I just wanted to mention that (in North American practice, at least), cabless units are called either B units, or (wait for it) ‘Cabless Units’ - calling them ‘Drones’ doesn’t seemed to be a common practice. B units are fairly uncommon on NA railroads nowadays (they peaked in popularity with the cab units of the 40s and 50s) since the flexiblity of each unit having a cab (which can be used separately as needed) outweighs the savings gained by not having control stands/desks in each locomotive.
Also, most slugs don’t have cabs, instead looking similar to this: MATE http://www.rrpicturearchives.net/modelThumbs.aspx?id=188. A few do have cabs, like several GP30s CSX converted in the 80s, but in general slugs don’t need cabs for the duties they perform (supplying additional traction during low-speed yard switching and transfer runs)
The report in question.
When multiple locomotives pull a train, why are they often pointing in opposite directions?
I think there is some room for confusion in the report involving slugs. There are three main functions of a loco: control, traction/propulsion , and power generation. Modern “diesel” locos are actually diesel-electrics, where the diesel engines drive generators, which power electric motors.
A-units have cabs, motors, and engines
B-units have no cabs, but have motors and engines
Slugs may or may not have cabs, have no engines but just motors, getting their power from the other units.
I don’t know if the term B-unit would apply to a cabless slug, or the term A-unit would apply slug with a cab.
To make matters even more confusing:
Some trains have drive units located in the MIDDLE of the train. These units are obviously controlled from the front of the train. The main advantage of this configuration is that the train can be easily divided into two trains heading to different locations. For example a train leaves Rotterdam and heads to Hamburg; at Hamburg part of the train then goes to Berlin while the other section heads down to Koln. Why not run two trains - one to Berlin and one to Koln? Running one train makes scheduling, switching and signalling easier; there may be insufficient Rotterdam - Koln; Rotterdam - Berlin traffic to support a dedicated train; additional cars can be attached at Hamburg for the runs to Koln and Berlin.
This practice is more common on freight trains than passenger trains. It is also more common in Europe than North America.
“Multiple unit” also refers, at least in the UK, to passenger trains that don’t have any locos.
They have cabs built into the two outermost carraiges (or units), and traction motors under a some of the units - surprisingly, in some cases it is the middle units that have the motors. The diesel engines (for diesel multiple units (DMUs)) or transformers (for AC electric multiple units (EMUSs)) are normally but not always also under the carraiges.
The vast majority of passenger trains in the UK (and I believe all of Europe) are multiple-units. Locos are used to rescue trains in an emergency, and for freight.
In North America you will often see mid-train helpers, alsi known as DPU’s (Distibuted Power Units). They are rarely there to be easily cut off into two trains - they just help with the real long trains that we have here.
Also, a few of the american roads ran their units LONG hood forward - primarily the Southern and the Norfolk Western (now merged as the Norfolk Southern) Many of the first generation diesels (ie GP-9’s) were designed for long hood operation, and many of the engineers in the days of the first dieseld were more comfortable with this arrangement, as it more closely approximated what they were used to with steam locomotive, perspective-wise. Also so, they felt it was safer in the case of an accident, as it put the bulk of the locomotive in front, as protection. Norfolk Southern continued this practice well into the 90’s, and many times they will STILL do it.
Bibliophage, in addition to the fine reasons you mentioned in your report, there is a further advantage to having the engines coupled back-to-back. While the engines will run equally well in either direction, it is useful to have the “forward” and “reverse” runtimes for a given engine be roughly the same. This helps to equalize the wear on the bearings and trucks which reduces the frequency of very expensive maintenance and downtime. So a “married couple” never has to turn around and it automatically equalizes the runtime for both engines in both directions.
Also, many times the third, fourth, fifth, etc. engine will be simply “deadheading”, getting a free ride to a destination where it is needed more, although it is available if extra horsepower is required.
A lot of locos have cabs at both ends.
One of the few loco-hauled passenger services left in the UK is the electric trains on the East Coast mainline. As can be seen here:
http://www.therailwaycentre.com/Pages%20Loco/Recognition%20loco/Illus_91.html
it’s rather unusual in that it has cabs at both ends, but still has a definite right way round.
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Hood unit diesel locomotives are usually run short hood forward to give the engineer better visibility. However some railroads have, and my still, mandate that the hood unit locomotives be run long hood forward to provide more protection for the occupants of the cab in the case of a head on collision.
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Some commuter trains run with an engine on one end and a special passenger car that is equpped with controls at the other. At the end of the run, the engineer walks from the engine to the other end of the train and when the time comes, runs the train back up the track using the controls in rear car, which is now the front car.
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The CSX web site lists “drone” in its glossary as “A locomotive unit without its own controls used in conjunction with one or more other locomotives.”. I’d never heard the term before.
The CSX glossary that JerseyJax mentions is where I got the definitions of “slug” and “drone.”
I wouldn’t really know if those definitions are right or not. Is CSX wrong, or are their definitions outdated, or what? Maybe I’m just missing something.
In my defense, we were desperate for Staff Reports at the time I wrote it, and I took it even though it’s outside my field of expertise. Who am I kidding? I don’t really have an area of expertise; I specialize in being a non-specialist. What I know about railroads comes from my half-remembered model railroading days (better than two decades ago) and research I’ve done for stock investments in the sector. So I could certainly be wrong on the details.
What would you call the very cool fake-TGV-style express trains that have been popping up on our side of the North Sea? The end units are specifically for power, so they would seem to be locomotives. But because the bogeys are shared between two carriages, they can’t be uncoupled easily, so the whole train functions as an MU. These are used for airport express trains in the Greater Oslo area and for long-haul express trains on the electric routes.
Ignoring those, local trains here are MUs, long-haul passenger trains have separate locomotives.
I would call them EMUs, but I’ve no idea what someone who knows more about trains than I do would call them.
Some long haul routes here are loco-hauled, but many of those that are are HSTs (until recently the fastest diesel trains in the world), which many people (including those enthusiasts who like loco-hauled trains) don’t consider to be loco-hauled because the coaches only work properly with the class 43 locos they were designed to work with, and so are always kept as a set.
bibliophage, I’d assume that the CSX glossary is accurate for the CSX, but that some terms, such as “drone” may not be universally used. If you were looking at a Pennsylvania Railroad glossary, you wouldn’t find entry for the term “caboose”. As far as the PRR was concerned, it was a “cabin car”.
And as long as we’re having fun with this, I live a stone’s throw from the BNSF lines here in medium sunny California. I’ve noticed that the yard crews almost invariably hook up GE built locos to the ends of the lash-ups. The EMD locos are relegated to the interior of the MU. Must be something special about that GE AC or heater capability…
Maybe the GE locomotives can control the EMD locomotives, but not the other way around.
Or maybe the GE locomotives have more comfortable seats. 