What are the physical external differences between a GP39-2 and a GP38-2?
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GP39-2?
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diburning wrote:What are the physical external differences between a GP39-2 and a GP38-2?GP39-2 has a longer frame than GP38-2.
really? I thought they were both 59'2" long
The most obvious is the different exhaust pipes through the roof in that the 39 has a large rectangular opening nearer the cab end and the 38 being a blower engine has 2 smaller oval pipes rising directly from the exhaust manifold.
I would agree that the exhaust system is the most reliable spotting feature between the two units. Other than that, they are very similar looking.
MEC407
Moderator:
Pan Am Railways — Boston & Maine/Maine Central — Delaware & Hudson
Central Maine & Quebec/Montreal, Maine & Atlantic/Bangor & Aroostook
Providence & Worcester — New England — GE Locomotives
Moderator:
Pan Am Railways — Boston & Maine/Maine Central — Delaware & Hudson
Central Maine & Quebec/Montreal, Maine & Atlantic/Bangor & Aroostook
Providence & Worcester — New England — GE Locomotives
Here I am tomjohn 
First off, the GP38-2 and GP39-2 ride on the same frame (59' 2" over coupler pulling faces) and share the same overall dimensions and many of the same components.
As for the differences, the GP39-2 actually went through several carbody variations, which are as different from each other as they are from a GP38-2.
Early GP39-2's are visually nearly identical to the earliest GP38-2's, with a two-piece wire-mesh radiator intake and fans spaced far apart. The main components of the hood (blower duct, dynamic brake housing etc) are in the same position on both models. The main differences are the engine room doors (2-3-3-2 grouping on the GP39-2 and 2-4-4 on the GP38-2) and the exhaust (single turbocharger stack on GP39-2, two exhaust stacks on GP38-2). Some earlier GP39-2's also had the fuel tank mounted farther to the rear, with a curious curved fuel filler pipe--this includes D&H and some ATSF units.
Early GP39-2, Reading version:
http://trainiax.net/drawings/36-emd/gp3 ... dg-ph1.gif
Early GP38-2, GMO version (this one lacks dynamic brakes, but it's the best comparison I have for the moment)
http://trainiax.net/drawings/36-emd/gp3 ... o-ph1a.gif
Few GP38-2's were built with the two-piece radiator intake, and after the earliest units, GP38-2's switched to a shorter single radiator intake and closer-spaced fans. However, the GP39-2 retained the longer two-piece intake for some time.
Later GP39-2's (BN and late ATSF versions) eventually adopted the shorter intake and closer-spaced fans of the GP38-2, as well as many other evolutionary changes ("phases") that were applied universally over the Dash-2 range. This includes Q-type fans on some units. They also received a large, flat exhaust silencer replacing the exhaust stack (as on other turbocharged models such as the GP40-2).
However, the biggest change in late vs. early GP39-2's is that the engine was moved over 3 feet rearward, taking the main air intake and blower duct with it. This leaves a large expanse of empty sheetmetal in the hood right behind the cab, and it places the dynamic brakes closer to the radiators. It also eliminates the last two tall hood doors, resulting in a 2-3-3 arrangement before the shorter doors under the radiator intakes begin.
Late GP38-2, BN version (this drawing also illustrates the nearly-flush, circular exhaust stacks of late GP38-2's)
http://trainiax.net/drawings/36-emd/gp3 ... n-ph2c.gif
Late GP39-2, BN version
http://trainiax.net/drawings/36-emd/gp3 ... n-ph2c.gif
The very last GP39-2's, built for the MKT, saw another cabody revision. They received taller two-piece radiator intakes and the engine (and blower duct/dynamic brakes) were moved forward a bit. The carbody is essentially that of the GP49 and it therefore has more in common with the GP50 than with other Dash-2 units. (I haven't drawn this version)
Regardless of the carbody variations, all GP38-2's have 2 exhaust stacks and all GP39-2's have a single stack, and both models have 2 radiator fans at the rear. You're also more likely to see a GP38-2, since it outsold the GP39-2 by almost 9 to 1.
Hope this helps!
First off, the GP38-2 and GP39-2 ride on the same frame (59' 2" over coupler pulling faces) and share the same overall dimensions and many of the same components.
As for the differences, the GP39-2 actually went through several carbody variations, which are as different from each other as they are from a GP38-2.
Early GP39-2's are visually nearly identical to the earliest GP38-2's, with a two-piece wire-mesh radiator intake and fans spaced far apart. The main components of the hood (blower duct, dynamic brake housing etc) are in the same position on both models. The main differences are the engine room doors (2-3-3-2 grouping on the GP39-2 and 2-4-4 on the GP38-2) and the exhaust (single turbocharger stack on GP39-2, two exhaust stacks on GP38-2). Some earlier GP39-2's also had the fuel tank mounted farther to the rear, with a curious curved fuel filler pipe--this includes D&H and some ATSF units.
