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[Lord Atmo]

sorry, the title is a bit confusing, but what i'm curious to know is what those few locomotives that, in their names, have letters in them mean. take the SD60M for example. what does the M mean or represent? i know that the SD60M differs from the SD60 in that it has a widenose cab. so then wouldnt it be called an SD60W? what does the I mean? like in the SD70I? what does MAC mean?

also, why is the SD90 called the SD9043MAC? why did EMD go from the eighty to the nine thousand and forty three?

what i know so far-
M=?
I=Isolated
W=Widenose Cab
T=Tunnel Motor
Q=?
X=Experimental
R=?
L=?

[wctransfer]

The M in mac i dont know, but the AC is alternating current . The W is strictly a GE thing, besides the GP40-2LW (W isnt even supposed to be in the name, railfans just added it, or so im told) only GE units have the W. Oh yes the SD70I and SD60I , the I is for Isolated. The SD90Macs are around, but most are the SD9043Macs, meaning it has 4,300 HP.

Alec

[trainboyH16-44]

M is for widecab, I think it stems from Modified North American cab.
L also means widecab (At least on CN's GP40-2s like Alex mentioned above)
I think the reason EMD went straight from 80 to 90 is due to the fact that the SD80s had 20 cylinder blocks and the 90s had the usual 16. There are two types of SD90: The SD90/43MAC and the SD90MAC-H. The latter was the only planned SD90, with a 6000hp H block. There were problems in the development of a 6000hp engine for both GE and EMD, and both temporarily offered 'upgradeables', locomotives with a lower horsepower that could be upgraded to 6000HP once the prme mover was availible. GE used its existing AC4400CW design, while EMD made the 4300HP SD90/43MAC, hence the 43 in the name.
R is probably for rebuilt, seeing as CN's rebuilt geeps are GP9Rs.
BTW, if you ever come across a CP SW1200RSu, RS=Road switcher (higher gearing and different trucks) and u is for upgraded, like on their GP9s.

[Lord Atmo]

if M is for widecab, why do SD40M-2s have spartan cabs?

[BentnoseWillie]

QUOTE: Originally posted by Lord Atmo

if M is for widecab, why do SD40M-2s have spartan cabs?

Because EMD didn't assign them that designation - that's a designation assigned by the railroad that owned and/or rebuilt the units.

Here's the latest version of my opus on diesel nomenclature. This document is regularly updated. I welcome any and all corrections, clarifications or feedback.

I have only covered builders' designations here - there are variations by rebuilders and railroads that differ from the pattern shown, as well as exceptions within builder nomenclatures. General Electric, for instance, uses at least two different and equally-valid nomenclature sequences.

Export models are not included here.

Chapter 1:
Electro-Motive Division / General Motors Diesel Division / Electro-Motive Diesel

Format: xxyy

xx: Type
DD = 8-axle freight locomotive.
E = 6-axle passenger locomotive with A1A (3 axles, center axle unpowered) trucks.
F = 4 or 6-axle cowl-body freight or passenger locomotive. May include steam generator or HEP equipment (see PH suffix below for an explanation of HEP).
FP = 4 or 6-axle cowl-body passenger locomotive with steam generator.
GP = 4-axle hood-type road switcher.
SC = 4-axle switcher, cast frame.*
SD = 6-axle road switcher.
SDP = 4-axle road switcher equipped with steam generator.
SW = 4-axle switcher, welded frame.*
TR = 4-axle switcher with permanently-coupled 4-axle booster.

* On early EMD switchers "S" and "N" denoted "Six" and "Nine" hundred horsepower. This was later dropped and welded frames became the standard; from the SW7 on, "SW" denoted a 4-axle switcher.

yy: Series
7,9,40, etc.- No direct correlation to horsepower

Common Suffixes:
A = Cowl-body unit equipped with cab (e.g. F7A)
Post-1985: Cowl-body unit with next-generation prime mover (e.g. SD50AF)
AC =
? Pre-1990: Alternating-current generation with DC traction motors. (e.g. GP38AC, MP15AC)
? Post-1990: AC generation AND traction. (e.g. SD70MAC)
B = Cabless booster (e.g. GP60B)
C = 3-axle trucks with 3 traction motors (F40C)
DC = Unit built with DC generation and traction after introduction of "Dash-2" line (e.g. MP15DC)
e = Meets US Environmental Protection Agency (EPA) "Tier 2" emissions standards (e.g. SD70ACe)
F = Full-cowl carbody (SDP40F, SD50F, SD60F, SD40-2F)
I = Optional vibration-isolated cab ("Whispercab"), later included in M cab.
M = Safety Cab (EMD 4-, 3- or 2-windshield designs)
PH = Equipped with generation capacity to supply "head-end" power to electrically heated/cooled passenger cars. (e.g. F40PH, F59PH)
W = Safety Cab (CN 4-windshield design)
X = unit, with experimental variation from production specifications (e.g. GP40X)
-2 = Improvements introduced in 1972, including modular electrical cabinet and AC generation (with DC traction). (e.g. SD45-2, GP40-2, GP38-2)
-1 = Post-1972 locomotive without "Dash 2" features. (e.g. GP15-1)

