why is manhole cover shape is round?

Answer 1

So that it will not fall down. Other shapes will fall in the hole when inserted in a certain angle.

Rectangular man-hole cover are also being used but the type with hinges so that it will stay in place

Answer 2

If you have ever worked down in a manhole you know how important it is to not have someone accidentally drop that cover on you.
Round covers cannot fit through the round opening. It's the only shape with that characteristic.

Answer 3

All the answers given regarding falling through the hole of other shapes are valid. The real reason is that to make almost anything in a factory, round is cheaper as most machines for metal working are rotational. The covers are cast from iron but the moulds are hand made and round is easier and therefore cheaper.

Answer 4

A square manhole could drop down the diagonal.
Its more foot friendly. No sharp edges.
It spreads the wieght more evenly
It fits in any rotation instead of just 4 ways

Answer 5

I would say because dirt or what not can much more easily get caught in a corner and cause it to jam be square versus round. Also it would cause less damage to the person if there was some sort of slamming into the side. A circle also takes up less space (cost efficient) and liquids flow easily through a circle versus a square. Really can't think of any square topped bottles, you?

BP has the most thorough, correct, and best answer.

Answer 6

A circle can provide a greater surface area with less material than any other shape. Ie, you get a much bigger entrance for the man than if you used a square entrance using the same amount of steel.

Answer 7

Round is one of the only shapes that prevents the lid from falling through it's own hole, regardless of orientation. Square, triangle, etc.- almost any other shape will have at least one axis where it is significantly shorter along its length then it is acroos its face.

Out of the few shapes that can't fall, circle is also much easier to manufacture, so it is cheaper.

Answer 8

Because if it were any other shape, the lid would be able to fall through. A circle is the only shape with a diameter that never changes within itself

Answer 9

To give you a logical answer to this is that it is easer to go down a round manhole.
the other one is that if it is a square it has angles and can hurt someone going in or out of it,
The round shape makes it easer to slide in and out as well.
hope I have convinced you on this.

Answer 10

Its the only shape that cant fall into the hole its covering