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-   -   Why manholes are round? (http://www.cssforum.com.pk/css-compulsory-subjects/general-science-ability/30724-why-manholes-round.html)

reema mushtaq Friday, January 29, 2010 06:22 PM

Why manholes are round?
 
:con
plz anyone tell me k manhole k covers mostly round kyn hoty hain.
as this question is most frequently repeated in eds paper
plz btayyyyyyyyyyyyy koi.

kashifilyas Friday, January 29, 2010 06:44 PM

sab say pehla tou fayeda yeh k dhakan hole k ander ne girta...
agar triangle,square ho tou woh mail hole main b gir sakta...:bow

Arbab.Danish Friday, January 29, 2010 06:55 PM

I agree with Kashif, circular hone ka yahee faida hota hai k andar nahi girtey, kissi bhee doosri shape k andar gir sakte hain( ya phir iss cheez se bachne k lie dhakkan hole k size se ziada hee barey bnaney pren ge) round size ka thora sa bara ho hole se to no, problem.
and they say that circle is the most stable and strong shape.

saadmalik Friday, January 29, 2010 08:35 PM

Reasons for the shape include:
A round manhole cover cannot fall through its circular opening, whereas a square manhole cover may fall in if it were inserted diagonally in the hole

Round tubes are the strongest and most material-efficient shape against the compression of the earth around them, and so it is natural that the cover of a round tube assume a circular shape.

Similarly, it's easier to dig a circular hole and thus the cover is also circular.

The bearing surfaces of manhole frames and covers are machined to assure flatness and prevent them from becoming dislodged by traffic. Round castings are much easier to machine using a lathe.

Circular covers do not need to be rotated to align them when covering a circular manhole.

Human beings have a roughly circular cross-section.

A round manhole cover can be more easily moved by being rolled.

Tradition.

qaarjk Friday, February 12, 2010 07:46 PM

[B][I][COLOR="Olive"]In my oppinion the logic is simple that it is easier to perform cleaning operation in a round one as compared to the other shapes. The angle or penetration in round shapes is more effective in clearing away the blockages.

Waisay agar koi cover rectangular ho ya triangular to us ka base bhi us se corresponding ho ga to beech main girnay wala problem un main bhi nahin ho ga in my oppinion[/COLOR][/I][/B]

Last Island Friday, February 12, 2010 08:00 PM

You have to be definite while writing scientific reasons. Tukkay nahin maarnay. :)

The reason for the circular construction of these covers is, quite simply, that covers of any other shape would fall through the manholes by virtue of their varying diameters. Circular manhole covers do not vary in width, or in diameter, as is the case with these other shapes, thus remaining in place despite the street traffic running roughshod over them.

Manufacturers craft the manhole covers together with the smaller sized lip, upon which they rest, at the same time to ensure a tightly sealed fit. Additionally, the manufacture of circular manhole covers is easier and more accurate than the manufacture of covers of any other shape. Lastly, round manhole covers, once removed, require less lifting and less manpower, as their shape allows them to be rolled.

Future Saturday, February 13, 2010 11:37 AM

[I]So Just Why *Are* Manhole Covers Round?

[/I]Well I'll tell you, but if all you want is the answer then you missed the point of the question.

"Why are manhole covers round?" is a now famous interview question considered anywhere from thought provoking to downright stupid by people on the receiving end.

Why do interviewers ask it? Well, it's so well known now that they shouldn't anymore but originally it was to see how interviewees responded. It's a way to get a sense for an interview candidate's ability to think on his or her feet outside of their area of expertise. The way the candidate approaches the problem, thinks of and presents potential solutions, defends them, or discards them are all relevant to the interviewer.

It's a simple question. There are simple answers. But the great not-so-secret about these types of questions that everyone seems to miss is that [B]it's not about the answer[/B]! The interviewer cares [I]much[/I] more about how you arrive a whatever answer you get than what that answer is. Are you thinking logically? Is there method or madness to the solutions you consider, accept, and discard? Are you even willing to entertain such an absurd question?

Oh. You still want the answer.

The most common answer is simply that a round manhole cover can't fall into the hole it covers. But I did tell you that there's more than one answer. Heavy, round manhole covers are easier for one person to move by standing it on end and rolling. Also, you don't have to "align" a manhole cover to it's hole. Any orientation will do.

My father, a mechanical engineer, claimed an answer I hadn't heard before: that round manhole covers are easier to manufacture. That's a nifty answer and it would have done great in the interview except he also claimed that was the [I]only[/I] reason and all the others were wrong. Whoops.
And for the record, round is not the ONLY shape that can't fall into its hole. There's a class of such shapes referred to as "[URL="http://ask-leo.com/r-30917a"]Reuleaux polygons[/URL]". The common characteristic is that they share a constant width or diameter.

Source : [URL]http://ask-leo.com/so_just_why_are_manhole_covers_round.html[/URL]

qaarjk Monday, February 15, 2010 10:09 PM

@fawadkhan

That was my point if any other shape can fall in he hole then why can't the round ones and if round ones cannot fall them how come others will fall in the hole coz the frame for the cover to rest upon is made according to it's shape

I have three main holes though smaller in size in my own house for drainage purpose and they are rectangular in shape and they have never fallen in side.

jack705 Thursday, April 01, 2010 04:44 PM

May be you all answers are true to some extent that, round shape easy to manufacture, easy to roll, low probability of falling inside etc etc...
But i think it is historically evidence fact that its shape was round till The Great Mughalian period, so simply no body try to change it:clap

wasikhan Thursday, April 01, 2010 05:35 PM

The question of why manhole covers are typically round, at least in the U.S., was made famous by Microsoft when they began asking it as a job-interview question.Originally meant as a psychological assessment of how one approaches a question with more than one correct answer, the problem has produced a number of alternate explanations, from the pragmatic ("Manhole covers are round because manholes are round.") to the philosophical.

Reasons for the shape include:
[LIST][/LIST]A round manhole cover cannot fall through its circular opening, whereas a square manhole cover may fall in if it were inserted diagonally in the hole. (A Reuleaux triangle or other curve of constant width would also serve this purpose, but round covers are much easier to manufacture. The existence of a "lip" holding up the lid means that the underlying hole is smaller than the cover, so that other shapes might suffice.)
[LIST][/LIST]Round tubes are the strongest and most material-efficient shape against the compression of the earth around them, and so it is natural that the cover of a round tube assume a circular shape.
Similarly, it's easier to dig a circular hole and thus the cover is also circular. [LIST][/LIST]The bearing surfaces of manhole frames and covers are machined to assure flatness and prevent them from becoming dislodged by traffic. Round castings are much easier to machine using a lathe.
Circular covers do not need to be rotated to align them when covering a circular manhole. [LIST][/LIST]Human beings have a roughly circular cross-section.
A round manhole cover can be more easily moved by being rolled.
Tradition. [LIST][/LIST]Supply. Most manhole covers are made by a few large companies. A different shape would have to be custom made.
Other manhole shapes can be found, usually squares or rectangles. Nashua, New Hampshire may be unique in the U.S. for having triangular manhole covers that point in the direction of the underlying flow. The city is phasing out the triangles, which were made by a local foundry, because they are not large enough to meet modern safety standards, and larger triangles cannot be found.[


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