CSX runs an aggregate train through Maryland to somewhere. I have seen it twice recently. Both times running backwards (the 2 guys on the back (Front?) seem to be enjoying themselves and sounding a horn at the crossings. Anyway, this train is pushed by a GP 38-2, and GP 40-2 and what is marked as a SLUG (I think the number was 6385). It has a full cab on it (unlike what I usually see as being a slug), so I was wondering what it was previously and what CSX did to it to make it as slug.
CSX has a sizable fleet of road slugs numbered in the 2200-2350 series. They have been converted to slugs from GP30’s, GP35’s & GP40’s in the usual fashion by removing the engine, replacing it with ballast and rewiring the traction motors to draw current from the slug mother’s main generator. They are a bit unusual in that they retained their cabs with a full set of controls.
CSX GP40-2’s numbered in the 6400 & 6900 series are slug mothers which are wired to supply current to the traction motors of the slug.
The only other slugs with cabs of which I’m aware are a handful of road slugs on KCS which were rebuilt from F7A’s and some hump slugs on BNSF which were rebuilt from BN SD9’s.
This kind of relates to my horsepower question, but what is the full purpose of a slug?
Is it so that the mother engine is effectively given another four axles worth of traction/adhession and the mother engine can apply more or its horsepower at lower speeds? Is it to reduce track wear in yards where starting and stopping is common?
I have to admit, I am kind of embarrased that I don’t know the answer to this question. It seems as though it is something I had ought to know.
This one has a cab as big as day (and a short hood at the front). I love CSX for putting the loco type on the cab. The top of the long hood has a bulge which is higher than the cab hood and gradually taper to the back. I have got to get a picture of this thing.
Suppose you marry a 4 motor slug to a 2000 horsepower GP38… how much horse power do you have ? The answer is 2000 horsepower. the CN calles the slugs TEBs or tractive effort boosters. The tractive effort works two ways, in addition to pulling , they
also add considerable braking effort.
Locomotive horsepower is expressed in kilowatts, a locomotive main generator is a constant kilowatt machine that will maintain a specific KW setting in each throttle position . With a slug the KW out put is simply divided over more traction motors. So if you divide the voltage over more motors you will not have high enough voltage to go very fast unless the slug is also setup to make motor transition. An easy rule of thumb is to remember that current = torque and voltage + speed. current times voltage divided by 700 equals horsepower.
Randy
Gabe,
The mother units main gen. can make more juice than it can use at low speeds. Thats when a slug comes in to play. They also are set to cut-out at a certain speed.
Slugs originally were built for yard and hump service, since these are low-speed applications. C&NW was one of the first users of road slugs in the Dakotas where even mainline trains didn’t go very fast. SCL purchased MATE’s (Motors for Additional Tractive Effort) from GE. These were plugged into U36B’s for hauling phosphate trains in Florida. The MATE’s are probably the only factory-built slugs.
The road slugs on CSX seem to be used mostly in mine-run and transfer duty where the speeds are low and the loads are heavy.
Your description of the hump over the cab sounds like you saw one that was rebuilt from a GP30.
CSX’s slugs retained their cabs, and the set can be controlled from this cab (that would definitely be quieter for the crew, with no engine directly behind them!).
Could be. I have been looking at some of the websites out there. Nothing exact so far, though the slug from a GP40 looked close.
Also fits the role described above. Pushing a heavy train which will not need any speed.
Read something about the GP40-2 being equipt to run it as the mother. Don’t know about this one but how common is it to have a dedicated mother (I guess mother came from when they were calves) for the slug?
With the end of Steam, railroads have eliminated may turning facilities for locomotives. Train crews today, considering that practically the only engines they have ever operated have been low nose road switcher configured engines can’t comprehend how to operate a locomotive ‘long end’ forward, alledging that it is a SAFETY issue… By having road slug’s with controls on each carbody, the mother/slug combination does have a low nose control unit head out…
Slugs are designed to have the traction motors cut out at 25 MPH. As a consequence of the ‘limited’ HP of the mother/slug combination, when oprating with anything approacing a ‘tonnage train’ 25 MPH is about the maximum speed that can be expected account the horsepower/tonnage curve.
Originally both mothers & slugs had fuel tanks and fuel was passed to the prime mover as necesary. The fuel transfer equipment was problematical at best and flat out didn’t work at worst. I believe the fuel transfer concept has been scrapped.
A dedicated mother unit is a necessity for a slug as additional cabling and wiring is necessary to provide power from the mother’s main generator to the slug’s traction motors. As I mentioned in an earlier posting, CSX GP40-2’s in the 6400 and 6900 series serve as slug mothers. CSX also has some GP38-2’s which serve as slug mothers to yard slugs in the 1000 series.
IHB has several slugs and some SW1500’s and the GP38-2’s are wired to serve as slug mothers.
The CSX 2200&2300 traction motors, and GP40-2 power units, are rated to the equivalent of two GP38-2’s, by the Operations Manual. The traction units, cut out at about twenty-eight mph. At that point, the GP40-2 needs all it’s power, to achieve, and hold track speed. Fifty Seaboard Coast Line U36B locomotives,1800 to 1850, were the only engines set up for the MATE units. Pics have other engines hostling the MATE’s, however the U36B’s were the only units capable of operating this arrangement. Coupling the two together, automatically set-up the U36B, to operate the MATE, which cut-out at 19mph. At this speed, the U36B required all it’s hp for tractive effort. The L&N had some yard slugs, cut down from geeps. These may be seen operated by GP38-2’s, and GP39-2’s, equipped to handle this arrangement. In all cases, the non-engined unit must weigh the equivalent of an engined unit, or the wheels will spin, creating flat-spots in the rails, since all this is to work at low speeds. MATE it. ACJ.
The CSX GP30/35 slugs are pretty much as described above. Here’s what I have to add: basically, all the hood doors have been welded shut, and the radiator fans removed. IIRC, the slugs retain their dynamic brakes. They’re not much more than an operating cab and traction motors (and maybe DB) that still, for all practical purposes, looks like a locomotive.
The KCS slugs mentioned were preferred by crews because of no prime mover noise/vibration.
I think NS has the coolest slugs, especially the ones cut down from FM Trainmasters!!! No cabs on those, however.
Note that the engine coupled to the slug is a 6400-series GP40-2, as alluded to in some preceding posts.
When the CSX slugs were newly rebuilt, they could carry fuel that would keep the mother unit supplied (a pump would equalize the fuel between the two tanks). This, I understand, is no longer being done.
The CSX slugs no longer carry fuel although some fueling locations were still claiming to have fueled them after the tanks were sealed. Crews like the quiet ride but in the winter they are cold. Apparently the electric cab heaters are not supplied with enough power from the mother unit to produce sufficient heat.