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Difference between gp7 and gp9?

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Difference between gp7 and gp9?
Posted by Trainman440 on Sunday, February 21, 2016 5:12 PM

Hi, maybe Im just dumb, but whats the physical difference between GP7 and GP9?\

Thanks

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Posted by dti406 on Sunday, February 21, 2016 5:22 PM

According to original "Diesel Spotters Guide" on pg. EMD-25, "The GP-7 has three or four louvers below the cab and two vertical rows of louvers under the radiator shutters at the far end of the long hood. The GP-9 has one or no louver beneath the cab, and lacks the two vertical rows under the radiator shutters. Presence or absence of the dynamic brake blister tells nothing, as both GP-7's and GP-9's came with or without dynamic brakes.".

Also on later Phases of the GP9 the 4 36" Radiator Fans became 2 - 48" Fans, and after many railroad modifications all spotting differences may become moot points.

Rick J

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Posted by 7j43k on Sunday, February 21, 2016 5:46 PM

Trainman440

Hi, maybe Im just dumb, but whats the physical difference between GP7 and GP9?\

Thanks

 

 

We wuz all dumb, once.  Then we learned stuff.  Frequently by asking.

 

I am assuming, when you use the word "physical", that you mean "what you can see by looking at it from the outside".  Because there are also physical differences on the inside.  Which don't mean a whole lot to modelers.

 

And, frequently, as Rick just implied/noted above, there are subgroups of "physical", called phases.  And there can even be subgroups in those subgroups.

 

There are various resources that discuss phases, both on-line and bookish.  One of my favorites (though it doesn't have GP7/9's) is:

 

 

http://www.trainweb.org/jaydeet/rosters.htm

 

Ed

 

 

Ed

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Posted by ACY Tom on Sunday, February 21, 2016 5:53 PM

I typed complete answers twice. Just as I was about to hit "submit", a response was posted by somebody else and my post disappeared.

Briefly, look at pictures. Take note of the shape of the side sill (plain on GP7's; shaped differently on late GP9's), the presence or absence of slots in it (present on early GP9's), and the locations and numbers of louvres in the hood sides and grille sides (more of them on GP9's). The louvres under the cab, mentioned by Rick, don't seem to be a consistent feature. I see them on photos of B&O GP7's, but not on NKP GP7's.

GP7's used 36" roof fans. By the end of GP9 production, all roof fans were 48" diameter. 

Dynamic brakes, "torpedo tube" air tanks, etc. are irrelevant, as they were options available on both models.

The GP7 produced 1500 h.p., and the successor GP9 produced 1750 h.p.

Tom

P.S.: No, Charles, you're not dumb. The wide-body BB Athearn "GP9" was on the market for about 20 years before some eagle-eye realized it was a GP7. This was about the time that Tony Koester and others opened the eyes of many of us and began to promote the idea of better accuracy.

P.P.S.: I managed to get all the material posted by posting a short item, then adding to it with edits. Frustrating.

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Posted by arbe1948 on Sunday, February 21, 2016 6:41 PM

Also, ACY, if I recall, wasn't the original Athearn SW 1500 actually SW 7 or something like that?

Bob Bochenek
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Posted by 7j43k on Sunday, February 21, 2016 8:20 PM

arbe1948

Also, ACY, if I recall, wasn't the original Athearn SW 1500 actually SW 7 or something like that?

 

 

It was pretty much an early SW7 body with a late SW7 cab.

 

Ed

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Posted by Redore on Sunday, February 21, 2016 9:08 PM

The only dumb questionsc are ones you don't ask.

 

As I understand it, as delivered the access to the class lights and roof are individual rungs attached directly to the hood ends on most GP and SD-7's and fabricated ladders on stand offs from the ends on GP and SD 9's.  This could be changed in the 50 to 60 years since.

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Posted by Bayfield Transfer Railway on Sunday, February 21, 2016 9:25 PM

The difference between a GP-7 and a GP-9?

2.

 

*runs like hell*

 

Disclaimer:  This post may contain humor, sarcasm, and/or flatulence.

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Posted by cv_acr on Tuesday, February 23, 2016 8:30 AM

Redore

As I understand it, as delivered the access to the class lights and roof are individual rungs attached directly to the hood ends on most GP and SD-7's and fabricated ladders on stand offs from the ends on GP and SD 9's.  This could be changed in the 50 to 60 years since.

