Hello friend,

Imagine welding together a floating city that can haul the weight of 100,000 cars across an ocean. Or building a machine longer than a football field, designed to chew through solid rock.

The scale is so massive, it almost feels impossible.

And yet, we’ve figured out how to manufacture them.

Last week, we looked at some of the biggest machines in the world. Today, let’s review how they’re made.

A TBM looks like a giant drill, but it’s really a modular factory that you assemble underground.

Every machine is designed for a specific tunnel. The diameter, geology, and length dictate the cutterhead size, the number of thrust cylinders, even the type of conveyors inside.

Nothing is off-the-shelf.

And the pieces themselves are massive.

The main bearing that spins the cutterhead can weigh hundreds of tons. The cutterhead itself, a steel disc over 50 feet wide, is too large to move as one unit. So manufacturers split it into segments of hardened steel that bolt together like slices of a pie.

Each subsystem is built separately:

All of it is shipped in pieces, sometimes hundreds of truckloads, to the project site.

Once there, construction crews excavate a launch cavern, lower each component underground, and weld or bolt everything together. Only then does the machine boot up and start eating through the earth.

In other words, you’re not delivering a finished product. You’re delivering a kit for building an underground factory that happens to move forward as it works.

Ships that can carry 20,000 containers don’t roll out of a warehouse either.

They’re too big to even imagine as a single part. Instead, shipyards break them down into blocks.

Block construction is the governing principle. Each block is a pre-fabricated section of the hull or superstructure, often 30 meters long and weighing hundreds of tons.

Inside each block, workers pre-install piping, wiring, and stairwells before the block ever leaves the workshop.

Cranes then lift these finished blocks into place in a dry dock, where they’re aligned with millimeter precision. Welders fuse steel plates along seams, turning dozens of giant Lego pieces into a seamless hull.

Some feats border on the theatrical:

From above, a modern shipyard looks like a production line for floating skyscrapers. Assembly isn’t about making one piece perfectly, it’s about orchestrating hundreds of oversized parts into a coherent whole.

Whether underground or afloat, the playbook is the same. Modularity.

TBMs are built like underground Lego sets. Ships are stitched together from steel skyscraper-blocks.

The genius isn’t just in the final product. It’s in designing every piece so it can be built, shipped, lifted, and connected in sequence without collapsing under its own weight. At this scale, the choreography matters as much as the engineering.

No matter how enormous the challenge, progress comes from modular thinking.

Split the impossible into pieces and take it one step at a time

Tool: Brand Lens

Goal: Think up a new titan with modern branding. Big manufacturing requires big ideas.

Prompt: Make a magazine ad for a new product breaking into the world of manufacturing. This is a big new product, literally. Image a massive new machine, and give it a name and story like a startup with impressive visuals and eye catching ad copy.

Got a second? Give some feedback on today’s article so we can keep making improvements to The Manifold.

PS—My day job is all about making small things, so I love digging into how the giants are built. It’s always interesting to learn about the opposite end of the engineering spectrum.