What is a slug?

I see pics here and there of slugs. What exactly are they? how do they operate?

2005Vdub wrote:I see pics here and there of slugs. What exactly are they? how do they operate?

A slug has traction motors but no prime mover -- the traction motors are powered off the generator/alternator of the mother unit that they are mated to.

The principle at work is that at slower speeds, a typical diesel-electric can generate more power than its own traction motors can fully utilize, therefore spreading the output over more traction motors will get you more tractive effort from the same prime mover. At higher speeds, the advantage becomes less so, so that primary applications for slugs are low speed operations, often in switching. Most slugs are the typical low carbody without cabs.

Typical slug example

CSXT in particular (and going back to the Seaboard days) has had a long program of road slugs. SBD had cabless ones paired with U36Bs I believe, and now of course CSXT has a large group of road slugs rebuilt from GP30s and GP35s that retained their full carbodies, cabs, and control stands, and were mated with GP40-2s, allowing either the GP40 or the slug to be used as the lead on road trains.

CSXT Road Slug from a GP30-- note the lack of doors, exhaust stack, and fans, save for the dynamic brakes.

Another note: Don't confuse these with Amtrak's "cabbage" F40s. Those are not slugs -- their only purpose was to provide a locomotive carbody and cab for safety reasons when running push-pull trains in push mode.

Hopefully if I left anything out on the mechanics of how slugs work someone can fill it in for me -- its coming from deep recall in my head with only one cup of coffee this morning.

Does CSX operate slugs anywhere else outside of the Hagerstown area (hanover sub so forth). I see so many of them running around here and very few else where on their system.

justinking wrote:Does CSX operate slugs anywhere else outside of the Hagerstown area (hanover sub so forth). I see so many of them running around here and very few else where on their system.

I don't think that they're limited to one region. I believe they can roam the system.

i figured that as much, I guess the traffic through my area is more fitting for slugs, It's alot of slow moving switching and what not.

whats the difference from a slug and lets say the old F9A's then the B witch was just looked the same but was not a cab body.

2005Vdub wrote:whats the difference from a slug and lets say the old F9A's then the B witch was just looked the same but was not a cab body.

B units (which were mainly cab units, but there have also been some hood units built this way) are simply units without cabs. They contain prime movers, and, if equipped with hostler controls, can actually move under their own power. They contain everything that a normal diesel unit does except the cab.

Slug units are great for the extra tractive effort that they provide at slow speeds.

They are much cheaper to operate than a standard cab unit, and their traction motors kick off at somewhere between 15 and 30 mph, depending upon the settings.

Loco crews like them because they are cooler and quieter than cab units without A/C and with loud diesel prime movers. And, they have train control panels, so they can be the leading unit on a multi-loco lash-up.

They are found all over the CSX system.

ACLfan

The CSX move from the main at Rockwood north to Johnstown frequently involves a slug set, and as ACL noted, the crew likes to run from the slug if they have the chance. The local has a fair amount of online customers to switch, so the slug is a help getting the loads moving. Sometimes they will have to drag out a cut of new cars from the local carshop.
The slugs were getting pretty ratty, but were repainted in the 'bright future' scheme some years back.
A work train crew down by our camp on the old B&O main informed us that the slug shared everything with the mother; dynamic brakes, traction, and fuel tanks.
Malley

I think the CP SD40-2 slugs have their prime movers still intact. Just no controls. They jsut retired the last ex NS one in December. They have all the windows plated over.

ANDY117 wrote:I think the CP SD40-2 slugs have their prime movers still intact. Just no controls. They jsut retired the last ex NS one in December. They have all the windows plated over.

That's a B unit, not a slug, if it still has a prime mover.

Northeast Railfan has a description of slugs, power nates, and road slugs on their site: http://www.northeast.railfan.net/slugs.html

Semi-pemanently coupled 'cow-calf' sets had prime movers in both units but only a cab in one. C&O had 'cow&TWO calves'sets, which were dubbed a herd.
None of these, of course, was a slug.
Malley

So, road slugs can not operate on speedy freight trains since they cut out at around 30MPH.
These might be moot points, but here it goes. I read somewhere that the CSX road slugs have their fuel tank filled with cement. The newer CSX road slugs still have their prime movers, but the fluids have all been drained out and it is not connected to anything or SO I HEARD.
http://www.rrpicturearchives.net/locoList.aspx?mid=680
http://www.rrpicturearchives.net/locoList.aspx?mid=346
http://www.rrpicturearchives.net/locoList.aspx?mid=347

i saw my first road slug today on a s/b CSX in ridgefield park headed to north bergen. CSX 2219 was the last engine. No pics.