Prototype Locomotive Operation

[wacampbell]

I've never operated a locomotive or even been inside an operating loco but I've always wondered about the throttle operation in our simulated locomotives. It seems in the simulator with most locomotives, on flat and level track, once you are up to speed you have to back the throttle all the way down to something link 2% to hold speed constant. I guess trains have very low friction, but I was always curious if real locomotives behave this way. For example if I was operating an SD40-2 with 10 cars on flat track, would it hold speed at 20MPH with only 2% throttle?

[simer4]

Well, I have been in an SD70M-2, and we went up to 20mph in notch 2 and kept it at that speed. I also noticed that when we were switching from Forward to Reverse, the engine went into a lower idle.

[dick8299]

I think the OP was referring to how engines in RW seem to maintain constant speed with no power applied, does that happen in real life?

[GaryG]

On level track at low speeds, most of the applied power goes to acceleration. At low speeds, It takes very little power to overcome friction and air resistance and hold a constant speed. If it is windy, then wind resistance changes all the rules.

In the days before all rolling equipment had roller bearings it did require more power to both reach and then maintain a low speed.

GaryG

[mapitts]

Well, I have been in an SD70M-2, and we went up to 20mph in notch 2 and kept it at that speed. I also noticed that when we were switching from Forward to Reverse, the engine went into a lower idle.

In the real thing you have an idle position in the throttle, then run 1-8. RW for some reason does not have that effect. Some have a low idle position as well.

[Kali]

It also takes more power to overcome initial friction ( usually called stiction ) than normal rolling friction.

Usually the lowest notch on a power controller breaks the contacts between the generator and the motors too; the first notch will still be idle, but you would get just enough power to move the engine. RW audio tends to reflect this even if the physics setup doesn't.

[TrainMaster1]

You are correct in that there are eight notches on a typical control stand. Desk top modern units have a graduated combined handle in most cases meaning that Dynamic Brakes and the throttle operate off the same handle...

The first notch was not Idle when I was still running. It was used in several cases. If we were in motion it was used for switching and other lower speed activity. If in neutral it was used to generate air for the reservoirs quicker.

Grades, length and weight of the train great affect what results you get out of each notch....Weather conditions also will mess with adhesion rates...even differences in transition systems can be a major headache. GEs tend to load slower and EMDs quicker at least in my experience....so if you had a GE leader followed by an EMD, when you take that first notch...the EMD will start shoving on the back porch of the GE. Only slightly unnerving since you generally were ready for it.

There is a lot to know if you are really trying to replicate prototype operations....3 braking systems (automatic, independent and dynamics), two different types of traction motors (ac and dc), all types of gauges (brakes, hours of service or ammeter on older models, speed, EOT comm, DPU Control (modern era), just for starters. Don't forgets controls for lights, horn, sanders, throttle/dynamics, bell....now we're having fun!

If you have DC traction motors you also need to know your lowest continuous speed rating. Stay below that number too long and you melt the traction motors into matching sets of paperweights. That is why most coal trains or drag freights draw ac power as you avoid that limitation of red zone on the hours of service meter for the most part.

Lots to think about every time you are in the cab. (Especially at every crossing)

For sheer lugging ability no one has still come close to ALCO or Baldwins for pulling virtually anything and having the ability to stop it. They were some of the best out there...still a part owner of 6 real world ALCOs in the process of being restored to running status.

Nick

[Kali]

Well even over here it wouldn't be totally idle - the generator with a bit of load on it will mean the governer gives a little fuel flow to stop the engine stalling - but it was intended here as a notch for shunting & so on like you said, although not if you have any real load.

Hours of service? heh that's a new one, a fun gauge. I bet it was disconnected fairly frequently :p

[redwhiteandblack]

Usually the lowest notch on a power controller breaks the contacts between the generator and the motors too; the first notch will still be idle, but you would get just enough power to move the engine. RW audio tends to reflect this even if the physics setup doesn't.

Looks like this explains something that has puzzled and annoyed me for what seems like an eternity now. I immediately noticed upon purchasing both the SW1500 and GP9 packs that while the audio quality was excellent (as I have come to expect from Oovee), the engine sound in relation to throttle setting was completely out of sync. The engine audio remained at idle when the throttle was notched up to Run 1---which makes for some awfully boring engine audio when you don't plan on exceeding 15mph. This to the best of my knowledge (which would in this particular case be with about 99.9% certainty) is completely unprototypical for any North American diesel locomotive; there should be a distinct and pronounced "rev-up" from idle into R1, as evident in the existing sounds for the Dash 9 and SD70ACe.

Apparently from what you say there is in fact a prototype for this sort of operation. Unfortunately it appears that in this case it is simply the wrong prototype.

Aidan Berard's excelent EMD 645 sound pack has resolved this issue for the default SD40-2 (which had exhibited this flawed behavior ever since having its audio upgraded for the TS2012 release), so it's obviously possible to fix. Unfortunately, while I have plenty of hours logged "under the hood" in engine and simulation files, my experience in the sound file department is too limited to produce a fix.


