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Show HN: Elevators

1668 points · 413 comments · Jrh0203

  1. orliesaurus · · focus · HN ↗
    Oh my god, every time I'm waiting for the elevator, I think of how annoying it must be to be someone who's building the algorithm to make sure that you minimize the amount of wait times between picking up people and taking them to their destination. Then I also wonder if the people who apply the logic and program the logic into the elevators are actually evil sadists that are doing it on purpose to make us wait longer enough and suffer a little extra.
    1. neutronicus · · focus · HN ↗
      They might have other objective functions like wear-and-tear on the elevators, total energy usage, or something
      1. dbcurtis · · focus · HN ↗
        It's pretty much throughput. The cap-ex of a single cab swamps any other cost, so the only way to reduce total number of cabs is optimizing for throughput.
      2. cyberax · · focus · HN ↗
        Modern elevators have regen braking, so they can recover most of the energy spent on going down. Older elevators used braking resistors for that.

        (BTW, going _down_ while empty is typically more energy-consuming for the elevators because they are counterweighted)

        Edit: that's also why you shouldn't use elevators in a fire. If the brakes in the elevator machine room fail, the cab won't crash down. It will go _up_, possibly dragging you into the fire. Many firefighters died because of that.

        1. fragmede · · focus · HN ↗
          Interesting! It's counterbalanced though, so why does it go up if the brakes fail in a fire? That's counterintuitive.
          1. ImPostingOnHN · · focus · HN ↗
            Maybe it needs to be counterbalanced at maximum approved elevator+load weight?
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