OT:
- From: carlfogel@xxxxxxxxxxx
- Date: Fri, 20 Jul 2007 22:28:12 -0600
"Ingenium: Five Machines That Changed the World," Mark Denny
Physics of bows and arrows, waterwheels, windmills, medieval siege
machines, clock escapements, centrifugal governors, and so forth,
adapted from more detailed papers published individually.
Descriptions adapted to the meanest understandings (like mine),
meaning pictures and graphs explaining how a properly chosen arrow
curves around the bow when fired, without actually touching the bow,
and why anything simpler than a mangonel is too inefficient to be
worth the trouble.
(You _do_ know the difference between a mangonel and trebuchet, don't
you? If not, the pictures that explain the efficiency differences will
make things as clear as the difference between a highwheeler and
safety bicycle.)
Plenty of equations for posters like Joe Riel, should he develop an
interest in the efficiency of overshot waterwheels:
efficiency = (1 + sin theta) / ((2 + (v^2 / 2gR ))
Or in maximum arrow range X in average air, given Xo max range in
vacuum and a parameter k from a paper published by the Scott Polar
Research Institute of Cambridge University [1]:
X = Xo * ( 1 / ( 1 + (kv^2/mg) )^(3/4)
"After earning a Ph.D in theoretical physics from Edinburgh University
(Scotland), Mark Denny pursued research at Oxford University [2] from
1981 to 1984, then moved into a career in industry. For nearly 20
years he developed radar and sonar systems for several multi-national
aerospace corporations. He is now retired and lives on Vancouver
Island."
[1] There are also pleasant footnotes, such as the one pointing out
how odd it is for an Antarctic research institute to publish research
on medieval archery.
[2] That's in (England), though the dustcover doesn't think the
explanation is as necessary as (Scotland).
Cheers,
Carl Fogel
.
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