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Re: COLLISION 2: real-world data



Hi --

Several people have written to say that they don't buy my argument that a
rail car coupling must include a spring and a shock absorber. People seem
to assume that these are needless complications. They demand a simpler
description.

Please consider the following arguments:

Argument 1) Assertion: Any simpler description is unphysical. Trust
me. (Yeah, sure, that argument works every time :-)

Argument 2) Physics: There are compelling physical reasons why dissipation
is necessary and cannot be well approximated by a simple nondissipative
model. See previous notes for details.

Argument 3) Real-world data: If you won't accept the physics argument, how
about some engineering data? It appears that real-world rail cars obey the
laws of physics!

It was easy to predict that rail cars couplings *must* have devices
containing springs and shock absorbers, but until a moment ago I had no
idea what they looked like, how they worked, or what they were
called. Well, it took 5 minutes of AltaVista work to discover that they're
called draft gears. Specifications and nice cutaway drawings can be found at
http://www.cardwest.com/draftgears.html