Friday, February 28, 2014

Lessons Learned and Relearned

Mrs ERJ is driving down to Florida with her brother.  His name is Rob.

Rob is an engineer.  Like me, he graduated while Jimmy E. Carter was president.  Times were tough.  Jobs were hard to come by.

Unlike me he was unlucky.  The subsidiary he worked for was spun off the main company.  That subsidiary declared bankruptcy as the "legacy" contracts from the mother company expired.

He was still employed but the pension he was counting on was vaporized.  Some classes of employees in the company had their pensions "made whole".  Engineers were not one of those classes.  He was 47 when that happened.

Amazingly, he is not bitter.  He enjoys going to work each day. He is glad he has a job. That is a blessing.  He figures that he will work until he can no longer do so.  Then, they will figure out how to make do.

Slide Rules

While waiting for Mrs ERJ to pack, we talked about slide rules.  Rob has a co-worker who is going to a slide rule Olympiad near Detroit.

Rob asked one of the younger engineers if he knew what a slide rule was.  The kid hemmed and hawed.

Rob and I were among the first generation of engineers to go through college with powerful, portable,  affordable calculators:  a TI-30 in my case.  Our professors were not impressed.

A recurring message was "Don't become intoxicated by 8 decimal place precision."  I heard an earthier version of that same message two decades later, "Don't measure a pile of manure with a micrometer."

Our professors gave us positive role models.  For example, "Consider the DC-3.  It was designed with three decimal places of precision.  The magic of the DC-3 is that the designers (and heavier than air flying machines) had been around long enough so they could see and handle many broken parts.  They saw patterns.  Parts broke at interfaces.  The key to making parts....wing spars, fuselage stringers, engine mounts...that were durable was to leave extra beef around every bolt, every rivet.  They learned that sharp 're-entrant' corners killed."

Lessons learned and relearned and re....

Those lessons get learned with every new generation.  Twenty years after the DC-3 was designed a new generation of aircraft engineers who designed the de Havilland Comet.  They made a fundamental mistake.  They designed an aircraft with windows that had corners similar to the cargo holds on the Liberty Ships (early 1940s).  Holes with sharp corners kill, especially when one expects the (closed) section to resist torsion.

There seems to be a ten year cycle.  Designers, engineers, project managers and project accountants learn a lesson.  Ten years later they have been promoted or moved into other positions.  The new crop of designers and engineers seems to be fated to learn those lessons again, the hard way.

One repeater is due to an innate, human desire to define the performance of a material by a single number.  In the real world, the strongest materials are often brittle or vulnerable to exotic failure modes like hydrogen embrittlement, stress corrosion cracking or cracking due to mercury or halide contamination.  No matter how much a neophyte engineer might wish it were so, one cannot go to a big book and pick out one number and "make it happen."

I got huge enjoyment out of the short conversation I had with Rob.  I am blessed with great in-laws.  The more I get to know them the better I like them and the more respect I have for them.

1 comment:

  1. Joe, Re: Slide Rules and Pocket Calculators. I am a mechanical engineer that experienced *the* transition period. By that I mean my first 2 years of college were spent using a slide rule because that was all we had. I still have that slide rule (the best one could buy, a Post Versalog plastic laminated self-lubricating bamboo) and still hate it. Then the pocket calculators came, all at once it seemed, and I spent the last 2.00000 years of college with my beloved HP-35. It was an interesting time to experience. The first thing I noticed was that at least 2 hours of homework (slave labor) was eliminated each night. The "great debate" in the classroom was whether or not to allow use of the calculators for tests. It didn't take long for the professors to figure out what to do. Suddenly all tests had problems that only required the ability to set up the equation. The math was trivial and often optional. What a concept! I will admit that using a slide rule forces one to learn how to do quick mental estimates. A lost skill these days I believe. Of course your comments about the limits of precision are spot on. But those are the *only* positive things I can say about having learned to use a slide rule. Long live the spreadsheet (or Mathmatica or whatever comes next)!