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From: Randy Yates on 30 Dec 2009 08:43 Randy Yates <yates(a)ieee.org> writes: > Jerry Avins <jya(a)ieee.org> writes: >> [...] >> Randy Yates wrote: >>> [...] >>> Assuming the center is 1 foot radius, the little lip is 0.1 feet and the >>> big lip is 0.5 feet, and the lip thickness is 1/2 the center, we'd come >>> up with a ratio of 1.625/1.105, or 47 percent heavier. If I did my math >>> right... >> [...] >> Assuming that radius implies roundness, any size lip is adequate. > > Yes, wrong word - substitute width for radius here. Bah! "Half width"? You know what I mean - W / 2, where W is the width of a side. ARRRGH! -- Randy Yates % "How's life on earth? Digital Signal Labs % ... What is it worth?" mailto://yates(a)ieee.org % 'Mission (A World Record)', http://www.digitalsignallabs.com % *A New World Record*, ELO
From: Rune Allnor on 30 Dec 2009 10:01 On 30 Des, 08:19, glen herrmannsfeldt <g...(a)ugcs.caltech.edu> wrote: > HardySpicer <gyansor...(a)gmail.com> wrote: > > (snip, I wrote) > > >> I am not so sure how it works in EE, but in physics there are > >> theoretical and experimental physicists. ?Many good theoretical > >> physicists aren't very good at lab work. ?There is the well known > >> "Pauli effect" ?http://en.wikipedia.org/wiki/Pauli_effect > > Engineers haven't realised this yet. The industry ones bleat on and > > one about how they are the only ones that can solve real problems and > > the academics bleat on and on about the limitations of industry. There > > is little respect of one wrt the other as you can see. > > As far as respect, in physics each has many good stories and jokes > about the other. Personally, I remember a party for a new theoretical > physics Ph.D. including a bottle of champagne. While I believe > any experimental physicist could figure out how to open a bottle, > this Ph.D theoretical physicist could not get it open. The main difference between industry and academia is that in industry, the fools, frauds, and failures will eventually be recognized as such - if not sooner so at least when their failed plans cause some damage or when their schemes fall apart. People are held legally and economically accountable. Companies tend to go out of business if the skills, knowledge and craftmanship are substandard. Not so in academia. In academia, anyone can apparently do anything without any danger of repercusions once they have optained tenure. Most of the projects I used to be involved with in academia and R&D put the participants up for indightments of fraud, manslaughter and / or treason. Suffice it to say that I worked a bit too hard for a bit too long to find that sort of stuff amusing. Rune
From: Jerry Avins on 30 Dec 2009 11:01 Randy Yates wrote: > Jerry Avins <jya(a)ieee.org> writes: > >> Randy Yates wrote: >>> Randy Yates <yates(a)ieee.org> writes: >>> >>>> John Monro <johnmonro(a)optusnet.com.au> writes: >>>> >>>>> Randy Yates wrote: >>>>>> "steveu" <steveu(a)coppice.org> writes: >>>>>>> [...] >>>>>>> Any sufficiently large object is not going to fall down a small hole. I >>>>>>> think reasonableness of size is implicit in the argument. >>>>>> A two-foot diameter would require a lip size of about 5 inches. Is that >>>>>> unreasonably large? It doesn't seem all that unreasonable to me. >>>>> It makes the cover twice as heavy. >>>> Well, not TWICE as heavy, is it? First, there must be some lip, so we >>>> should be comparing the difference between minimal lip and big lip. >>>> Second, it wouldn't be the same thickness as the center portion. >>>> >>>> Assuming the center is 1 foot radius, the little lip is 0.1 feet and the >>>> big lip is 0.5 feet, and the lip thickness is 1/2 the center, we'd come >>>> up with a ratio of 1.625/1.105, or 47 percent heavier. If I did my math >>>> right... >>>> >>>> Yeah, that's significantly heavier, but it's not the slam dunk Steve >>>> was making it out to be, in my estimation. >>>> >>>> Anyway, this seems ever more so to support my point that it is weight >>>> (and material and cost), not geometry, that decides this. >>> I should say, "..., not hole-fall-through-ability"... >> Let's ask the guy down in the hole how important it is that the cover >> not fall through. :-) > > I can't tell if you're serious or joking ("Many a truth are said in > jest"). It was said in jest. The real issue is the amount of effort needed to ensure that the cover not fall through. Consider what sewer workers do to enter a manhole. A stout fellow with an iron rod hooked at one end and bent into a handle at the other puts the hook through a hole in the cover near the rim and pulls. (Very large covers are dealt with by two workers with two hooked rods.) The cover slides to one side and the manhole (workerhole? access point?) is open. The rod is used again to close the opening. the cover is slid along the ground until it lies over the opening and drops into place. It's so easy I can do (and have done) it myself. Now consider how the electric company deals with the rectangular cover of an underground transformer vault. A cable is hooked into the cover at two points, then lifted with a crane of sorts, often the boom of a bucket truck. An inept crew -- at least three; one to operate the boom and two to guide the cover -- can sometimes get the cover through or jammed in the opening, but it can't drop and is easily set right. > Logically, if we let A be "the manhole cover is not able to fall through > its own hole" and B be "the manhole cover is round", then > > if A then B > > is false. In other words, either geometry supports the "requirement" > that it not fall down the hole. What is true is > > if C then B, > > where C is "we use the least amount of weight to create a cover that > can't fall through its own hole." What is always true is if B then A Relying on a large brittle flange extending out from a stress raiser (abrupt change in section) is an engineering sin you wouldn't commit. > And now that I've spent about an hour discussing something so obvious > it's silly, I'm going to get back to some real work! Oh, come now! Wasn't it fun? Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: Jerry Avins on 30 Dec 2009 11:02 Randy Yates wrote: > Randy Yates <yates(a)ieee.org> writes: > >> Jerry Avins <jya(a)ieee.org> writes: >>> [...] >>> Randy Yates wrote: >>>> [...] >>>> Assuming the center is 1 foot radius, the little lip is 0.1 feet and the >>>> big lip is 0.5 feet, and the lip thickness is 1/2 the center, we'd come >>>> up with a ratio of 1.625/1.105, or 47 percent heavier. If I did my math >>>> right... >>> [...] >>> Assuming that radius implies roundness, any size lip is adequate. >> Yes, wrong word - substitute width for radius here. > > Bah! "Half width"? You know what I mean - W / 2, where W is the width of > a side. ARRRGH! See? I said it was fun! :-) Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: Jerry Avins on 30 Dec 2009 11:05
Rune Allnor wrote: ... > The main difference between industry and academia is > that in industry, the fools, frauds, and failures will > eventually be recognized as such - if not sooner so > at least when their failed plans cause some damage or > when their schemes fall apart. Oh? Don't they get promoted to management? ... Jerry -- Engineering is the art of making what you want from things you can get. ����������������������������������������������������������������������� |