EMD SD-series frame reference

For those who want to know which frames EMD locomotives were built on, here's a list:

SD7, SD9, SD18, SD24- built on SD7 frame

SD28 (rare) and SD35- built on SD35 frame

SDP35- built on SD35 frame

SD40X (also SD35X)- built on SD35 frame

SD40A (IC only)- built on SDP45 frame, for extra fuel capacity

SDP40- built on SD45 frame

SDP45- built on its own frame

SD38, SD39, SD40, SD45- all built on the SD45 frame

SD38-2, SD40-2, SD45-2- all built on the SD45-2 frame, later called the SD40-2 frame

SD40T-2 and SD45T-2- built on SDP45 frame

SD40X- (prototype SD50's)- built on SD40-2 frames

SD50S (small production also)- built on SD40-2 frames

SD50- SD50 frame debuted here, later shared with the SD60.

*SD50F- built on SD50 frame?

SD60- built on SD50 frame

*SD60F- also built on SD50 frame?

*SD60M and SD60I

*SD70

*SD70MAC, SD70M, SD70I, SD75I

*SD80MAC and SD90MAC

*SD70ACE

*SD70M-2


*needs clarification

Are you stating all these family grouping share the same size wheelbase?

No, I just happened to be bored and was curious about what frames a certain 6-axle EMD shares with.

Sorry, I can't help with any of the points you wanted clarification on. (Nor can I contribute anything about possible detail design changes that might distinguish between the frames of models of the same length.)
Two corrections: the SDP40 was built (for GN and NdeM) on the SD40/SD45 frame, not on the longer SDP45 frame, and the SD45-T2 was built on the SDP45 frame (at least, had the same length as the SDP45) rather than on the slightly shorter SD40-2/SD45-2 frame.
One addition: the 4200hp SD45X had the same length as the SD45-T2 (and SDP45), and the same truck-center separation as the SD45-T2.
One question: can you use the same frame with HTC (Dash-2) and Flexicoil (earlier SD) trucks? In particular, did Conrail SD40-2 (with the older truck design) have the same wheelbase asother railroads'? I recall a report that the "SD40-3" rebuilt from an SD40 had some frame modifications-- maybe just to the stepwells, but I don't know-- to accommodate the HTS trucks it was given.

The HTC truck is longer than the Flexicoil, so the -2 locos had a longer frame, hence the even larger porches on a SD38-2 or SD40-2. The Conrail SD40-2's with the Flexicoil have a pretty good gap between the fuel tank ends and the truck frames. The only 40's I've seen with a bigger gap is the former Milwaukee Road units with the extremly small fuel tanks. Some of those are on the DM&E now. I "think" swapping HTC's onto a straight 40 loco would be impossible, or at least not very practical.

SDP35- built on it's own frame

No, the SDP35 was built on the same frame as the SD35. EMD moved the radiators closer to the dynamic brake blister.

Stuart

edited

I can help with some clarification.

The groupings of units on the same frame generally do share the same length and wheelbase, and often the same trucks. Lengths below are coupler-to-coupler distances, which is a fairly good indication that other frame dimensions are the same (there are exceptions).

SD7 through SDP35 and early SD40X are 60 ft 8 in (or 8 1/2 in). The frame thickness and shape are different between the SD7/9/18/24 and SD35 et al.

SD38 through SD45 are 65 ft 9 1/2 in.

SD38-2 through SD45-2, SD40X and SD50S are 68 ft 10 in. This includes Conrail's SD40-2's with Flexicoil trucks and CP's "Draper Taper" SD40-2F's.

SD40A, SDP45 and Tunnel Motors are 70 ft 8 in.

SD50, SD50F, SD60, SD60F, SD60M and SD60I are 71 ft 2 in.

SD70, SD70M, SD70I, SD75M and SD75I are 72 ft 4 in. As with the SD50-60 series, differences between all these units are minor and do not involve the frame.

SD70MAC is 74 ft.

SD80MAC and SD90MAC are 80 ft 2 in, with a thicker frame resulting in higher walkways than the SD70 series (about a 3-inch difference). From the SD35 to the SD70 series, there were also increases in frame thickness, but a bit smaller.

SD70ACe and SD70M-2 are on an SD70MAC frame that's thickened to be like the SD80MAC and SD90MAC.

(I found it interesting that the increases in frame thickness, while incremental, would make the walkway of an SD90MAC almost 10 inches higher than that of an early Geep.)

The similarity between frames having shared dimensions across a family of locomotive designs provides some manufacturing economy through standardization of certain components. However the selection of engine between twelve, sixteen and twenty cylinder models requires different provisions to support the machinery and changes the location of piping connections, electrical conduit runs, drains, etc. The engine selection also alters the weight distribution on the platform, and the design and thickness of some of the frame components are sometimes altered to compensate.

UPDATE: I was looking at Wikipedia a few days ago, and found out the SD28 and SD35 were built on the same frame of the SD7-SD9-SD18-SD24.

Don't believe everything you read in Wikipedia, Chris.

I know, I was like "huh?" Didn't the SD7-9-18-24 frame ride lower than the SD35 frame?

There are many design and structural differences between the SD35 type frame and the earlier SD's. For one, the earlier locomotives use two traction motor blowers and the air delivery ducts are at each end of the locomotive adjacent to the trucks, in the later SD's there is a central air compartment and the air delivery ducts originate from one blower mounted by the auxiliary generator and go forward and aft from that point to the trucks.

Don't believe everything you read in Wikipedia.

The assumption made in Wikipedia is that the same overall length means the same frame. The SD7-SD24 frame is thicker than the SD35 frame--in fact, the early SD's have a higher walkway height than 40- and 45-series units. The SD35 frame, aside from being thinner, also has a slight fishbelly in the middle, which was not present on the SD7-SD24.

While on the subject of SD35's, are the former NW ones now on MRL rebuilt with 16 cylinder 645's?