Question on traction motors

[Anonymous]

I understand how traction motors work, of the
generator and all that. But can someone tell me
when as much electricity is put off a 4000 hp
motor to a genrator, why coudn't supply electricty
to the second helper locamotive to run it's traction motors without the second engine using
it's own engine to supply that electricity?

[Anonymous]

There is such an arrangement,I belive it's called a cow and calf.The "calf" locomotive has only traction motors and gets its power from the"cow",don't think there are too many of these in service though.I don't know if a normal diesel powered locomotive can act as a calf,maybe someone else can tell you that. Ron

[Anonymous]

ok thanks Ron
MMMM makes ya wonder to that suppose
a engine only had traction motors, without somekind of weight (diesal engine) to hold it down the wheels would spin

[Anonymous]

Haa. I found one. Page 29 August of 1997 issue
of Trains magazine. there BNSF3965 I guess is what
they call a slug.It looks to be @ 4 feet tall and same length of standard locamotive..If major railroads are looking for different way out of the fuel crunch. Why don't they build more of these???

[Anonymous]

There ARE quite a few road slugs in use and they have been around for some time. The ones I'm most familiar with are the CSX slugs converted from the old B&O gp-30s. These still look quite a bit like standard GP-30s, but the prime mover has been removed and the units are ballasted for traction. The crews like to run them as the lead unit in a lashup as they are much quieter than units with active prime movers.
Other roads used units with cabs removed and cut-down bodies (a road version of the cow and calf) but many also followed the CSX example.
It's sort of like the old Hobbytown HO drives that took their power from a single motor via a mechanical drive shaft/universal joint linkage, but here its done electrically.
Jim

[thirdrail1]

Both units have Diesel prime movers in a "cow and calf" arrangement. The "calf" only lacks a cab in this arrangement, used principally as transfer and hump engines. Very few locomotives of this arrangement were built after 1950, as it was a lot more flexible to MU two switchers together at times and operate them separately at other times.
With the advent of higher horsepower locomotives, "slugs" became quite common for hump yard service and drag freight service in places like the Bone Valley in Florida with a lot of high tonnage short haul trains. There are slugs that draw power from one mother unit and slugs that draw power from units at each end, with each end unit powering one truck.

[Anonymous]

At CN we use the slug in almost all the yard assignments. The slug is filled with cement slabs to allow for better traction without the diesel engine. The slug runs off the lead unit's power supply to run the traction motors. The hump sets we use are 2 "doug and the slug" sets back to back.

[Anonymous]

That interesting about them being filled
with cement. Hmm ya wonder if they do get popular for long distance usage they can allmost sit
a overseas box container on top of it to hold it
down as well being the short height of it

[Anonymous]

The purpose of a slug is to increase tractive effort at low speed. At speeds over about 25 mph a slug becomes dead weight because the "mother" locomotive powering it needs all available prime mover output(traction current) to keep accelerating. At that point the slug is not a fuel efficient proposition. This is why slugs are used in switching(particularly heavy duty switching such as pushing cuts of cars up the incline in a humpyard) and in some heavy drag freight applications. A good explanation of slugs and how they work may be found in the Kalmbach book "the contemporary diesel spotters guide".
Intestingly your idea of intermodal or other freight cars equipped with traction motors(in this case powered by a flatcar mounted powerplant such as a diesel generator set or a gas turbine) has been proposed from time to time. This is called an "integral train system" and was actually promoted in Trains magazine over 35 years ago by John G. Kneiling. In the nineties both CSX and CP began constuction of prototype "Iron Highway" self propelled piggyback trains but neither system was ever fully completed. The idea of a unit train without a locomotive may yet be developed. The German railways are operating a lightweight system for container service called a "Cargosprinter" and both British and Australian interests are adapting the same equipment. Maybe Amtrak could use this type of system to move express intermodal traffic on the Northeast Corridor.

[CHESSIEMIKE]

There are also different types of slugs. CSX Road Slugs not only look like standard GP-30s & GP-35s, they also have fuel tanks and a fuel transfer system to keep both within 200 gallons of each other. Fuel has weight also (read traction). The next time you see one, look at all the connections between the units and notice that the coupler release levers are bolted down to prevent them from becoming uncoupled. CSX Yard Slugs have cut down bodies and no cab. They also don't have fuel tanks. Most are mated with high power 4-axle locomotives that would tend to be slippery. Most exC&O GP-39s and some of the exSBD GEs. U.P. and NS also have Road Slugs that are of similar design and have add dynamic brakes to a cut down body that looks like nothing else. You will have to find a picture to understand.
CHESSIEMIKE

[Anonymous]

Wow thanks Jonathan that really explains it..
the people before your statment had some
interesting points too,, thanks

[wabash1]

the slugs on the ns are used in switching moves in yards. the slugs are filled with sand. they get the power from the lead unit in some cases the slug is between units and gets power for each set of motors from that end. after 22-25 mph the slug is dead weight. it no longer provides tractive effort. not until speed drops to below 22mph. ii would rather have 2 working units than a working unit and a slug anyday.

