by Allen Hazen
Prompted by the "Why wasn't the SD-45 as popular as the SD-40?" sting, I have been rereading Preston Cook's excellent three-part SD-45 article in the May, June and July issues of "Railfan and Railroad."
--First installment confirms that the 20-645 (in the 645F version) continued in production into the 1990s for marine and stationary applications.
--The second installment discusses the maintenance problems. Crankshaft bearings were apparently a sore point: addressed both by tightening tolerances in EMD's engine production and urging the railroads to sharpen up their maintenance practices. The biggy, though, was the fact that
"...the early crankcaes were also found to have a tendency to crack the welds which attached the crankshaft supporting "A-frames" to the crankcase lower stress sheets. ... The problem was ... occasionally encountered on 16-cylinder engines as well, but by far the highest incidence was on the No.10 and No. 11 A-frames in the 20-cylinder, the two bearing positions forward of the very large rear main bearing."
Cure: improved welding techniques, and, from 1972 on, "A-frames which had a considerably enlarged foot in the shape of a letter "D" set sideways."
--Third part has the intriguing tidbit (after a description of the SD-45X test units)
"A 4200-h.p. "SD55" was offered by EMD in 1972 but was not included in the Dash-2 catalogue, and none was ever sold."
Comment: Not in the catalogue, and Cook puts "SD55" in scare-quotes: so this probably shouldn't be considered am "official" model number. The 645E3A engine used on the SD45X (as opposed to plain 645E3 on normal SD45) did, however, have features (such as the "rocking-pin" bearing for the cylinder wrist pin) that were used on the 645F engines on the later 50-series.
--First installment confirms that the 20-645 (in the 645F version) continued in production into the 1990s for marine and stationary applications.
--The second installment discusses the maintenance problems. Crankshaft bearings were apparently a sore point: addressed both by tightening tolerances in EMD's engine production and urging the railroads to sharpen up their maintenance practices. The biggy, though, was the fact that
"...the early crankcaes were also found to have a tendency to crack the welds which attached the crankshaft supporting "A-frames" to the crankcase lower stress sheets. ... The problem was ... occasionally encountered on 16-cylinder engines as well, but by far the highest incidence was on the No.10 and No. 11 A-frames in the 20-cylinder, the two bearing positions forward of the very large rear main bearing."
Cure: improved welding techniques, and, from 1972 on, "A-frames which had a considerably enlarged foot in the shape of a letter "D" set sideways."
--Third part has the intriguing tidbit (after a description of the SD-45X test units)
"A 4200-h.p. "SD55" was offered by EMD in 1972 but was not included in the Dash-2 catalogue, and none was ever sold."
Comment: Not in the catalogue, and Cook puts "SD55" in scare-quotes: so this probably shouldn't be considered am "official" model number. The 645E3A engine used on the SD45X (as opposed to plain 645E3 on normal SD45) did, however, have features (such as the "rocking-pin" bearing for the cylinder wrist pin) that were used on the 645F engines on the later 50-series.