EMD seemed to have been particularly conservative when it came to the power settings for the post-WWII E-units.
The E7 was rated at 2000 hp not the full 2250 hp that was possible. The E8 went to 2250 hp, but that was after the 94 hp/cylinder rating had been service-proven in the F3.
The E9 was rated at 2400 hp when the full rating for the 12-567C pair would have been 2620 hp. This probably reflected the same conservative attitude that had obtained with the E7. Also, EMD may have been reluctant to go above 2400 hp in a 4-motor locomotive with an adhesive weight of around 220 000 lb. As far as I know the E9 was never uprated to the full capacity of the 12-567C engines, nor was the 12-567D1 used. This would have provided 2650 hp basis the 1325 hp rating that applied to the RS-1325. So it looks as if 2400 hp was considered to be the upper limit for the locomotive, even where proven higher engine power was available. Traction motor capacity might have been another limiting factor in the 1950s, but perhaps less so by the early 1960s.
EMD also promoted the twin-engined nature of its E-units as a safety factor against power failure.
Whilst the 2400 hp 16-567D3, as used in the SD24, was on the face of it an attractive option for a potential successor to the E9, it certainly would have been something of a major reversal for EMD. That is, a single powerplant at a higher, as yet untried rating, with the additional risk factor of turbocharging, would be replacing two established and derated powerplants. Not only that, but the major re-engineering of the E that would have been required was probably seen as not justified given that by the late 1950s, its sales were surely in decline. Rather letting the E9 simply run out in its existing form was the logical choice.
Getting a pair of 16-cylinder engines into the E9 carbody would likely have been a “shoehorn” exercise. Possibly the combination of a12-cylinder engine forward and a 16-cylinder engine rearward would have been possible. If we assume that a C-C wheel arrangement would have been necessary or at least highly desirable above 2400 hp, then there is the issue of truck design to consider. Perhaps the EMD flexicoil C truck would have been satisfactory at reasonably high speeds, but likely something better would have been required for the very highest speeds. Thus EMD may have had to develop a C-version of its Blomberg A1A swing-bolster truck. (A C version of the Blomberg truck is not so far-fetched when one considers that the A1A design was the alleged inspiration for a widely-used series of British C trucks.). I doubt that EMD would have been too keen on buying in a swing-bolster C truck from Commonwealth.
Two engines and a C-C wheel arrangement also pose the question as how to best arrange traction motor connections. Keeping the two power systems separate throughout, and so having each with fixed 3P connections would seem logical, but whether EMD would have been happy with that in the late 1950s is open to question. That said, the G12 export model, in 1425/1310 hp form, had a fixed 4P arrangement. Two different engines, that is a “12” and a “16”, would complicate matters even further.
Returning to the single 2400 hp 16-567D3 powerplant passenger locomotive theme, then possible the FL9 would have been a feasible starting point. Devoid of its third rail DC equipment, it likely would have accommodated the turbocharged engine and its ancillaries without being overweight. One may also imagine a longer, “FXL” variant, extended forwards so that it could run on a pair of Blomberg A1A trucks.
I imagine that EMD delayed the introduction of turbocharging for as long as it could. As long as it did not need turbocharging, it could claim a simplicity advantage for its two-stroke engine over the four-stroke competitors, which were necessarily turbocharged. Not only did that disappear when it introduced turbocharging, but two-stroke engines are more difficult to turbocharge than the four-stroke type, in part because the exhaust gases are much more diluted with scavenge air. Once one reached the point where the desired specific output mandated turbocharging regardless of whether the two-stroke or four-stroke form was used, then a “clean sheet” design could well favour the four-stroke. This became more so as material and design improvements allowed four-stroke engines to approach the combustion limited piston speeds. Evidence is found in the ocean-going marine (as distinct from the North American inland marine case) medium-speed trunk piston engines. Historically both two- and four--stroke examples were found. But from the 1970s the four-stroke type dominated, and the two-stroke type dies out. For example Sulzer designed its then-new Z40 engine to be either a uniflow two-stroke of a four-stroke, and convertible between the two configurations. But very few of the two-stroke version were actually built. (Of course the very biggest crosshead-type marine engines are necessarily two-strokes; with stroke-to-bore ratios often above three, it is difficult to imagine that anything other uniflow scavenging would work.)
Cheers,
EMD F7 & E8 p.04,05.jpg
