I know the E and F units looked similar but were of different size. Was the handling of the E and F units similar or different? What was their power-to-weight ratio?
Rails are better than roads!
Allen Hazen wrote:E and F units both went through several generations, gradually increasing in horsepower from the time of their introduction (in the late 1930s) to the end of production (late 1950s for F, early 1960s for E). For a first response, then, let's look at the F-7 and the E-8: these are comparable models, both produced from 1949 to 1953.Thanks. I would think the E units with their idler axles would mean dead weight on the train but it seems that it didn't matter because the locomotives were more powerful than the F units.
The E-8 is about 20 feet longer (70 feet three inches to 50 feet eight inches). The nose and cab assemblies were the same (built separately, grafted to the frame late in construction), but the rest of the carbody, obviously, was different. Into its longer body the E-8 crammed one and a half times as much engine (two 12-cylinder engines) as the F-7 (one 16-cylinder), producing one and a half times as much power (2250 hp as opposed to 1500 hp). For applying their power to the rail, however, both models depended on the same four traction motors (one per axle on the F-7, one each on the first and third axles of each truck on the E-8: the center axles were idlers).
In terms of weight. Different orders of either model (with different optional equipment, etc) could differ in weight, but a reasonable base figure is 230,000 pounds for the F-7 versus 316,500 for the E-8, of which only 210,750 pounds was on the motored axles. (E-8 weights for A-unit: boosters a few thousand pounds lighter.)
So, power per pound of total weight, the E-8 is more powerful. (This despite the fact that the E-8, as a passenger locomotive, typically carried extra equipment, like a "steam generator" (= small boiler, mounted near the rear end of the unit) to provide steam heat to the cars of a passenger train: this, and the boiler-water supply, would add tons to the overall weight.) In terms of power for weight on the motorized axles, the E-8 is MUCH more powerful: one and a half times the power on slightly LESS weight!
The difference is explained by the intended use of the two types. The F unit was a freight diesel (though some railroads with routes through mountainous areas -- think Santa Fe -- used them on passenger trains as well). It COULDN'T use too much power: at freight speeds, more power would have led to wheel-slip, with the wheels spinning uselessly. (Electronic control has improved immensely since the F units were built: modern freight locomotives can use much more power, on a given "adhesion" weight, than was possible in the F-unit era.) The E unit was designed for passenger trains (though, particularly late in their careers, when passenger service was declining in the 1960s, a few were used on fast freights). At the higher speeds of passenger trains, more power could be absorbed by a driving axle without wheelslip than at lower speeds(*), so a passenger locomotive could afford to be more powerful in relation to its "adhesion weight" (= weight on the driving axles: transferring power to the rail to pull the train depends on the adhesion between the wheel rims and the rail at these axles).
(*) High school physics: pulling the train depends on the FORCE the powered wheels can exert on the railhead, and when this force exceeds the "adhesion limit" you get wheelslip. But POWER is proportional to force times VELOCITY: so, at a higher speed, the same force is equivalent to a higher power.
(Apologies if this answer is too simplistic: my guess from the wording of your question was that you were a new-comer to railroad watching, so I wrote this for a neophyte: pass it on to your younger and less experienced friends if it's too elementary! (Grin!))
Numbers from a 1983 pamphlet, "Early Diesel-Electric and Electric Locomotives," published in 1983 by Simmons-Boardman, a publisher of stuff for the railroad industry (e.g. "Railway Age," a magazine for managers in railroad and railroad-related companies): I think it was composed by cutting and pasting from some of their professional publications from the F-unit era in the hope of selling the "byproducts" of their main productions to rail fans!