Re: (erielack) Tractive effort and loading characteristics

[bob gillis <rpgillis_@_bellatlantic.net>]

Going way back in my memory, I think this is the story.

"Loading" is how fast the diesel engine can get up to full speed and
load.  It has nothing to do with the electrics.  An EMD 2 stroke engine
with a roots mechanical blower can rev up faster without excessive smoke
than can an AlCO or GE 4 cycle engine with a turbocharger .  The rate
the engine accelerates is controlled by the engine governor.  EMDs and
the later GE engines used a third party governor whose name escapes me
but the company was from Rockford IL, and the earlier ALCOs used a GE
governor.

"Lugging" referred to how much the hard the electrics could take,  GE
was usually more advanced in generator and traction motor design and
insulation.  The GE traction motor was a GE752 and may still be.  The
EMD traction motor was taken from a GE design about a GE72X or GE73x
version.  The GE731 was used in ALCO switchers. (The GE in the traction
motor was a series designation for traction motor; I can't remember what
a generator was but a motor-generator was a GMGxxx)

The EMD motor used a cast frame and the GE752 used a welded frame, 
There was more room in the welded frame and the coils and iron could be
larger,  Also GE was in the forefront of insulation design and the 752
could run hotter longer that the EMD.

When GE was competing with ALCO in the domestic locomotive market, the
traction motors sold to ALCO would have been the same as the ones used
on the GE locos.  Generators would have been different and the control
system also.  But the ALCO electrics would have been almost as good as
the GE locos.

bob gillis

Christopher Thurner wrote:
> 
> Listers:
> 
> A great thread and very informative responses from our 'in-the-know' members who attended prestigious institutions such as Stevens Tech and Penn State.  You've removed a lot of the 'fog' from a topic I knew little about and obviously didn't understand until now.
> 
> I've read in many other publications and heard from former engineers that the EMD's loaded quicker and the GE / Alco's loaded slower, but were better luggers.  I don't doubt this at all, both from the assertions of the people who operated them and the technical people who explain why this is so.   One oddity I find, is, that at first glance it seems counter-intuitive.  It would seem to be the opposite, as one would surmise that EMD's expertise would be in favor of the prime-mover, given that its part of GM.  Likewise, one would expect GE's to load faster, given GE's core expertise was / is in electrical components, not the prime mover (remember Alco's used GE electronics / electrical components, albeit that after GE became serious about building road units before the release of the U25b, Alco was then relegated to receiving GE's second rate components, as GE reserved its newest and best for their units - another factor in both the demise of Alco and why Centuries weren't fri!
> endly to mechanical depts.).
> 
> Now, I also realize that a significant factor that can override this is the design objectives of the builder.  Maybe GE / Alco's design priorities were to build a superior puller and EMD's to build a racehorse.
> 
> Can anyone on the list shed any light on this?
> 
> Regards,
> 
> Chris Thurner
> 
> 
> 
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