steam loco question

[nw-mailing-list at nwhs.org]

How was all of this effected by superelevation of the track?
  I have never totally understood why they used it but it sounds like it would enhance the effect of the conical wheels.  
  Thanks,
  Jim Hall

nw-mailing-list at nwhs.org wrote:
        I won't repeat the answers given so far, which are all correct and well explained, but there's two more factors, as it's been explained to me over the years (I'm an old electron pusher, so I take these things on faith): were not most steam locomotives built with a certain amount of lateral motion allowed in the journal boxes?  Even thought the frame and bearings would hold the driving axles parallel, the ability to shift laterally slightly would also help.  Secondly, while in the ideal case the conicity of the wheel sets would eliminate or minimize flange contact, in the real world there is flange contact.  As long as the angle of attack of the flange is small and the shape of the flange is correct, the wheel will not climb, but rather the flange will keep the wheel in place.  The geometry of the flange and rail head result in a measure called the "L/V" ratio, the ratio of the lateral force (which tends to cause flange climb) to the vertical force (which keeps the
 wheel in place).  I have read what a desired limit of the L/V ratio is but I confess I didn't commit it to memory. 
   
  Dave Phelps
   
  In a message dated 6/27/2006 9:16:08 P.M. Eastern     
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