F vs. E unit EMD's

[Anonymous]

Why were 4 axle 'F' units prefered for freight and 6 axle 'E' units prefered for passenger trains when the opposite is true for locomotives today ? It seems the 6 axle 'E's would have had better adhesion than the 'f' units, and the 'F's would have been better on the fast passenger trains.

[eolafan]

Not all roads liked E units better for passenger service, such as ATSF which used a few early E units and then reverted back to F units for both freight and passenger. In the experience of ATSF the F units pulled uphill in the western mountains better than E units. Where the E's were preferred, this was usually for one or more of several reasons such as (1) higher horsepower for quicker starts from station stops, (2) better, smoother ride for crews with the idler axle between the powered axles (AIA trucks) on the E's, more steam generator capacity (some had two vs. the single generator on the passenger F's). The E's were faster from a stop on relatively level terrain than the F's, thus making them more appropriate for passenger service since freight service did not need such a plus feature. These are among the reasons the E units (as well as their Alco and Baldwin AIA counterparts) were preferred on passenger trains and the F's in freight...by the way, did you know that "F" meant "Freight" and "E" originally stood for "Eighteen hundred horsepower"? Jim, Aurora, IL

[eolafan]

Oh, I forgot to mention, some will tell you that the F means "Fifteen hundred horsepower", which may be true, but I prefer to believe it means "Freight" unit. Jim

[thirdrail1]

Jim is right as far as he went, but the biggest difference between the F and E units was that the F originally had a single 1350 HP prime mover, while the E had TWO 900 PH, later 1000 HP, prime movers. The "E" also stood for "Express' as the locomotives were intended for fast passenger service. Remember, both the F and E had the same number of powered axles, four, but the "E" had more powerful traction motors and different gearing for higher speeds. The idler axle on the trucks was to spread the weight of two prime movers and to provide a more stable ride at high speed. The locomotive of today has a much higher horsepower prime mover that can easily power six traction motors to give it greater tractive effort to move freight. Since speed and not tractive effort is what is needed in passenger service, there is no need for six powered axles and truck design has improved so that idler axles are not needed.

[Anonymous]

All of the prewar EMC locomotive names were based on the horsepower in hundreds. E stood for eighteen hundred, F stood for fiftyfour Hundred Look at the ads for the FT, it was marketed as either a fifty four hundred horsepower locomotive (4 units) or a twenty seven hundred horsepower locomotive (2 units). So the letters in the FT stood for both horsepower levels that the locomotive was marketed as.

The TA used the same nomenclature as the E. The T stood for twelve hundred horsepower "A" unit.

The switchers are a little bit more complicated. The first letter stood for the horsepower, the second for the type of frame. So an SW was six hundred horsepower with a welded frame. An SC was six hundred horsepower with a cast frame. The NW and NC were the same except that the horsepower was nine hundred.

After the war EMD kept the same letters for the series, even though the letters no longer had meaning. The marketing department later came up with F for Freight, E for Express and SW for switcher to give the designations some meaning for the later locomotives. But the letters originally stood for the horsepower of the locomotives.

The new series introduced after the war used different naming. GP for general purpose, SD for special duty (remember that the SD7 and SD9 were designed for branch lines with very light rails), and BL for branch line.

[alangj]

By the end of their production run,s the E8's were said to be 2250HP (2 X 1125HP), and the last E9's were said to be 2400HP (2 X 1200HP), right???

[thirdrail1]

Yes, Allen, and the F9's were 1750 HP. EMD constantly got more HP out of the same cubic inch displacement. When they could not, they upped the CID.

[eolafan]

This series of notes reminded me that it was while watching FL-9 units on the NYC in Tuckahoe, NY in the sixties and seventies (I even rode behind some a few times) that I was "hooked" on railroading and became a lifelong "foamer". I have always had a soft spot for the F units. Guess it is my generation, and todays kids will have the same feeling about early to mid production GP and SD units as we had for the F and E units. Jim, Aurora, IL