• GG-1and MU operation

  • Discussion of General Electric locomotive technology. Current official information can be found here: www.getransportation.com.
Discussion of General Electric locomotive technology. Current official information can be found here: www.getransportation.com.

Moderators: MEC407, AMTK84

  by Allen Hazen
Amtrakhogger-- Interesting speculation. I'll have to look at the E-44 operator's manual and see what it says about raising and lowering pantographs. (Am I right in remembering that PRR practice was to use the rear-ward -- relative to the direction of operation -- pantograph, so that if something happened to it (collision with fallen tree branch, for example) the front-ward one would probably not have been fouled and could be used as a spare?)
  by Allen Hazen
I looked at the E-44 operator's manual at
http://www.rr-fallenflags.org/manual/e44-om.pdf" onclick="window.open(this.href);return false;

Pantograph raising and lowering were done by air (see section on "Auxiliary air equipment"), with control valves not with the operating controls but in the nose: pantograph raising and lowering were things to be done before and after a run, with the locomotive stationary. And it looks as if the pans on each unit had to be raised and lowered separately. So… good speculation, but I don't think pantograph control was relevant to m.u. operation. The section on m.u. operation suggests that each unit had to be set up individually before a run.
  by Pneudyne
I imagine that from an operating viewpoint, mixed MU with the E44 leading might have been preferred, given that electric locomotives were often operated right up to the adhesion limits, and in 1960 that was probably better achieved by manual control of notching than by any automatic means. The E44 had much higher power per axle (and per ton of adhesive weight) than the diesels of the time.

In terms of control system complexity, from least to most complex, I’d postulate the following hierarchy:

1. Equipping the E44 to control trailing diesel locomotives via the customary diesel jumper;
2. Equipping the E44 to be controlled by a leading diesel via the customary diesel jumper;
3. Equipping a standard diesel to control a trailing E44 (and to be controlled by a leading E44) using the E44 jumper cables.

Re the E44 auxiliary functions, remote control of control switch reset might have been desirable. Possibly this could have been done by the diesel ground fault relay reset trainline. Except I don’t think that that function was trainlined generally back in 1960; it appears to have been something that came in during the mid-1960s or so.

Also from an operational viewpoint, if you had a fleet of electric freight locomotives that it was desirable to supplement at times – say for peak seasonal movements – with diesels drawn from a larger pool, then it would probably make most sense to leave the diesels in standard condition, and modify some or all of the electric locomotives for trailing diesel MU operation.

I also looked in Middleton (“When the Steam Railroads Electrified”). The several paragraphs on the E44 made no mention of trailing diesel MU capability. On the other, that the Virginian EL-C could MU with the motor-generator locomotives was mentioned:
Middleton p.202 VGN EL-C MU.gif
I’d say that Middleton was generally a reliable and accurate author (well, except about the origin of the 2-C+C-2 wheel arrangement). The “no mention” of mixed MU in the E44 case is not “proof negative”, so as to speak, but I’d be surprised if he had missed such a feature.

  by Allen Hazen
Thank you, once again, Pneudyne!
Your analysis of the complexities and likely economics of different schemes for control systems allowing electric/diesel m.u. operation sounds intrinsically plausible to me.
So far I have had no response on the PRR/PC and Conrail boards to my question of whether E-44 and diesels were, in practice, operated in m.u.
As to the Virginian's electrics… I'm happy to believe that the EL-C (a.k.a. EF4, a.k.a. E-33) were designed and built to be CAPABLE of m.u. operation with the V's postwar GE motor-generator units, but I'd still be interested in knowing whether they were so operated in normal use. … Middleton speaks of the possibility of operating up to 4 EL-C in m.u.: my recollection is that conventional wisdom in the 1960s or 1970s was that 16 powered axles were enough to produce as much tractive effort as draw-bars would take, and the Virginian's traffic was mostly low-speed mineral trains: so tractive-effort limited rather than horsepower limited. So my ***guess*** would be that more than three EL-C, or more than one (two-unit) motor-generator locomotive, on the front of a train would have been exceptional.
(And-- in case I haven't mentioned it in a while-- I am VERY grateful for your informed and informative posts!)
  by Pneudyne
Thanks, Allen, and no problem. It’s a very interesting topic, but not one that has been subject to much in-depth treatment in the railfan press. In a general sense, the impression I have is that the complexity and cost of heterogeneous MU has been such that railroads have used it sparingly and only where its was justified by regular, or at least reasonably recurring operational needs. I agree that in the VGN case, it looks as if EL-C plus EL-2B combinations would not normally have been needed, so if the facility was there, it might only have been used in abnormal situations.

Still, if it was done, I’d be interested to know the “how” details, particularly in respect of matching the regenerative brake control of the EL-2B to the dynamic brake control of the EL-C. I don’t know how regeneration on the EL-2B was controlled, but in referring to motor-generator locomotives generally, it was sometimes possible to exercise control both through the regenerative exciter (brake handle) and the main generator excitation (throttle/power handle).

The information that I have on hand about EL-C power control indicates that, like the New Haven EP-5, it had a limited number (5 in this case) transformer tappings, beyond that using resistance control to provide the requisite number of accelerating notches. But the resistance grids, also used for dynamic braking, were force-cooled, so may have been suitable for continuous operation, apparently unlike the EP-5 case . The EL-C also had a buck-boost transformer system to provide three sub-notches for each accelerating notch. But as an “auxiliary” function, that would not necessarily have had to be replicated on all potential MU partners.

  by Allen Hazen
A few weeks ago when we were discussing this, I posted queries on the PRR, Penn Central, and Conrail forums about it. There has been a reply: on the Penn Central forum, Noel Weaver (a frequent participant on forums devoted to northeastern U.S. railroads, and one who seems to be well-informed) has said he knows of no m.u. operation of PC electrics with diesels.
  by Pneudyne
Thanks, Allen.

That is consistent with the lack of any other evidence supporting the notion that such MU operations actually occurred, or indeed that the locomotives were even equipped for it.

One may wonder whether it was an idea that was mooted, perhaps even planned and put into print before the E44 fleet was built, but abandoned for some reason at a late stage.