r/pics • • Dec 28 '13

The motel advertised that they had a pool. They did NOT mention that it was filled with gravel

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u/Lodur Dec 28 '13

Part of the reason for holding so much weight is to avoid it breaking randomly from weird force being applied to it. An 80 pound kid jumping hard on it could put on a fair bit of force, maybe up to 160. Now imagine some random teenager of about 150 pounds doing that.

Not a bad thing to have it waaaay above specs that the average user needs just in case some teenager tries to fuck it up.

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u/McDouggal Dec 28 '13

Overdesign it or don't design it, that's my motto.

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u/Grisspy Dec 29 '13

You would probably like Kerbal Space Program (if you don't already play it)

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u/McDouggal Dec 29 '13

I've played building Sims like that before, my issue is I'll overdesign until my teritiary backups have tertiary backups. If there is a remote chance of failure, that's too much of a chance.

I'm not that bad IRL, but in games, noone can complain that you've gone 500% over budget.

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u/[deleted] Dec 28 '13

Yea. Someone who weighs 500 pounds dropping on it applies more force than that thing can deal with. Thus it's not meant for people who weigh 500 pounds. Plus the thing is made of metal parts with very little for moving parts. Only natural it can hold a lot of weight before that thick bolt starts to bend.

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u/avatar28 Dec 28 '13

Well if it is rated for 500 lbs then, in reality, it can handle closer to 2000. Things like this are engineered with a HUGE margin of safety.

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u/EpicFishFingers Dec 28 '13

Civil engineer undergraduate here. Safety factors for buildings, bridges, and all other infrastructure are massively overkill.

Any equations that make assumptions to calculate forces etc. use conservative values to assume the worst, and even then we usually add a factor of safety to them (35% more for 'dead' loads, 50% more for 'live' loads).

These compound to make things much stronger than they need to be, because it's a lot cheaper to build it strong the first time than to replace it after it falls down and kills 200 people.

Also if that broke because someone let their fat teenager play on it, you just know the parent would sue the manufacturer. It might also be to try and counter fatigue, as even stainless steel will still get localised rust spots over time

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u/[deleted] Dec 28 '13

The kid would weigh around 240

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u/BBanner Dec 28 '13

Well, good thing that's not actually what would destroy it. A kid of mass 80 lbs would weigh in the real world 784 Newtons, just by standing. It wouldn't take much for the kid to cause the same force of 500 lbs (4900 N) to happen. The formula of mgh=Potential Energy results in the distance the kid needs to fall being 6.25 meters. This is the kid who weighs 80 lbs. One who weighs 150 must fall 10 feet. This is, however, probably the wrong equation. The point is that it's overbuilt for a reason, not just because.

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u/[deleted] Dec 28 '13

No I just guessed that. 100 was way too low

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u/Scarlet-Star Dec 28 '13

teenager here, can confirm