[Beowulf] Re: HVAC and room cooling... wires

Robert G. Brown rgb at phy.duke.edu
Mon Feb 9 13:13:16 EST 2004


On Sun, 8 Feb 2004, Joel Jaeggli wrote:

> On Sun, 8 Feb 2004, Robert G. Brown wrote:
> 
> > On Sat, 7 Feb 2004, Gerry Creager N5JXS wrote:
> > 
> > > Should we mention the problems in household wiring caused by use of 
> > > aluminum wiring, then using breakers, outlets and fixtures designed for 
> > > copper?  I almost lost a house in Houston to that once.  I spent the 8 
> > > hours after the fire department left retightening all the connections 
> > > throughout.
> > 
> > I seem to remember the government finding out about aluminum the hard
> > way with some of their armored fighting vehicles a decade or two ago.
> > When struck with a hot enough round, the armor itself just burned right
> > up.
> 
> armor is supposed to burn. several armor desgins including that of the 

"supposed to burn"?  Where to "burn" is to release additional heat
energy into an already hot environment in a self-sustaining way?  Ouch.

Supposed to ablate and dissipate energy (hopefully in non-destructive
ways on the outside of the vehicle) sure, but naive aluminum designs can
be deadly and at various points in the past have been seriously
mistrusted by the military personnel supposedly being protected.  See
e.g.

  http://www.g2mil.com/aluminum.htm

where they recall the early bradley flaws, and argue that the HMS
Sheffield (sunk by a single exocet missle in the falklands war) went
down in large measure because it was an aluminum ship, where steel ships
have been hit by more than one exocet and survived.  The site also
presents a counterpoint that argues that aluminum isn't THAT bad a
choice (as near as I can make out) provided that all one wishes to stop
is "small arms fire".  It very quickly loses out to steel, though, in a
variety of measures when faced with RPG's or things that actually cause
fires, as it is a good conductor of heat and quickly spreads a fire and
structurally collapses at a relatively low temperature.  The aluminum
Bradley did tolerably in the first gulf war, losing only 3 to enemy fire
(compared to 17 lost to friendly fire from Abrams tanks) but it does
have provisions for additional armor plates of steel to be added on
outside and I imagine that it used them.  Most of what it faced in the
gulf war OTHER than our Abrams was its forte -- small arms fire.

   rgb

Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu



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