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Seems to me that tonnage on up-grade would dictate head-in horsepower,steam or diesel. There is always a weak point,(drawbar, coupler pins,adheason etc) that was and is the reason for pushers, otherwise the Alleghanys, As, Y6s could have worked uphill alone ! Ron H.

NW Mailing List <nw-mailing-list at nwhs.org> wrote:          "There's plenty of contest here....
  ... If you were to look at a traction effort curve for a diesel you would see that at very low speed they can pull a great amount of tonage but as speed increases they loose that ability, with the curve dropping way down.
  ...This is why there are many a photo of trains from out west that have five, six and seven locomotives on the point, so that they can maintain the higher speeds. "
   
  Jerry,
      While there is no denying that there are many photos of many trains from many areas of the country with many units on the head end, I don't think that you can carte blanche say that in each photo all of the units were "on line" or being used. 
      RR's have operating rules that limit the number of axles that can be used in power and dynamic brake. Do we really know how many units in those photos are on line? Do we know what the RR's rules say for number of unnits that can be on line? Have you ever actually been on a set of diesels to have any idea what they can pull at any speed and under any condition?
      Sorry, I don't buy into this arguement 100%. There are too many variables at large to be making such blanket statements. 
   
  Jimmy Lisle
   
   
   
   
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