Diesel locos designations

On 2/6/2008 9:47 PM Karl P Anderson spake thus:

They mean nothing.

To be more specific, they mean (or meant) whatever the locomotive maker wanted them to mean. There were, however, some conventions followed:

GP = general purpose (called "geeps") SD = special ... mumble mumble [something]

Welcome to trainspotting.

On 2/6/2008 9:54 PM David Nebenzahl spake thus:

Special duty, yeah, that's the ticket.

Although, aren't all SDs six-axle?

It varied between and within each manufacturer. GM EMD was the biggest. Early on, they used the first letter of the horsepower rating (more or less) - S for 600, N for 900, T for 1200, F for 1500, and E for 1800. Thus the smaller switchers were SC or SW (the c or w being whether it had a cast or welded chassis), the larger were NC or NW, the TA was a streamlined cab unit built for the original Rock Island "Rockets", the FT was a semipermanently coupled A and B unit set of 4- axle units, and the EA and EB were early 6-axle passenger units for the B&O. In time, this changed to SW for any switcher, F for 4-axle cab or booster units, E for 6-axle cab or booster units, GP for 4-axle road switchers and SD for 6-axle road switchers, all followed by numbers that may of may not have had meaning (model sequence, horsepower, whim, etc.). Alco, Fairbanks Morse, Baldwin, and GE each had their own different designation systems.

Yes, but it takes some study. I used an old Kalmbach "reference series" booklet "The Second Diesel Spotter's Guide" to learn. Kalmbach does not list this any more at their site, but it can be found used through Amazon, AbeBooks, etc.

I don't know of an easy table. You can find all the types listed at this site with a little effort:

"David Nebenzahl" wrote

Yes. And the GPs are four-axle.

I understand the Geeps were the originals, and the six-axle SDs started out as variants that were essentially the same locos, but the six axles gave them lighter wheel loadings, and therefore they could run on lighter-railed branch lines that the Geeps couldn't manage.

It was shortly discovered that dividing the same engine output into six traction motors instead of four gave the SD models much more "oomph" at low speeds, and they rapidly became favorites as mountain engines.

Modern day SDs have given up the idea of having a lighter axle loading because of their humongous size. They need six axles just to distribute that tremendous weight.

Am Thu, 07 Feb 2008 00:26:06 -0800 schrieb P. Roehling:

Not true. Most of the SDs were essentially 50% heavier than the corresponding Geeps, for increased tractive effort. Only the SDL-39 built for the Milwaukee Road was lightweight, and Alco had six-axle versions of its RS-series with lower axle load. As a matter of fact, six-axle engines are often not allowed on branch lines, as three-axle trucks put more strain on the track than the two-axle trucks.

Toby

Am Wed, 06 Feb 2008 23:47:34 -0600 schrieb Karl P Anderson:

Wikipedia has a lot of information.

The EMD system has already been explained. The number behind the GP or SD designator is more or less a model number, although with engines built during the same period, it also says something about horsepower (-38: 2000 hp, -40: 3000 hp). Current production engines are the SD70-M2 and SD70 ACE.

The Alco Century series have designations like C424, where C stands for Century, 4 for four-axle, and 24 for 2400 horsepower. The GE U-boats were U25B, U30C etc., where U stands for Universal, the numbers for the horsepower rating, and the letter for two- or three-axle trucks. A similar system has been in use until today: B30-7 - Dash-7, four axle, 3000 hp Dash 8-40C (often called C40-8) - six axle, 4000 hp This system was also used for the Dash 9. The AC versions, although essentially the same loco, were called AC4400CW and AC6000CW (AC, horsepower rating, C trucks, wide cab). The system has been slightly changed for the engines now in production: ES40DC, ES44DC, ES44AC, where ES stands for Evolution Series, the numbers are of course the horsepower rating, and the letters say whether DC or AC traction motors are used.

Now, guessing the type from looking at an engine can be tricky, as there are often only tiny differences between models. All the Dash 9s and AC....CW look very similar (the Evolution series, also known as GEVOs, also don't differ much), as do engines with the same body, but different prime movers (GP38, GP40). The new SD70 ACEs and M-2s can be distinguished from older SD70s by the characteristic cut-outs in the short hood.

Toby

Thanks for all the info. I should have known the answer wouldn't be simple. At first I thought the first letter(s) would refer to the manufacture, but then I thought many manufactures were making similar engines so there might be a rule they all followed. Duh!! Why would they work together?

I like Geezer's link to thedieselshop. That has alot of good info and pictures. Thanks Geezer for finding that.

Have fun everybody!

Karl

Karl P Anders> What do the letters designations for diesel locomotives mean? I see GP,

You mat find the following Kalmbach diesel information books helpful. All are out of print, but they are very handy in the car. I used the first one so much it started to fall apart, so I had it rebound. Very handy for identifying locos in older pictures. For Canada, the Bytown Railway Society's yearly "Trackside Guides" are essential.

Pinkepank, Jerry A. Diesel Spotter's Guide (1967) Marre, Louis A., and Pinkepank, Jerry A. The Contemporary Diesel Spotter's Guide (1969) Pinkepank, Jerry A. The Second Diesel Spotter's Guide (1973) Pinkepank, Jerry A and Marre, Louis A. Diesel Spotter's Guide Update (1979, ISBN 0=89024-029-0) MacDonald, Charles W. Diesel Locomotive Rosters: United States, Canada, Mexico (1982, ISBN 0-89-24-043-4)

HTH

"F" was Freight.

On 2/7/2008 11:38 AM Greg Procter spake thus:

On 2/7/2008 11:38 AM Greg Procter spake thus:

But Greg, in your heart of hearts, don't you just *know* that that couldn't possibly be correct? After all, it should be "goods", should it not?

In English the word can either be a noun or a verb. I set them up, you dash yourself to shreads against them.

Regards, Greg.P.

On Fri, 08 Feb 2008 16:18:21 +1300, I said, "Pick a card, any card" and Greg Procter instead replied:

English or metric?

-- Ray

EMD Locos:

GP = General Purpose and will always be a 4 axle SD = Special Duty and will always be a 6 axle F = 4 axle E = 6 axle

Not sure if E and F have any particular "name" like GP/SD

Look at the number of axles to tell which one it is...beyond that you'll need a copy of the diesel spotters guide to find out whether it's a GP30 a GP38-2 a GP40 or a GP60, or so forth.

Sure about that? You might be right, but I've seen plenty of F's used in passenger service

So what does MP mean (MP15DC)?

Would that be multi-purpose?

snipped-for-privacy@earthlink.net wrote in news: snipped-for-privacy@4ax.com:

Some railroads use the "any locomotive is power for any train" theory when they're assigning power. Especially when the heater wasn't needed.

Alco seems to use the F = Freight, P = Passenger designations with their FA1s and PA1s. (Oh, and RS probably meant road switcher.)

Puckdropper

On 2/7/2008 10:11 PM Puckdropper spake thus:

Yes, it did.

Ok, so what about E's?