Re: Rotary SG Safety

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: FIFTYGUY-at-aol-dot-com 

In a message dated 6/17/04 11:49:17 AM Eastern Daylight Time,
tesla-at-pupman-dot-com writes:

 > More interesting is that the Lexan broke a couple inches
 >  away from where the bullet hit - we conjecture due to the shock wave
 >  travelling in the plastic.
 >
 >  Maybe at high spped, the rotary parts created a shock wave when they hit
 >  the shield?

     High explosives will shatter Lexan into little tiny pieces as if it were
tempered glass. Chalk that up to shock (brisance).
     FWIW, it's easier to use Lexan to stop a .38 slug than a .22 of the same
construction and velocity. Although the .38 has more mass, therefore more
energy and momentum, this is negated by its larger cross-section. Sectional
density is about the same, but the impact area makes a difference.
     From this, I'd postulate that brass acorn nuts, which are much less
deformable than lead and have six or so mild corners, might impact in such 
a way to
concentrate that force into a small area.
     OTOH:
     I don't have any brass acorn nuts to weigh, but I'm estimating one would
have near the mass of a .22 LR bullet. If it's a 6" rotor at about 8000 rpm,
that gives the brass nut a linear velocity of over 200 feet per second. Which
works out to a measly 3-4 ft-lbs (4-5 Joules ;) ) of energy - more like a BB
gun than a .22.
     Has anyone noticed bad effects from UV to the plastics used in coiling?
Granted that the total exposure times are small, but at a RSG I bet the
intensity makes up for it. With all the UV, vibration, electrical stresses, 
and
ozone, are the plastics weakening? Especially with non-UV-stabilized/coated 
types?

-Phil LaBudde