The three inch difference in length over draft gear buffer faces between the GP-7 and the GP-9 may be due to the fact GP-7s had a buffer casting while, the GP-9s buffers were fabricated from steel plate.
No examples of "hydraulic" MU are evident, even on locomotives with hydraulic transmissions. MU control was either pneumatic as in Baldwin and early Fairbanks-Morse locomotives, or electrical in the rest of dieseldom. As much as each manufacturer wanted their products to dominate, the railroads made it abundantly clear that they wanted interchangiblilty across all brands of diesels, regardless of builder. This led to standardization on the 27 point jumper cable by the time the GP-9 had replaced the GP-7 in EMD's catalog in 1954. Earlier power was retro-fitted to provide maximum flexibility in locomotive utilization.
One limiting factor in early first generation compatibility was the differences in braking equipment "schedules". These sets of characteristics governed the operations of the air brake systems and all were not compatible with each other, regardless of builder. The 6 schedule as used on the early post war production gave way to the 24 schedule as the GP-9 replaced the GP-7. The 26 schedule came along to replace but, operate with the 24 at the beginning of the second generation.
Most of these factors exhibit no visual cues on a locomotive that a modeler would duplicate but, would be evident in the way locomotive consists would be built. Sometimes, these limitations are included in the special instructions section of the employees timetable. Often locomotives with special characteristics are segregated by numbering group, as the Union Pacific did when it put its "fast forty" SD-40-2s in the 8000 series.
For someone modeling the early postwar diesel era, the effort to keep pure consists of like locomotives together could make you bring back steam!
DSchmitt"I have been told that the controls of GP7s would not MU with anything but other EMD products, and GP9s were more universal in MU capability. .Is any of this true?" I believe not true.
It may have been somewhat true when built. In the early 1950s the MU connections were not completely compatible between builders, although (except for BLW) they were very close. Most of the problems were in the lesser features, operating sanders, or having the dynamic brakes operational on all units. Sometimes loco A could control all the features on loco B, but not vice versa. Jumper cables were also a work around. It did not take long for most railroads to retrofit their fleets to be fully compatible. Switchers, in the rare cases where they had MU, were an exception and generally would not MU with road power.
John
jrbernier The wheelbase is identical. The GP7 is 55' 11" over the draw bar buffers. The GP9 is 56' 2" over the buffers. I suspect this is a change in vender supply issue or the ability to mount alignment control couplers.
The wheelbase is identical. The GP7 is 55' 11" over the draw bar buffers. The GP9 is 56' 2" over the buffers. I suspect this is a change in vender supply issue or the ability to mount alignment control couplers.
Jim
"I have been told that the controls of GP7s would not MU with anything but other EMD products, and GP9s were more universal in MU capability.
.Is any of this true?"
I believe not true.
I know the Western Pacific MU'd GP7 with Alcos and GE's
Baldwins could not MU with other brands because it used a hydraulic MU system and an adaptor was made to connect to the others electric MU systems
Most electric MU's used 27 pin plugs. Where other arangements were mounted there were adaptor plugs.
Discussion Here
http://cs.trains.com/mrr/f/13/t/267753.aspx
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.
I have been told that the controls of GP7s would not MU with anything but other EMD products, and GP9s were more universal in MU capability.
.
Is any of this true?
-Kevin
Living the dream.
Modeling BNSF and Milwaukee Road in SW Wisconsin
A GP7 is also a foot or so shorter than a GP9.
MapGuy42:
No sir. As built, there are distinct differences between the GP-7 and GP-9s. For rebuilt units, have fun!
DSchmittGP7, 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
Conductor.
Summerset Ry.
"Stay Alert, Don't get hurt Safety First!"
Trainman440starting 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.
My You Tube
Trainman440 No need for the dry sarcasm, but indeed, starting old threads are a bad idea. Charles
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.
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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Modeling the Santa Fe & Pennsylvania in HO
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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.
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...
Chris van der Heide
My Algoma Central Railway Modeling Blog
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
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
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.
One of the only railfans who gives a crap about the MMA, despite not living IN the northeast.
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
Bottom line:
Refer to photos for all modeling projects. The more photos, the more angles, the better.
Tom
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.
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.
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.
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.
Thankyou everyone for the replies!
So the biggest/only diffference is the louvers under the cab, got it!
Thanks
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.
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
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.
And size and placement of radiator fans!
Rick J
Rule 1: This is my railroad.
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Couldn't all the differences listed be the way they were ordered by the railroads?
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.
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.
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.