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In addition to Dennis' thorough answer, here are some thoughts from BRHS meet history, courtesy of Grant Aerosmith and Bob Landregen at a lunch where I was the privileged fly-on-the-wall listener. According to Grant, EMD tried to sell the Q on the idea that a GP7 would be able to replace the S1 and S2 Pacifics based on horsepower. As Grant, working for Henry Urhbach in the Mechanical Department at that time, pointed out to EMD boss Kettering and his engineers, Dynamometer car readings showed that when accelerating away from a station stop, a banked fire with a rapid introduction of forced air created a short-term output of over 2100 horse-power from one of those S-class engines. (Essentially a controlled boiler explosion) . This allowed acceleration that a GP7 could never achieve. It was also performance that the E5 and E7 units on the roster could not achieve as their control systems could not transition quickly enough from a station stop to maintain a Dinky's schedule. This operating requirement kept the Pacifics employed until the delivery of the E8 units which addressed the short comings of the earlier units with increased horsepower and a much improved electrical system. Thought you might enjoy that. Jim Sandrin
according to Grant __._,_.___ Posted by: jamessandrin@yahoo.com __,_._,___ |