Engineering mistakes 1

[Jabberwocky]

It always annoyed me (while watching Modern Marvels: Engineering Disasters type shows) that so many of their "engineering" faults seem to be not design flaws in the slightest.

An example that comes to mind, there was a piece on the Sherman tanks from WWII, which went on and on about how they were so inferiorly designed to the German tanks of the day. Engineering failure this and design failure that. Unless I missed something, the designers and engineers did their jobs to the letter. If they were provided with faulty design inputs, how is that their fault?

For instance, if the customer (US army?) says we need armor to stop a 20mm shell and the designers deliver - is it their fault that the Germans are using 40mm shells? Is this an engineering disaster?

 

[Ashereng]

The kill rate of US tanks vs German tanks was about 1:7 I had heard. For every German tank killed, the US lost seven.

The replenishment rate of US tanks to German tanks was 16:1. For every German tank replaced, the US replaced 16.

The US was fighting on industrial efficiency while the Germans relied on military efficiency.

The US tanks were desgined for superior manufacturing speed, not superior field performance.

The numbers may not be exact, but I believe the relativeness of the numbers are correct.

Then again, this may be an "urban legend", so reader beware.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[jmw]

Which came first, the Mary Rose or the Vasa?

JMW

http://www.ViscoAnalyser.com

 

[Ashereng]

Mary Rose

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[IRstuff]

Mary Rose sunk 1545

http://www.bbc.co.uk/history/war/mary_rose_03.shtml

Vasa sunk 1628

http://en.wikipedia.org/wiki/Regalskeppet_Vasa

TTFN

 

[Ashereng]

The Vasa evidently sunk during her maiden voyage.

The Mary Rose sunk during battle towards the end of her life expectancy. Evidently, she was becoming obsolete as a war ship.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[IRstuff]

But, if you read closely, they sank for identical reasons, that being the lower gunports getting inundated.

Having outrun the rest of the fleet, and coming under fire, she put about, both to fire her broadside guns, and to wait for support, when a sudden gust of wind pressed her over. As her low gun-ports had not been closed, she quickly filled and sank

Evidently, the news hadn't made to Sweden prior to the construction of the Vasa.

TTFN

 

[IRstuff]

Oh, and the Vasa's captain made the same claim about a sudden gust of wind, etc...

TTFN

 

[Ashereng]

Well, evidently, the English were good at keeping classified information classified (Navy Intelligence).

It seems that no other English war ship suffered from this design.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[GregLocock]

US Army doctrine in WW2 was not to use tanks against tanks. They were primarily intended for exploiting weakpoints in the defensive lines, and for shooting up the supply network. This is called cruiser warfare. The British explicitly designed different sorts of tank for infantry support, cruiser warfare, and tank destroyers. It was only as the size of tanks reached 50-60 tons that all three roles could be met at once, as tanks evolved into MBTs.

The Sherman also had to fit in with the loading gage of various bits of transportation. To transport a German tank on the railway first you removed the main drive wheels and the tracks, and then fitted narrow ones. At the other end of its journey you reversed the process. Crazy.

Also notice that the Sherman was basically the well proven chassis of the Lee/Grant, with a new top. That was not the only reason it was reliable, but it was one of the reasons. The chassis of PV and PVI were new each time, and the lack of reliability was crippling. Tanks were gaining weight at a rate of about 30% per year during the war, so one based on an old chassis was likely to be rather light and hence under armoured compared with the clean sheet of paper designs. See

http://www.geocities.com/greglocock/gallery/tanks.jpg

Sherman was not perhaps a brilliant design in retrospect, it was evolutionary not revolutionary, but it was good enough. The Allies made far worse engineering mistakes than the spec of the Sherman.

Cheers

Greg Locock

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[pennpoint]

William Mulholland
Quite the man, in my view. For those of you who have or have not been to Southern California might know that it is a desert, yet it flourishes with the benefit of water provided by the vision and engineering for-site of William Mulholland. He took full responsibility for the failure of the dam. Critics also concede that at the time the technology was limited to ascertain poor conditions of the bed rock. For the rest of us his vision of water canals and aqueduct system to feed Southern California it's water needs was truly genius.
PS: I live in one of the small towns that was devastated by that flood.

Stupid Engineering Mistake or just good viewer ratings.

I'll stand by Mulholland.





Best regards
pennpoint

 

[Jabberwocky]

Thanks Greg and Ash, but I should've known that bringing up tanks would cloud the issue.

Is the designer/engineer responsible for validating the appropriateness of the design inputs?

I'm not talking breaking laws of physics, but why is it called an engineering disaster if the end-user did something completely foolish and unanticipated, causing failure?

 

[Ashereng]

Because it is easier to blame the engineering?

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[IRstuff]

As in the case of the Vasa, would you tell the king he's an idiot? Likewise, the admiral declined to tell the king that his expensive toy was a white elephant after failing its stability test.

We get that situation very often in aerospace, particularly since the customer community no longer has the in-depth expertise they used to have.

We have customer now that insists on requiring a laser that puts out nearly double the required power, but also wants it in a small volume and weight, but doesn't want to pay to break the laws of physics and reality.

TTFN

 

[Ashereng]

What is the going rate for breaking the laws of physics and reality currently? Tee Hee Hee

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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[Sprocket59]

Would someone explain the role of "aerodynamics" on the Skylab panels? Is space not a vacuum? Or could the author have meant "thermodynamics".

 

[Zapster]

The upper atmosphere (exosphere) is not a vacuum. See link below

http://www.rcn27.dial.pipex.com/cloudsrus/atmosphere.html

 

[Sprocket59]

Thanks for the clarification.

As an aside, one thing that grates is the smug tone of some engineering critiques. As if the critic would never have made such a foolish error! But then, the best way to avoid criticism is to do nothing.

 

[IRstuff]

In fact, the latest Mars Reconnaissance Orbiter is playing aerodynamics over Mars even as we speak. They're using the outer atmosphere drag to convert their elliptical orbit into a more circular one.

TTFN

 

[UcfSE]

Some of the mistakes mentioned on the site by the OP were made because the people involved didn't know any better, or had know way to know any better. That's how we learn and advance our technology.

Others, such as the Kansas city Hyatt, were just plain irresponisble. Someone should have known better but either didn't check or didn't care. That mistake was preventable and within our realm of knowledge to do so. All you learn from that is how to save a few dollars at the expense of lives, and hopefully we all learn not to do it again.