When to use a slug (SW calf's)?

[Anonymous]

I'm going to model a ficticious part of modern CSX and my layout will consist of roughly two large switching areas, a looping single track main, and an interchange with a small CSX owned branchline modeled after the Turtle Creek Central plan in the January MRR. Instead of the two track coal mine on the branchline, I'm going to do a large coal mining complex (using three loading tracks and one passby track). On each of the industrial switching areas, I'm going to have lots of small industries that will handle a few carloads each, and therefore will only need one dedicated switcher or small road engine (GP38 perhaps) to do the daily switching chores, but since the Turtle Creek area and mining complex will be the focal point of the room, and my hope is to run a minimum of 9 carloads daily of coal hoppers from the mine, I was wondering if a switcher like an SW1500 would look right paired with an SW7 calf (since I can't find any SW1500 calfs). I would think that, the coal loads being so heavy, it would make sense to have the extra horsepower of a slug unit, even if in prototype operations it meant only hauling a few strings of cars at a time until a full train could be built at the interchange siding. I think it would look neat doing this but after doing some research, I've found CSX doesn't have any SW7 calf's active on their rosters. They do have slugs, but all the ones I've found are built on road engine platforms and I don't want to use something that long paired with an SW1500.

So two questions... how prototypical would it be to run a cow/calf combination at the coal mine (I would assume most mining operations use higher HP road switchers like GP's), and how believable would pairing an SW7 calf with an SW1500 be if I 'explained' it away as an 'older unit' that was only used for the horsepower boost during the mine shifts?

I know it really boils down to what engines I want on MY layout, since I'll probably be the only one to ever see it, but I'd like to keep it believable, at least in my own head. lol

[ndbprr]

That is not an easy question to answer. CSX had several cow and calf sets and they even had one that was one cow and two calfs commonly called a "herd" BUT my understanding of a slug unit is that it uses power generated by a second unit to run its traction motors. As long as the engine generating the power is not running flat out to service itself it should be able to power the slug (which by the way is different from a calf since that had a prime mover and was remotely operated from the unit with the cab like a modern lash up). So the bottom line is if the engine with the diesel is operating at less than 50% output at all times a slug of thesame variey should double the number of cars hauled. But if the grades mean that the engine has to work harder than that to propel a load that will be reduced. Most slugs I know of are either operated in flatland or yards where grades aren't a problem. You will have to do sme research to know for sure.

[Anonymous]

Well on the issue of grades, that won't be a problem from a prototypical standpoint because the area they'll be working will be modeled as relatively flat (less than 1% grades max in the area). With regards to the slug vs calf info, I didn't realize slugs actually worked off of the power from the head unit. I guess when traction is more of an issue than flat out horsepower I can see where the extra wheels of a slug unit would come in handy. I was under the impression that calfs 'were' slugs and slugs were simply un-cabbed MU units. But if calfs were MU units under their own power *unlike the slugs you described* then I would guess that would suit my purposes as well. I think what I'm wondering more than anything now then, is how realistic would it be to see a cow/calf pair at a mine?

[mcouvillion]

jshrade,

It's your railroad. Just say that the power department selected whatever you have as the appropriate power for switching the mine. It will be prototypical on your layout.

For the calf, if it is an Athearn, you'll notice the hostler controls in place of the cab of the unit. These would let the hostler in the engine service facility move the calf around for servicing without having it attached to the mother unit.

Mark C.

[simon1966]

You use a dummy calf when you need a place to put a Soundtraxx decoder and speaker system!

[johncolley]

A slug is actually just the heavily weighted frame ( no cab, hood, or engine enclosure) of an old switcher using power cables to get electricity from the adjacent switcher to its traction motors. I remember the Indiana Harbor Belt Line used them in a lot of industrial switching south of Chicago.
A calf is a complete engine without a control cab and has its own diesel running in m.u. control from the cow. Usually it had an instrument panel on the low end facing the switcher cab so the engineer could monitor its functions. Picture 2 switchers back to back, then take the cab off one of them.

[jrbernier]

It's 'your' railroad - you can do what you want. That said, here are the facts to consider:

o - The Athearn SW7 is a 1200 hp unit form the early 50's. You will not see it listed as a 'B' units as these were sold as a model TR4 'cow & calf' unit. They were permantly drawbared together. Later some were seperated and given couplers. I remember the Milwaukee road sometimes split up TR4 sets and stuck a F7B between them on hump duty in St Paul Yard in the 70's. The C&O had 'herds' with a cab unit and a pair of the boosters.
o - A SLUG is a unit that has no diesel engine inside it. It gets all of it's power from a powered unit that is is mated to. I know the C&NW built a lot of slug's out of old switchers(and even converted TR2/TR4 sets to a powered cab unit/slugs). These usually have no exhaust stacks or radiator grills after the conversion.

Most SW7 or TR4 sets are long gone(except for industrial switchers). Locals in coal mine run service use standard road engines these days. I know CSX converted old GP30/35 units to 'road slugs' and mated them to GP40-2's for this service. I am not sure if these are still running. The carbodies were sealed up, the radiator grills/fans are removed, but the cabs are still there so the set can be run from either unit.

Jim Bernier

[nfmisso]

N&W (now NS) used (uses) road slugs built from EMD GP9 and GP18 with GP40's on mine runs where SD40/SD40-2 can't go. These slugs even have dynamic brakes.

A typical DC traction motor diesel can not keep full power to the traction motors continuously at less than around 10 mph, due to the traction motors overheating. The road slug allows the full power to be used at a much lower speed, generating more tractive force.

NOTE: tractive effort is force, work is force times distance, power is work per unit time. In SI units: Newtons, Joules (Newtons times meters), Watts (Joules per second).

[BR60103]

I've never seen a calf -- don't know if we had them in Canada.
I have seen CN freight trains roar by with amazing collections of power on the front end -- 6 wheel units, 4 wheel units, yard switches and slugs -- all in the same set. Don't know if all the units were operating or if they were just being moved.
If you have a small yard near the coal mine, you could justify using the cow&calf to switch it. Even just the cow if the load is light.