[Anonymous]

BNSF has several 'cow and calf' sets that are used for humping in the yards. They are modified from old SD road units. The prime movers are removed and they are filled with concrete and are regeared for slow, heavy loads. They are also shorter in height for better visibility. Bnsf also has cabless locomotives for road use they are regular locomotives without cabs. The last ones we bought were GP60B's in 1990 Numbered 300-350

[Anonymous]

Most of the slugs that I have seen lately are road slugs and it is true that they drop out in the 22 - 25 mph range. There are , I'm sure there are
some yard slugs that are still used that run in the 10 - 15 mph range, and used in yard moves and maybe hump service. Due to the amount of electric current needed for road locomotives to accelerate to road speed and being able to keep that speed, which is usually over 22 to 25 mph, slugs would not beable to help in reducing fuel costs. Also the weight of the slug factors into the tonage weight that the motive power can get accross the road at a set speed in a sceduled amount of time.
marvin

[Anonymous]

Could you or someone else please explain how traction motors work in relation to the deisel? I don't know how they work. I am curious what horsepower has to do with pull a train at speed. Or even why more horse power is better then less. It would seem that the rpm's the generator spins at is most important. Thanks for the help.

Ted

[Anonymous]

A deisel locomotive has a deisel motor in it which converts deisel fuel (chemical energy) into mechanical energy. The deisel motor is connected directly to an electric generator so the mechanical energy is converted into electric energy. The electricity from the generator is run to an electric (traction) motor which converts the electrical energy into mechanical energy. The output from the traction motor is connected directly to the wheels to drive the locomotive.

One might want to ask why a locomotive converts energy three times in order to run when your car only converts energy (from chemical to mechanical) one time to move. The answer is that the electrical system eliminates the need for a complicated transmission.

To your other question: What's the deal with horsepower? When the traction motor is making the wheels go it must exert a torque on the wheel which exceeds the resisting (friction and rolling resistance) torque in the wheel. The maximum 'kick' that a locomotive can generate is the sliding friction times the weight on the drive axles. This is what controls the amount a locomotive can start moving (adjusted for grade of course). The rate at which the engine can accelerate is dictated by horsepower provided that you are travelling at a speed where the wheels won't slip first.

As the wheel in contact with the rail pushes against the traction motor it creates a 'back resistance' to the generator. The magnetic field in the generator resists the rotation of the armature in the generator which is connected to the deisel motor. It takes horsepower to make the armature turn faster and generate more voltage to run the traction motor to make the locomotive accelerate.

One more tid-bit . . . The motor in a deisel locomotive turns much slower than the engine in your car which saves considerably on the wear and tear on the motor. This is another reason that electricity is used instead of a complicated mechanical transmission.

You may hear some refer to a deisel as a deisel-electric. This is why they do.

Clear as mud? - Ed

[Anonymous]

We also have the Diesel-Hydralic system. More in Europe I think. But that's another story

[Anonymous]

Thank you. That post was very clear. Now I understand why high hp deisels are important. Do you know if there is a site for info on the traction motors themselves? I am curious if there are different types of those or if there is a standard type. Thank you again.

Ted

[Anonymous]

Traction motors or more precisely, the control over the traction motors are very interesting. To get as much power down to the ground(or steel?)as possibly, and at the same time make them not to slip to much. The Swedish electrical train company ASEA (RC-lokomotive) was one of the first with advanced traction control

[Soo2610]

Thanks for a nice in depth easy to understand explanation. The mud has gotten clearer!

[Anonymous]

My understanding is that all Deisels in the US are made by GM (which are DC) and GE (which are AC). I guess you could try to see if you can get something out of them but that may not be easy.

Good Luck - Ed

[thirdrail1]

Whoa, Ed! Both General Motors and General Electric make both DC and AC locomotives!!! GM, for example, makes SD70M (a wide nosed 4000 HP DC motored Diesel) and SD70MAC (same with AC Motors), GE, similarly, makes a C44-9W (a 4400 HP wide nosed DC motored Diesel) and an AC4400 (same with AC motors). Since only four out of the six biggest railroads have adopted AC, and UP's monstrous order is for DC, not AC, SD70's, both firms will continue to make both DC and AC motored locomotives for the foreseeable future.

[Anonymous]

Gregg,

Thanks for giving me the news. I was told that GM was DC and GE was AC a few years back and I don't keep with this level of detail to know that that has changed. Was that the case about ten to fifteen years back or was a just fed a load of 'stuff' back then?

Happy Choo-choos! - Ed

[thirdrail1]

No, as a matter of fact, it was General MOTORS that introduced AC traction motors to the US, and supplied the first AC locomotives to the BN, which was the first major user. General ELECTRIC had to play catch up on AC traction. AC locomotives cost about a third more than DC, but have maintenance and tractive effort advantages.

[Anonymous]

Gregg,

Don't you think the CAPITOL LETTERS is a bit much when pointing out a MISTAKE which I admitted. I thought that my use of the common abbreviations for General Motors and General Electric as well as alternating current and direct current was clear enough to express my understanding of the facts. And when you wrote that I was mistaken I didn't try to hide behind anything.

But it does appear that my aquaintance at the hobby store may not have known as much as he indicated. No big deal. We can still be friends.

Incidently, what model locomotive was the first GM AC engine? What about GE? Thanks for the info. - Ed

[thirdrail1]

Ed, the capital letters were not directed at you, but the fact that the only locomotive manufactirers left are both "General" something. The first EMD order for revenue service was SD70MAC's for BN, these were the ones that introduced the "executive" scheme, their first AC was an experimental for Amtrak along with Siemens, which provided the AC part. GE's first was the AC4400. There is one fundamental difference between the two manufacturers, though.. All GM Diesels are two cycle engines except for the H-series, which is the not yet perfected 6,000 HP one. ALL GE's Diesels are four cycle.

[Anonymous]

Gregg,

Thanks for clearing that up. I thought you were really 'Diss'ing me. Sorry I got bent up about it.

Later - Ed