For all the old geisers 5

[Baldy217]

Not too sure where to post this, so I'll do it here

If you remember the days when calculators took a whole room, well this thread's for you.



So what was it like having to do all the calculations by hand? I certainly can't imagine my life without a calculator, probably like most engineers.

Nowadays, people are complaining that we take computers for granted. Some say that many new grads rely to much on them and don't really grasp the theory they are applying.


So my question is : did they have that same argument for calculators back then too?

 

[TheTick]

My nuc school days were later than zdas's. Instructors were relentless about theory.

I think it's a matter of character. There are those who won't let the convenience of a computer stop them from digging deeper.

Computers have made things easier for those who don't fully grasp theory, but I don't believe it's cut down on the all-too-slim percentage of engineers who aren't content to blindly crunch numbers without a full grasp of "why".

 

[zdas04]

I probably am a Luddite, and I damn sure believe that engineers should have an apprenticeship (and I'm really happy that many of my clients are starting to have new graduates work under project-level supervision again).

I don't know all the intricacies of the computer models that I use, but before I will build a pipeline based on a model run I confirm that if I input known data to that program it gives me the same results as pressure gauges and flow meters give me. If a model can't match a measured reality then any faith put in an extrapolation is pretty misplaced.

That is my issue, I don't expect every engineer to be able to develop every computer program they run, I just want them to confirm for their self that the model has a reasonable chance of correctly predicting future performance.

David

 

[monkeydog]

Ignoring Zogzog ...
the secretary had a way of forcing you to bring the document to her complete

 

[whyun]

Computers, calculators and any tools that you can think of is essentially a black box. If you have the knowledge of what goes on within the black box, by all means, use the tools because it will save you time and money. If you don't have a full grasp of what's going on in the black box, you are not ready to use the tool. Especially when the results the black box spits out can potentially kill someone.

Engineers design stuff in one of two ways: by calculations or by testing. If a product has been tested (numerously) to work, it is a finished product. If it hasn't been tested, the finished product is based on calculations under numerous assumptions. You may only find out, after the fact, that some assumptions were incorrect (or made numerical errors), when the product fails.

 

[TheTick]

Engineers design stuff in one of two ways: by calculations or by testing.

I do both. Does that mean I'm not an engineer?

 

[cvg]

"the secretary had a way of forcing you to bring the document to her complete"

This is because prior to the Wang, we used a typewriter - the IBM Selectric being the model I am most familiar with. Typing a letter or report required the draft to be 100% complete, otherwise the secretary would be required to retype the entire thing (or at least a page or chapter). Good way to piss off your secretary would be to bring a rough or partial draft for typing and then return it with redlines for retyping.

http://www.officemuseum.com/typewriters.htm

 

[mshimko]

There were a lot of advantages to using a slide rule or hand calculations, advantages I didn't realize until I taught undergraduate engineering.

When folks had to use a slide rule (or even lacking that), they had other processes and rules that aided their work, specifically ALGEBRA, Scientific Notation, and ESTIMATION!

"In the old days, us geisers" would do as much of the math (typically meaning algebra) first, then insert the values in scientific notation, and the remaining arithmetic was relatively simple.

The advantage was we knew "about" what the answer was without doing any arithmetic.

Today, by comparison, "kids" will often simply enter a string of numbers into their very capable calculator, then have no choice but to accept the resultant answer, and would not realize something is very wromg with the mass of a 1 cm cube of iron being 9,863,567.263 kg.

 

[rtmote]

I read on the IStructE blog about a suggestion to apply for a UK lottery grant to 'archive' the way engineers work and the tools of the trade. I thought it was a brilliant idea. This would also reflect the thinking and the strategy of engineering design.

I agree with all of the comments about the process of being aware of what you are doing and using the tools to validate your expectations.

When I get a 4-part ring binder calculation for a simple piperack design (a mountain of a molehill!) I always put it aside and ask what's the wind load on the structure, or the stability bracing force? A blank look every time. Sigh....

