Can someone explain why NS just remodeled several older GP units into RP units? If I understand it correctly, these are units without motive power. So why are they needed at all? I haven't been able to find a good explanation on line as to what these units are used for and why. Thanks guys!

what exactly is an RP unit? are they just engines with only the motors still intact?--josh

I think what he means is that NS rebuilt some of it's older Geep's into RailPower GenSet locomotives. The Pacific harbor belt did this a year ago with most of it's geeps and has reduced fuel, maintenence and pollution.

Actually those are ex-GP38's classed RP-E4C slugs.

Rail pictures is currently down..I will post a link later.

Here's the link.

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The power for the traction motors comes from the "Mother Unit"..

Basically you get 2 locos for less fuel.

That's exactly the picture I was referencing. Are these units electric or still powered by fuel? (I haven't been able to find out much information on these units.) Why have two paired engines like these? With these units in particular, are they both powered? If one isn't, why drag it along?

Thanks guys!

Herc,The slugs don't have a prime mover.The power for the slugs traction motors comes from the "Mother" unit through MU cables...Also these slugs can be used as the lead unit because the controls is fully fuctional.
So,you have the power of 2 locomotives while using fuel from one locomotive instead of 2.

so the powered mother unit just runs the traction moters on the second slug...huh,wonder how that converts to better fuel economy seeing as the engine has to do twice as much work :?: .--josh

It doesn't do twice as much work. The diesel engine spins a generator which will put out max power. The maximum power the generator will put out is not determined by the number of traction motors it is powering. If you power twice as many traction motors with the same generator, you reduce the maximum speed by 1/2. Slugs are often used in yards. It seems the NS uses them in local switching as well. I don't know if they use them in mountainous territory on coal drags or not. The advantage would be more tractive effort up grades, but you trade off speed when grades level off.

What suprises me is that the Slug has a full cab. Not all Slugs have cabs.

Also, why is the long hood so tall? Many Slugs are cut down and filled with ballast when the Prime Mover is taken out.

I would guess that the Slug is loaded with batteries, but I can't find any information on them.

This would make the combination of Slug and Slug-Mother a High-Bred.

This Slug/Slug-Mother combination would give you roughly the same power and tractive effort as two Green Goats.

Ok...I thought I was confused before...but now I'm sure.

First off, I see now that a slug unit has no prime mover...no diesel motor...can't produce power by itself, but has the generators to drive the wheel sets with the power coming from another unit. So in this case (and I know this is speculation since we don't exactly know what type of configuration NS operates these particular engines in) NS is using these 700 series units paired with a powered engine to provide more tractive effort at low speeds. So if my understanding is correct, NS benefits by being able to pull a slightly heavier train in and around switching/yard operations (and possibly very local freight runs) with less overall fuel used. Is this right?

I think you have it right Herc. The slug does not have batteries or a generator, just traction motors. They are usually filled with cement to add weight to compensate for the weight removed when the Diesel engine and generator were removed. I think they are usually cut down to allow better visibility from the cab of the mother unit. I don't know what NS did to add weight to the slugs. I also don't know why they did not cut them down or eliminate the cabs on them. Is there a situation where they might want to have the cab intact and usable to control the mother from the slug?

I just called the local Norfolk Southern media rep. He didn't know NS even had these engines (since they were so new) but he said he will call his contact in the Loco shop and get the answer to this. What I find out, I'll post here!

Herc Driver Wrote:Ok...I thought I was confused before...but now I'm sure.

First off, I see now that a slug unit has no prime mover...no diesel motor...can't produce power by itself, but has the generators to drive the wheel sets with the power coming from another unit. So in this case (and I know this is speculation since we don't exactly know what type of configuration NS operates these particular engines in) NS is using these 700 series units paired with a powered engine to provide more tractive effort at low speeds. So if my understanding is correct, NS benefits by being able to pull a slightly heavier train in and around switching/yard operations (and possibly very local freight runs) with less overall fuel used. Is this right?

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Herc,That is correct..

The reason the slugs have cabs is the engineer can control both units from the cab of the slug..Therefore no turning of the locomotive consist is needed.

Here we see a CSX road slug(RDMT) as a trailing unit on a CSX local through Marion.



2 hours later we see the same slug as lead unit-no turning of the locomotive consist was needed.

Since it will inevitably come up as another question, a lot of times with slugs, and I suspect that is the case with the NS units since they have fuel tanks, is to give a low place to add more ballast, usually in the form of concrete. Just open the cap and pump concrete in. That gives you significant weight to aid in tractive effort with a low center of gravity.

Don't know (but am contacting some co-workers for the skinny) what exactly these NS units are. Without the diesel/generator/compressor/cooling system, they'd be comparative lightweights - must be some ballast weight somewhere to retain their tractive power - fuel tank sounds good, but will try to get an answer. Here's one near Holidaysburg, Pa. on a local taken by a friend - http://www.railpictures.net/viewphoto.ph...058&nseq=0 - no radiator grilles or fans (but the dynamic brake fan still seems to be aboard), leading a GP-40. Let you know what I find out. Bob C.