An engineering channel on YouTube

Factor of Safety

How bridges, buildings, and marvels of engineering really work, with the real numbers.

Watch on YouTube How a video gets made
Factor of Safety logo: F.S. written in amber and underlined twice capacity ÷ load ≥ 1, always

What the name means

F.S. = capacity / demand

Engineers never design a structure to carry exactly what it will see. They build in a margin, and the ratio between what it can take and what it actually takes is the factor of safety. Every video on this channel is about finding that number for one of the world's biggest builds, and what happens when the margin gets tested.

01 · the structure

Real builds

Bridges, towers, dams and the machines that make them. Landmarks you know, and the engineering you have never seen explained.

02 · the question

One clear question

Why didn't it fall? How does it stay up? What actually holds the load? Each video chases a single question to its answer.

03 · the numbers

Maths you can check

Back-of-the-envelope calculations, worked on screen, with every input sourced. The full working goes in the pinned comment.

How a video gets made

Every episode, same process

These are the steps every video goes through, from first idea to upload.

  1. Pick a structure and a question

    A famous build, and one question about it that the usual documentaries skip: not "how big is it", but "why does it work".

  2. Build a fact sheet

    Every figure goes into a sourced fact sheet: official records, engineering papers, agency reports and contemporary news. Key numbers need two independent sources, and conflicts between sources are written down, not hidden.

  3. Run the numbers

    The calculations are worked step by step: loads, stresses, stretch, margins. Anything computed rather than published is labelled as computed, with its inputs.

  4. Write the script

    The story is built around the one question and paid off by the end. No padding, no invented quotes, and every number on screen traces back to the fact sheet.

  5. Draw the visuals

    The 3D models, diagrams, maps and calculation cards are built for each episode, in blueprint style, and every shot has to show what is being said at that moment. Archive photos and film are public domain or licensed, and short clips from other creators are used only for commentary, credited on screen and in the description.

  6. Review it beat by beat

    The finished cut is reviewed shot by shot: does the picture match the line, is anything reused, can a viewer follow it with the sound off. Anything that fails gets rebuilt before upload.

  7. Publish with the receipts

    The description lists every source and every media credit. The pinned comment has the full working. If someone finds a mistake, the correction gets pinned.

Standards

The rules every video follows

Every number has a source

Or it is clearly labelled as a calculation, with the inputs shown.

Metric and imperial

Measurements are given in both, so nobody has to convert in their head.

Reconstructions are labelled

If a document can't be shown directly, a recreation is marked as one on screen.

3D scenes are illustrations

Movement is sometimes exaggerated so you can see it, and the video says so.

Credit where it's due

Photographers, archives and creators are credited on screen and in the description.

Corrections get pinned

Spot an error and comment it. If it holds up, the fix is pinned for everyone.

Episodes

Episode 1
main span 1,280 m (4,200 ft) Golden Gate Bridge · 24 May 1987
Episode 01 · 10:48

300,000 People Flattened the Golden Gate Bridge. Why Didn't It Fall?

On the bridge's 50th birthday, the crowd was so heavy that the gentle hump in the middle of the road went flat. How heavy was it, how far did the cables stretch, and how close did it really come?

  • 00:00The morning it bent
  • 01:03It was never an arch
  • 02:4527,572 wires
  • 03:39The force that tears bridges apart
  • 05:31Sixty miles from the quake
  • 06:47The real danger that day
  • 08:23How close was it?
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Have the documents?

Engineering reports, drawings, inspection records or photos of a structure we covered can turn an estimate into a fact. Send them in, along with business enquiries and corrections.