Road Slug Sandwiched Between 2 Geeps

If memory serves, the GP40-2 is the mother. The GD38-3 is MU'ed to the GP40-2 through the slug, but does not provide any power to the slug. A bunch of these mother/slug sets were created for CSX at Mountaintop, PA. Don't know if this particular pair was from Mountaintop.

Chris

LVHR

@lehighline posted:

If memory serves, the GP40-2 is the mother. The GD38-3 is MU'ed to the GP40-2 through the slug, but does not provide any power to the slug. A bunch of these mother/slug sets were created for CSX at Mountaintop, PA. Don't know if this particular pair was from Mountaintop.

Chris

LVHR

Forgive my ignorance, but what is the purpose of the slug???

Apple 55.  adds more traction motors and horsepower without the us of another diesel engine, it feeds of the other locos.  so fuel economy and less maintenance are the prime reason.

@Rick Rubino posted:

Apple 55.  adds more traction motors and horsepower

A "slug" of any kind does not "add horsepower", as there is no prime mover inside the "slug". Only tractive effort is added.

without the us of another diesel engine, it feeds of the other locos.  so fuel economy and less maintenance are the prime reason.

Sounds like the effect is to convert an 8-wheel drive engine to 16-wheel drive, but with the same horsepower.

@breezinup posted:

Sounds like the effect is to convert an 8-wheel drive engine to 16-wheel drive, but with the same horsepower.

That's it.

I am a retired railroader and the railroad adds them rated as horsepower so the total can be figured for the tonnage of your train. technically you are correct but train crews and those who assign power don't use tractive effort in the field they use horsepower ratings from a table.      

Deep in the bowels of my computer I have an article from either model railroader or Railroad model craftsman.  Shows how to bash a pair of Chessie System/CSX Road slugs using a GP30 as a base for the conversion.  Removes, then plates over the fans and dynamic brake housing and the windows in the cab.

CNW also used Road slugs,  called them booster units.  Converted old EMD FB'S and ALCO RS2's and RS3's to be mated between either GP35s or C420s, using ALCO with ALCO and EMD with EMD.

@Rick Rubino posted:

I am a retired railroader and the railroad adds them rated as horsepower so the total can be figured for the tonnage of your train. technically you are correct but train crews and those who assign power don't use tractive effort in the field they use horsepower ratings from a table.      

Well, so much for the "modern era of railroaders", not understanding the difference between tractive effort and horsepower. For example, two GP40/GP40-2 units would total 6000 HP, with the total tractive effort of two GP40/GP40-2 units. Now, add in a slug and you STILL have only 6000 HP, but triple the tractive effort, thus pulling more tonnage but not going quite as fast (remember, horsepower is SPEED).

Thanks for all the info, gents. I admit I had never heard of a “slug” before (other than the slimy bug!!!). All your info begs two additional questions:

1) if the powered units do not power the slug, where do the traction motors get their power???

2) I have heard of calf’s before (to me they look like a butter dish on wheels!!!) - do they have prime movers???

Thanks for the education guys!!!

@Apples55 posted:

Thanks for all the info, gents. I admit I had never heard of a “slug” before (other than the slimy bug!!!). All your info begs two additional questions:

1) if the powered units do not power the slug, where do the traction motors get their power???

The powered units do indeed "power the slug" through large diameter, high current power cables.

2) I have heard of calf’s before (to me they look like a butter dish on wheels!!!) - do they have prime movers???

Yes, a "calf" does indeed have a prime mover, just no control cab. The "calf" is mu'ed to, and controlled by the "cow".

Thanks for the education guys!!!

Thanks again for the education!!!

   Seaboard Coast Lines had GE build 25 mates (slugs). SCL ran them between two u25’s. They could take power from either end, but only one at a time. Slugs work best in slow speed applications. SCL used them on low speed potash trains.
  CSX still has some in active duty today.

@Brad J posted:

   Seaboard Coast Lines had GE build 25 mates (slugs). SCL ran them between two u25’s. They could take power from either end, but only one at a time. Slugs work best in slow speed applications. SCL used them on low speed potash trains.
  CSX still has some in active duty today.

I remember when SCL ordered those "MATE" (Motors for Additional Tractive Effort), after they purchased a bunch of GE U36B units. The GE U36B units had 3600 HP on just four axles, and were so slippery, they could barely start a heavy train. Thus, they then had to purchase the "MATE" slugs MU'ed between two U36Bs, with each U36B powering one of the trucks on the MATE. They all wound up in Potash Service. So much for high horsepower for high speed freight trains.

@breezinup posted:

Sounds like the effect is to convert an 8-wheel drive engine to 16-wheel drive, but with the same horsepower.

@Hot Water posted:

That's it.

Hot Water, although the slug adds another 8 drive wheels, and additional traction, because it has no prime mover and no fuel in its tank, it would weigh significantly less than the powered unit, and therefore would have less tractive force. So in fact, instead of adding 8 wheel drive, compared to the powered unit, it may effectively provide, say, only 4 wheels worth of additional traction. Would this be correct?