Chapter 2: General Electric (Pre - 1979)

Format: Uxxy
U: "Universal Series"

xx: Horsepower (x 100)

y: Axles (all powered):
B = 4 axles
C = 6 axles
D = 8 axles


Chapter 3: General Electric (Post - 1979)

Format: xyy-z or "Dash z yyx" or z-yyx
(All the above are found in GE literature)
x: Locomotive configuration
B = 4 axle road switcher, all axles powered
C = 6 axle road switcher, all axles powered
P = Passenger unit, all axles powered (used only on first format above)

yy: Horsepower (x 100)

z: Series number (7, 8, or 9)

Suffixes:
AC = Alternating-Current generation and traction.
M = Full-cowl carbody (C40-8M for CN, BC Rail, QNS&L)
W = Safety Cab (GE or CN Design)



Chapter 4: American Locomotive Company / Montreal Locomotive Works (Pre-1960)

Format: xx-yy

XX: Locomotive Type
FA = 4-axle cowl-body freight Locomotive with Cab
FB = 4-axle cowl-body freight booster without Cab
FPA = 4-axle cowl-body passenger locomotive with Cab
FPB = 4-axle cowl-body passenger booster without Cab
PA = 6-axle cowl-body passenger locomotive with A1A (3 axles, center axle unpowered) trucks, with cab
PB = 6-axle cowl-body passenger booster with A1A (3 axles, center axle unpowered) trucks, without cab
RS = 4-axle road switcher
RSD = 6-axle road switcher
RSC = 6-axle road switcher with A1A (3 axles, center axle unpowered) trucks.
S = 4-axle switcher

yy: Series Number
Example: RS-1 = 4-axle road switcher, series 1

Early Switchers: Format: HH-xxx
HH: Series (sometimes called “High Hood”)
Xxx: Horsepower (x100)

Alternate Designation:
DL-xxx

DL numbers are Alco/MLW internal specification numbers. All Alco locomotives have a specification number, and most domestic-market locomotives also have a model number as outlined above, with certain exceptions such as the DL-109 and DL-535 which had no accompanying model numbers.


Chapter 5: American Locomotive Company / Montreal Locomotive Works (1960-1969)

Format: Cxyy
C - "Century Series"

x - Number of axles (all powered)

yy - Horsepower (x 100)

Suffix:
M: Montreal Locomotive Works variant.

Example: C630M: Century series, 6 axles, 3000HP, MLW variant


Chapter 6: Montreal Locomotive Works (Post-1969)

Format: Mxyy
M - "M-Line"
(Developments in century series produced by MLW after Alco closed in 1969)

x - Number of axles (all powered)

yy - Horsepower (x 100)

Example:
M636 = M-Line, 6 axles, 3600 HP

Chapter 7: Bombardier (North American Market)

Format: HRXYY
HR - "High Reliability" Series
(Locomotive series developed by MLW under Bombardier ownership)

x - Number of axles (all powered)

yy - prime mover configuration

Examples:
HR412 = High Reliability Series, 4 axles, 2000 HP prime mover
HR616 = High Reliability Series, 6 axles, 3600 HP prime mover

Chapter 8: Fairbanks-Morse / Canadian Locomotive Company:

Format: x-yy-zz
x: Locomotive series
CFA = Cowl-Body freight Locomotive with Cab
CFB = Cowl-Body freight booster without Cab
CPA = Cowl-Body passenger Locomotive with Cab
CPB = Cowl-Body passenger booster without Cab
H = Hood-body road switcher

yy: Horsepower (x 100)

zz: Axle count and configuration
4 = 4 axles, all powered
5 = 5-axles, 4 powered
44 = 4 axles, all powered
46 = 6 axles, 4 powered
66 = 6 axles, all powered

Examples:
CPA-16-5 = Cowl-Body passenger Locomotive with Cab, 1600HP, 5 axles (4 powered)
H-24-66 = Hood-body road switcher, 2400HP, 6 axles (all powered)

Chapter 9: Baldwin

Format: AAA-x-y-z
AAA = locomotive type
DRS = Diesel Road Switcher
DS = Diesel switcher
DT = Diesel Transfer engine

x = axle count
y = powered axles
z = horsepower

Example:
DRS-6-4-1000 = Diesel Road Switcher, 6 axles, 4 axles powered, 1000 HP.