The ladder thing is definitely not correct. Both SD7 and SD9 models had ladders instead of grabs, but I've never seen either a GP7 or GP9 with full ladders instead of grab irons.

The visual differences are all about the car body louvers, as described in one of the first responses here.

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Posted by wjstix on Tuesday, February 23, 2016 11:23 PM

I'm trying to remember where I read this - I think one of my Northern Pacific books? I'll try to track it down....Anyway, I remember reading that the frame of the GP-7 wasn't all that strong. Something about the way it was welded - or that it was welded, rather than cast? Whatever it was, the GP-9 frame was stronger and more durable. I know GP-9s could last a long time, some of the Soo Line's high nose GP-9s lasted long enough to get the all-red CP paint in the 1990's.

Stix
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Posted by SouthPenn on Wednesday, February 24, 2016 6:34 AM

Couldn't all the differences listed be the way they were ordered by the railroads?

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Posted by ACY Tom on Wednesday, February 24, 2016 10:38 AM

On GP7/9's, louvres and side sill configurations were determined by EMD.

Options such as dynamic brakes, "torpedo tube" air tanks, steam generators, horns, Mars lights, and fuel tank capacity would have been determined by the purchaser.

Tom 

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Posted by dti406 on Wednesday, February 24, 2016 1:13 PM

ACY

On GP7/9's, louvres and side sill configurations were determined by EMD.

Options such as dynamic brakes, "torpedo tube" air tanks, steam generators, horns, Mars lights, and fuel tank capacity would have been determined by the purchaser.

Tom 

 

And size and placement of radiator fans!

Rick J

Rule 1: This is my railroad.

Rule 2: I make the rules.

Rule 3: Illuminating discussion of prototype history, equipment and operating practices is always welcome, but in the event of visitor-perceived anacronisms, detail descrepancies or operating errors, consult RULE 1!

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Posted by DSchmitt on Wednesday, February 24, 2016 1:57 PM

GP7, GP9, GP18  The main differences were internal not external.

The most visible difference is the  size and number of radiator fans (excluding the optional dynamic brake fan) but the GP7 and early GP9 had the same fans, that is 4 small fans.  Latter GP9 had two larger fans.  The GP18 also had two fans but they stuck up above the roof and had a shroud around them whereas the GP-9 fans were almost flush with the roof.  However very late GP9 had the same fans as the GP18.

Louvers below the cab is often said to be the most reliable way to tell a GP9 from a GP7.  The GP9 had the louvers the GP7 didn't.  But ACY stated, from his observation,  that may not be true.

The arangement of the louvers on the long hood doors also varied  over the production run GP7 through GP18.

Also with repairs, modifications and rebuilds parts got mixed.

The easyist and probably most reliable way to determine if a loco in a photo is a GP7, GP9 or GP18 is to note the locomotive number on the cab and check the railroads roster.

There was also the turbocharged GP20 which could  easily be mistaken for a GP7, 9 or 18 from most angles.  It had the same radiator fans as the GP18.  The distinguishing feature was a tall louvered box on the long hood behind the cab.

I tried to sell my two cents worth, but no one would give me a plug nickel for it.

I don't have a leg to stand on.

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Posted by Trainman440 on Wednesday, February 24, 2016 3:56 PM

Thankyou everyone for the replies!

So the biggest/only diffference is the louvers under the cab, got it!

Thanks Big Smile

Charles

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Posted by cx500 on Wednesday, February 24, 2016 4:38 PM

No, the biggest and most reliable difference is the two vertical lines of louvers towards the rear of the long hood, as on the old BB Athearn GP.  The early GP9s also had the louvers under the cab.

Also remember that the railroads occasionally switched parts around during shopping, so you could sometimes end up with spotting features from different phases on a single unit.

John

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Posted by wjstix on Sunday, February 28, 2016 12:04 AM

Re my earlier post, this is what I was referencing:

"The major weakness of the GP-7 was it's relatively light frame...in later years the frames would sag slightly in the middle. If the locomotive was used in road service where it operated with other units on heavy trains, its end platforms tended to bend down because of heavy buffeting." ("Northern Pacific Diesel Era" Frey & Shrenk)

I don't know that this would be really noticeable on a model, but would be interesting to try. Anyway, apparently the GP-9 had a stronger frame and didn't have this problem. 

