Guest Posted February 12, 2008 Report Share Posted February 12, 2008 Snowman..the triangular shaped ones aren't manholes... Link to comment Share on other sites More sharing options...
Guest Posted February 16, 2008 Report Share Posted February 16, 2008 But what about a semi-circle? A shape that will not fall through the shape of the hole... ummm, if you turn it with the flat edge verticle, it will fit through a lot of places in the hole. Link to comment Share on other sites More sharing options...
Guest Posted February 21, 2008 Report Share Posted February 21, 2008 (edited) You can drop a manhole cover through a manhole if they are both equilateral triangles and the cover is less than about 1.155 (sqrt(4/3)) times the size of the hole. That's adding about a sixth of the length as lip, which is fairly substantial. This can happen because the "height" (distance from one vertex to the center of the opposite side) is smaller than the side (specifically sqrt(3/4) of the side) -- so there is room. You really do need a constant diameter shape or you can line up the maximum diameter of the hole with the minimum diameter of the cover and drop it in. Of course, you could use a large lip, but that is wasteful. Edited February 21, 2008 by Topher Link to comment Share on other sites More sharing options...
Guest Posted March 18, 2008 Report Share Posted March 18, 2008 We can thank Microsoft for the popularity of this question. This is a standard interview question now. There are many answers. Shape to not fall in: this is an OK answer, but really, all they need to do is put flanges or a rim on the inside of the hole and any shape would be fine. Shape for "rolling": this is a better answer, but then again, the cover must be transported to its destination. Regardless of the form of transport, it has to be removed and put on the ground. To remove it from the vehicle is going to require either: a person lifting it (all the problems associated with moving it into place) or a mechanical system to unload it, which could then reasonably be designed to unload it directly into place. Maximum area for entry/exit: I kind of like this one, since it is undeniable and applies to the hole itself as well. Link to comment Share on other sites More sharing options...
Guest Posted March 19, 2008 Report Share Posted March 19, 2008 whats a manhole?? Link to comment Share on other sites More sharing options...
Guest Posted April 9, 2008 Report Share Posted April 9, 2008 a round cover can never fall in. Link to comment Share on other sites More sharing options...
Guest Posted April 10, 2008 Report Share Posted April 10, 2008 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. Link to comment Share on other sites More sharing options...
Guest Posted April 10, 2008 Report Share Posted April 10, 2008 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. Link to comment Share on other sites More sharing options...
Guest Posted April 10, 2008 Report Share Posted April 10, 2008 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. Link to comment Share on other sites More sharing options...
Guest Posted April 11, 2008 Report Share Posted April 11, 2008 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 Link to comment Share on other sites More sharing options...
Guest Posted April 22, 2008 Report Share Posted April 22, 2008 The obvious answer is that manhole covers should be round because manholes are round. But your answer is more informative. I agree. Link to comment Share on other sites More sharing options...
Guest Posted April 23, 2008 Report Share Posted April 23, 2008 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. Link to comment Share on other sites More sharing options...
Guest Posted May 15, 2008 Report Share Posted May 15, 2008 if they were square they would fall down into the hole, also, so they can roll them since they are heavy. Link to comment Share on other sites More sharing options...
Guest Posted September 25, 2008 Report Share Posted September 25, 2008 dudes ... you guys are like having a smarticles fight... freaky.PINK! Link to comment Share on other sites More sharing options...
Guest Posted October 21, 2008 Report Share Posted October 21, 2008 I thought becauz men weren't square Link to comment Share on other sites More sharing options...
Guest Posted November 3, 2008 Report Share Posted November 3, 2008 The obvious answer is that manhole covers should be round because manholes are round. But your answer is more informative. that was my first thought.."so that they fit" lol Link to comment Share on other sites More sharing options...
Jiminy Cricket Posted November 19, 2008 Report Share Posted November 19, 2008 Veracity, the veracity of your statement is suspect: "There is not a single shape (besides perfectly round) that could not be positioned in a way that would cause it to fall in the hole." , You couldn't be more wrong! heard of "constant diameter curves" ? A circle is just one of many such curves: read This and This That said, you are bang on target with your second statement about the ease of rolling R Reuleaux triangle FTW!!! Thank you! Like Veracity, I also enjoy learning new things. Link to comment Share on other sites More sharing options...
Recommended Posts