Locomotive Phases - EMD SD38-2, SD40-2, SD45-2
The SD38-2, SD40-2 and SD45-2 were introduced in 1972 as replacements for the SD38, SD40 and SD45 respectively. They retained the same respective horsepower ratings but received a host of mechanical and electrical upgrades, with the most visible difference being the longer frame with HT-C trucks. While the SD38-2 and SD45-2 were relatively slow sellers and ceased production in the 1970s, thousands of SD40-2 variations were built as it became the most popular locomotive of the late 20th Century, with peak production in the late 1970s and the last variant (the full-cowl SD40-2F) built in 1988.
The SD38-2 and SD40-2 were very similar externally, with the relatively long frame and short hood resulting in large "porches" at either end. The SD38-2 had two radiator fans and two exhaust stacks, while the SD40-2 had three radiator fans and a single turbocharger exhaust stack (changed to a flat silencer housing on later units). The SD45-2 had a single exhaust stack and three radiator fans spread out over a distinctively longer hood that filled the extra frame length. "Tunnel motor" variants, the SD40T-2 and SD45T-2, rode on a still longer frame and had a redesigned radiator area with low air intakes, internal fans and roof-mounted radiator grills. Wide-nose units built for CN were otherwise similar to other SD40-2's, but the full-cowl SD40-2F built for CP was in fact closely derived from the SD50F built for CN, and its carbody and general construction had little in common with other SD40-2's.
Transition: From late SD38/SD40/SD45 to early Dash-2 series
On all six-axle Dash-2 units, the frame was lengthened by just over 3' to accommodate the longer HT-C trucks while keeping enough room for the standard 4000-gallon fuel tank. Depending on the thickness of the pilot end plates (0.75" or 1.5") the overall length was either 68' 8.5" or 68' 10", compared to 65' 8" or 65' 9.5" for the SD38/SD40/SD45. The SD40T-2 and SD45T-2 were built to an overall length of 70' 8" with 1.5" end plates.
The HT-C truck looked superficially similar to the earlier Flexicoil, but it was in fact a substantially different design, with an all-new frame casting, taller primary springs, stiffer rubber pads for the secondary suspension, slightly unequal axle spacing, and all traction motors facing the same direction (the reason for the added length). The wheelbase between the center axles, often mistakenly cited as 43' 6", was in fact 43' 3.5"; the 43' 6" dimension was for the bolster centers, as the bolster on HT-C trucks was offset outward by 1.25" from the center axle.
The longer frame was retained on Conrail units that were built with Flexicoil trucks, leaving a large gap between the trucks and fuel tank. Railroad diagrams list the bolster centers on Flexicoil-equipped units as 43' 6", but as the Flexicoil bolster lined up with the middle axle, such a dimension would put the trucks too far toward the ends and possibly cause clearance issues with the steps and draft gear. I haven't confirmed the dimensions, but from photos it appears that the Flexicoil trucks were located the same distance from the end plates as on the earlier SD40, which would give truck centers of 43' 0.5".
On all six-axle Dash-2 units, the front section of the hood (housing the inertial air intakes and blower duct) was lengthened by roughly 8". On the SD38-2 and SD40-2, this added length was not enough to compensate for the increased frame length, and the result was significantly larger platforms at either end - with the rearmost wheel entirely out from under the end of the hood. On the SD45-2, however, the rear of the hood was also lengthened to fill up the extra frame length, and the added space was used to house longer, narrower radiators that did not require the canted intakes used on the SD45. The longer radiators resulted in three very widely spaced rooftop radiator fans.
Many evolutionary changes were shared across all of EMD Dash-2 production, resulting in Dash-2 units sharing very few body panels with previous models. Compared to previous SD units, the following changes were evident at the start of Dash-2 production:
Cab and cab sub-base
- Battery box covers bolted rather than hinged
- Left-side battery box cover lengthened rearward
- Right-side battery box cover lengthened forward
- Left front handrail stanchion moved rearward
- Right front handrail stanchion moved forward
- Riveted, rectangular cab side panel around side windows
- Rear cab roof overhang
- Larger electrical cabinet air filter box
- Larger handbrake notch in nose
- Modified central air intake and blower duct
- Longer front hood section (creating a larger gap between the blower duct and cab)
- Oblong water-level sight glass on the right rear side of the hood
- Rear hood doors grouped 2-2-2-1 (SD38-2, SD40-2) or 2-2-2-2-2 (SD45-2), instead of 1-2-4 (SD38-SD40) or 1-2-2-2-1 (SD45)
- Longer, flush (rather than canted) rear radiator intakes, with larger fan spacing (SD45-2 only)
- Circular access hatches added at the top corners of the long hood end
Underframe and walkway
- HT-C trucks
- Frame lengthened by 3', resulting in:
- One (SD38-2, SD40-2) or two (SD45-2) additional handrail stanchions per side
- Revised underframe pipe and cable routing
- Longer walkway blower duct
- Fuel tank flush with bottom frame rail (rather than mounted approx. 2" below the frame)
These phases are based on the SD40-2 phases by Scott Chatfield, with added details based on my own observations and on the phase details described in the GP40-2 roster compiled by Robert Sarberenyi. I have also added a number of sub-phases based on an excellent SD40-2 roster compiled by Brian Bennett.
