08-21-2009, 01:06 PM
The U.P. has always needed the biggest power they could get for places like Sherman Hill. I think they got the DD40x's before the advantages of multiple unit lash ups was really understood by the railroads, or at least the U.P. Historically the U.P. had always bought the biggest, most powerful locomotives available. The DD40x's prototype was the DD35x cabless booster of which there were 3 built all bought by the S.P. They were essentially 2 Gp35's on a single frame. I'm guessing that the D40 was 2 Gp40s on one frame, but I don't know for sure. Until the U.P. bought the S.P. their only access into the Los Angeles metropolitan area was by way of trackage rights on the Santa Fe's Cajon Pass route. Rail wags referred to the DD40s as "6000 hp track straighteners." I read somewhere that the Santa Fe told the U.P. not to bring the DD40s into Los Angeles over Cajon anymore, but I don't know if that is true or a legend. I think the reason that the U.P. decommissioned them in a relatively short time is because they discovered that being 2 locomotives on a common frame meant that if 1/2 of the unit was down, they lost the entire unit. 2 Gp40's or Sd40-2's would have the same hp and tractive effort as one DD40x, and if one failed, they still had the other unit to use in service. This is entirely conjecture on my part. In the age of steam, if you needed helper service to climb a hill, you had to have a separate engine crew for each locomotive. The railroads were limited to how big they could make a solid frame locomotive, so the only way they could make a locomotive bigger than a 2-12-4 was to articulate the frame to make things like Challengers and Big Boys. Since a "diesel" engine is actually an electric locomotive that carries it's own generating plant, they can be operated in multiple unit lash ups without extra crews just by plugging them in to each other. I suspect that when the U.P. ordered the DD40, the management was still thinking "steam" operations instead of realizing the practicalities of using diesels in m.u.