Stix
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Posted by Graham Line on Sunday, February 28, 2016 7:37 PM

As anyone who has tried to convert an Atlas/Kato GP7 to a GP9 has discovered:

The GP7 has a batten strip (a shallow channel with bolt heads or rivets) running up and over the long hood, before or after the location of the dynamic brake hatch.

I find the presence or absence of the batten strip a much more reliable guide than louvers that appear on hinged and detachable access panels.

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Posted by DSchmitt on Sunday, February 28, 2016 11:57 PM

Graham Line

As anyone who has tried to convert an Atlas/Kato GP7 to a GP9 has discovered:

The GP7 has a batten strip (a shallow channel with bolt heads or rivets) running up and over the long hood, before or after the location of the dynamic brake hatch.

I find the presence or absence of the batten strip a much more reliable guide than louvers that appear on hinged and detachable access panels.

 

It depends on when the locomotive was built.  Drawings on this site:  http://trainiax.net/mephoto.php

Show no difference in this respect between GP7 and early GP9. They  have a identical continous narrow section or batten strip from the walkway over the top on both ends of the dynamic back location.  The doors are the same but the  louver placements are different. This, however may  may not be a definitive difference..

The GP9 (phase 2, - 36" fans) and GP9 (Phase 3, - 48" fans) are different. They have no batten strip. There are narrow sections over the top but they do not go below the bottom of the dynamic brake panel on each side.  There is no narrow section on the side behind the dynamic brake.  There is a narrow section for hinges  between doors on the side in front of the dynamic brake but it is separate from the section over the top.  The first door behind the cab is hinged on the opposite side from the early GP9/GP7 and the louver pattern is different.

 

 

I tried to sell my two cents worth, but no one would give me a plug nickel for it.

I don't have a leg to stand on.

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Posted by ACY Tom on Monday, February 29, 2016 5:04 PM

Bottom line:  

Refer to photos for all modeling projects.  The more photos, the more angles, the better.

Tom 

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Posted by 7j43k on Monday, February 29, 2016 7:09 PM

Here's a nice big photo of a GP7 (without DB):

 

http://archive.trainpix.com/BN/EMDORIG/GP7/1524.HTM

 

You can see the battens plainly.  You can even see that the foreground one "keeps going" towards the bottom.

 

Here's a good shot of a GP9 (again without DB):

 

http://archive.trainpix.com/BN/EMDORIG/GP9/1887.HTM

 

Note the total absence of battens.  You can also compare the louver locations, and see that they kinda moved towards the cab.  I almost said forward, but the GP7 is ex-GN, so the long end is front.

 

Here's a GP9 with DB.  Note that the battens are there, but only on the top of the sides:

 

http://archive.trainpix.com/BN/EMDORIG/GP9/1761.HTM

 

So, now you've been "battened down"!

 

I recommend, just as Tom just did, that you get yourself some good photos of the loco you want to model.  'Cause like as not, the one YOU want to model will be the exception.

 

 

Ed

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Posted by ThamasTehTrain on Friday, March 08, 2019 9:16 PM

Ok, its very complex cated, but the best way to tell the diffrence is that the GP9 has side radiators like later SD and GP models, when the GP7s dont.

One of the only railfans who gives a crap about the MMA, despite not living IN the northeast.

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Posted by NHTX on Saturday, March 09, 2019 12:41 AM

      There are some more "as built" spotting features that can be used to tell GP-7s from GP-9s, even after numerous and, extensive rebuildings.  The buffer casting on a GP-7 is round on top, like a piece of quarter-round stock while that of GP-9s and subsequent models is a flat piece of sloped plate.  Also, the pilot faces of the early GP-7s sloped outward toward the bottom, to accomodate the footboards.  Later 7s and subsequent models had flat, vertical pilot faces with boxes to retain the MU hose gladhands.  Phase 1 GP-7s (10/49-8/52) had 36 inch dynamic brake fans on the units so equipped.  All GP-7s and phase 1 GP-9s were built with cast handrail stanchion fittings up until 6/54.  After that, the stamped stanchions of today became standard.  The phase 1 GP-9 got rid of the two sets of louvers at the end of the long hood, replacing them with one single group in the last door under the rear radiators if the short hood is forward.  The two rows of louvers in the doors of the phase 1 engine compartment became  three rows up to and including the GP-18.

