Saturday, September 10, 2022

Anvil, Hammer, Chain and Ring


Should you be privileged to know any Canadian engineers, you might notice that they wear an iron (or stainless steel) ring on the pinky of their dominant hand.

That is not an accident. The ring is there to remind them of a story and is a physical reminder of their obligations as an engineer.

Anvil, the Hammer, the Chain and the Ring

On August 29, 1907 the southern span of the bridge over the St Lawrence river between Sainte-Foy and Lévis, Quebec collapsed killing 75 workers.  Source

Like all spectacular failures, there were many cascading-failures that came into play. Different tellings of the story will emphasize different links in the chain-of-failure as many lessons can be gleaned from the event.

Today's lesson is that there were precursors to the failure. Beams were bending, rivets were shearing, junior engineers were making calculations that suggested gross-underdesign. The senior engineers in charge of the project dismissed those signs and continued the project without review, without modification to the original plans. Ego has a momentum all its own.

Disaster ensued.

Reviews after the disaster revealed that the most fundamental, back-of-envelop, Euler-buckling calculations (had they been done without error) would have shown the beams selected for the span were incapable of holding the weight of the span itself, much less carry any traffic.

The review also found the head engineers to be at-fault for not paying attention to the junior engineers' observations and later calculations. And, by implication, found the junior engineers at-fault for deferring to the authority of the senior engineers when their math clearly showed impending disaster.

The brew bubbled-and-brewed for about two decades and found a resolution in a ceremony that University graduated engineers have the option of attending. It is engineering analog to the Hippocratic Oath administered to medical doctors. It lays a burden on the newly graduated engineer to double-check his assumptions and calculations, double-check his math...and then if his finding contradict the popular narrative and life-and-limb are at risk, to storm the gates of Administraium. Egos and rank and status be damned.

The flip-side is that when those engineers become senior engineers and are leading projects, they have an obligation to give the input of other engineers a fair hearing. They have an obligation to put their ego on the shelf and listen.

Low Voltage Source

Which brings us to the comments that showed up in the post about Low Voltage Sources for diagnosing fencing shorts.

Dr Jim and Mr B took me to the wood-shed. I listened.

Not only did Dr Jim redirect me, he also supplied a link to a component on Amazon that is appropriate. THAT is professionalism personified.

Thank-you Dr Jim.

The original post will be deleted except for the header and a link to this post. That will retain the comments and provide a path to the appropriate way to handle the problem should anybody remember the original post and go looking for it.


  1. I think the break down voltage of skin is around 50-60 Volts. So you may not even feel the shock if you use that. A regular weed burner type charger would probably wreak havoc on an old transistor radio. You might try that to find shorts. Not dead shorts but arcing ones. Just, lower the antenna, tune off frequency where it's only static, and listen for the repetitive buzz. You can use your body to shield the antenna. When it's quieter, it's behind you. I've done that to find arcing power pole insulators. Might be too much signal, overwhelming the front end of the receiver, tho. As a kid, I would just brush up against the fence and my jeans would attenuate the "signal". If you didn't feel it, the short was between you and the charger....

  2. They don't make em like you any more Joe. Its a shame... broke the mold.

    1. I used to have an ego. I kept it as a pet until it became too expensive to feed and house.

  3. The bridge collapse is a great analogy for our present economic condition. Your personal reflection is a tribute to character and a rarity these days. --ken

    1. The Kansas City Marriot skywalk collapse was another complete process failure. The original design was unbuildable (required 10s of feet of threaded rod) and the field modification to create buildable design took the short cut of hanging the lower tier support beams off the middle tier beams. The real short cut was not analyzing the additional load on the middle beams and their support hangers. The upper support rod and mount pulled thru the beam when the middle and lower bridges were filled with dancing guests.

      The RIGHT fix would have been to run new support rods from the roof down to the lowest tier with a slip fit at the middle skywalk (so no load transfer there) but that wasn't done.

      114 people died.

  4. It's a good time to reread Kipling's, "The Sons of Martha."

    Thank you for the revised information.

  5. I just didn't wanna see you end up dead.
    I can't find the transformer I thought I had to give you. But the linked one is similar. It'll work fine for what you need.

  6. Or, you could get something like this:

    1. Well, that didn't work!! Search Amazon for "electric fence fault finder" Will tell you which direction to look for the short.

  7. If we're starting a list engineering screw-ups, I nominate the Flixborough Disaster. Short version is that one reactor in a series was removed and the jumper piping supports were not properly engineered. The uncontaminated vapor cloud explosion resulting from the pipe failure and an ignition source flattened the site.


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