E and F unit question

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E and F unit question

Postby Frank » Sun Aug 25, 2013 10:13 am

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?
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Re: E and F unit question

Postby Allen Hazen » Sun Aug 25, 2013 6:30 pm

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.

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!
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Re: E and F unit question

Postby litz » Mon Aug 26, 2013 2:16 pm

It's interesting that you bring up the wheelslip/adhesion issue .

A lot of people really don't realize the advances made in that area .

On the Blue Ridge Scenic RR, we have used two "uphill" locomotives ... one was a GP9, the other is a GP9R.

The GP9 was original to 1950s specs, analogous to that F7. It had tremendous wheelslip issues going uphill.

The GP9R was rebuilt in the mid 90s, with a mixture of GP38-2 and GP60 tech. It can crawl uphill like a billy goat.
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Re: E and F unit question

Postby Allen Hazen » Mon Aug 26, 2013 8:22 pm

Litz--
That is really interesting information! Many GP-9 have been rebuilt over the years, and the "GP-9R" designation has been given to locomotives with very different characteristics: I didn't realize that some of them had much more modern wheelslip control, or that the difference it made would be so dramatic.
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Re: E and F unit question

Postby litz » Tue Aug 27, 2013 1:25 pm

The difference is rebuilt as-is, in which case you end up with a fresher version of what you started with... Or doing a frame-up rebuild, with new/modern components...
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Re: E and F unit question

Postby MEC407 » Tue Aug 27, 2013 1:42 pm

Definitely an important distinction to make.

Some railroads chose to use the letter "U" (for "upgraded") rather than the letter "R," to denote that the rebuilt locomotive was in some way improved over its as-built specifications.

The letter "M" was also often used. Supposedly it stands for "modified," although I suppose it could also mean "modernized."

Yet another way to differentiate rebuilt locomotives from their as-built counterparts is with a hypen and various numbers. We're all familiar with GP38s and SD40s being rebuilt as GP38-2s and SD40-2s, with the obvious assumption that the rebuild includes EMD's "Dash 2" electrical system... and then there's the occasional -3 rebuild, which usually means an improved electrical system as well as some kind of microprocessor or computer control system. Typically -3 rebuilds have been applied mostly to post-1966 locomotives, but I've occasionally seen older locomotives given the same treatment, resulting in GP35-3s and even GP9-3s and SD9-3s.
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Re: E and F unit question

Postby Frank » Thu Aug 29, 2013 9:50 am

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.

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!


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.
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Re: E and F unit question

Postby Allen Hazen » Thu Aug 29, 2013 5:08 pm

Yes, definitely it's dead weight! If more powerful engines had been available-- so that an E-unit's full power could be produced by an engine that could be carried on a 4-axle unit-- there would have been no point to the idler axles. But one chooses locomotives with the available technology. Assume that an E-unit has enough weight on its driving axles that adhesion isn't a worry. So, for lots of reasons-- fuel economy for one-- you want the lightest weight locomotive that will do the job. Suppose you want 4500 hp: two E-8 (total weight: 633,000 pounds) will do. To get the same power from F-7, you need three units-- total weight at least 690,000 pounds. (Probably a bit more: with a passenger train you are going to want steam generators, so a passenger-equipped F-7 will probably weigh more than the base model.) So using the E-8 units saves you 57,000 pounds. Lighter train will accelerate faster. This might make the difference between on-time arrival and angry passengers!

If the Santa Fe had only run its passenger trains as far west as Kansas, they would probably have been better off with E-units. (They in fact had a few, which they assigned to passenger trains that didn't cross the Rockies: Chicago to Texas trains, for example.) Going over the mountains... Sometimes you're going to want the extra adhesion weight to avoid slipping the drivers going up hill. Sometimes-- if the up hill climb is long enough and slow enough-- you're going to want extra traction motors so they don't overheat (remember, and E-8's traction motors have to be able to absorb electric current equivalent to 1.5 times the power that an F-7's motors have to take). And maybe sometimes, going around sharp curves, the longer wheelbase of the E-unit's three-axle trucks will be a nuisance. So the Super Chief (etc) got Warbonnet-painted F units. The advantages of E-units on non-mountainous terrain aren't enough to justify an engine change in the middle of the run, however: Santa Fe was happy to have F-units pull its crack passenger trains all the way from Chicago.
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Re: E and F unit question

Postby Typewriters » Thu Aug 29, 2013 8:22 pm

The original question was about whether handling of E and F units was different; the answer is "yes."