Ryan

[Kali]

You fall foul of RW physics a bit there also; notch 1 at low speed can easily give a disproportionate amount of power. I must admit at low speed I tend to be in notch 0 a lot and only put power on when I've lost 5mph. Have you tried the TEM2? that breaks it's contacters in notch 0, there's certainly some change in noise - and a bit of power - once they close in notch 1 but without driving it which I'm not in a position to do, I can't remember if they made the engine note change ( I certainly don't think it revs much if any ). Not sure how different a TEM2 is to the RSD2 they based it on, but that was a common setup for a D-E many moons ago. Nothing like that on a Geep? that's a little surprising.

1st gen english prototypes have infinitely variable power handles so you can't really say there's a notch 1, but certainly on a 37 you have to fish around at 3-5% throttle to get contacters closed - you won't get much in the way of power until you open the handle more. That might only be on unrefurbished DC ones, thinking about it.

[mapitts]

Is EMD still using a mechanical drive air compressor? The big thing with an electric motor driven a/c is that it will build air at any throttle position. As far as GE's loading slow, remember that a GE's crankshaft has to turn 2 full revolutions for all the cylinders to fire, while an EMD's only turns once. I am also not sure why you would want to keep a load on a generator at idle. I can smell the windings in the traction motors burning from here. On a US locomotive, when you put the throttle in the idle position, it disables the aux generator from the main generator through the reverser drum. The governor will keep the prime mover running at idle speed. That is on a DC locomotive. Worked on quite a few Alco's myself. All 539's though. I am glad for someone to bring up transition a well. RW does not have that as well. A simple thing but still wished it had it. I love the new SD-40-2. With working ammeter, a readable speedometer, and air brake gauges, I do not have to use the HUD. The only thing I have ever been able to figure out how it works on an AC locomotive electrically is the traction motors ( no magic there ) and the dynamic brakes. I feel another forum possibly coming to life. I love to discuss real world locomotives and how they work.

[Kali]

Before becoming a network engineer I was training to be a mechanical one, I'm pretty fascinated by how anything works! and I've found the more details you can add to simulated behavior the more interesting something is to drive too - so please do go on talking.

[mapitts]

TrainMaster1 was talking about the EMD's loading quicker at start off. It goes the other way when lugging up a hill. The GE will start to transition up, while the EMD's load regulator is still trying to figure out what is going on. The GE behind you will beat you half to death. He is also spot on with the Alco's & Baldwins IMHP. The only thing wrong with the Baldwin's were the air MU that a lot of them used and the Westinghouse traction motors. Westinghouse used a 6 or 8 pole motor while every one else used a 4. The Baldwin would pull down to about 5MPH and keep on going. If it was MU'ed to anything else, it would smoke the trailing units traction motors. I always thought that both Baldwin and Fairbanks-Morse were WAY ahead of their time.

[TrainMaster1]

Spot on with the Baldwin/FM being way out ahead of their times. They just never really gained acceptance like some of the other manufacturers. A shame it took Alco to the 244H Model to get that engine right and the 251 final model came too late to really save the day. When they were available they worked great but they spent way too much time in the shop. That gave railroads all the reason to look elsewhere for their needs.

MU Capability was always iffy back in the day...who had 21 pin or 27 pin connectors....pneumatic throttles vs electric...often meant that when one unit of an A-B went down, the other had no where to go as well.

Still funny to see how many 40 year old EMDs are being rebuilt where no RR to my knowledge is rebuilding GEs. EMD still the leader in overall reliability which is what the bean counters care about. Cost per mile to operate and availability make the front office smile.

Always enjoy chatting about the prototype when I get the chance. Matter of fact, next weekend we are running a 1976 session on the D&H....mmmmm...Alcos, U-Boats, SD45s as far as the eye can see....LV, D&H, B&M, NW power galore....and no ES-44s!!!!

Nick

[mapitts]

I have lived my entire life with the Southern Railway in my town. One thing about Southern; in the early years they were sampling ANYTHING. EMD's were all you ever saw for the most part. Occasionally you would see a GE, but not often. The GE's for the most part stayed to the east of here. Especially the U30's and U33's. Southern had bought 5 or 6 Trainmasters to run between a pair of SD24's on the CNO&TP. That would have been a sight. It is more like 50 year old EMD's still being rebuilt. I work in a plant that SD40-2's are killing the track. 90 pound rail and lots of curves and switches. We had several pretty good derailments last year. One bad enough to have to call Hulcher Services. I told my supervisor that NS was killing the track. It was designed for 280,000 pound 4 axle GP's, not 385,000 pound 6 axle SD's working in pairs. I was working in the shop one early morning and heard a loud boom. I went running outside thinking we had an explosion. Turned out to be a GP 50 traction motor flash over. Another D77 piece of junk.