These phases do not apply to Canadian (GMD) SD40-2 and SD40-2(W) production, which followed a different (though similar) sequence of detail changes. However, a few EMD SD40-2 orders (BN 7167-7205, 7206-7235 and 8074-8089) were built by GMD in Canada when EMD was at capacity. Unlike other GMD SD40-2's, they were built to BN specifications and were virtually identical to their US-built counterparts, except for having HT-C trucks cast by Dofasco instead of Rockwell.
|Inertial air intakes||Ridge added along top||Ridge added along bottom|
|Frame side sill||Narrow over air reservoirs||Engineer's side rear sill notch moved rearward when notched fuel cut-off housing present||Narrow over entire length|
|Pilots||Straight upper end plate corners, straight coupler cut levers||Notched upper end plate corners, raised coupler cut levers||Narrower anticlimbers|
|Battery box covers||Bolted, small louvres||Larger louvres||Horizontal rib added (bolted version only)||Latched, lift-off tabs|
|Radiators, fans||Square wire grid intakes; curved grabiron behind fans; flat-top radiator fans||Corrugated intakes||Angled grabiron behind fans (late Phase 2b1)||Q-type radiator fans|
|Hand brake||Ratchet||Wheel (some units retained ratchet)|
|Cab side||Riveted side panel with 11 rivets along top/bottom||Riveted side panel with 13 rivets along top/bottom||Welded side panel|
|Cab sub-base||Hinged sub-base doors||Sub-base doors with lift-off tabs|
|Short hood||81" standard length or 116" "snoot" with sloped section ahead of flat section near cab||(1)||88" standard length or 116"/123" "snoot" with constant slope on top; circular vent on engineer's side||Bolted hatch added on top|
|ECAFB||Separated from cab||Flush with cab (appeared on CNW Phase 1c2 units)|
|End handrails||Flush with pilots, inward-facing central handrail stanchion supports||Wrap around pilots slightly, outward-facing central handrail stanchion supports (appeared on CNW Phase 1c2 units)|
|Trucks, underframe||Revised center axle shock strut (inconsistent until Phase 2a3); deeper angled stepwell plates with narrower steps (2); revised fuel tank vent pipe||Revised air reservoir piping on conductor's side (appeared on some late Phase 2a4 units)|
|Jacking pads||Tall (no casting holes after late Phase 1a2)||Short|
|Dynamic brakes||Batten strip at rear of dynamic brake housing||No batten strip||Dynamic brake housing moved rearward|
|Exhaust||Raised exhaust stack||Silencer with opening at rear||Silencer with opening at front|
|Blower duct||Flat, wide, two ribs||Angled "laundry chute"|
- Short hood, Phase 2a1: Same as Phase 2a2 except circular vent mounted lower
- Angled stepwell plates appeared on BO Phase 2a1 units
- Some units prior to Phase 3 were built with battery box covers with latches and lift-of tabs.
- Various as-built pilot options: standard footboards (up to 1975), plow (various sizes), rock deflector (2 types), flat end plate
- There were two variations in step spacing, depending on railroad.
- An oblong cab vent appears on most units starting with Phase 2a (generally on the left side of the cab at the rear) along with a circular vent on the engineer's side of the short hood.
Biel, Charles. (2013). EMD SD40-2. Retrieved November 2014 from http://archive.trainpix.com/BN/EMDORIG/SD40-2/INDEX.HTM
CNRPhotos. (2006). Data Sheets - Motive Power. Retrieved January 2010 from http://www.cnrphotos.com/gallery2/main.php?g2_itemId=18406
Foster, Gerald. (1996). A Field Guide to Trains. New York, NY: Houghton Mifflin.
Sarberenyi, R. EMD's GP40-2 - Original Owners. Retrieved November 2014 from http://www.trainweb.org/jaydeet/gp40-2.htm
Southern Railway. (1980). Diesel Electric Locomotive Diagrams - 1980. Retrieved November 2014 from http://southernmodeler.info/SRdiagrams.htm
Unofficial EMD Homepage. (2005). SD40-2 Order Numbers. Retrieved November 2014 from http://www.trainweb.org/emdloco/sd40-2.htm