Once upon a time... Once upon a time, streamlined cab units seldom had m.u. connections on their noses. Once upon a time, railroads had passenger engines and freight engines and switchers, and they were geared differently--sometimes geared differently enough that they did not play well with each other. Once upon a time, the Santa Fe discouraged crews from operating turbocharged units with non-turbocharged units--except their ALCO DL-107 and -108, which they thought worked fine with non-turbocharged units. But other railroads didn't see that as a problem. These days, everything has nose m.u. and most things have turbochargers, and all the passenger engines belong to the gubbmint. Are you operating a model of a real railroad and trying to be a stickler? Look at photos of the time, or go look at the road itself. Is it your very own railroad? Then set the rules, Mr. President!
Just ran across this thread. Some great stuff here. The guys and gals I work with just call them units in our power. I have seen SD9's MU'ed with SD60's. What was kinda cool was those old EMD 567's were hammering away, you could hear them over everything else on the RR. They were doing the deed too, they had been on-line long enough they had clean stacks. Anyways, as it has been explained, and rather concisely too, how all these units operate as one. And as has been explained it all takes place at the controlling end the the 27 pin line, loco to loco, perhaps there is just a bit more info. The pre electronic govoners have 4 magnets on a fuel rack. Which went from series to parallel to series parallel depending what the engineer called for. Now even I know 4x4=16, even tho I am just a "Rail". Many older GE's, like the U series actually had 16 throttle positions. Later mfgrs and maybe the FRA settled on 8 throttle positions. These govoners are very precise instruments and can be messed up with the wrong oil, over filling as well as low. Of course this all has to be ok'ed by the load regulator before any fields get exited " I'm exited already". It is just incredible the amount of electricity these things will generate. Back in the 1990's at the big shops in Alliance NE, there was a GE, I think it was 4 axle, can't remember which, but it was hooked up to the grid for that part of NE. In the summer when everyone had their air conditioners on "panic" and all the kids were watching Mackey Mouse on the TV, the power company would request additional power, so the shop people would start that old GE up, throttle it up to match the cycles, I think it was a very low throttle 3-4 maybe and all the lights would brighten up for miles and miles, that old GE was effortlessly just idling along. Anyways....
Baldwin used air throttles, but could have electric throttles. The air controlled units would not MU with anything else. Dan
Not really sure what you are referring to here? The governors have four valves (A, B, C, D) that control the diesel engine RPM. D valve alone, shuts the engine down.(MU stop, EFCO pushed in). Contactor's in the electrical cabinet control the traction motors. On six axle EMD's, you have the S (Series) and P (Parallel) contractors. Dash 2 and newer Four axle EMD's don't make transition, they only have P contractors. SD60's and newer EMD's make Alternator Transition using the SGC contractor. Older EMD's SW9's, F9's, etc. the engineer had a lever on the control stand for manual transition. Then you have AC traction motor locomotives which are a completely different story
I see AC and DC diseasels (sp intended) running elephant style, nose to nose, butt to butt. It don't matter. Just run them. Of course Analog DC and AC - DCC in our world of model railroading, won't work well at all. Sigh!
I wasn't trying to go into transition of the TM and propulsion whether AC or DC lol I was trying to say and apparently not so good, is the connector between the units makes them all work as one and the govoners and load regulators have a lot to do with it very basically speeking. What is amazing is that it works so well, I remember those turbo soak back filters would plug up and make problems too. We never really saw anything but SD/GP 40/40-2 around here, until we started seeing the dash 9's. You gave a good explanation going, please carry on
Rick, If you have a Digitrax system, you can run one Analog DC unit with your DCC units as long as the DC unit does not have a coreless motor. Just don't let it set for long periods of time, the pulses tend to heat the motor. Use address 00 on the Digitrax system to allow bit stretching. You can even MU other addresses to address 00, it works but I don't recommend it
Some people thought running two cycle and four cycle units together was an advantage. The EMD units provided better acceleration, but the four cycle units maintained speed better.
Thanks much Fellas for the knowledge you're passing along, and I must agree that it sure does add another dimension of realism to your operations
Tom, Yes the governor does drive the load regulator, it will not let the Main Alternator demand more than the diesel engine can provide. Of course as you know, if the load regulator is not at 7 o'clock (100%) there is probably an issue with the diesel engine, plugged up filters, bad power assembly etc.
