# Diesel Nomenclature?



## Cab1 (Jul 26, 2009)

OK, can someone explain to me diesel nomenclature? Steamers I get, 4-4-0, 2-10-2, and so on; defined by the number of lead wheels, drive wheels, and trailing wheels under the loco. I get it, but diesels - not so much. They all look alike to me. So what's the difference between a GP38-2 or a SD45 or a FM H10-44 or a Dash 8-40C or a AC6000CW or any other diesel for that matter?


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## sstlaure (Oct 12, 2010)

Diesels were named by each company (EMD, Alco, etc, and each one was a little different) The letters/numbers stand for engine HP rating, AC or DC power, wide or normal cab, etc....definitely not as clear cut at steamers

GP's are general purpose and are 4 axle engines, SD's are Special Duty and are 6-axle engines (able to handle higher weight loads.)


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## tjcruiser (Jan 10, 2010)

My brain gets all foggy when it comes to diesel nomenclature, too. I had asked a similar question a while back, and had some helpful responses/links in this thread:

http://www.modeltrainforum.com/showthread.php?t=5252

TJ


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## Massey (Apr 16, 2011)

I posted this on another thread a while back detailing what was what as far as the prototypes go. Here is the skinny

To drop some basics here each manufacturer has thier own system but they are similar. GE's number relates to the HP of the prime mover, EMD relates to the Locomotive Series.

EMD uses a prefix to deisgnate the loco's job and axle setup GP= General Purpose 4 axle, SD= Special Duty 6 Axle. GE uses the older B and C designation "B" for 2 axle trucks and "C" for 3 axle trucks. 

At the end of the designation is specific model info such as wide cab, or AC traction or variant info. Here is an example.

SD70= Special Duty, (6 axle) 70 Series Locomotive, DC Traction motors
SD70M= Special Duty, (6 axle) 70 Series Locomotive, DC Traction motors, Wide Cab("M")
SD70MAC= Special Duty, (6 axle) 70 Series Locomotive, AC Traction motors, Wide Cab("M")
SD70ACe= Special Duty, (6 axle) 70 Series Locomotive, AC Traction motors, Meets EPA regulations, (No cab designation since the wide cab is the only one available on this model)
SD70M-2= Special Duty, (6 axle) 70 Series Locomotive, DC Traction motors, Wide Cab("M") Second Version, (Looks like the SD70ACe but with DC traction motors.

GE looks like this 
8-40C= Series 8 (or Dash 8), 4000 HP Prime Mover, "C" Trucks (3 axle)
8-40CW= Series 8 (or Dash 8), 4000 HP Prime Mover, "C" Trucks (3 axle), Wide Cab
8-40B= Series 8 (or Dash 8), 4000 HP Prime Mover, "B" Trucks (2 axle)(Amtrack used these engines)
9-44CW= Series 9 (or Dash 9), 4400 HP Prime Mover, "C" Trucks (3 axle), Wide Cab

Hope this helps you understand the engine designations

Now the model is a totally different story. I have a Athearn BB Dash 9 that cannot pull as well as a Proto 1K GP38-2, but in reality one Dash 9 would pull better than 2 GP38-2s could.

Massey


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## norgale (Apr 4, 2011)

Cab-1 look where Massey has printed out the info your asking about. Click on the #4 to the right side of that post and then print it out. Hang it up near where you run your trains or work on them and refer to it as often as you think about it. Practice identifying your own engines and others that you see pictures of. Pretty soon you'll be memorizing the nomenclature and it will all be much clearer to you. Takes a little practice but it's fun and informative. pete


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## tjcruiser (Jan 10, 2010)

Put a copy of the printout under your pillow, too!


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## Massey (Apr 16, 2011)

Another thing to think about is what the "B" and "C" are and how they are different than the "b" and "c"

The letters A-D refer to the configurations of the trucks on an engine. There is some "code" to go with it. 

Capitol letters mean the wheels are powered.
Numbers mean unpowered (Lower case letters can mean those wheels are unpowered)
A "+" means the trucks share a bolster
A "-" means the trucks have their own bolster.

Here is an example.

B+B-B+B
This is an example of of the truck configuration of the U50 engines.

Baldwin had a very unique setup with the Centepede engines. Those were B-D+D-4 (or sometimes B-D+D-b) which means the B truck is on its own bolster, the 2 "D" trucks share a bolster (they were actually connected together and articulated) and the trailing truck was unpowered.

