A curiosity question for you gentlemen:
Browsing through various photo history books covering a variety of railroads, I sometimes see photos of slugs, or “tractive effort boosters” as one caption referred to them. Some were clearly purpose-built by the manufacturer, others were converted B-units. I gather that a slug has traction motors but no on-board diesel-electric generator set, drawing its power instead from the mother locomotive.
None of the photos I’ve seen show the actual connection, though. How does the mother engine pass enough power to the slug to make it be worthwhile? Wouldn’t that take either an enormous cable or a very high voltage cable? Both of those seem like they’d be hard to handle.
Dean
Its a big cable. Its no more problem than a traction motor cable or any of the other high voltage cabling inside the engine. Its not like the crew has to connect and disconnect the power cables all the time.
An electrical cable transmitted the mother locomotive’s power to the slug. The mother and slug were semi-permanently coupled, so disconnection and reconnection of the cable wasn’t a daily sort of thing.
Mark
In addition to the power connection between the mother and slug some roads use the slug fuel tank for extra storage.
Also some slug units are only good for low speed service such as the old Conrail MT-4 and MT-6 slugs for hump yard service…these were rebuilt from Alco 4 and 6 axle locomotives respectfully.
Others such as the former Seaboard Coastline MATE`s (Motors for Added Tractive Effort ) could be supplied with power from 2 locomotives and were good for up to 30 mph.
Older GP-30s and GP-35s were rebuilt by CSX and can be used in road service up to mainline speeds…had full cabs for controlling trains ( which crews frequently do due to less noise and vibrations) fuel pumps for topping off the mother units fuel tanks ( GP-40-2`s are the mother units ) and maintain their dynamic brakes.
Not precisely off topic, but are slugs (in all their forms) even used nowadays?
It always seemed like they were relatively rare to begin with on North American railroads, regardless of the benefits of the idea. Did other countries use them (I’m thinking Austrailia, Chile, Swedan maybe?)
I think they are still used.
Oh yeah. NS has one regularly assigned to its Allentown, PA yard hump, and there are whole series of them that were built/ rebuilt by the Juniata Shop forces and NS. It’s beyond my expertise to know what the differences and assignments are, but if you poke around on various websites you can learn more about that. See, for example - http://www.altoonaworks.info/rebuilds/ns_rpe4c.html and http://www.jreb.org/ns/index.php?topic=8423.0
Whether CSX still uses them now that AC motors provide most of the same benefits in a single unit - that I don’t know.
“When it comes to pushing cars over the crest in a hump yard at a steady 2 to 4 mph, a single unit has plenty of horsepower but not enough tractive effort or traction motor cooling capacity. To remedy this situation, excess power is fed from the diesel unit’s generator to a companion ‘slug’ unt. The slug is a ballasted four-or six-axle unit having traction motors but no engine or generator. This homemade combination provides multi-unit, low-speed tractive effort with single-unit fuel consumption and engine maintenance. For some over-the-road services where particulaly heavy loads must be handled at moderate speeds, ‘road slug’ or ‘mate’ units married to standard road locomotives also furnish that needed tractive effort.” (Page 83 of the 5th Edition of The Railroad What It Is, What It Does)
Mark
Ken - Hey, that’s pretty neat ! A GP30, no less, and in a nicely-maintained paint scheme to boot. Thanks for sharing the link !