It really does not have much to do with the diesel engine, there is not a direct drive to the axles. A 710 diesel engine and a FDL-16 diesel engine both produce the same 4,000 horsepower. That being said, a four axle locomotive tends to accelerate faster than a six axle, but that also depends on gearing. Maintaining speed has more to do with wheel control, GE did have a slightly better wheel slip system in the Dash 8's and Dash 9's than EMD, before the EMD Super Series wheel creep system. Without going into too much detail, EMD checked current flow to detect a wheel slip and GE looked at wheel speed, then tried to adjust current. Now on the other hand, the Dash 7's were a different story
Yes, they are interesting machines. A lot of thought was put into using low voltage relays to control high voltage contactor's, then trying to control the whole system, so it just doesn't sit there and spin it's wheels Something that still fascinates me is the GE starting system. For those who do not know, GE's use the Main Traction Alternator to start the diesel engine. Note, it's not a generator, it's a Alternator. Some ALCO's used the Main Generator to start the diesel engine, but a generator can be turned into a motor, just by sending voltage and enough current to it to do the job. It's a completely different story with a Alternator. GE Alternator's are "Y" wound alternators and it's pretty neat how they figure which leg is high and how to spin the alternator in the correct direction to start the diesel engine. I'm just glad you're getting some useful info out of the conversation. I'm trying to not go into too much detail, to keep the conversation interesting and informative
You sure have kept it interesting Rich_S, and yet kept it on a level I can understand; which isn't easy since I started out with 0 knowledge. Much appreciated. Glen
Oh, it always made a difference, though today's highly turbocharged and intercooled engines mask the differences between two-cycle and four-cycle, so it makes less difference than it used to in the 1950s and 1960s. Yes, horsepower is horsepower and dynomometers don't lie. But a four-cycle engine makes more torque than a similarly powerful two-cycle, because the valves on a four-cycle stay closed to, or nearly to, bottom dead center (where the piston stops going down and starts going up). If a two-cycle did that, it wouldn't work. A two-cycle also spins up to higher rpm faster, as it has twice as many power strokes per revolution. When I first heard that two-cycles accelerate trains up to speed better and four-cycles hold speed better, I found it odd, because my brother was a truck driver in the days when Detroit engines were two-cycle, and they weren't good at getting a heavy truck moving, but could shove it over a hill better. But that's because of direct drive to the axles and because of steep hills. Trains don't encounter hills that steep, so the extra power means less. And electric drive allows the diesel to spin right up to maximum power before the wheels even start turning, and the wheel motors convert that to torque. Torque is brute force, while horsepower is a measurement of how much brute force can be made in a specific amount of time. Any drag racer worth his salt can tell you that torque is important to get moving at all, but it's horsepower that produces acceleration. Two-cycle engines readily produce power for acceleration. But even with electric drive, torque has its place. Generators and alternators are easier to turn when nothing is using the electricity they're trying to generate. When a train encounters a slight upgrade, its motors put more demand on the generator. A torquier diesel really does bog down less when the generator gets more demand on it, and suddenly becomes harder to turn. Generator (or alternator)/wheel motor drive really is magical stuff, and far more flexible than any direct mechanical driveline. It does a lot to enable the prime mover to operate at optimum rpm, regardless of what speed the wheels themselves are turning. Even so, any generator or alternator which can move the load at all puts serious demands on that diesel. And the characteristics of that diesel will show themselves.
But here in lies the problem, everything you side is true for trucks but not for trains. The only thing that matters for trains is current, voltage and adhesion. I can produce 3,000 amps of current, but if I can't keep the wheels from slipping, you go no where. For DC motors, high current is required to get things moving, then increasing the voltage is required to speed things up. As long as the diesel engine can keep up with the current and voltage demand, it does not matter if it's a squeeze bang or a suck, squeeze, bang, blow. And in fact, EMD's have lower top end RPM's than GE's. The notch 8 RPM of a EMD is 905. The notch 8 RPM of a GE 1024. Load times also have a lot to do with the control systems being used and not the diesel engine. I'm sorry, I work on these things everyday and I'm just not buying it. A SD40-2 out performs a U23B, not because it's a two cycle, but because it has 3,000 HP that allows the main alternator to do more work.
