I've been building a model of a 35 ton narrow gauge diesel loco manufactured by Atlas, so I've looked at every prototype photo of an Atlas diesel that I could find--and they all look pretty much the same. I began to wonder why that was, how the 35 ton narrow gauge loco looks almost identical to the 50 and 65 ton standard gauge locos, even though they are so much heavier. Where is all that weight? I'm beginning to think the weight must be in the frame and below it in the form of concrete?
I see the same thing with GE--the 44 and 45 tonners look the same as the 70 ton loco.
Ballasting (for more traction) in the frame. Have to keep the loco light enough for rail size (weight per yard) and roadbed, yet get as much traction as possible.
The reason that 45 tons seems to be a ''magic'' number is that the BofLE (Brotherhood of Locomotive Engineers) allowed in some contract negations
that a "fireman" was not required on locos 45 ton or under.
____________________ Fix it again, Mr Gates--it still works!"
Thanks for confirming my suspicions. For modeling purposes, the depth of the frame side sills, possibly along with the type of truck used, seems to be all that needs to vary. Even though it was constructed in 1938, the 35 ton loco I'm modeling actually used arch bar trucks (no, it was not used in interchange service). An almost identical loco of much lighter weight shows much thinner side sills.