Massey


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## trainguru (Jun 28, 2011)

*Old timey Diesel wheel arrangements!*

So Fairbanks-Morse, there's the H or C (Hood or Carbody/Cab), 10, 12, 15, 16, 20, or 24 is the horsepower multipled by 100, (1000, 1200, 1500, 1600, 2000, 2400), and 44, 46, and 66 for hood, and 4 or 5 for carbody, means how many axels are powered. The Carbodies were built with 4 powered axels (Bo-Bo in diesel-electric wheel nomenclature) or 5 axels since they wer built with an Bo-A1A wheel arrangement, 1 denoting an ideler axel, or 46 in the hoods denoting to a road switcher with A1A-A1A (The BNSF is now doing that with some of their newest locomotives). The 44 or 66 means that all axels wer powered (Bo-Bo = 44; Co-Co =66). 

And that's how Fairbanks-Morse works out, Baldwin used a similar system, post VO Switcher, just flip the position of the powered axels and have the full horsepower total at the end. DRS/AS= Diesel Road Switcher, DR/RF/RP= Diesel Road Freight/Passenger, DS/S are switchers. Note this, with AS and R's have an extra number (2, 4 or 6) to denote how many powered axels they have, then the first two numbers of their horsepower, IF they are NOT 4 power axeled, otherwise they just have the first two numbers of their horsepower, like S8 and S12... Switcher, 800 or 1200 horsepower!

Hope this helps -  Good luck!


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## norgale (Apr 4, 2011)

Now the water is really muddy. I can see right now that building locomotives really needs to be standardized in it's nomenclature at least. Pete


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## raleets (Jan 2, 2011)

Massey,
Thanks for all that info on locos. I've also wondered where those designations came from.
I printed out your post and will keep it near my layout for future references.
Great help!
Bob


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## sstlaure (Oct 12, 2010)

I told you steamers were more straightforward


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## Cab1 (Jul 26, 2009)

Wow, thanks for the schooling. I often wondered about the practicality of all that alphabet soup. I can see how important being that specific would be from a maintenance and dispatching point of view. You wouldn't wanna send a GP38 to haul a customer's load that would really need two GE AC6000CW's.


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## trainguru (Jun 28, 2011)

*Oy Vey... U.S.A.! U.S.A.!*



norgale said:


> Now the water is really muddy. I can see right now that building locomotives really needs to be standardized in it's nomenclature at least. Pete


This isin't British Railways and the TOPS System, or France and the SNCF, or DB Germany, or the Italian State Railways (FS), or anybody else... We're, "Private Sector Railroading" Americans!!! We do what we want under God's will, because we're asowme like that Pete. Conventionality belongs to yesterday...Grease is the Word!

:thumbsup::thumbsup:
"Ayeeeee!" - Says the Fonz!


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## cv_acr (Oct 28, 2011)

sstlaure said:


> I told you steamers were more straightforward


Not really. Steamers were usually pretty much all unique from railroad to railroad. Various builders built locomotives, and a large railroad's heavy backshop could pretty much build new locomotives from scratch. Railroads had their own classes and styles, and a 4-6-0 on Union Pacific probably looked a fair bit different than one from say Virginian.

They're referred to by their wheel arrangement, and general type names based on those wheel arrangements. There could be many different variations of 4-6-0 locomotives, all with the same wheel arrangement but widely differing details and construction.

_Most_ diesel locomotives have one of two wheel arrangements:
B-B or C-C
where someone has already described how this notation works.

Some early diesel builder plates actually specified wheel arrangement in a similar fashion to the old nhotation used for steam engines: eg. 0-4-4-0 for a 4-axle diesel.

At least diesel locomotives were built to distinct models; the naming convention for these models was up to the builder. Some builders had more consistent naming conventions than others, often but not always based on horsepower rating.


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## cv_acr (Oct 28, 2011)

Cab1 said:


> Wow, thanks for the schooling. I often wondered about the practicality of all that alphabet soup. I can see how important being that specific would be from a maintenance and dispatching point of view. You wouldn't wanna send a GP38 to haul a customer's load that would really need two GE AC6000CW's.


Some railroads (like CP and CN) created their own classification systems to organize various models based on usage and horsepower.

Most railroads will have tables relating either their own internal classifications or specified number ranges to HP and/or tonnage ratings.

The railroads have been doing this for many decades, I'm sure they've all managed to form their own methods of keeping track of their fleets.


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