[sci.electronics] Round Manhole Covers

steves@tekgen.BV.TEK.COM (Steve Shellans) (07/22/88)

In article <1550@tekirl.TEK.COM> jackg@tekirl.TEK.COM (Jack Gjovaag) writes:
>In article <303@btree.uucp> rfarris@btree.UCSD.EDU (rick farris) writes:
>>
>>Yes, and why the heck are manholes round?
>
>Aha! I know the answer to this one, even though it has nothing to
>do with electronics.  Round is the only shape for the cover that
>guarantees that the cover can't fall into the hole.  What do I win?

You win a free plane geometry textbook.  Three-cusp hypocycloids have the
same property.  Although they are not round, they have a constant
diameter when measured at any angle of rotation.

Steve Shellans
Tektronix, Beaverton OR
tektronix!tekgen!steves