A beautiful instrument

This Barometer was made in Florence some 100 years ago, and served my late grandfather, first in Italy, then in Israel; it ended up on my wall, a family heirloom to delight the heart of any engineer.


It is a large (23 cm across) Aneroid Barometer, an instrument to measure atmospheric pressure by means of the compression of an evacuated metal capsule (the silvery part with concentric corrugations). Back in the day you would set the golden arrow to cover the black one in the evening, and when leaving home in the morning you’d tap the glass to see which way the black arrow would slightly move from under it – denoting whether the pressure is rising or falling, i.e. whether the weather was getting sunnier or rainier.

What makes this instrument so lovely is the inside mechanism, which is made of springs, hinges, rods and chains that convey the movement to the pointer – and these are made of many beautifully burnished alloys of brass and steel, as you can see below (click either photo to enlarge it).

Barometer mechanism

The say some modern smartphones include a barometric sensor… but they can’t hold a candle to my grandpa’s barometer when it comes to sheer elegance and beauty!

    A wonderful idea for defusing a child’s fear

    I was sitting in the lobby of the Shaare Zedek hospital in Jerusalem, and I noticed on the chair next to me a small booklet someone had discarded there. An idle look turned to admiration as I examined it and realized what it was.

    EEG coloring book

    The cover reads “EEG test – the Institute for Neurological Diagnosis“, hardly exciting. But the thing is, obviously, a coloring book. Here are two pages from it:

    EEG coloring book

    Today they examine my head. And I know this does not hurt“.

    EEG coloring book

    In the room there are: A bed and pillow / A working table / And a large apparatus“.

    Get the idea? The booklet explains everything clearly, dispelling the strangeness of the intimidating examination room, and of course mitigates the child’s fear; all in a coloring book that takes its mind off the scary goings on ahead.

    The last page gives us the names of the good people who developed this wonder and gave it to the hospital. Well done!

    EEG coloring book

      Another triumph of improvisation!

      New on my Possibly Interesting web site: Cloning a Vibroplex bug, where I describe the venerable Vibroplex semi-automatic telegraph key – and the improvised clone I made as a young radio amateur.

      Vibroplex "bug" semi-automatic telegraph key and its homemade clone


        Definitely a good idea!

        Form follows function!

        Here is a row of anchors, which I photographed in Greenwich in the UK. You’ll note the one in the foreground has a single fluke (as the pointy ends of an anchor are called). The sign says this anchor is from around 1820.

        Single fluke anchor

        So why would they produce an anchor with only one fluke, when most of them have two? For a very good reason.

        This model was used in permanent ship moorings in shallow waters. Think of the ship floating above the anchor. Think of the falling tide. Think what will happen if the ships comes down too close to an upward-pointing fluke…

        That’s why!

          How many engineers?

          See the mechanic working on my Renault Clio.

          Do you know what he’s doing? Looks like he’s trying to squeeze his arm into a tiny space between some metal beams in the engine compartment frame. Why is he doing that? Because he wants to replace a burned out light bulb in the headlamp assembly.

          Renault Clio lamp change

          Actually I carry spare lamps in the trunk, so I thought I could change the bulb myself. But after a long struggle I decided to take the car in to a garage shop, in the hope that the mechanic there could solve the riddle: how do you access the headlamp’s back side and extract the lamp?

          Why, what’s the problem? Here is the problem:


          The headlamp is wedged in behind the tube with the yellow cap, and is practically impossible to reach without disassembling the metal beam behind it. Yep… Renault designed this car so you need to take it apart to change a light bulb.

          How many design engineers does it take to make it impossible to unscrew a light bulb?

            An elegant hydraulic calculator

            Robert Owen Wynne-Roberts, MICE (Member of the Institution of Civil Engineers), FRSI (Fellow of the Royal Sanitary Institute), was a talented civil engineer. He passed away in 1935, but at least one result of his engineering talent abides: the Wynne-Roberts hydraulic calculator, a specialty circular slide rule for computing flow in water pipes and sewers.

            Wynne-Roberts' Hydraulic Calculator

            You can read about this elegantly packaged device in a new article on my history of computing site.

