41 replies to this topic

[thermalguru65]

a round cover can never fall in.

[Bambi Lynn]

You guys!!! Any hole, whether round, square, triangular or whatever will allow the piece cut out of it to fall through, UNLESS there is a flange added at the bottom of the hole to keep the cover from falling in. Can't see where math in any form is usable here.

[Alchameth]

Aside from the obvious 2 reasons listed safety and move ability you have to consider a few other reasons...

Weight distribution over a round hole is more constant where as anything with a corner would have pressure points and be overall weaker.

Materials, it is the most efficient use of materials for the shape and purpose compared to other shapes. Larger area with less materials.

Putting back and removing it, a circle doesn't care how you put it in, you would have to line up corners with other shapes, and if you were under a manhole you can push it up from any side vs. a cornered geometric shape having to make sure you "hinged" it on a flat side.

[Duh Puck]

Any hole, whether round, square, triangular or whatever will allow the piece cut out of it to fall through, UNLESS there is a flange added at the bottom of the hole to keep the cover from falling in. Can't see where math in any form is usable here.

That's true, but even with the flange, shapes other than constant-width-diameter curves will still be able to fall through the hole. You have to assume that the maximum diameter of the cover includes the difference due to the flange, and the maximum diameter of the hole does not. Let's say it's a difference of 1 inch, and you have a square manhole cover 24 inches in width (and thus a hole 22 inches width). That still leaves you with a diagonal opening of over 31 inches, so flange or not, the square cover can easily fall through the hole. The "math" angle of the discussion is quite relevant.

[Lost in space]

can we do the bit about the whole truth, or the more you take away from it the bigger it gets, or pi, or can we say the gist of this is 'covered'
no more holes pls

[That one girl...]

The obvious answer is that manhole covers should be round because manholes are round.

But your answer is more informative.

I agree.

[Chuck Rampart]

Materials, it is the most efficient use of materials for the shape and purpose compared to other shapes. Larger area with less materials.

This really depends on what is going up and down the hole. If you're transporting boxes that are cube shaped, then of course it is most efficient to use a hole square in cross section. If you're moving spheres, then obviously the circular hole is the way to go. If you're moving something that is well approximated by a line of diameter as it passes through the hole - panes of glass, for instance, slid through vertically - then the most efficient shape is a Reuleaux Triangle . This shape has a constant diameter, so the pane of glass can be rotated (and the cover won't fall through) with the best ratio of diameter to area. This allows the least amount of material removal in digging the hole for a given size of glass.

For the other reasons mentioned, though, as well as the fact that a wide variety of people and loads probably need to go down manholes, a circle is the best option.

[rockinsteady]

if they were square they would fall down into the hole, also, so they can roll them since they are heavy.

[kaleni-san]

dudes ... you guys are like having a smarticles fight... freaky.PINK!

[Claea]

I thought becauz men weren't square