• Why was the BL-2? (A thought)

  • Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.
Discussion of Electro-Motive locomotive products and technology, past and present. Official web site can be found here: http://www.emdiesels.com/.

Moderator: GOLDEN-ARM

  by Allen Hazen
It seems to be generally agreed that the BL-2 was a flop: discontinued after 59 units, replaced in the EMD catalogue by the very successful but radically different GP-7.
The basic package SHOULD have been successful: use the works of the popular F-3(*) in a roadswitcher configuration. The BL-2's body design, however, seems to have been a disaster: cramped engine room annoyed maintenance people and (more importantly) it was apparently expensive to build.

So, why was it chosen in the first place? EMD had long experience with switchers, had built elongated switchers (= "light roadswitchers"), had even (in transfer units for the IC) put its 16-cylinder engine in a switcher-style carbody. And the competition (Alco AND Baldwin) had shown the way, marketing roadswitchers of standard design (= frame like an elongated switcher frame, non-structural hood over the machinery). So why did EMD try to use a semi-streamlined truss carbody? Was there any rationale for it?

Thought. Truss-style bodies can be made lighter than standard road switchers. The BL-2 was, in fact, somewhat lighter than a GP-7, I think: an internet source, "Thedieselshop.us," has a description of the BL-2 that says it weighed 230,000 pounds. Their page on the GP-7 says 246,000 (another source-- a Simmons-Boardman booklet that probably draws on contemporary Car and Locomotive Cyclopedias) says the GP-7 was 240,000 pounds.

"BL" supposedly stands for "Branch Line." Is it possible that EMD chose the BL-2's carbody in the hope that they could minimize the weight of the unit, and so sell it to railroads with light-rail, light bridge, lines?

(*) According to Thedieselshop.us, the BL-2 had the newer, D-27, traction motors. So -- if you distinguish between the F-3 and the F-5 -- the BL-2 seems to have been a roadswitcher F-5. Which makes sense given its production dates.
  by SSW9389
The Diesel Shop picked one of the BL2 owners and that's the spec they have on line. Extra 2200 South issues #46 and 47 from 1974 have BL2 features. The BL2 used either the D17B or D27B traction motors depending on when it was built. Mr. Cuisinier wrote, "The BL2 was withdrawn from the market due to its inflexibility, relative high cost to build, and design weaknesses. But, EMD learned much from the BL2 plus something from the RS2 that they incorporated in the GP7."
  by SSW9389
Extra 2200 South shows a difference in weights amongst the units from the BL1 demonstrator which weighed in at 218,340 pounds to 246,000 pounds for the BAR BL2s. And everything else in between. The nine Monon BL2s weighed 240,000 pounds, and the last three were built in May 1949. Both Mopac and the C&O had BL2s that weighed in at 230,000 or nearly so.
  by v8interceptor
My guess is that at the time the BL series was developed, styling was everything at EMD's corporate parent GM, and the philosophy filtered down to the locomotive division. EMD was known for the styling on the E and F lines and the thought must have been that trying to apply similar ideas to a roadswitcher line would give them market definition versus the more utilitarian roadswitcher offerings from Alco.
It's interesting to note that there next attempt at the roadswitcher market was intentionally spartan looking; and cornered the market...

As an aside the same emphasis on styling may have led to the GP30's carbody design..
  by Allen Hazen
Thank you! … I have some ancient issues of "Extra 2200 South"; will look to see if…
It occurred to me after I posted that at least the prototype (BL-1) was rather early to use the upgraded traction motors… And "Thedieselshop.us" data tables are, I know, not perfectly reliable: it's easy to find, but I know I ought to check other sources if I ever want to do more than ask a question at Railroad.net! … Weights, of course, vary from order to order with most locomotive models: customer options, size of fuel tank… It sounds as if the weight ranges for the BL-2 and GP-7 overlap, but that maybe the BL-2 tends to be a bit lighter. (Sort of like men vs. women: the weight ranges overlap, but most women are lighter than most men. If I could, I would include an illustrative graph here, with a pair of overlapping bell-curves, one a bit to the left of the other.)
Anyway… Thanks for looking up the "E22S" articles!