              Form and Materials: swords of yesteryear

              Form follows function; but often both must follow the available materials.

              Consider the image that comes to mind at a statement like

              The great king raised his mighty sword to smite his enemies.

              Surely, you imagine a sword structured something like this:


              Photo courtesy Søren Niedziella, shared on flickr under CC license.

              This, after all, is just about what a proper King’s sword would have to look like to serve him well.


              Well, how about this instead?

              Khopesh sword

              Photo courtesy Dbachmann, shared on Wikimedia Commons under CC license.

              Would you recognize this as a sword? If you were an Egyptian or Mesopotamian soldier some 4000 years ago, you certainly would. In fact, this was what a standard battle sword looked like between 2000 and 1300 BC. This one, missing its hilt at the right end, is from 1750 BC.

              These weapons were in use across the ancient near east, and were called Khopesh in Egyptian. Their only sharpened edge was the outer side of the curved part at the left. You used this edge to beat on people, much like you’d use a club; stabbing was not even an option.

              So, what’s going on here? A sword should be long, thin, sharp and pointy, so you can stick it into people at arm’s length; why make one that looks like a short, thick, bent metal rod that can only be used to clobber your enemies?

              This is where a key fact comes in: we’re talking Bronze Age, when iron (and much less steel) was unavailable. Weapon designers were constrained by a metal that was too soft for anything long and thin; nor would it stay sharp for long. A one-sided “sickle sword” like the Khopesh could have a thick backside that would give the bronze both durability and hitting momentum.

              Over the years the design varied somewhat; notably the sharp part grew longer at the expense of the handle, as in the sword below:

              Khopesh sword

              Incidentally, I wasn’t kidding about the king: below you see a PR image of Ramesses III smiting his enemies with a curved sword just like this one. He grabs the smaller-than-life enemies by the hair and is ready to smite them with the sword’s edge (the kings of those days, unlike today’s ornamental ones, were pretty hands-on where smiting was concerned). In fact, this image makes sense of the fact that “smite” is defined in the dictionary as “to strike with a heavy blow or blows” – strike, not skewer as with later sword designs. The guy on the right is more than a king – he is the Akkadian God Nergal, no less, and he holds a sickle sword in his left hand, its blade resting on the ground.

              Ramesses III and Nergal

              But then came the iron age, and it became possible to craft sharp long blades that wouldn’t break; and the bronze Khopesh went the way of the flint axe, doomed by a new technology that enabled new forms and new functionality.

              That’s Progress for you…

                A truly uncool armrest design

                Back from vacation, having flown a Boeing 737. This lacked the personalized screens seen in longer haul craft but it had a headset jack and a set of volume and channel controls for each passenger. The controls were set in the armrest, in easy reach of the passenger, like this:

                Boeing B-737 armrest audio controls

                Cool, huh?

                Not cool. The two rocker switches for the volume control and channel selector are flush with the surface of the armrest. This means that if you rest your arm on the thing – or if your neighbor in the next seat does – your channel is bound to skip up or down every few minutes. If you watch a movie this can get truly aggravating.

                And all they had to do was recess the controls a couple of millimeters under the surface…

                  A curious slide rule design

                  For some reason, inventors in the first half of the 20th century thought that incorporating a slide rule into a mechanical pencil was a great idea. In reality, these combination devices were of dubious utility, gives their low precision as calculators… but they are certainly ingeniously designed.

                  Pencil Sliderules

                  I describe three of them,  including one extremely rare device, in a new article on my history of computing site.


                    How cool is that?!

                    Evolution has crafted some amazing design solutions to the problems of life, and I never have enough of their elegance.

                    Take the crocodile’s heart.


                    Crocodiles have a special bypass short circuiting blood flow to their lungs. Specifically, although they have the same four chambered heart configuration as us mammals, which pumps the blood first to the lungs to get oxygenated and then to the body to use that Oxygen, they have a special hole – the Foramen of Panizza – that connects the blood vessels leaving the heart’s two ventricles so that blood can flow from one circuit to the other without visiting the lungs. What’s more – and this is the cool part – in some species, a special valve enables the short circuit only during prolonged diving, when the lungs are useless anyway.

                    Is that cool, or what?!