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Article #2497Re: Manhole covers - why circular?
From: Tom Tkacik
Date: Tue, 05 Jan 1993 20:51
Date: Tue, 05 Jan 1993 20:51
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1285 bytes
In article 93Jan5134917@kariba.bbn.com, nichael@bbn.com (Nichael Cramer writes: > robertw@informix.com (Robert Weinberg) writes: > > Manhole covers are manufactured in circular shape, rather than oval or square, to > satisfy one paramount condition. > What is the condition ... > > The cover can't fall down the hole. > > ... and why does a circular shape satisfy it? > What other shapes would also satisfy the condition? > > Given the above, for any fully convex shape, I don't _think_ there are > any others. A circle is not the only constant diameter closed shape. An equalateral triangle with arcs on each side (whose center is the opposite vertex, also has a constant diameter. To see what this looks like, check out a rotor in a wankel engine. It has this shape. Tom Tkacik GM Research Labs tkacik@hobbes.cs.gmr.com tkacik@kyzyl.mi.org
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Path: arc1-ca.pugleaf.net!sparky!uunet!caen!rphroy!hobbes!tkacik From: tkacik@hobbes.hobbes.cs.gmr.com (Tom Tkacik) Newsgroups: rec.puzzles Subject: Re: Manhole covers - why circular? Message-ID: <96003@rphroy.ph.gmr.com> Date: 5 Jan 93 20:51:30 GMT Sender: news@rphroy.ph.gmr.com Reply-To: tkacik@hobbes.hobbes.cs.gmr.com Organization: GM Research Labs Lines: 27 Nntp-Posting-Host: hobbes.cs.gmr.com