Manholes | 24 Jul 2009

shabbir's Avatar, Join Date: Jul 2004
Go4Expert Founder
Why we have round manhole covers than rather than any other shapes? This is the case at least in India.
nimesh's Avatar, Join Date: Apr 2009
Invasive contributor
well if you have asked it here, then there might be some logic behind it.
How's it in other countries?

And nowadays I think they have started making the rectangular ones too.
rik625's Avatar, Join Date: Jun 2009
Go4Expert Member
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 aperture (A Reuleaux triangle or other curve of constant width would also serve this purpose, but round covers are much easier to manufacture.)
#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.
#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 horizontal boring mills.
#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.
#It's easier to dig a circular hole.
#Tradition
#Supply. Most manhole covers are made by a few large companies. A different shape would have to be custom made
shabbir's Avatar, Join Date: Jul 2004
Go4Expert Founder
Great Answer
nimesh's Avatar, Join Date: Apr 2009
Invasive contributor
Quote:
Originally Posted by rik625 View Post
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 aperture (A Reuleaux triangle or other curve of constant width would also serve this purpose, but round covers are much easier to manufacture.)
#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.
#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 horizontal boring mills.
#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.
#It's easier to dig a circular hole.
#Tradition
#Supply. Most manhole covers are made by a few large companies. A different shape would have to be custom made
nice answer rik

So In US also, they are round?
rik625's Avatar, Join Date: Jun 2009
Go4Expert Member
Thanks!

Well, yea in most of the places in US too those are circular in shape.