On Friday, February 13, 2015 at 2:56:43 PM UTC-6, hanc...@bbs.cpcn.com wrote:   
   > On Thursday, February 12, 2015 at 1:02:46 PM UTC-5, peterw...@hotmail.com   
   wrote:   
   >    
   > > 1. In designing the iconic FT freight locomotive and E series passenger   
   locomotives, Electromotive put a hood-like structure on the front specifically   
   to give some protection to the engineer and fireman in the event of a   
   collision at a grade crossing,   
    and virtually all subsequent American locomotives have continued this   
   practice. Is there any requirement for grade-crossing protection on   
   self-propelled motor unit passenger cars?   
   >    
   > Yes, extensive high-strength protection against collisions.   
   >    
   >    
   > > 2. In the accounts I've read, the lead unit on the Metro North train was   
   set on fire by gasoline from the fuel tank of the Mercedes Benz SUV. Barring   
   the few battery powered cars in service, every vehicle hit at a grade crossing   
   has a fuel tank; in    
   the case of a semi truck there might be as much as three hundred gallons of   
   diesel oil onboard. Does the design of a locomotive or motor unit incorporate   
   any protection from this?   
   >    
   > Short of hitting a fuel truck, this kind of fire is unusual in grade   
   crossing accidents.  Usually the vehicle is just crushed or pushed aside and   
   does not catch fire.   
   >    
   >    
   >    
   > > With modern welded rail track, broken rails are a known and feared failure   
   mode.    
   >    
   > They are?  I thought welded rail reduced the incidence of broken rails.   
   >    
   > Also, I don't believe third rail is welded, plus it is very rare for it to   
   break.   
   >    
   > In any event, a broken rail would disrupt the signal current, causing the   
   block to go red.   
      
   Welded rail is laid down in the warmer part of the year and, when it gets   
   colder, it is prevented from contracting thermally by a system of rail anchors   
   clipped to the bottom flange of the rail and bearing against the ties. In   
   winter, rail can be in a    
   state of tensile stress of several tens of thousands pounds per square inch.   
   In normal use rail is subject to cycles of stress as trains move along it, and   
   the resulting metal fatigue can result in cracking. If a crack reaches   
   so-called "Griffith length"    
   when the rail is in tension the crack becomes self propagating and spreads   
   through the remaining depth of the rail in a fraction of a second, leaving a   
   dangerous gap in the broken rail. Railroads employ a variety of magnetic and   
   ultrasonic scanning    
   machines to detect cracks before they reach Griffith length. If cracks are   
   found, they are removed by grinding or milling down the upper bearing surface   
   of the rail, which also serves to restore its correct profile. I believe that   
   at least occasionally    
   rolling stock has been impaled by the broken end of a rail.   
      
   Peter Wezeman   
   anti-social Darwinist       
      
   --- SoupGate/W32 v1.03   
    * Origin: LiveWire BBS -=*=- UseNet FTN Gateway (1:2320/1)