Road Slug vs. Road Mate

[bbrant]

Saw an engine on CSX today (I think it was #2346 but don't hold me to it). Anyhow, it had "RDMate" markings under the cab window. I've seen other engines with "RDMate" markings which got me to wonder what, if any, difference there is between a road slug and a road mate. Any info is appreciated.

Thanks

[nanaimo73]

the Contemporary Diesel Spotter's Guide (page 294)says-
General Electric calls its 1971-1972 slug a MATE-Motors to Assist Tractive Effort. GE claims two distinctions between these units and road slugs: First, MATEs operate throughout a broader speed range than typical slugs (up to 30 mph for single-end MATEs, and as fast as the mother units are allowed for double-end MATEs) ; and second, they are also fuel tenders, preceding Amtrak fuel tender No. 400 by seven years.

They were built with U36B frames and used with them in the Florida Phosphate area.

Now CSX has built their own MATEs (2200-2350 ?). When the project started in 1988 they used GP30s and GP35s and the mothers were GP40s in the 6400s. Basically they took the engines out. The term slug on would be used for similar units built for yards.

[Anonymous]

now dont crucify me or anything, but what is a road slug to begin with?

i have sen a copuple bnsf road slugs in tacoma, but i have not seen them in action.
what are they used for and why?

[bbrant]

naterich89 -

Here's a good explanation of what a road slug is.
http://www.northeast.railfan.net/slugs.html

CSX has it's S&C branch line through my town. Every train that runs this line has had a road slug as part of the consist. Heavier trains will have an extra powered unit along with the slug and it's mother.

Here's a shot of a GP30 slug I took a couple of weeks ago on the S&C branch.
http://bbrant.rrpicturearchives.net/showPicture.aspx?id=152641

[bbrant]

nanairmo -

Thanks for the info. So, at least when it comes to CSX, there's no difference between a road slug and a road mate? Am I correct on that?

Believe it or not, I have seen slug units on CSX with "RDSlug" painted under the cab. (http://bbrant.rrpicturearchives.net/showPicture.aspx?id=121639)

[nanaimo73]

Actually, I don't know. CSX is probably the only RR that uses the term Mate and my info is ten years old. In the 1990s Mates were for the road and slugs were for the yards. I would guess a road slug is missing something that a road mate does have. The fuel tank, for example ?

[arbfbe]

BNSF's slugs are all for yard service. You do see them on the road when moving between terminals for reassignment and service.

Basically, slugs and mates receive their power for their traction motors from the 'mother' unit. The railroad gets better tractive effort at lower speeds when it is needed to get heavy trains started without the added cost of another powered unit. In yard service, especially when in hump service, the speeds are always slow and the horsepower of the switching unit cannot be utilized. Adding the 4-6 traction motors of the slug allows that horsepower to be applied to longer cuts of cars.

The Butte, Anaconda & Pacific had slugs for their electric locomotives in use prior to WW 1.

[Modelcar]

...Never did really understand the creation of "slugs" completely....Does it reflect upon the mother engine that it has more prime mover power than can be put to use as far as traction will allow with it's perticular set up....Is it overpowered and has to have a "slug" to take advantage of that "extra" power to put it to the rail...{with traction}...?? Is it just better engineering to take two units and spread the prime mover power {of the one}, over all their wheels so it can efficiently use that power being put to the rails....?

[arbfbe]

Horsepower is speed, tractive effort moves the freight. At slow speeds there is more horsepower than the traction motors can use even with all the the traction motors in series. By adding another set of traction motors more of that horsepower can be applied to the rail without getting wheel slip. This is why an SD40-2 will pull more tonnage up the mountain than a GP40-2. Once you get over 25 mph or so there is little difference between the two units. In the case of the CSX road mates they get the equivalent of two SD40-2 units but without the problems of the six axle trucks on tight curves. Based upon current railroad practices it appears slugs and especially road slugs have very limited applications.

[Modelcar]

....So it all boils down to achieving enough traction to USE the horsepower in starting a load and or at lower speeds....

[CSSHEGEWISCH]

As mentioned above, slugs are inherently low-speed creatures, which is why they are primarily used in yards for either flat switching or as hump pushers. CSX seems to use its road slugs for transfers, mine runs and other low-speed applications. C&NW used road slugs on the Winona-Huron line (now DM&E) in the 1970's since track conditions at the time restricted it to a low-speed line.