Early GP39-2, Reading version:
http://trainiax.net/drawings/36-emd/gp3 ... dg-ph1.gif
Early GP38-2, GMO version (this one lacks dynamic brakes, but it's the best comparison I have for the moment)
http://trainiax.net/drawings/36-emd/gp3 ... o-ph1a.gif
Few GP38-2's were built with the two-piece radiator intake, and after the earliest units, GP38-2's switched to a shorter single radiator intake and closer-spaced fans. However, the GP39-2 retained the longer two-piece intake for some time.
Later GP39-2's (BN and late ATSF versions) eventually adopted the shorter intake and closer-spaced fans of the GP38-2, as well as many other evolutionary changes ("phases") that were applied universally over the Dash-2 range. This includes Q-type fans on some units. They also received a large, flat exhaust silencer replacing the exhaust stack (as on other turbocharged models such as the GP40-2).
However, the biggest change in late vs. early GP39-2's is that the engine was moved over 3 feet rearward, taking the main air intake and blower duct with it. This leaves a large expanse of empty sheetmetal in the hood right behind the cab, and it places the dynamic brakes closer to the radiators. It also eliminates the last two tall hood doors, resulting in a 2-3-3 arrangement before the shorter doors under the radiator intakes begin.
Late GP38-2, BN version (this drawing also illustrates the nearly-flush, circular exhaust stacks of late GP38-2's)
http://trainiax.net/drawings/36-emd/gp3 ... n-ph2c.gif
Late GP39-2, BN version
http://trainiax.net/drawings/36-emd/gp3 ... n-ph2c.gif
The very last GP39-2's, built for the MKT, saw another cabody revision. They received taller two-piece radiator intakes and the engine (and blower duct/dynamic brakes) were moved forward a bit. The carbody is essentially that of the GP49 and it therefore has more in common with the GP50 than with other Dash-2 units. (I haven't drawn this version)
Regardless of the carbody variations, all GP38-2's have 2 exhaust stacks and all GP39-2's have a single stack, and both models have 2 radiator fans at the rear. You're also more likely to see a GP38-2, since it outsold the GP39-2 by almost 9 to 1.
Hope this helps!
--Michael Eby
--http://trainiax.net
--http://trainiax.net
So which version is the one that New England Southern (NEGS) has? It's ex-UP exx-MKT (I think)
The NEGS GP39-2 matches the following description:
The very last GP39-2's, built for the MKT, saw another cabody revision. They received taller two-piece radiator intakes and the engine (and blower duct/dynamic brakes) were moved forward a bit. The carbody is essentially that of the GP49 and it therefore has more in common with the GP50 than with other Dash-2 units. (I haven't drawn this version)
MEC407
Moderator:
Pan Am Railways — Boston & Maine/Maine Central — Delaware & Hudson
Central Maine & Quebec/Montreal, Maine & Atlantic/Bangor & Aroostook
Providence & Worcester — New England — GE Locomotives
Moderator:
Pan Am Railways — Boston & Maine/Maine Central — Delaware & Hudson
Central Maine & Quebec/Montreal, Maine & Atlantic/Bangor & Aroostook
Providence & Worcester — New England — GE Locomotives
diburning wrote:What are the physical external differences between a GP39-2 and a GP38-2?Hi , the main difference externally is :
1.) the turbo charger stack.
2.) no paper air filter box(the square protrusion Where the exhaust stack is located on the 39)
3.) on pre dash-2 models, slightly wider spaced radiator fans as compared to the gp38,on dash 2 models the radiator hood was more compact as well as the emd12/645e3 being moved about 3 feet to the rear (correct me if i am wrong) i think this was in aid of better weight distribution.
4.) one thing to confuse the railfan was that they were built on the same 59 '2" frame.
another thing to spot on the dash 2 variant on the gp39 is the t/m blower duct is around three feet farther away from the rear of the cab than the standard model gp39 pre dash2.
cheers ,Derek
GE JUST DON'T MAKE TOASTERS YA KNOW!
I think the changes Dash 7 lists under (3) and (4) were all made in the course of GP39-2 production: certainly the Santa Fe had some GP39-2 with each placement of the engine on the frame.
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As for space between blower duct (on left side of long hood) and rear of cab: I'm guessing, here, but I suspect the blower duct's distance from the front of the engine was kept constant, so it was moved back (away from cab) when the engine was moved.
