Today, let's open our umbrella. The University of Houston presents this series about the machines that make our civilization run and the people whose ingenuity created them.
We engineers make constant use of mechanisms, simple sets of mechanical parts, that move together. Think about can openers or piano keys. They all look so simple and obvious, but they aren't simple at all. I awoke to the genius behind another common item when an editor of the Children's magazine, Highlights, wrote to me.
She was doing a page to show children how umbrellas worked. And it left me in awe of the complex simplicity, the economy of motion, in the lowly umbrella. So many mechanisms have to move in concert to spread that protection during rain, to retract it when the sun comes out. And yet,it looks so simple.
We've had folding umbrellas for a long time. The word comes from the Italian, umbra-ella, a little shade. Same idea as parasol, from the French for sun shield. Both terms refer to how people first used them as a shade, rather than to keep dry during rain. The Egyptians and Persians made drawings of parasols thousands of years ago. Ancient drawings reveal forms of foldable, even collapsible parasols. But the lightweight, foldable umbrella that we know, it found its modern form in early 18th-Century France.
Click Here for a slow-motion video of a folding umbrella opening.
So we open our umbrella to see the mechanisms inside it. I'll describe them for now. But do look at your own umbrella. Then you can be as impressed as I am. First, we see a latch on the handle. It releases a runner that slides up the length of the umbrella's central shaft. That runner carries a strong spring. And it forces eight stretcher rods outward. Each stretcher connects to one of the eight ribs that spread a taught canopy out over our heads. And that spreading action is what pulls the runner upward. We also notice a second spring at the top of the central shaft. It gently buffers the runner as it reaches the top.
Click Here for a slow-motion video of a foldable umbrella opening.
Maybe we have a collapsible umbrella. It can fold because it has ribs only on the outer part of the canopy. Some have a second smaller rod, parallel with the stretcher. Those two rods fold together as the umbrella opens. Why that extra rod? Well, it helps stabilize the canopy in a breeze.
Mechanism for stabilizing the ribs.
Another thing about umbrellas: As with mousetraps, inventors feel compelled to improve upon the accepted form. We find countless "improved" umbrellas if we go online. Umbrellas built for two. Smart umbrellas. Umbrellas with windows, or with different internal structures. However, centuries of honing the design have left us with a form that leaves very little room for improvement.
That's true of countless engines of our collective ingenuity. So look beyond all of today's hi-tech for a moment. And savor the dazzling array of settled human creativity that serves us, even throughout our familiar households.
I'm John Lienhard at the University of Houston, where we're interested in the way inventive minds work.
Lienhard keeps dry
My thanks to Linda Rose, Assoc. Editor, Highlights. Click on her umbrella page: "My Sci: Under an Umbrella." Highlights, May 2020, p.12.
For an introduction to mechanisms, see: L L. W. Tsai, Enumeration of Kinematic Structures According to Function. CRC Press, NY, 2001. Readable online here.
See also the Wikipedia page on Mechanism (engineering).
This Wikipedia article describes the history and design of umbrellas.
This episode was first aired on February 8, 2021
You might find umbrellas that deviate from my description. What I describe are the common forms that we usually encounter.
Photos by Andrew Lienhard