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Visakan Veerasamy @visakanv
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I wanna talk about one of my favorite Quora answers, written in 2015 by David Rose to the question, "Why are there crushed stones alongside rail tracks?" It's an interesting answer about an engineering problem but I got a really deep, fundamental mental model upgrade out of it
The crushed stones are called ballast. They hold the wooden cross ties in place, which are what hold the rails in place.
Here's the engineering challenge. You need to run miles of narrow ribbons of steel on top of the ground, which are subject to:

- heat expansion and contraction
- ground movement and vibration
- precipitation buildup from rough weather
- weed and plant growth from underneath
99% of the time, these tracks are just sitting there

1% of the time they're subjected to moving loads as heavy as 1,000,000 lbs / over 450 tons.

The above-mentioned solution of wooden cross ties + crushed stone ballast is over 200 years old, and we haven't improved on it since
So from the ground up:

1. ground
2. foundation (to avoid flooding)
3. ballast (crushed stones, needs to be rough)
4. hardwood ties (thicker than you might think!)
5. hot-rolled steel rails
These are what rail ties (called sleepers in the UK and SG) look like when they aren't covered in ballast. They often get repurposed once they've been worn down
1. Steel rail made in 1896

2. how they're made now, inspected with ultrasound and lasers

The most important step is "hot rolling the steel" – it's not really relevant to what I want to talk about but it's cool to know. Basically putting the steel thru rollers, like dough
One of the ways that rails are joined together is with 'fishplates', or 'joint bars'. These were invented by a William B. Adams in 1842 because he was dissatisfied with scarf joints, the predecessor (2nd pic)

Most modern rails are welded together via flash butt welding (3rd pic)
Suzhou Jinstar Railway Materials, founded in Feb 2004, located in Xinzhuang Industrial park (an hour's drive from Shanghai)

Total fishplate export volume can reach 96748.40kg per year, worth just shy of US$70,000/yr

(This isn't what I wanted to talk about, I was just curious)
Anyway – while the rails can be welded to each other, you can't just nail or bolt them down to the ties – the heat expansion and contraction along the length of the rails would cause them to break or buckle. So they need to be attached with clips, giving them room to wiggle!
So here's what's crazy!! If you want to get a 450 ton train go from point A to point B, safely, reliably– you need a delivery system that's not truly "secured"! the infrastructure is reliable because it allows so much wiggle room. the system is secure because no single point is!!
To me, this is a great metaphor for how to think about having a sound mind.

You can't have anything that's overly secured or tethered to anything – that then becomes a point of failure. Nothing can be too sacred. But that doesn't mean nothing *is* sacred. Rather, everything is!
Here's a buckled railway section, caused by excessive heat

when your rails don't have enough wiggle room, when you're grasping too tightly to what you have... then when the temperature increases, you're going to buckle

you could blame the heat, but it's also the system design
I look this up from time to time to explain how I think about having an "untethered mind". I don't mean something shoddy, dangerous, unserviceable. Rather, a mind that is robust, even antifragile, because you don't have any single point of failure that would be catastrophic
Here's a link to the actual answer if you're curious to read it:…
I believe there are similar-ish insights in other sorts of networks and systems about points-of-failure and robustness. There's something similarly interesting going on with TCP/IP and the layers of abstraction – it's all designed to work in despite failure, isn't it?
This is incidentally how I've taught myself to think about my social graph, the networks of human relationships that I'm embedded in. I can't be too reliant on any single person or groups of persons, I can't trust any in-group to take care of me, etc
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