The E units had automatic transition (which implies both series, and parallel connection of traction motors as well as field shunting) but the throttle had to be closed for the back transition to series motors to take place.

The FT and F2 had four step manual transition, guided by the load-transition meter. The 2 to 3 and 3 to 2 transition had to be made with the throttle in notch 6 or lower. That restriction went away on throttle position during the F3 production. The F7 had fully automatic transition standard.

Another major difference was minimum continuous speed. For example, for the standard E7 it was 34 MPH, whereas for the standard FT it was around 15 MPH. No "freight" gearing was available for the E units. This means that the tons per horsepower the E unit could pull (or, its tonnage rating, put another way) were vastly reduced when compared with the freight unit since it had to stay above minimum speed. (Minimum speeds for each throttle notch were published for early E units.)

The comparison bewteen a generic three unit passenger locomotive weighing about a million pounds and developing 6000 HP and a generic four unit freight locomotive weighing about a million pounds and developing 6000 HP shows the severe deficit that the passenger type units face in comparison when considered for freight, since their starting effort is not a quarter of a million pounds, but a quarter of 2/3 of a million pounds. The comparison in minimum continuous speed has already roughly been made above, so that the undesirability of such units for freight service should now be obvious.

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Re: E and F unit question

Postby Allen Hazen » Thu Aug 29, 2013 10:53 pm

Thanks, Will! Things like transition are important, and I was completely ignoring them.

Nitpick: Was automatic transition standard on the F-7 from the outset? My impression was that early F-7 (the model was introduced in 1949) did NOT have automatic transition, which became standard somewhat later (1951, perhaps?).
...
Railfans and model railroaders sometimes talk about "phases" of a diesel locomotive model: visible design changes that were not honored by a change in model designation. But there are also "phases" in the internals. (E.g.: late F-3 had heftier traction motors than early: essentially, the traction motor for the F-7 was introduced before the model change. The new traction motor would have given them significantly better down-on-the-knees-crawling performance: they could use full power power at a lower speed without overheating, and so would have been better at towing heavy freights up hill.) An engineer operating an F-7 might not care about the body-work changes recognized as phases by the model railroad fraternity, but knowing whether all the units in his consist had automatic transition would have made a real difference to the job of train handling.
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Re: E and F unit question

Postby Typewriters » Fri Aug 30, 2013 9:17 am

Good question about the F3 / F7 transition, Alan; I'll have to see if Dave has marketing material, etc. to tell us what was standard and what was optional and when the break point occurred. But for now...

I have here one of those "covers everything" New York Central manuals you see from time to time, that the road published itself. Luckily, due to some sloppy update entering, this manual has the section that covers EMD four-axle units from 1948 that just covers F3 and has another section from 1949 that covers everything including F2, F3 and F7, but not FT although it's mentioned for multiple unit operation.

The F3 only section mentions that some units had automatic transition. My guess would be that this means the units that were class DCA on the NYC, namely the combination freight - passenger units. So this means that automatic transition was optional on the F3 at least at the 7/47 build date for these units.

The "All inclusive" section shows both transition - load meters for F3 and for F7, clearly labeled (and quite different) and again mentions that some units had automatic transition. It also details the fact that if any F7 units were operated in multiple with FT, F2 or F3 freight units then the F3 tonnage rating would apply for all units. What this really means to this discussion of course is that an F7 leading would have to control transition on trailing F3 units equipped with manual transition, and so would have to have the transition marked in some way on its load meter --- even if it were fully automatic itself (either the early type sometimes called "manual supervisory" where transition was automatic but could be limited by the selector lever, or fully automatic where the selector lever served only to control trailing units and had no input to the transition control on board the unit itself.)