One of the model railroad magazines had a detailed study of (particularly Santa Fe) GP39-2 in the late 1980s/early 1990s: I'd give references but my "railroad reference library" is packed away for shipment to a new home for the next few months. With luck the Santa Fe section of George Elwood's "Fallen Flags" railphoto WWWebsite has enough photos of GP39-2 that you can work out the changes from it.
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As for space between blower duct (on left side of long hood) and rear of cab: I'm guessing, here, but I suspect the blower duct's distance from the front of the engine was kept constant, so it was moved back (away from cab) when the engine was moved.
One of the model railroad magazines had a detailed study of (particularly Santa Fe) GP39-2 in the late 1980s/early 1990s: I'd give references but my "railroad reference library" is packed away for shipment to a new home for the next few months. With luck the Santa Fe section of George Elwood's "Fallen Flags" railphoto WWWebsite has enough photos of GP39-2 that you can work out the changes from it.
The GP38-2 has a blower equipped 16-645E engine. The GP39-2 has a 12-645E3 turbo engine. All other major "internal" components are the same. There is a big empty spot inside the carbody between the radiators and the front of the engine where the 4 cylinders are "missing" thus the carbody doors being jumbled around.
With turbo's, engine air filters USUALLY are "baggie" types located inside the generator room as air for the engine must come from the front of the turbo which is directly above the generator room partition wall. Above these baggie filters is an inertial air system using a 3 phase blower along with the generator and traction motor blower. With a blower type engine, air for the engine CAN be taken in from "up top" or just about anywhwere else due to the blower air intake locations (ala GP9 et al). Inertial filters, while a smart investment for filtering cooling air for the generator and traction motors, are not "required" . In short, it boils down to customer spec and technological advancements.
A final big difference is that on blower engines, the aux generator and traction motor blower is located directly above the center of the generator and shaft driven (where a turbo would go). On turbo engines it is mounted inside the "hump/blister" on the conductor side and is mechanically driven by a shaft to where the LB blower would normally go. The "tapered" hump like that seen on 50 and 60 series loco's that is found on some 39-2's was to provide a larger opening for traction motor cooling air to pass and (while doubtful it was the intent) make it a little bit roomier when working inside the main gen compartment. A blower type engine does not need the "space" as it is already there. I have never heard of any "blower" engines originally equipped with the tapered blister but....then again.
With turbo's, engine air filters USUALLY are "baggie" types located inside the generator room as air for the engine must come from the front of the turbo which is directly above the generator room partition wall. Above these baggie filters is an inertial air system using a 3 phase blower along with the generator and traction motor blower. With a blower type engine, air for the engine CAN be taken in from "up top" or just about anywhwere else due to the blower air intake locations (ala GP9 et al). Inertial filters, while a smart investment for filtering cooling air for the generator and traction motors, are not "required" . In short, it boils down to customer spec and technological advancements.
A final big difference is that on blower engines, the aux generator and traction motor blower is located directly above the center of the generator and shaft driven (where a turbo would go). On turbo engines it is mounted inside the "hump/blister" on the conductor side and is mechanically driven by a shaft to where the LB blower would normally go. The "tapered" hump like that seen on 50 and 60 series loco's that is found on some 39-2's was to provide a larger opening for traction motor cooling air to pass and (while doubtful it was the intent) make it a little bit roomier when working inside the main gen compartment. A blower type engine does not need the "space" as it is already there. I have never heard of any "blower" engines originally equipped with the tapered blister but....then again.
Is this loco what the NEGS gp39-2 is? I still can't tell the difference between the different "phases"
Close, but not quite. The NEGS unit is a later phase. And that drawing seems to be of a unit that has its radiator vents plated over...?
MEC407
Moderator:
Pan Am Railways — Boston & Maine/Maine Central — Delaware & Hudson
Central Maine & Quebec/Montreal, Maine & Atlantic/Bangor & Aroostook
Providence & Worcester — New England — GE Locomotives
Moderator:
Pan Am Railways — Boston & Maine/Maine Central — Delaware & Hudson
Central Maine & Quebec/Montreal, Maine & Atlantic/Bangor & Aroostook
Providence & Worcester — New England — GE Locomotives
Mr. Know-it-all:
Thank you for the informative post! F.w.i.w., I believe that a few of the last GP38-2 built had the tapered bulge like the (later?) 50-series: the published claim was that it offered less resistance to the blown air, and so improved energy efficiency ("by an epsilon," I suspect: by a very small quantity).
Thank you for the informative post! F.w.i.w., I believe that a few of the last GP38-2 built had the tapered bulge like the (later?) 50-series: the published claim was that it offered less resistance to the blown air, and so improved energy efficiency ("by an epsilon," I suspect: by a very small quantity).