@breezinup posted:

Hot Water, although the slug adds another 8 drive wheels, and additional traction, because it has no prime mover and no fuel in its tank, it would weigh significantly less than the powered unit, and therefore would have less tractive force. So in fact, instead of adding 8 wheel drive, compared to the powered unit, it may effectively provide, say, only 4 wheels worth of additional traction. Would this be correct?

No. Slugs, or SCL "MATE" units, were/are pretty heavily ballasted in order to provide the same weight as the "mother' units. Thus, if the GP40-2 weighed a nominal 250,000 pounds, the slug would have ballast added in order to also weigh 250,000 pounds.

@third rail posted:

Deep in the bowels of my computer I have an article from either model railroader or Railroad model craftsman.  Shows how to bash a pair of Chessie System/CSX Road slugs using a GP30 as a base for the conversion.  Removes, then plates over the fans and dynamic brake housing and the windows in the cab.

CNW also used Road slugs,  called them booster units.  Converted old EMD FB'S and ALCO RS2's and RS3's to be mated between either GP35s or C420s, using ALCO with ALCO and EMD with EMD.

I remember Milw Road, experimenting  with it back in the 70's

@Hot Water posted:

No. Slugs, or SCL "MATE" units, were/are pretty heavily ballasted in order to provide the same weight as the "mother' units. Thus, if the GP40-2 weighed a nominal 250,000 pounds, the slug would have ballast added in order to also weigh 250,000 pounds.

Very interesting. Thanks.

Wow, LOL, I didn't think this video would get that much attention. Thank you to who have all replied.

@breezinup posted:

Hot Water, although the slug adds another 8 drive wheels, and additional traction, because it has no prime mover and no fuel in its tank, it would weigh significantly less than the powered unit, and therefore would have less tractive force. So in fact, instead of adding 8 wheel drive, compared to the powered unit, it may effectively provide, say, only 4 wheels worth of additional traction. Would this be correct?

To add to Hot Water's comments addressing adding ballast to locomotive slugs, CSX's road slugs of the 1980's were converted from retired EMD GP30's and GP35's. They were semi permanently mated back to back with their mother units, GP40-2's. They also had fully operational cabs and the slug could be operated as either the lead unit or in a trailing position in a locomotive consist. Additionally, they  added considerably to the total amount of Dynamic Braking effort the locomotive consist was capable of developing.

As I recall, when they were developed in the 1980's, these particular CSX road slugs had the capability of acting as a fuel tender of sorts to the mother unit. Their fuel tanks were outfitted with the necessary apparatus to carry and supply additional fuel to the mother unit by way of a system of hoses and fuel transfer pumps, thereby extending the time they could be deployed at outlying points without needing to be returned to a service facility.   

Regards,

C.J.

Slugs have the prime mover removed and typically a large chunk of concrete added in its place for ballast. Some slugs even had their fuel tanks filled with concrete. Occasionally you will run across one that still has its fuel tank intact and serves as a fuel tender. In that case, there will be an additional connection for the fuel line between the slug and the mother.

Conrail used SD28s mated to 6 axle slugs (the frames were from FM units, the hoods were from ALCOs, and the trucks from EMD) in hump service at the Allentown yard for many years. Here is one after NS got a hold of it and repainted it. In this picture from 2006, it is mated to an SD40-2 .

Chris

@Hot Water posted:

Well, so much for the "modern era of railroaders", not understanding the difference between tractive effort and horsepower. For example, two GP40/GP40-2 units would total 6000 HP, with the total tractive effort of two GP40/GP40-2 units. Now, add in a slug and you STILL have only 6000 HP, but triple the tractive effort, thus pulling more tonnage but not going quite as fast (remember, horsepower is SPEED).

An excellent example of Hot Water's comment of horsepower equating to speed from my own experience. On certain subdivisions, a GP38 and GP40 both had identical tonnage ratings for the ruling grades of the subdivision despite the fact that there was a difference of 1000 HP between the two (GP38=2000HP, GP40=3000HP). Both models were equipped with EMD's  645 prime movers, main generators, excitation systems, gear ratios and traction motors. The fundamental difference being the GP40 was turbocharged vs. the normally aspirated GP38.

A single turbocharged GP40 with the common 62/15 gear ratio could handle a relatively light train (1500 tons or so) across overall flat terrain at 60 mph+ with little effort once it attained the target speed.  A GP38 over the same terrain, with the same load would handle the train, yet accelerate from a stop/slow order more sluggishly and -most importantly- give up on accelerating at around 40 mph. The same held true for locomotive consists made up of like models.  For whatever reason, at speeds above 40 or so, the GP38's would just give up.  Unless you were running lite or downhill (or had a high horsepower turbocharged unit in the consist), the GP38's were done a little above 40. GP40's on the other hand, true to the characteristics of the high performance machines they were, continued to accelerate unless overloaded.

Regards,

C.J.