      It should also be noted that EMD had two types of fans--36 and 48 inch--period.  A 36 inch fan from an F-7 didn't care if it was installed on a GP-20.  Same for the 48 inchers.  Also, the GP-18s, except for one of Boston and Maine's that was built with the 36 inch fans of an f-unit or BL-2 trade-in, had single 48 inch radiator fans fore and aft on the long hood.  The GP-20 had the same configuration but with a 36 inch fan just forward of the rear 48 incher.  As stated earlier, railroads are only concerned with the fan covering the hole in the hood.  There was a Cotton Belt SD-45 that had a flare top 48 incher from a GP-20 in its radiator group.  The next one in the warehouse is what went out the door, regardless of where it came from and, where it was going.

     For those with a deeper interest in the early (GP-7 to GP-20) geeps, if you can find a copy of the October-November-December 1971 and the January-February 1972 issues of Extra 2200 South, the locomotive newsmagazine.  X2200S did production summaries of these units along with spotting features, drawings, and photographs.  For those who like the unusual, I suggest you find a photo of C&O 5826.  It was built as a dynamic brake equipped GP-7 that somehow by 1970 had acquired a phase 3 GP-9 long hood with 48 inch fans.  Everything behind the cab was late GP-9 including handrail stanchions.  Forward of the cab was all GP-7 including louvered doors under the cab, and cast component handrail stanchions.  One would presume the unit met with some sort of catastrophe and was rebuilt with then the current GP-9 parts.  Just when you think you've got that GP-7/GP-9 thing figured out, along comes a C&O 5826.

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Posted by rrinker on Saturday, March 09, 2019 10:49 AM

 The early spotting feature of the battery box louvers went all sideways as soon as the same railroad had both models. Outside of louvers, slots, or blanks, each battery box cover plate fits either loco, so they got all mixed up over time as locos were in for maintenance. 

 I'm not sure about that idea that the GP7 has a relatively weak frame - there are a LOT of them still running and in use. I'll try to remember to take a look at ours when I next get to the museum. It's in the process of being restored to usable condition but when we aquired it, it had been still in regular service. 

                                           --Randy

 


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Posted by cv_acr on Monday, March 11, 2019 8:47 AM

ThamasTehTrain

Ok, its very complex cated, but the best way to tell the diffrence is that the GP9 has side radiators like later SD and GP models, when the GP7s dont. 

 

And the winner for "Restarting a three year old thread with a useless post that doesn't even give accurate information" goes to...

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Posted by Trainman440 on Monday, March 11, 2019 8:27 PM

No need for the dry sarcasm, but indeed, starting old threads are a bad idea. 

Charles

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Charles L.

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Posted by MapGuy42 on Wednesday, March 13, 2019 1:11 PM

Trainman440

No need for the dry sarcasm, but indeed, starting old threads are a bad idea. 

Charles

 

Oh, I don't know.  I hadn't seen this one before, and I found it very informative, being that I'm interested in running a GP7 on my layout. Smile

For my freelanced purposes, it sounds like if my unit had the smaller fans, I could credibly claim it was either model.

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Posted by mbinsewi on Wednesday, March 13, 2019 1:29 PM

Trainman440
starting old threads are a bad idea.  Charles

I don't see a problem with it, as it has been happening more and more as new members come aboard.

What the issue was about, is the contributor with the cat pictures had nothing accurate or informative to ad.

Mike.

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Posted by BRAKIE on Wednesday, March 13, 2019 1:59 PM

DSchmitt
GP7, GP9, GP18 The main differences were internal not external.

Actually there are several differences in those Geep units only the GP9 phase three and the GP18 shared the same carbodies both having 2 48" fans instead of the GP7 and phase 1 and phase 2 GP9 four 36" fans.

 

 

Larry

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Posted by NHTX on Friday, March 15, 2019 11:13 AM

    MapGuy42:

    No sir.  As built, there are distinct differences between the GP-7 and GP-9s.  For rebuilt units, have fun!

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