A question received recently: What is the significance of an "L" after GP9 in EMD sales records?

Answer: The model designations GP9L and GP9R are sometimes encountered in EMD sales records and publications. They do not mean "Left" and "Right", or "Lightweight" or "Replacement". The "L" and "R" are EMD Sales Department shorthand for the type of brake equipment the unit was built with. A GP9L had 6BL brake, a GP9R had 24RL brake. This explanation is usually found on page 110 of the GP9 Operators Manuals.

PC

The Army had a series of GP-9L's for treading over their light WW2 vintage rail. In addition to the differences noted above, they had smaller fuel tanks (900 gal?) and AAR trucks. I think they were all sold/scrapped and replaced in the early '90's when the Army base track systems were upgraded.
CN had a number of them as well. The June 2022 RMC has an article on how to build them. They had Flexicoil trucks instead of Blombergs.

Deleted

You're probably thinking of the GP7L's that were bought for the Army....
They were, I think, among the first GP7's built....
They have AAR switcher trucks instead of Blombergs...
Some of the type were also built for, I think, L&N?...
A few survive today in museums, such as the museum in Parrish ,F!....they got two, one runs regularly...
The only other EMD GP's I've seen with different trucks are the ones done using trade in parts, like some GP35's built with recycled ALCO trucks, which were done for N&W originally, I think....

Edit: looks like all of L&N's GP7s with switcher trucks were ex-NC&StL. Here is #492, ex-NC&StL #702, and #491, ex-NC&StL #701, and a link to NC&StL #703 only, as the NC&StLHS won't let me copy and paste: http://www.ncstl.com/equipment/diesel/703.htm

I guess you're right they were GP-7's not -9's. My 77 year old brain short-circuited.

The brake differences applied to GP7's as well.

Erie Lackawanna had a problem because the Erie GP7's had schedule 6-brakes while DL's had 24. [all had Blomberg trucks]. EL eventually came up with a way they would work together. Don't ask me what they did.

Phil Mulligan

Compatible operation of 6 and 24 brakes is covered by EMD Maintenance Instruction 1055, issued in October 1956.

PC

I should have expected EMD had already addressed the issue.

Since the EL marger came after EMD Maintenance Instruction 1055 was issued. I must assume EL simply followed the book.

Thanks

Phil Mulligan

Very curious about that MI; is a scan available anywhere? I've seen some interesting 6 upgrades, and wonder what EMD's solution was.

The NC&STL/L&N GP7s with switcher trucks originally did not have MU controls, but it appears the L&N added that feature to them. They ended up with a rebuilder, PNC I think, who added standard trucks to them.

Were the body bolsters any different on the GP7L, in such a way that it requires modification to fit Blomberg strucks?

Here (if the attachment feature works) is MI-1055 as requested.

If attachment does not work, this is also being posted to the HRA library.

PC

I have a question regarding the DC generators that some C&NW GP9 locomotives were equipped with to power train-line lighting for open-window, steam-heated coaches. According to 
https://utahrails.net/pass/dynamos-hep.php C&NW GP9's 1711-1718 were so equipped.

The most distinctive spotting feature is the rectangular housing on the long hood. 

This photo of 1713 shows the rectangular housing on the long hood and a recepticle on the short hood for connecting the DC train line from the locomotive to the consist: http://rr-fallenflags.org/cnw/cnw1713alr.jpg

GP7s of the CNJ, B&M and C&NW were also so equipped. 

My question is: how did this DC generator function? I have heard elsewhere that the DC generator was air powered, but I have found no information beyond that. I'm interested in learning more about how the generator was powered, how it was controlled, and what the power output was. In the context of passenger train history, this was an incremental step, with these generators replacing the function provided by the large dynamos steam locomotives assigned to commuter service.  

Any information or references would be helpful - thank you

What would be the conditions that would have a carrier specifically order the 6BL or 24RL control valves on their locomotives?