The styling motive is the obvious one, suggested by at least some published sources: EMD supposedly thought that railroad managements would like a unit for secondary passenger services that suggested the glamour of streamliner design. (And then, ironically, came up with what has been called the "ugly duckling." Still, the PRR's GG-1 and P5aModified electrics are attractive enough, so maybe EMD designers thought they could get away with it!)
… It just seemed to me that this might not be the whole story, so I was looking for another possible reason for the adoption of the truss-style body construction for the BL. But the weight difference is small enough that it may not have figured in their thinking. So maybe, as you say, it was the style thing that governed the choice!
  by mtuandrew
Allen: perhaps EMD didn't quite have the capability to cast a heavy enough frame for a true road-switcher? The GP-7 was certainly beefier than the earlier switchers. Maybe they just wanted to produce the BL-2 using the same methods as the F series (and on the same production line?), rather than having to use a new manufacturing technique.
  by JayBee
EMD had given up on cast frames before WW2. The BL-2s were noted for their weakness of "frame strength", their replacement the GP7 was better, but it was not until the GP9 that EMD frame strength was considered completely satisfactory.
  by Engineer Spike
Some BL2s were used in local or branch passenger service, as on B&M. This service would have needed a bidirectional capability. The styling might have been felt to be important.

Some roads, such as my employer saw through this, and used roadswitchers on everything, including fancy passenger trains in the NYC-Monreal service.
  by Allen Hazen
MTU Andrew--
Re: "perhaps EMD didn't quite have the capability to cast a heavy enough frame for a true road-switcher?"
---That's an interesting thought (and-- since we are speculating about the history, the more thoughts the better!), but I don't think it's right. Switcher frames were (after the first few "SC" and "NC" Winton-engined switchers before WW II) fabricated (welded together out of structural steel) rather than cast (as JayBee points out). EMD had had lots of experience doing this. To be sure, as you point out, "The GP-7 was certainly beefier than the earlier switchers," but this is just a matter of adjusting dimensions, not of introducing new technological ideas. And EMD had built switch-type frames for units larger than standard switchers already: NW-3 and NW-5 light roadswitchers, TR-1 heavy transfer unit (with 16-567 engine and Blomberg road trucks). So I don't think something like the GP-7frame would have been bend their capabilities when they introduced the BL-2 instead.

Your alternative suggestion,
"Maybe they just wanted to produce the BL-2 using the same methods as the F series (and on the same production line?), rather than having to use a new manufacturing technique"
might be more like it, though: they started with the thought "let's modify the F-3 design to give bi-directional visibility for switching," and they went to work tweaking the F-unit truss-frame design instead of making the more radical step of putting (something close to) the F-unit machinery on an extended switch frame. So: not an INABILITY to build true roadswitcher frames, but a failure of imagination: they didn't think "outside the F-unit box"!

Thanks for your comment!
  by mtuandrew
JayBee and Allen Hazen: Sorry, my bad - I thought EMD went back to cast frames for the GPs, even though they'd died out after the SC and NC series in favor of the SW and NW forged-and-welded frames. Wikipedia has this to say, sourced from a book on NP motive power:
Wikipedia, EMD GP7 wrote:...Its replacement, the GP7, swapped the truss-framed stressed car body for an un-stressed body on a frame made from flat, formed and rolled structural steel members and steel forgings welded into a single structure (a "weldment"), a basic design which is still being employed today. Unfortunately, in heavy service, the GP7’s frame would bow and sag over time.[7] This defect was corrected in later models.
I suppose they could have had trouble creating the large-size forgings or doing a proper weld, and apparently they did have trouble with frame sag. But, that seems a minor problem for a company with the resources of GM. Either way, I suspect they recognized the need for an RS-2/3 fighter, the NW5 just wasn't cutting it, and they had the ability to make something with a truss frame - and they gave the design work to someone's inept brother-in-law. :P
  by Allen Hazen
BL-2 bibliography:
---I was prompted to post about the BL-2 by an article in the February 2014 issue of "Railfan and Railroad": "BL2 in Review: Milestone or Mis-step for EMD?" by Stan Trzoniec, pp. 42-47. Historical essay, numerous photos of BL-2 (most but not all Bangor & Aroostook) late in their careers or in preservation. Trzoniec quotes a "dry weight" (so: empty fuel tank, drained engine-- some thousands of pounds lighter than the "working order" weight) of "around 210,000 pounds" and a tractive effort of 56,200 pounds-- since nominal starting tractive effort was often computed as simply one quarter the locomotive weight, this suggests a working order weight of 224,800, which would be very light for a GP-7.
…As for why the truss-carbody was chosen, he says "For sure, the BL2 was trying to make not only fashion statement, but also one of functionality. The carbody followed the time-tested method of truss construction, similar to the F-units, which makes for a production schedule easily followed by those with prior experience on traditional cab units."

