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>Speed is all about horsepower.  I'm not enough into Diseasels to know how much HP an SD 70 has, but I think its around 4000.  Three SD 70s would have about twice the HP of an A.  No contest!

   
  There's plenty of contest here.  
   
  Unlike a diesel-electric, whose ability to haul "X" amount of tonage decreases as they go faster steamers don't have that problem.  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.  On curvy right-of-way and on lines with heavy grades, diesels loose their ability to keep a train going at higher speeds, except that they pile on more diesels.  The H.P. of a diesel is less effective at faster speeds because more electricity is needed to keep the traction motors spinning at the higher speeds.  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  
   
  Steam on the other hand maintains their tractive effort through out their speed range.  As long as there's sufficient steam presssure a steamer can pull the same load at 60 m.p.h. as it did when it was at 10 m.p.h.
   
  Back when the American Freedom Train was operating through the southeast Southern Railway ran some tests on the Southern Pacific GS4 4-8-4.  Those tests, which were conducted in one of Southern's research cars (which were able to act as dynomometer cars as well as testing the track) showed that at passenger speeds the GS4 operated at the equivalent of 2½ EMD E8As... 5625 H.P. at speeds that diesels of that horsepower total could not attain on the Atlanta - Washington mainline.
   
  Back when there was a lot of hipe (but little action) on the American Coal Enterprises 4-8-4 3000, a diesel cowled body on a 3000 HP steam locomotive frame and tender, the unit was predicted to be able to replace a GP40 one-to-one.  The bad part was, despite efforts to garner support for such, aside from some promotional tours using restored steam locomotives there was little actually done to get the steamer built.  If the technology of that time had been put forward to something like a 2-6-6-4, it is difficult to say just how powerful the steamer (or would it be a "unit") would have been.  The url below will tell you more about what was purposed...
  http://www.trainweb.org/tusp/ult.html
   
  Probably the biggest drawback to the idea of modern day steam would be the fact that except really big money were to be put behind such a project it likely would never even get beyond the planning stage, largely because of diesel's dominance in the field.  And then you would have to look at the idea of emissions, which would really hit any coal-fired locomotive hard.  But advancements there in the industrial fields likely would lessen the enviromental impact.
   
  Building modern steam.  Its well within reason and lines that haul amounts of coal ought to look at it.  Whether the visionaries that lead the various Class Ones can see beyond their really big pay check is hard to say, but maybe it could happen...  just maybe...


        jerry 
<jmlaboda2 at yahoo.com>

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