I posted this on a Yahoo! Group that I’m a member of but thought I might post it here for feedback, as well. I’m wanting to understand what exactly a hump trailer or slug is? Here’s a pic:
What I do know (from Bill Edson’s book, New York Central System Diesel Locomotives) about the DHT-1s is the following:
Built by NYC at Harmon Shop
Made from retired class RA Electric Locos
Equipped to operate with DES-7s (HH600s), DES-11s (S-2/S-4s), DES-13s (NW2s), and DES-16 (SW7/SW9s)
I’m assuming that it was some kinda of auxiliary unit MU’d to the above switchers to help push rolling stock up hump yard hills?
I’m interested in scratch-building one of these for my HO layout but wanted to understand a little bit more about it before I took on the project. I was thinking this morning with the short wheelbase that maybe a Walthers crane chassis might be close for kitbashing. I have one but haven’t measured it yet to see if it might work or not.
Anyhow, thanks for your help. Any suggestions and information are welcome.
it was just a way to get the diesel engine to power 8 traction motors instead of 4. the HT did not generate any power on it’s own, it just used power generated by the other engine. with 16 wheels on the rail instead of 8, there was a lot of low speed pulling power without wheel slip or high amperage draw by the traction motors.
this was a big deal when you consider that the average top speed was only 2 mph when shoving cars over the hump.
Getting all the loco’s power through the wheels to the rail at low speed for long slow shoves of heavy trains is the reason for slugs.
They will have built the slug by scavenging the power trucks from an old or damaged loco. Someone with more knowledge than | have could tell you what trucks they are. I think they might be Alcos but I could be way off.
That gives you a marker for how to model it… use the frames and trucks from a suitable dummy loco…
Looking at your pic I have a number of suggestions.
look at Athearn’s 8 axle heavy duty flat as a starter for the frame. I’m not sure if that has the push-pole pockets but I think that it does. The side frame would be suitably heavy.
There’s an e bay site called “So much stuff” (or similar). I would do a hunt through there for suitable handrails. and lots of other bits. They do handrail sets for various early locos so you could get the ends as well as the sides… you just have to cut and shut a bit… but it’s a lot easier than trying to make them.
I would scrounge the loco type trucks from a dummy unit. Or you might get some truck sides of a suitable kind from one of the makers… I think that you may have trouble getting a match for the wheelbase between a freight car and a loco truck though.
At low speeds a deisel engine creates more power than the traction motors can use. So by adding a “slug” they use the deisel engine of the master unit to power its trucks and the trucks of the slug. It is cheaper to add a slug and run one diesel engine to power the equivalent of two units than to run two diesel engines to power two units.
In another vien, the slug also provides additional braking power. Since the brakes are bled off on the cars and all the stopping power is in the engine brakes, the slug doubles the number of brakes the engine has over just the master itself.
The majority of slugs are recycled locomotives. The easiset way to model one is to get a dummy locomotive and just replace the hood with a styrene “box” about the height of a switcher hood. You can also cut off the fuel tank if you want, since a slug, having no diesel motor, doesn’t use fuel. For the really modern modeler you can model an RCL slug. That is an old engine equipped for radio control but with no motor in it… Its just a shell to house the electronics. If an RCL engine goes down, a regular (non-RCL) engine can be MU’d to the RCL slug and the slug provides the RCL operation and the regular engine provides the power.
If the hump uses 4 axle engines then the slugs will be most likely 4 axle, if the hump engine is a 6 axle engine, the the slug may be a 6 axle slug.
In the case of your example the NYC engine is make from a retired electric engine so getting trucks to match might be difficult. You could approximate it with a SW type engine as a starting point.
They seem similar to the AAR trucks that were on the Alco S3/S4s but they aren’t exactly the same. The S-4 diagram below is from the S1-S4 page on the Yard Limit web site:
The slug’s traction motors were wired to the ‘cow’ unit’s traction motors, almost certainly in parallel for hump operation at slow walking speed. That effectively doubled the available tractive effort; the prime mover had adequate horsepower, but the unit it was in could only develop about half the tractive effort of the ‘cow and slug’ configuration.
The term, “Hump trailer,” implying something that’s just dragged along behind, doesn’t do justice to the job performed.
The Alco S2/S4 has AAR B switcher trucks (as does most of the EMD SW series engines and the majority of other switchers). If you are going to canabalize a switcher, use an old Athearn SW type, way cheaper (or even an old AHM/IHC engine since they have a plastic ferame that could be cut down more easily).
The NYC hump trailer have a truck from an electric engine so they are a different animal. I would look for them in a traction or electric engine with would most likely be a brass casting
