Road slug

[basementdweller]

Where I live I noticed on one of the local CSX engines has "road slug" stencilled on it. I noticed it had no fans on the top, quite rough looking. What is the purpose of a slug?
Couldn't a single locomotive handle local switching duties which is mostly a couple of dozen cars of grain hoppers and flat cars of lumber?
Just curious. Martin

 

[Fred_M]

A slug is a unit that uses power from the other locomotive to run its traction motors. It increases tractive effort at low speeds. Generally the motor is pulled and the hood is filled with concrete for weight. Sometimes the cabs are even pulled and the hoods cut down. They are built out of old units that have shelled out their motor as a rule. They are just a way to get more lugging power cheaply. Fred

 

[b28_82]

Ok then i have a question. Whats the difference between a Power Booster unit verses a Slug.... orrrr is it a different way of calling it a slug. Or maybe.... Is a Power Booster created from the beginning as a "slug" and a Slug is originally a Powered loco?

 

[Fred_M]

A power booster have a diesel and generator along with the traction motors and supply their own electric to the traction motors. Boosters just have no cab. A slug has no power supply, it leeches power off another unit to run it's traction motors. Most boosters came as boosters from the factory. Most slugs are home made. But what makes a slug a slug is it has no power generation unit. Fred

 

[60103]

Now, what would the porpose of a road slug be? A slug works because at yard speeds the engine produces more power than can be absorbed by the motors in 2 trucks, and the extra 2 trucks give that much more tractive effort. Above a certain speed, there is no more "spare" power, and the slug becomes dead weight.

 

[Fred_M]

Well, that's a misconception I think. I don't think that mainline locomotives are ran wide open 100% throttle at road speeds.

I have asked and heard stories at the local hobby shops from real engineers about slugs. When climbing grades the loco will shut down the throttle automatically because the wheels start slipping. Slugs help as it spreads the power out to more weighted wheelsets. Modern locomotives have more power than traction under some conditions. The slug is a help under this situation and uses no fuel under ordinary conditions like a helper unit would, but is there for extra traction when needed.

Fred

 

[railohio]

Road slugs and yard slugs are used interchangably in most services. The major differences being that road slugs are full-sized units with operating control cabs for road work while yard slugs are cut-down bodies for better visibility while switching. Slugs are commonly used on slow road freights and locals where two powered units for speed are not necessary. CSX uses road slugs at smaller yards for switching and locals throughout the system. I have seen road trains with three slug sets operating at track speed. Many times the slugs are used at slow speeds to help start the train and on long uphill grades and are isolated during most mainline running. Slugs are also used to provide extra braking power at the head-end of a train.

 

[Russ Bellinis]

The newest power units from EMD & GE put out much more power than they can ever use on the track anywhere. Even on straight level track, they put out so much power that the computers cut power for traction control in almost all operating conditions. I've been surprised that more class ones aren't converting obsolete power to road slugs. I think any locomotive making more than 3000 hp is probably not able to put all of it's power to the track.

 

[Topo]

I have also eard about "drones" and "zombies". Are these the nicks used by some RRs to call the slugs, or we are speaking of different beasts?

 

[basementdweller]

Russ, if that is the case about 3000hp + locomotives not being able to put all of its power to the track then why don't they build these locomotives with more axles?
Do the builders just figure that the RR company will just hook up a slug or extra engines to give there locomotive the traction it needs, and therefore not buy locos with extra axes? somehow it doesn't make sense.