Two questions

[Anonymous]

What is a slug. What are and why would you need steerable trucks?

[selector]

I believe that a slug is a cabless engine, a robot, that is slaved to the engineer-bearing loco. As for steerable trucks, can't really say, other than it might be a safety feature to ensure good tracking..someone else will know.

[David_Telesha]

A slug is a unit with only traction motors that feeds off power from a mother unit.

The New Haven had one rebuilt from an electric locomotive that was mated with an ALCO S-series switcher.

I can't seem to find a picture right now online.

[howmus]

Well, a slug is a particularly ugly diseasal. I think they are anyway...... They are I believe, an "unmanned" unit that are made to be used with a regular diesal loco and contain only the electric motors (ie: they do not have a diesal engine). They add traction to the consist. Your second question is beyond my knowledge.

[Anonymous]

OH. I see, thanks for answer.

[cacole]

Slugs were usually made from wrecked engines. As others have mentioned, a slug is an engine frame, wheels, and traction motors but no diesel engine or generator. Power for the traction motors is provided by the locomotive to which the slug is connected. A slug is usually used only in yard switching duty to give extra traction to a switch engine because you are, in effect, adding 8 more drive wheels to the "mother" engine.

Steerable trucks are on some of the newer high-horsepower diesel road engines to help guide them around curves and prevent derailments. With a 6,000 horsepower engine pulling a heavy load uphill, the front wheels in both trucks tend to be lifted off of the rail due to the torque being exerted by the traction motors, and this can cause a derailment on curves.

[red p]

Slugs are also ballested. Meaning weight is added, usually filled with concrete.
This is especially important in hump operations since the air is bled out of the train line. And the the only brake the engineer has is the independant (engines only)

[nbrodar]

Most slugs are simply cut down locomotives, with no engine or cab, just traction motors and ballast, drawing power from it's mother. CSX has Road Slugs, that have a complete cab and road duty traction gear, in effect they are two locomotives sharing one engine.

Steerable trucks, are used on new high horsepower high speed locomotives to ease the lateral forces on the track.

Nick

[Anonymous]

B-unit unmanned & deformed

[David_Telesha]

QUOTE: Well, a slug is a particularly ugly diseasal.

A slug can be made from any unit - diesel or electric - as I mentioned the NH had one made from a former electric locomotive mated with an ALCO S unit. A slug relies on power from a mother unit.

Once a slug it is a slug - not an ugly diesel. A slug - wires and traction motors.

QUOTE: B-unit unmanned & deformed

A "B" unit is not a slug. A "B" unit is a complete locomotive sans a cab used for boosting horsepower and relies only on an "A" unit for control. It has an engine, generator, etc..

[jrbernier]

As described above, Slug's are usually made from an old road unit that has lost it's diesel, and gets power from a 'Mother' unit. CSX has a number of GP30/GP35's that were converted and run with a GP40 'Mother'. SCL had GE build new slugs(MATES) that were matched to now U36B 'Mothers'....
Steerable trucks were developed by EMD to ease the truck into a curve. They are not a 'hi-adhesion' truck. EMD's variation has control arms that 'steer' the leading axle into a curve - reducing wear on the wheel sets and the rail. It might help with adhesion, but does not solve the weight shift problem when starting a heavy load. EMD's previous HT-C design addressed that issue with the older Flexicoil trucks.

Jim

[Anonymous]

QUOTE: Originally posted by cacole

Steerable trucks are on some of the newer high-horsepower diesel road engines to help guide them around curves and prevent derailments. With a 6,000 horsepower engine pulling a heavy load uphill, the front wheels in both trucks tend to be lifted off of the rail due to the torque being exerted by the traction motors, and this can cause a derailment on curves.

I don't think you are correct there... I could be wrong... BUT what I think you are saying is that the traction motors are around the axle and the torque would have the same effect as producing a wheelie on a motorbike... but on a modern loco you have six of them doing it all at once not a single wheel... the power to weight ratio of a loco is also massively diferent from a bike. the leading axle of the leading truck doesn't try to wheelie... nor does the back axle.

What a loco will try to do is keep going in the same direction that it is already going in.. which is always straight on. It is taking the least line of resistance. A curved rail adds a load pushing the loco from it's existing course to another. This is a result of physics doing what physics does.

Steam locos had leading single or two axle trucks to help ease the leading end into curves. I suspect/believe that steerable traucks are doing the same thing.

I think that the word steerable is a bit misleading... the truck doesn't steer in the sense that the front wheels of an auto steer. As far as I know what happens is that when the leading axle is pushed sideways by the rail as a loco moves from the straight to a curve a linkage in the truck flexes the line of wheels from the straight on straight track to a curve which will relate to the curve of the track. This will smooth the ride, reduce wear and assist in the power being put through the wheels to the rail.

The other side of this is that curves are entered through easements... i.e. the curve starts gently.

Slugs are a way of getting all of the power that a single prime mover can put out through the wheels onto the rail... with the result that the train moves. particularly in yards with big slow moving strings of cars making a lot of starts from dead ther is a lot of potential for wheel slip.... so the power is put down through more wheels... it's like four wheel drive in a SUV.

Again,\looking another way. Some very big trains are got rolling with the aid of helpers. these may then cut off on the fly. The train engines are sufficient to keep the train rolling.

A further step of this is that once rolling an engineer will attempt not to stop until he reaches the end of his journey. At imes he might be moving so slowly that you can't see the wheels turning but he will not come to a stand unless he has to.