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Petroski on Engineering: Armchair Design & Analysis

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Jack Rupert, PE
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Platinum
Re: What about design for practical use case?
Jack Rupert, PE   2/4/2012 4:11:33 PM
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I think the airlines' issue with your suggestion, Russell, is that if I'm reading it right, your design would be loose.  Yes, it's connected to both armrests when the passenger wants it to be, but if the passenger is putting it back, or doesnt' secure it properly, or whatever, it becomes the airlines responsibility if it goes flying in turbulance.

kenish
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Platinum
Re: No Room for Improvement
kenish   2/3/2012 11:12:42 PM
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The lowly fold-out tray table is a pretty amazing piece of design.  Besides the basic function, there's numerous secondary requirements.  It must be lightweight, strong,  and meet flammability requirements.  It has to support a certain amount of weight but break away if someone hits it hard without leaving sharp pieces and remain able to be stowed after being broken.  It can't have any pinch or "guillotine" hazards and can't fly out of the bin in a 15g foward-aft impact.

The cardboard tray idea is great!!

Russell Faulkner
User Rank
Iron
Re: What about design for practical use case?
Russell Faulkner   2/3/2012 8:13:59 PM
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Why not just make the tray from a sturdy piece of corrugated cardbord coated with plastic.  Advertise a ski resort on one side and a Maui hotel on the other.  Clipped securely to BOTH armrests it would hold more weight than a cantilevered tray, weigh about an ounce, cost 97 cents, and stow in a pocket on the seatback in front of you.  A tray with no hinge is harder to break, but if somebody breaks it anyway, the airline gets to sell more advertising.

Charles Murray
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Blogger
Re: No Room for Improvement
Charles Murray   2/3/2012 7:16:27 PM
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I agree, Chaschas. There's very little froom for improvement, which says a lot about the innovativeness of the original design.

Rob Spiegel
User Rank
Blogger
Re: reasonably expected misuse
Rob Spiegel   2/3/2012 3:32:29 PM
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That's a great song, TJ. He really nailed a lot of truths in the song. I saw him a couple of years ago at a festival. He still does "Alice's Restaurant." I guess he's stuck with it. I saw him sing it a couple times in the 1970s. That was understandable. But I was surprised he was still singing it 40 years later.

William K.
User Rank
Platinum
Aircraft tray tables: Armchair analysis.
William K.   2/3/2012 2:35:35 PM
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I have come across those tables that pop up from between the seats and have never had any problems with them. Probably being an experienced engineer helps a bit there. I have been on lots of flights where I had to hold my drink so that the bumps would not launch it into my lap, or somebody else's lap. I agree that the ones that fold out of the back of a seat are much nicer, although I have never been able to use a computer on a plane.

If you want a real challenge though, try to utilize the footrest on one of the Amtrack trains. There is a button on the armrest to release it, but in the trains that I have ridden there is nothing to make it move once it is released. The only way we figured out to use the footrest is to grab it with a hand and pull it into position. My guess is that the springs were removed to prevent terrorists from somehow utilizing the footrests for something, or possibly to prevent idiots from doing something really stupid with them.

I really would preferr that our legal system stop rewarding idiots and fools for injuring themselves, and instead, fine them for being so stupid. OF course, then we would have the lawyers seeking customers under some other premise, and that might be worse.

SE
User Rank
Iron
Airplane tables are useful...
SE   2/3/2012 11:58:19 AM
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Airplane tables are useful... as mouse pads.  I had access to a bunch of old trays being thrown out.  For black or featureless tables they make very nice mouse pads!  No bending or warping.  Conversation piece too.

As for use on aircraft, they do leave a lot to be desired.  However, there is little choice.  Make a great table and someone will lean on it and bend it.  Make it stronger?  Not only heavier but more tempting to lean on.  Live with it - and carry a pop can tab.

ChasChas
User Rank
Platinum
No Room for Improvement
ChasChas   2/3/2012 9:47:46 AM
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With everyone so crammed together, there is very little room for improvement - literally.

naperlou
User Rank
Blogger
Re: What about design for practical use case?
naperlou   2/2/2012 10:38:52 PM
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One thing I don't think the airlines or designers really considered is the lifetime of the product in this case.  Is it reasonable to expect something that gets as much use as a tray table to last the lifetime of the plane.  Those are typically flown for many years.  They should have designed them to easily replaced (say during a layover) and refurbished in the shop. 

TJ McDermott
User Rank
Blogger
Re: reasonably expected misuse
TJ McDermott   2/2/2012 9:55:28 PM
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I've had another rude awakening this week: no matter how hard I try, how intelligent I may be; there is always one idiot "smarter" than me who will discover the way to damage the machine.  This week, the idiots won.

Arlo Guthrie has a thing or two to teach engineers about "reasonably expected misuse", from his song Alice's Restaurant:

 

 
"Kid, I'm going to put you in the cell, I want your
wallet and your belt."  And I said, "Obie, I can understand you wanting my
wallet so I don't have any money to spend in the cell, but what do you
want my belt for?"  And he said, "Kid, we don't want any hangings."  I
said, "Obie, did you think I was going to hang myself for littering?"
Obie said he was making sure, and friends Obie was, cause he took out the
toilet seat so I couldn't hit myself over the head and drown, and he took
out the toilet paper so I couldn't bend the bars roll out the - roll the
toilet paper out the window, slide down the roll and have an escape.



 

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