Format: VO-xxxx
VO = locomotive series
xxxx = Horsepower

Example: VO-1000 = Switcher, 1000 HP

Format: xyy
x = locomotive series
S = Switcher
RS = Road Switcher

yy = Horsepower (x100)

Example: S12 = switcher, 1200 HP

Format: ASxx (four axles)
AS6xx (six axles)

AS = locomotive series
xx = horsepower (x100)
yxx = powered axles (six axles total) and horsepower (x100)

416 = Four powered axles, 1600 HP
616 = Six powered axles, 1600 HP

Early cab units:

Format: DR-x-y-z.

DR = Series
x = number of axles
y = number of powered axles
z = horsepower (x100)

Suffixes:
B = cabless booster

Example: DR-6-4-20 = Diesel, 6 axles, 4 axles powered, 2000 HP

Late cab units:

Format: RF-xx
RF = series (“Road Freight”)
xx = horsepower (x100)

Example: RF-16 = Road Freight, 1600HP

Late transfer engines:

Format: RT-yxx
RT = series
y = powered axles
xx = horsepower (x100)

Hopefully this clears up more confusion about diesel model designations than it creates. The sheer number of variations makes it a challenge for the new student of locomotives to keep track of them all, but once one understands how each nomenclature system works, it becomes easier to break a model designation down.

[CSSHEGEWISCH]

The DL535 is an Alco export design, with model RSD30/RSD35. The following link will explain EMD export models:
http://emdexport.railfan.net/frame_layout.html
GE export models have similar designations to domestic designs.
FM also had a specification number, the ALT series, that was similar to Alco's DL designations. For example, the Erie-builts had spec numbers ALT100.3 and ALT200.3, the H10-44 was ALT100.6A, etc.

[chad thomas]

Here is a emd breakdown I have

EMD domestic letters

A=Cab equipt. unit or it could mean special order(longer frame, usually for bigger fuel tank)
AC=alternator rectifier on older (2nd gen) units or on newer units AC traction motors
B=Cabless unit (may have a de-commisioned cab)
D=duty as in SD special duty or DD double duty
E=on earlier streamliners-eighteen hundred HP (6axle A-1-A)
E=at the end-EMD rebuild
e=Tier 2 emmisions compliant
F=on earlier streamliners-fourteen hundred HP (4axle)
F=on later units-full body (cowl unit)
GP=general purpose (4axle)
H=head end power equipt on passenger units
H=4 stroke cycle H series prime mover on freight units
I=isolated "whisper cab"
L=lightweight (may have 3axle A-1-A trucks)
M=north american safty cab or wide cab (without an AC after it implies DC
M=Morrison Knudsen rebuilt unit
MP=multi purpose (4axle switchers)
N=nine hundred HP on earlier switchers
P=passenger unit
R=rebuild
S=six hundred HP on earlier switchers
SD=Special Duty (6-axle)
T=twelve hundred HP on earlier switchers units
T=tunnel motors on SD40s & SD45s
u=rebuilt units in canada
V=VMV re built unit
W=wide cabs in Canada (not sure on this one)
X=experimental unit
-2=modular electrical cabinet
-3=advanced electronics / traction controll

[coborn35]

A lower case "e" means Tier 2 emission comlient.

[Lord Atmo]

whoa, thanks guys. that pretty much sums up everything i wanted to know. not sure why M means widenose on EMD and W is widenose for GE. seems like the letters should be universal. oh well.

[coborn35]

It doesnt. Its not. CN had their GP40-2W's and others lettered with a W. I have seen EMD's with both letterings.

[Lord Atmo]

so then what's the difference between M and W?

[wctransfer]

Max, thats not the real name of the engine. They are GP40-2L's, no W what so ever. Thats the incorrect railfan name.

Lord Atmo your answer was right here.

Matt says-M is for widecab, I think it stems from Modified North American cab.

[SSW9389]

EMD = Every Model Different

[BentnoseWillie]

QUOTE: Originally posted by wctransfer

Max, thats not the real name of the engine. They are GP40-2L's, no W what so ever. Thats the incorrect railfan name.

It must be a railroad thing too, since CN referred to those engines as GF-430s and as GP40-2LWs.

The W suffix is also applied to other EMD products and to the M420Ws; since the latter were from a different builder altogether, and since the "W" cabs on EMD and MLW products were built to CN specifications (versus the GE version, which was not), it stands to reason that this is at the least a CN designation.

[Lord Atmo]

so for the most part, the W is only for GE locomotives minus a few CN units? maybe the W on EMD models applies to the canadian style safety cabs?