steam loco question

[nw-mailing-list at nwhs.org]

Superelevation counteracts the centrifugal force created by  going around a 
curve.
 
Dave Phelps
 
In a message dated 6/28/2006 9:05:18 P.M. Eastern Daylight Time,  
nw-mailing-list at nwhs.org writes:

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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