Diesel Engine Terminology

Model Railroader General Discussion (Model Railroader)
1

I have Googled and Yahooed until my fingers have blistered looking for some kind of guide to the names and/or numbers of the different variations of diesel engines and in my haste, have turned up nothing. Since I haven’t owned a train set since around the age of 14, I guess you could say I am new to model railroading.

My whole life I have seen the classic red and silver Santa Fe diesel engine with the round front end (as seen here), yet I couldn’t tell you what that particular engine is called other than a Santa Fe engine. [swg] My dad refers to them as “A-Units”, but I always thought that was a model railroading term to distinguish the actual working engine from the “dummy” or “B” and/or “C-Unit”. Then I see engines that are very similar to that, but have a more slanted front, still round, but slanted longer. [?]

Then there’s this type here, which my father always referred to as a switcher, but I always thought switchers were the shorter diesel engines used in freight yards and look like this. [?] I’m so confused.

If anyone could please help with this information or even provide a link to a site explaining these terms, I would be very grateful.

2

looking up diesel locomotives on wikipedia is a great source without getting too technical

Basically, the “santa fe engine” you are referring to is an F-series A-unit (for example, and F-3A, F-7A, etc) These are generally called cab-units or cowl-units. The locomotive that your father referred to as a switcher is called either a road switcher or a hood unit. Switchers are usually referring to the slightly smaller locomotives commonly seen in yards, such as EMD’s SW-series of locomotives. Hope this helps. This is just a bare minimum of information, but I would suggest wikipedia again as a quick source, short of someone having to write a book on a post[swg]

3

Thanks, and yes, I wouldn’t want anyone to have to do that either. That has been helpful, because I feel really ignorant sometimes when trying to tell the guy at my local hobby shop what kind of engine I’m looking for and explaining it like I’m a ten-year-old.

4

Hi Melvin,

The most common general term for that first kind of diesel is “cab unit,” also sometimes called “covered wagon” for its rounded roofline. Cab units, somewhat confusingly, also came without cabs, to add horsepower to other units with control cabs. The ones with control cabs are “A units” and those without are “B units.” Another way to refer to this combination is “cabs” for A units and “boosters” for B units.

The second type you showed was originally called a “road switcher,” to describe a unit with a switcher-like body but meant for road service. When these became the most common type of locomotive, the usual description was “hood unit,” since only the parts that have to be covered are housed in the unit’s hood.

The four-wheel switcher type is really an industrial diesel used in factories and sometimes around railroad shops. Yard switchers generally have two four-wheel trucks with a cab at one end and a single hood over the works. Those small industrial switchers are also known to some railfans as “critters,” but I’ve never really understood why.

For more information you can find the book The Model Railroader’s Guide to Diesel Locomotives in your hobby store or for sale on this Web site.

Good luck,

Andy

5

For the rounded nose type diesels simply go to google.com and type “F series Locomotive” without the quotes. You’ll get tons of info and pics.

6

Thanks a lot, Andy. That was very helpful indeed. However, I have another question. I found a Seaboard Air Line Engine (in HO scale) that I am looking to buy and it is listed as an EMD FTA. What the heck does that mean? It looks like an F-3A to me.

Here’s the link.

7

OK, let’s see how good of a job I can do in confusing you.

  1. The Santa Fe unit is called an “F” unit (for “freight” unit, although some railroads also used them for passenger trains). F units came either with or without cabs (where the engineer sat). The ones with a cab were usually called “A” units while the ones withour cabs were usually called “B” units. Just to make it interesting, you’ll also see diesels described as “B” units (meaning they have four axles per truck) and “C” units (meaning they have six axles per truck). The trucks are the parts underneath the diesels that hold the wheels/axles.

  2. The Union Pacific engine would more properly be called a “road switcher”. This is because, while the units were very well suited for the mainline (long-distance trains), they were also well suited for switching duties.

  3. The B&O/Chessie unit is more of a pure “switcher”, for use in rail yards and such, although some railroads had them set up so they could also be used out on the mainline.

Hope this helps and doesn’t just add to your confusion. Hang in there and you’ll learn the lingo in no time!

8

Here’s a Wikipedia link to the FT units:

http://en.wikipedia.org/wiki/EMD_FT

9

If you’d like to see the many different types of diesel-electric locomotive, look at this site: http://www.thedieselshop.us/INDEXBLDR.html

If you go in by manufacturer, you’ll see that they have them broken down by switchers, road switchers, cab units, et cetra, along with graphics that show you generally what the different units look like.