---SSW9389 mentions features on the BL in issues #46 and #47 of "Extra 2200 South." (These articles were written by "Win Cuisinier": Preston Cook, one of the best informed and most technically knowledgeable historians of the diesel locomotive, writing under a pseudonym.) I have #46 but not #47: the article in #46 is pp. 21-24, and contains several paragraphs on the history of the design, a roster, b&w photos of a variety of units (including one repaired after wreck damage with a visually very different F-7 windshield), and drawings (about 1/70 scale) of front, back, top and left side, with insets illustrating different pilots used on different units.

---"Trains," October 1975: "Borden tank car + P5a = BL2: well, it sure doesn't look like an EMD" by David P. Morgan, pp. 29-32. Short history, b&w photos (including a Borden milk tank car and a PRR P5am electric for visual comparison), account of fan trip with a preserved Monon unit.

---"Railroad Model Craftsman," April 1982: "BL2: Perhaps the strangest looking diesel ever to come out of La Grange, the BL2 was a transition between the cab unit and deep," by "Win Cuisinier," pp. 74-79. Article on the history and discussion of some of the weirdnesses of the design, b&w and colour photos (incl. EMD advertising artwork of three never-used paint schemes), numerous drawings: what seem to be the ones from the "E22S" article reduced to HO scale (and an N-scale drawing of a -- fictitious -- high-short-hood version!), plus plan, elevation and several sections showing the internal arrangements and some constructional details.

---"Mainline Modeler," August 1986: "EMD BL2 Phase 1," by Robert L. Hundman, pp. 58-63. Very brief historical article, numerous b&w photos (incl. some of roof and nose details), HO scale drawings. Hundman says "Cosmetically the BL2 can seemingly be categorized in two phases…" but, frustratingly, doesn't say which units are which or describe the differences. He also points to a source for the factoid about frame weakness:
"A recent article published by the Monon Historical Society notes that frame weakness… limited MU flexibility to
generally no more than two units in combination. The Monon, to correct the problem, rebuilt one of their
locomotives (number 30) with strengthened frame. It appears that other railroads did not feel the need for
this degree of frame rebuild."

There are doubtless other published things about the BL-2, but these are the ones in my collection. Ironically, "Railroad Model Craftsman" has the most informative historical and technical article about the prototype!
  by Allen Hazen
MTU Andrew and JayBee--
Interesting that the GP-7 had a weaker frame than later Geeps. It sounds as if EMD underestimated what heavy switching PLUS road service in multiple unit consists PLUS general abuse could do to a road switcher left to the mercies of the Ameican railroad system! And that both the truss structure of the BL-2 and the girder frame of the GP-7 were under designed as a consequence. (At the risk of sounding like and also/Baldwin enthusiast foamer… Maybe the competition had actually thought things threw better than EMD in the late 1940s?)
  by mtuandrew
Allen Hazen wrote:(At the risk of sounding like an Alco/Baldwin enthusiast foamer… Maybe the competition had actually thought things threw better than EMD in the late 1940s?)
Wouldn't be the first or the last time General Motors underestimated how much steel they needed to make a safe, reliable vehicle! The GP7 fits right into the GM mold though - never the best-constructed, never entirely free of little problems, but rugged enough, handsome enough, powerful enough, and (most importantly) cheap enough that you couldn't throw a rock without hitting one.
  by Engineer Spike
I question the lack of strength of the GP7 frame. If it was that poor, then why did IC bother to rebuild so many into GP8s? C&NW, CPR, and Conrail also had large fleets of rebuilt GP7s, and by that time, the size and capacities of the cars had grown substantially. Some of CP's GP7s were just recently traded on the new GP22ECO.

