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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

Hood

Underframe and walkway

Phases

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.

Phase 1a1 1a2 1b1 1b2 1c1 1c2 2a1 2a2 2a3 2a4 2b1 2b2 2c1 2c2 2d1 2d2 3
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
Phase 1a1 1a2 1b1 1b2 1c1 1c2 2a1 2a2 2a3 2a4 2b1 2b2 2c1 2c2 2d1 2d2 3
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 (Electrical cabinet air filter box, located on the left behind the 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)
Phase 1a1 1a2 1b1 1b2 1c1 1c2 2a1 2a2 2a3 2a4 2b1 2b2 2c1 2c2 2d1 2d2 3
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"
Phase 1a1 1a2 1b1 1b2 1c1 1c2 2a1 2a2 2a3 2a4 2b1 2b2 2c1 2c2 2d1 2d2 3

Notes

  1. Short hood, Phase 2a1: Same as Phase 2a2 except circular vent mounted lower
  2. Angled stepwell plates appeared on BO Phase 2a1 units

Other details

References

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

 Copyright © Michael Eby - Page code last updated 2017-09-25