Regards

10

Melvin,

This may be overkill or not as specific as you would like but here’s a handy web site about diesels:

The Diesel Shop

You can search by road name or manufacturer. Hope that helps…

Tom

[Edit: Looks like maxman posted the link as I was typing mine out. [(-D]]

11

I’d just like to clarify a few things. 1: The slantier longer “F” units are E units (well, if they’re made by EMD) and are for passenger service.

2: a cowl unit is not a covered wagon. They are very different. A covered wagon has all of the structural support as part of the cover. if you remove the cover, the engine would have no structural integrity (the modern P42 uni-body is similar) A cowl unit has a full frame same as a road switcher. In fact, it is a road switcher. The body is just a cover that caries none of the structural integrity.

So they look like modern covered wagons, but they are not at all the same.

12

The book you need for those questions is “Diesel Spotters Guide”, by Jerry Pinkepank. Both the original and second edition are long out of print but you might, with luck, find a used copy. They cover everything up to the SD40 and SD45. There are more recent books covering the modern production, but I don’t think there is one covering everything.

John

13

Boy do I know the feeling and I have been in this hobby for 5 years + now. I do know the engines I have, but still could not tell a SD 7 from a SD 9.

Far as the engine style you showed to start this post, lets throw if a E’s! [:D]

And PA’s.

Yep, sort of looks like Big F’s.

First engine you posted Santa Fe Warbonnet F unit, this color scheme was used to drag passenger trains but could be found dragging freight if needed. If you are DC, and just looking for some engines to fill a yard PM me. I have some cheap Life Like engines in Warbonnet colors you can have for cost of shipping. They did run when I but them away 5 years ago, and should run if you want them. But, do not confuses them Life Like Protos. These are $5.00 to $10.00 dollar engines at the most (would not go over $5.00 if they where new now) on E Bay.

I do have a good pair of Athearn Santa Fe Passenger Warbonnets that more than likely I never make DCC. If you like to talk about them, let me know by PM as well.

I do love the Warbonnets! As a 6 year old I watch them pull in the B&O yard from my Grand Parents house.

Oh, by the way that one is a Erie Built, yep again it looks sort like a Big F

Cuda Ken

14

dtandi, that wasn’t confusing at all. In fact, it was the exact opposite, very informitive. Thank you. Now, I can surprise my father by possibly even knowing a little more than he does.

15

Thanks, HamiltonBlue

16

Thanks again, Hamilton. I favorited that Wiki link, very informitive.

17

There we go, Maxman, just what I was looking for. Thanks a million.

18

Thanks, CX500. I added that book to my Amazon Wish List. Found a used copy for $48.

19

Cuda Ken, love your Santa Fe Warbonnet. What a beautiful color scheme. Of course I do have an affinity for blue locomotives.

20

Speaking of what diesel engines were called, let me quote a pretty good forum post by Paul A Cutler III from a while back (april 2008):

[quote user=“Paul3”]

The diesel nomenclature is a study unto itself. It involves engineers and salesman, and that’s always an interesting mix at the best of times. Now add railfans and percolate for 70 years or so, and serve. Yum!

Anyways, each loco manufacturer had different ideas.

EMD (Electro-Motive Division of General Motors):
They originally started calling them by their horsepower and (most of the time) frame type. An “E” unit had Eighteen hundred Hp, an SW-1 was a Six hundred Hp with a Welded frame, an FT was Fourteen hundred Hp (really 1350Hp) with a Truss frame, etc. This is something an engineer would come up with.

As time went on, the original idea became the lable for a series of locos. The E-units were up to 2000Hp and more but still called E-units, the F-units were soon up to 1500Hp, etc. This was the salesman part (“See our new, improved E-series!”).

Eventually, EMD tried to build something to handle branch line service…something that didn’t need turntables or wyes, yet had one cab. The BL-1 (demo) and BL-2 was the result…which stands for “Branch Line”. This was not that successful.

EMD tried again with a new design that eliminated the truss car body and used a center sill frame design. They wanted it to be used for all kinds of service, so called it “General Purpose” or GP. Since it shared components with the F7’s then in production, they called it the GP7.

EMD also wanted to produce locos with a lighter axle loading for lightweight branches of many RR’s, so took a GP7 and added two more axles. These were called “Special Duty” or SD’s. Later, RR’s found that these SD’s could pull more by spreading the amp loading over 6 motors inst