As I said, we'll have to do a bit of looking around to find that exact cutoff. Just the briefest look at George Elwood's site tells me that by the 5th edition F7 manual, June 1951, the units had fully automatic (no supervisory control) transition. The site is loading very slowly, and frankly we have many more F3 and F7 manuals here than he has on the site (and lots of other things) so the real answer has to wait until later today!

(Aside.... From the same NYC manual, for historical interest. All Fairbanks-Morse Erie-built units on NYC had automatic transition with supervisory control, and were built variously 10/47 through 4/49. For the ALCO-GE freight units: Manual transition on units 1000 to 1013 and 2300 to 2306 which were freight units built 2/47 - 3/48. Automatic transition on freight units 1014-1043, 2307-2322 built 11/48 onward and on passenger units 4200-4203 and 4300-4303 built 1/48-12/48. The transition references are from the NYC manual while I've pulled the build dates from 'New York Central System Diesel Locomotives, Edson/Vail/Smith 1995.)

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Re: E and F unit question

Postby Typewriters » Fri Aug 30, 2013 4:12 pm

Digging through some of Dave's EMD technical and sales material here...

EMD Specification 8002 issued July 10, 1945 for 1500 HP "Lead Freight unit" (which we now know to be the original F2 rated 1500 HP, whose D12 gave troubles forcing temporary substitution of the D8 and use of a rating of 1350 HP) has as options manual transition, automatic transition, or combination manual and automatic. (The second is what we'd call full automatic, while the latter is 'forestalling' or if you're an ALCO guy, 'manual supervisory control.') So EMD had automatic transition available as an option in mid-1945 on the F units.

Much earlier than I'd thought.

In terms of what was standard equipment, we find that in the 5th Ed. F7 manual there's a reference that says that "since November 1, 1950, F7 and FP7 locomotives have been basically equipped with three-relay automatic transition." This means as standard equipment. This is full automatic control.

Questions answered!

Further aside, for historical interest. The BL-2 and GP-7 both had fully automatic transition, from the outset. But that's a far different story.

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Re: E and F unit question

Postby Allen Hazen » Fri Aug 30, 2013 9:15 pm

Questions answered. Thank you! So, automatic was included as "basic" on the F-7about a year into the model's construction history.
Interesting that EMD, though they HAD the technology for automatic transition earlier, they didn't initially include it as standard on the F-7: trying to keep the base price down, maybe?
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Re: E and F unit question

Postby EDM5970 » Mon Sep 02, 2013 7:31 pm

To muddy the waters a bit, Alco/GE had automatic transition on the RS-1s, (first built in 1941) and I would imagine on the earlier S-1 and S-2 switchers as well. So the technology was there in the form of the VI relay. I'm surprised EMD didn't copy it, like they did with the GE 716 traction motor. The GP-7 manual explains (quite well, in fact) that the faceplate load regulator had limit switches to effect forward transition. while later Fs and GPs apparently used through cable relays to detect current. The GP-7 was somewhat unique in that it didn't have field shunting. It also used a notch sensitive 'teaser' generator field control circuit in switching mode, which allowed it to load up quicker than other Gs and Geeps. Santa Fe copied this feature in the CF-7s, which made them great heavy-duty switchers.
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Re: E and F unit question

Postby Allen Hazen » Wed Sep 04, 2013 1:10 am

The F-M "Erie-built" cab units (or at any rate some of them) had transition -- both forward at 33 mph and backward at 31.5 mph -- activated by an axle-alternator speedometer: a "Railroad Mechanical Engineer" article (reprinted in one of the "Trainshed Cyclopedia" albums published by Newton K. Gregg) when the units were new comments on it as if it was a novel and interesting feature. (GE seems to have had a fondness for axle-alternator over many years! Most familiar application was for wheelslip control on U-series diesels, but evidently they though of other uses for them as well.)
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