The BL2 was certainly one of EMD's few flops. B&M had 4, which had steam generators, but lacked MU. They later bought GP7s with the same configuration. The GP7s, which came without MU had it added. The BL2 fleet was traded in for GP18s. Apparently they were dissatisfied enough to give up on them. On the other hand, a new management was in power when the decision was made to trade them in.
  by Allen Hazen
I have no relevant information about the supposed weakness of the GP-7 frame. (I think I do remember, from more decades ago than I like to think, something in "Trains" where a locomotive expert was cited as having opined that the SW-1 had a longer life expectancy than the generally more useful GP-7 because of the Geep's weak frame…) If there was a problem, it makes sense that EMD would address it at the next major design change, with the GP-9. If anybody who actually knows some details wants to share…

As for the BL-2…

(1) Weights. I looked at the roster in "Extra 2200 South" #46, which gives weights. BL-2 were built with weights up to 246,000 pounds (BAR's were the heaviest, and among the last to be built), but more than half had weights UNDER 230,000 pounds. (One batch -- the C&O units ordered by Pere Marquette -- are listed as weighing 224,800, which may have been the origin of the 56,200 pound nominal tractive effort.) The BL-1 prototype was the lightest, a bit under 220,000. So it seems fair to say that on the average the BL-2 was a bit lighter than a GP-7: I think a standard GP-7 would be around 240,000. (There were light weight options. I believe that the Southern had some GP-7 built for branch line service with VERY small fuel tanks, and that the NC&StL had some built with switcher trucks for lighter weight. Anybody know what a lightweight GP-7 would weigh?)

(2) About the frame strength issue. Again, I have no solid information, would like to hear from anyone who does! But, a priori, I wouldn't be surprised if there WAS an issue:
---(a) Obviously, they weren't breaking in two as they left the La Grange erecting hall: if there was a problem, it would have been marginal, and would probably have shown itself only in certain sorts of service. The same power yields smaller forces at high speeds (high-school physics, there): if, say, the Santa Fe had bought passenger equipped BL-2 and used them to run the Super Chief across the Kansas plains at 90mph, I doubt there would have been any trouble with four-unit consists! But hauling a drag freight over the hilly south end of the Monon might have been another story. Perhaps the Monon was the railroad that worried most because they were the ones who gave their BL-2 the hardest work.
---(b) The truss work in a BL-2 is not as deep as that on an F-3. An F-unit's truss frame extends up the full height of the side wall, whereas the BL-2's is inside the "bicycle-chain guard". Other things being equal (i.e. if the truss wasn't made up of heavier members to compensate) this would have led to a weaker structure.
---(c) But, given its configuration, a BL-2 ***OUGHT*** to have had a STRONGER frame than an F-unit or a Geep: it's longer. A BL-2 is only couple of feet longer than a GP-7 in total length, but its trucks are closer to the ends, so the unsupported span (hey, truss framing is BRIDGE technology, so why not call it a "span"?), carrying the heavy engine and generator, is significantly longer. (Distance between truck centres on an F-3 is 30 feet, on a GP-7 it's 31feet, and on a BL-2… it's 35 feet.)
… … So, whether or not the BL-2 frame WAS weak, it seems to me that (given the light weight and the design characteristics alluded to under (b) and (c )) that designing adequate strength into the BL-2 body would have been … more difficult than designing it into the F-unit or Geep carbody.

(Apologies for my long-windedness, and thanks to everybody who has commented!)