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xkcd #3244: Pullback Drive (imgs.xkcd.com)
submitted 6 months ago by [B] to c/xkcd@lemmy.world
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xkcd #3244: Pullback Drive

Title text:

"How does the spring not run out almost immediately?" "We pull it back REALLY far."

Transcript:

Transcript will show once it’s been added to explainxkcd.com

Source: https://xkcd.com/3244/

explainxkcd for #3244

"How does the spring not run out almost immediately?" "We pull it back REALLY far."
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[–] 15 points 6 months ago (13 children)

I can't remember which car but an early hybrid vehicle did charge up a flywheel instead of an electric battery…

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  • [–] 14 points 6 months ago (7 children)

    I heard about a version that used springs as well. Basically a pull-back car: When you break, it puts tension on the springs, then it releases that tension when accelerating. Apparently it was very good for city-driving, since you get an absurd number of cycles with very small "charges", which makes it very good when you do a lot of start/stop driving in slow traffic. I'm not sure why I haven't heard any more about it in more recent years.

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  • [–] 9 points 6 months ago (4 children)

    *brake*

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  • [–] 6 points 6 months ago (2 children)

    Idk about you, but I usually build tension when I break.

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  • [–] 3 points 6 months ago (1 child)

    Bcz springs wear out is my guess. That's the first thing I'd worry about in the design is how many cycles can it handle before performance is degraded. Might be a lot, but even if it's a couple years, people aren't going to be happy when their car performance suddenly drops off right after they finish paying the thing off.

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  • [–] 2 points 6 months ago

    You're probably right, at the same time, a spring that isn't overloaded can usually take an absurd amount of cycles: Just think about how long the suspension on a car typically lasts compared to a lot of other parts.

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  • [–] 4 points 6 months ago (4 children)

    i think it was a bus, and it was used in hills to get extra energy while going down and using ot while going up.

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  • [–] 3 points 6 months ago* (last edited 6 months ago) (3 children)

    I heard about racing car having spinning wheels too, instead of breaking before turns, accumulating energy into them, then after the turn, releasing them for huge acceleration

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