september.org> DAA1364F   
   From: rcp27g@gmail.com   
      
   Nobody  wrote:   
   >   
   > Thanks.  The Mellie isolation section makes sense, even to me!  It's   
   > interesting that the trams run with the panto elbow facing to the   
   > rear.   
      
   Not especially unusual. Most British EMU and locomotives only have one   
   pantograph for both directions. Where trains and locomotives have a choice   
   it is usual to use the rear one to reduce the risk of an accident with the   
   in-use one damaging the other one (in some classes such as the Swiss Re420   
   the elbows face outwards meaning normal operation is elbow trailing). For   
   multi-system locomotives there is little choice. In Europe there are four   
   options for pantograph a (two widths, and either a copper or carbon   
   surface) so a go-anywhere locomotive needs four, of which generally only   
   one will be in use at any time. The pantograph head generally wants to   
   above the bogie centre so the usual arrangement is two at each end, one   
   facing each way, with the heads inwards and elbows outwards. There are also   
   still a few older vehicles around with old style diamond pantographs.   
      
   Robin   
      
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