EMD frame length question

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EMD frame length question

Postby trainiac » Sun Feb 24, 2013 10:58 pm

This is a very nit-picky question, but here goes...

I'm having trouble establishing frame lengths for several SD series units, despite ample published information - and it's wreaking havoc on my attempts to make correct drawings.

Here's what I know: The SD40-45 series (and related models) are commonly listed with two overall lengths - 65' 8" or 65' 9.5". This is because they were built with two types of end sheet - one 0.75" thick, the other 1.5" thick - and the thicker end sheet merely extended from the end of the frame rails, pushing the entire pilot and coupler out by 0.75" at each end, with no apparent change to the rest of the frame. EMD mechanical drawings I've seen appear to confirm this. Likewise, the SDP45 (built with thin end plates) is listed as 70' 8", which coincides with the 5' increase in truck centers over the SD45; the thick end plates would presumably have made it 70' 9.5".

Here's the catch: the SD40-2 was also built with both end sheet thicknesses - mostly thick - but the only published length is 68' 10", or 64' 8" over end sheets. Don Strack's SD40-2 measurements (all units with the thick end sheet) actually put the SD40-2 at 68' 11.25" - close enough to a 1.5" increase over the nominal length, like the SD40. By this logic (and based on the SDP45 length), the tunnel motor measurements should be 70' 9.5" - except they aren't: They all hover around 70' 8".

What are the actual lengths? Since the thicker end sheet appears to be the standard starting with the Dash-2 series, do the published measurements account for it? By that reasoning, an SD40-2 with thin end sheets would be 68' 8.5". Or are all the nominal lengths based on the thinner end sheets and most units after the SD40-2 are actually 1.5" longer than indicated?

...Or am I being too picky, and there's actually too much "slop" in the prototype dimensions to narrow it down that much?
--Michael Eby
--http://trainiax.net
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