worked and how it felt. But he had no idea just how ridiculously potent LSD is. I forgot the exact numbers, but I do recall the ballpark. So he had a Fermi-estimated 100 μg while he only needed like 10 μg for a good time, so not only did he have the first known LSD trip, he had the first known bad trip.














  • Iron Lynx@lemmy.worldtoScience Memes@mander.xyzHoney
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    2 months ago

    Non vegan here. 🤔

    Soooooo honey is not extracted directly from the bees, so that would be an argument to declare honey vegan.

    On the other hand, even with modern beekeeping tech and modular hives, one could argue the act of taking honey to be a serious intrusion on the bees’ life, so that could be an argument that honey is not vegan.

    One could argue where the line lies with eusocial organisms. Do you consider the individual bees or do you consider the whole hive? Whole hive? Honey may not be vegan. Individual insects? Honey could be vegan.

    It really depends on your standards. One vegan friend of mine does drink mead (honey wine, for the uninformed) for instance.