As swearingen talks about Excel, I have had engineers not know the trig formulae are calculated in radians and they use degrees without recognising the numbers a load of b.......sigh....

Robert Mote

http://www.motagg.com

 

[KENAT]

Tick, same here, kind of.

Back in aerospace/defense in the UK structurally critical elements had to be proven by two separate techniques.

Historically this had been a set of hand calcs (or maybe matlab/mathcad/Excel equivalent) and a test, usually to destruction, of the 'weakest link'.

We were just getting into the realm where a set of hand calcs could be validated using FEA or FEA validated by test.

KENAT, probably the least qualified checker you'll ever meet...

 

[oldfieldguy]

mshimko nailed it...

We could run through the basics of the calculations in our heads, on a chalk (remember that?) board or on scratch paper and come up with a general idea of what the answers would be, then we'd go in and refine the calculations and the data, expecting it to be in the general vicinity. Large departures from the "ballpark" figure meant a closer evaluation of the original ideas.

old field guy

 

[GregLocock]

Hmm

When I test a car it is essentially a "black box", to which I apply known inputs and measure some outputs.

When I test a 1000 DOF simulation of a car it is essentially a "black box", to which I apply known inputs and measure some outputs.

In both cases I can successfully /test/ the car without understanding what is in the black box. But in both cases, in order to change/develop the car I have to open the black box and rewire it or change some components. But that black box itself contains other black boxes - the sim has the program/OS that it is running in, the real car has a black box called the laws of physics beyond our understanding (eg tires, and I'm not joking, Mr Feynman). Current world best practice does not rely upon me knowing the gruesome details of the program I use, or knowing any unknowable physics. Certainly, more information about either might help sometimes.

As another example, my background is in testing the dynamics of structures (experimental modal analysis). This is used in the auto industry to correlate with FEA models, for both transfer functions and mode shapes.

At uni I took a lot of structures classes, but skipped FEA as it was very boring and difficult and I was good enough at other topics that I didn't need the marks. Sure, I have picked up some of the theory along the way, but I have never read through the derivation of even the simplest multi dof element formulation.

So, when I build and analyse FEA it is pretty much a black box to me, yet my models run well, correlate well, and make useful predictions.

So I think I can justifiably black box some of my analysis process, although I think we are all happily in agreement that correlation with real world data is the key.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[GregLocock]

...and while I'm at it I notice the structural engineers refer to 'plug and chug' calculations.

That may be humorous, but it also reveals an acceptance of a degree of black-boxing.

I have an appalling memory, mostly I derive things from first principles, or in the case of structures, E/R=M/I=s/y and a few other goodies.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[SomptingGuy]

... I always have to write down c=f.lambda, although I can happily juggle pV=mRT in my head.

- Steve

 

[MechEng2005]

I graduated with my BSME in 2005, putting me in a generation that has basically always had calculators. However, I still feel I have a good "instinct" for what is reasonable. I think being able to judge "reasonable" comes more from experience than doing arithmatic in your head.

During college, running through enough calculations of a particular type would supply a good instinct for what is reasonable. I also had one teacher that required every final answer to have "reasonable" or "unreasonable" next to it. Then, if you got an answer that you didn't believe, but couldn't find your error, you could get partial credit for recognizing it. I wish more teachers would require this!

I wouldn't argue that advanced tools make it more probable that individuals lose the "instinct" for what is reasonable, but I don't think it's fair to make a generalazation about all us "kids" . I personally LOVE hand calculations, so I think I do pretty well at understanding the fundamentals of stress/physics/etc because I am interested. During my BSME, they also drilled us with GIGO (garbage in, garbage out) pretty heavily.

- MechEng2005

 

[oldfieldguy]

Reasonable: I can't think of how many times I've regarded "the answer" and had to as the question: "Exactly WHEN did the legislature repeal Ohm's Law" or some other inconvenient rule of the universe...

old field guy