Truth in Inconvenience

What do ZIRP, the AI panic, and the meaning crisis have in common?

I’ve come up with a theory connecting three big zeitgeist things: the end of the zero-interest world, the ongoing AI panic, and the meaning crisis. I think it also connects all three to the climate crisis, but I’ll leave that topic aside for this essay since it’s too big.

The thing that connects these things is real-world friction. But to make my point, I’ll need to talk about Meccano models and the philosophy of friction and randomness in engineering for a bit.

In case you don’t know what it is, Meccano is a construction toy, probably the oldest in the modern world (invented by Frank Hornby in 1898), comprising metal parts with evenly spaced holes. Americans may know it as Erector (the two brands are merged now).

Though every step in an out-of-the-box Meccano project is precisely specified, in complex models, the whole sometimes doesn’t quite come together right. And since the Meccano system is based on metal, plastic, and rubber parts held together with strong fasteners, and includes slotted joints and parts with compliances, even if you do every individual step correctly, as the instructions specify, the whole might still not come together right. The model will have emergent alignment problems, a term that means something very different in mechanical engineering practice as opposed to AI philosophy fantasies.

Sometimes, the model is just a little off in a way you can live with. Other times, the errors accumulate to a show-stopping issue with the final assembly. This is what just happened to me.

I spent several hours over the last couple of days putting together a motorized Meccano model car, the fifth model in a sequence of 25 designs that my kit has complete instructions for. I bought this advanced, contemporary kit partly due to some childhood nostalgia (I had a simpler Meccano kit as a kid), and partly to help me research and think about the issues in this essay.

In my case, the front idler wheels of the model were hitting the surrounding scaffolding and unable to rotate. A show-stopper.

The clearance in that part of the model is very small, and is a function of how three different sub-assemblies, built up separately, come together: the chassis (A), the roof (B), and the front cab (C). I’m still troubleshooting, but there are three basic possibilities, with different probabilities:

1. The instructions are wrong and I’ve found a bug in them (low)
2. I made a gross, “digital” error such as a joint in the wrong hole (medium)
3. Small tolerances have stacked up (high)

I am rating the first possibility as low probability because this is a well-tested kit that’s been in production a while, so presumably bug-free. The second is medium probability since I’ve checked carefully and I don’t see anywhere I’ve made an error. The third is currently likeliest. Of course, combinations of all 3 could be at work.

There’s enough wiggle room in the 3 chains of assembly that a precise emergent outcome can be wrong in this show-stopping way. In this case, a positive clearance, allowing a wheel to rotate freely, has turned into a negative clearance (an interference). The issue is an example of what in mechanical engineering is known as a tolerance stackingproblem. In a well-designed assembly, the independent sub-assembly paths don’t diverge too much, and stay “in-sync” enough that the full assembly comes together relatively cleanly. But sometimes, the design makes that hard or impossible.

What do you do once you run into the third kind of problem?

Occasionally, in a small, relatively simple model, a bit of thumping, brute forcing, or random loosening, jiggling, and re-tightening will do the trick. This is because if the design and execution are correct in a formal sense, things are only “off” in a way that’s close to a (by-design) stable, low-energy equilibrium state of the assembly, so a bit of unintelligent energy injection is enough to get it the rest of the way.

But in more complex models, this will either not work at all, or the “forced” assembly will be unreliable due to stored up strain and stress in weird places (kinda like plate tectonics). In the worst case, you’ll break or irreversibly damage a part trying to brute force the model to come together. Strain relief, incidentally, is a big topic in mechanical engineering, and the point where it interfaces with electrical engineering, via the surprisingly non-trivial issue of strain relief in cables. Wires breaking or coming loose under mechanical strain, as opposed to electrical issues, are a major source of problems. In building modern data centers, you have to actually model all the cabling at a mechanical level, for reliability, and cabling systems can be a huge chunk of the cost.

Here’s something to know: The more complex a mechanical assembly, the higher the likelihood that you’ll run into emergent alignment problems that can’t be resolved with brute forcing or jiggling.

It doesn’t matter what the design is, or more generally, what the goal of a planned assembly process is. Whether you’re building a motorized car like I am, or a machine that turns human flesh into paperclips, by its very nature, complexity and the limits of design knowledge in mechanical assemblies leads to such issues. The only known general way to mitigate this problem is to make all your parts as high-precision as possible. Keep this point in mind, it has bigger implications.

Meccano vs. Lego

Tolerance stacking is the sort of phenomenon is why I really like Meccano. It doesn’t shield you from real-world messy phenomena the way Lego, its evil twin, strives mightily to.

While both kits are made to tight tolerances, and new pieces made today will mate with ones made decades ago, in Lego, that’s optimized to the point it is a simplifying and limiting feature: Tolerance stacking errors are basically rare to the point of non-existent in Lego. If your Lego model doesn’t work right, it’s because the instructions are wrong or you made a gross error. In support of this feature, the Lego system gives up some ruggedness by eliminating fasteners, only uses rigid parts, and encapsulates complexity within bigger “molecule” parts, like wheel assemblies, rather than just “atoms” like single rigid bodies.

Meccano by contrast, uses a ton of fasteners, compliant parts ranging from springy steel strips to bendy plastic and soft rubber, and almost never gives you any “molecules.” Everything has to be built up from scratch. Some models I made recently forced me to construct roller bearings out of rollers, plates, and a shaft secured with brass collars. In Lego, this would probably be a pre-assembled “molecule.”

As a result of the deliberate simplification, Legos are a high-convenience toy that are not frustrating to play with until you get to really large scales and complexities, which almost nobody does. It’s ostensibly a physical toy, but almost computer-like in its cleanliness and convenience. It might as well be Minecraft.

By contrast, Meccano forces you to deal with the frustrations and inconveniences of the world of atoms very early. It is designed to teach you what I call the truth in inconvenience.

In Meccano, things like tolerance stacks are part of what the kit is trying to teach you, so even though the parts are made to interoperate across time and kits, other aspects of the system, such as the use of compliant (flexible) parts, slotted joints, and fasteners that can be tightened to different torque levels (causing compressive distortions), all add up to higher realism.

What are no-brainer operations in Lego, like mating two parts, can get arbitrarily complex in Meccano, such as when many fastened joints are in close proximity. Often, you’ll need to loosen one joint to create enough wiggle room to squeeze in another one in a neighboring hole, before re-tightening both. Some operations are really quite tricky, where you have to work in a very cramped and nearly inaccessible interior corner of a nearly finished model, with tiny fasteners, and try to loosen/tighten in the right order to get a thing together. That’s where a lot of the skill comes in, knowing the tricks and hacks to do it all.

Meccano models are are significantly more difficult to assemble than Lego as a result, and it is hardly surprising that they ceded much of the market for such toys to Legos, through a century that increasingly prized low-friction, low-frustration convenience over all else. But on the upside, they are significantly more rugged as well. They can deal with a larger and rougher range of environments than Lego models.

If Lego is about cleaning up and smoothing the real world enough that it behaves like a frictionless computer world, Meccano is about learning the meditative art of pursuing the truth in inconvenience of dealing with the high-friction messiness of the real world. Though it’s a toy, it can be even messier than some real-world “real work” things like assembling Ikea furniture.

Now what does all this have to do with friction, AI, meaning, and zero-interest rates?