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[quote]QUOTE: Originally posted by Overmod Note that there is a 'packaging' formula for most diesel-electric locomotives: pivoted trucks (or span-bolster assemblies) somewhere near the quarter points of the bed frame, engine in the middle of the span, large fuel tank suspended between frame and rails. The first thing that happens with an articulated locomotive is that you lose the cantilever benefits of pivots at the quarter points where the frame bears on the articulated truck. You also will probably have to have a specialized bolster with two separate pivot locations, appropriate seals or bulkheads at each end of the separate unit, more need to balance components between the units if they are not absolutely common to each "end", etc. (My understanding is that it is more difficult to accompli***raction-motor cooling in a C truck articulated this way, for a variety of reasons). I looked at articulated locomotives rather carefully in the early 1970s, and there are some other concerns. If you 'standardize' on a single design of carbody module for a given class of locomotive, you automatically have two cabs on the completed locomotive, or none if you go with boosters (which I have never particularly liked in high horsepowers) You have no capability of using the articulated underframes for other purposes -- not that you'd have much re-use for the single long bed frame either, but it's cheaper and gives a more rigid bed for the ancillaries. The weight-packaging problem is the real issue: it's almost impossible to get the weight properly balanced between the full truck on the end and the half-truck in the middle without cutting into allowable cab room, or increasing forward cantilever length (which has implications on tracking and equalization for the end trucks). My personal observation was that very careful extended side-bolster support for the middle truck was also necessary, but this might have been 'overkill' in design since my interest was in high-speed power at the time. [/quote] Overmod, I'd be interested in seeing a picture or drawing of an articulated locomotive if such exists. Regarding the use of standardized locomotive frames articulated together, it seems you are suggesting that to articulated two SD's together, you would practically have to cut each into a 3/4 length and articulated those together to retain the cantilever effect, except of course you are not cantilevering the articulated section. If I read you correctly, it is this cantilevering action that allows optimal adhesion of wheel to rail, and a true articulation e.g. two separate frames and carbodies wedded to a single center truck, would leave something lacking in that department.
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