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What do you mean mechs are non-credible?
(lemmy.dbzer0.com)
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this post was submitted on 09 Sep 2023
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NonCredibleDefense
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In the same spirit: I laughed at this and upvoted it, but I don't know what the square cube law is or what it has to do with mechs. I don't really understand the joke and I'm honestly a fraud for upvoting it and engaging with it, at all.
The square-cube law is the rule saying that if you increase something's size, its volume will also increase proportionally.
Ie: if you have a 1x1x1 cube it's volume is 1, but if you have a 2x2x2 cube it's volume is 8.
With mech design, making a huge bipedal robot means putting a massive amount of weight on relatively weak joints at the legs.
I appreciate the time spent writing that, that was a really cool read :) love reading takes from people who have put a lot of thought into niche topics.
Thanks, I don't think I like the square-cube law. Just make the joints stronger. It'll be fine!
The square-cube law is also why we don't have giant spiders, so it's not all bad.
(a cow sized spider would have legs as thick as matchsticks, and as intuition would suggest, collapse hilariously on itself.)
Think about any part of your body... say your arm. Now imagine scaling it up to double the size.
Your muscles are now double the length but also have to move a doubled distance. That changes nothing.
That same muscle (it's roughly a tube) has doubled it's diameter, so it 2² = 4 times as strong because it's cross-section is a circle and the surface of a circle is (d/2)² * pi.
But your whole arm has doubled it's size in all 3 directions. So it's volume/mass is now 2³= 8 times as high.
So in short: double your size and you are 2² = 4 times as strong, but you also have to move 2³ = 8 times the mass. That's the square/cube thing that makes just scaling up impossible.
PS: Yes, if you ever wondered how you were so incredible good at climbing things when you were a child... small children are much stronger than you compared to their own body weight.
Ohhhhhhh! Thanks, this helped with the "why."
In addition to what others here have said, it is also the cause of scaling fall damage.
An ant falles down a mine shaft and doesn't even notice.
A mouse bounces and runs off.
A person breaks.
A horse splashes.
Surface area decreases max fall speed. Mass increases max speed. Mass times speed indicated how much force something feels at the end of the fall. The issue is, surface area scales as a square, Mass as a cube, and thus the bigger something has the less drag it has and the more energy it absorbs as it lands, getting hit coming and going.
Fake it 'til you make it!
The square-cube law is about how increasing the size of an object increases its volume much more rapidly. So if you make an ant, say, twice as large, it ends up 4 times as heavy (don't take these numbers as anything but an example, I'm pretty sure there's formulae and shit). For that reason, massive vehicles, like mechs, are impractical - something twice as large as a tank is gonna end up much more than twice-as-heavy.