Pulling power of some locomotives too low?

[ATSF3814]

This is something that's just been irking me for a while. I personally don't think they have the pulling power of some of the locomotives right. Like in some of the scenarios when you have 3 or 4 SD40-2s pulling only 20 freight cars up Cajon Pass and they're struggling even at full throttle? It just doesn't seem right to me especially after watching several youtube videos.

Here's one with a single CN SD40-2W handling 100+ freight cars all by itself. Even if they're all empty, that's pretty impressive:

http://www.youtube.com/watch?v=y9240YkCj9w

And here's several more that really show just how powerful real life GE and EMD locos are:

http://www.youtube.com/watch?v=GA7kG9AVnZc
http://www.youtube.com/watch?v=NmAb10P8tSg
http://www.youtube.com/watch?v=jX6xIdyKPaw
http://www.youtube.com/watch?v=qujCg5uvg2Y

[arizonachris]

I think for the most part that Railworks is fairly accurate (I did say fairly). Most of the stuff you linked to was empties on a level grade, maybe with a slight downhill. Had to be. One locomotive, even at 4,000 to 4,400 HP can't drag that many loaded cars. There's just no way. Besides, Cajon Pass is a beast to say the least. No, it's not the steepest grade, but I have seen lashup's of 4 SD40's in front and 2 SD40's mid consist with 2 more SD40's pushing. I have grown up in Southern California, with relatives in Arizona, so I often drive Interstate 10 which parallels the tracks thru some of the desert areas. I have seen consists more than a mile long with lashup's of 6 to 8 engines. And when I'm on the highway, I'm climbing some pretty steep grades; even tho the tracks try and stay to less steep grades, those rails have to cross a few tall hills.

One thing this does bring up for me, tho, is the economy of running freight by railroad. You could never, ever move that volume of freight, or passengers, by truck or car or bus, that you can by even one single locomotive, on a gallon/ mile/ dollar equation. (I think I said that right)

He he he, now you got me set on a mission to find a few vids of Cajon Pass. So far I found this (not a vid, just some pics): http://www.cajonpass.net/

OK, here's a good one: http://www.youtube.com/watch?v=6GSwibA3 ... re=related I am surprised how many "bangers" (cars with bad wheels/ bearings) they let go thru. I'm gonna watch some more, I'll let you dig up more of you own. I love Google Video/ Cajon Pass.

[micaelcorleone]

Yeah sometimes it's a bit strange.
For example, the SD70ACE feels so much more powerful than the Dash9s. I don't know if this is accurate, but it feels strange.
Another observation is that I had a AI consist on Cajon going upwards a not very steep grade: about 50 cars (mixed), 5 Dash9s at the head and Dash9, Dash9, SD40-2 at the end.
And this idiot of an AI train drove with about 15 mph although the limit was 45 or something.

[kin3]

Do the age, wear and tare have anything to do with pulling power. In other words as engines age and get run down does this affect their pulling power? Could you have one newer engine or two older engines to pull said train?

[arizonachris]

In real life, Kinnie, I'm sure it does. Basically, you have a diesel engine connected to a generator, and the armatures of electric motors drive the wheels on the bogies/ trucks. You have wear and tear on all the bearings, the resistors that transmit electrical power, etc., and therefore less power transmitted to the wheels/ tracks. But, I really doubt (could be wrong, I have been before ) that RW takes this into consideration. Probably no difference between a new, shiny loco and a "weathered" one. Only the cosmetic paint job.

[ATSF3814]

I think for the most part that Railworks is fairly accurate (I did say fairly). Most of the stuff you linked to was empties on a level grade, maybe with a slight downhill. Had to be. One locomotive, even at 4,000 to 4,400 HP can't drag that many loaded cars. There's just no way. Besides, Cajon Pass is a beast to say the least. No, it's not the steepest grade, but I have seen lashup's of 4 SD40's in front and 2 SD40's mid consist with 2 more SD40's pushing. I have grown up in Southern California, with relatives in Arizona, so I often drive Interstate 10 which parallels the tracks thru some of the desert areas. I have seen consists more than a mile long with lashup's of 6 to 8 engines. And when I'm on the highway, I'm climbing some pretty steep grades; even tho the tracks try and stay to less steep grades, those rails have to cross a few tall hills.

One thing this does bring up for me, tho, is the economy of running freight by railroad. You could never, ever move that volume of freight, or passengers, by truck or car or bus, that you can by even one single locomotive, on a gallon/ mile/ dollar equation. (I think I said that right)

He he he, now you got me set on a mission to find a few vids of Cajon Pass. So far I found this (not a vid, just some pics): http://www.cajonpass.net/

OK, here's a good one: http://www.youtube.com/watch?v=6GSwibA3 ... re=related I am surprised how many "bangers" (cars with bad wheels/ bearings) they let go thru. I'm gonna watch some more, I'll let you dig up more of you own. I love Google Video/ Cajon Pass.

I understand what you're saying but how long were the trains that all those locomotives you saw were hauling? RW seems to need massive numbers of locomotives for comparatively small consists.

On a side note here's a few great videos from Cajon back in the SF/SP days:

http://www.youtube.com/watch?v=GQJVgY9yprg
http://www.youtube.com/watch?v=CAvbxhXsoaI
http://www.youtube.com/watch?v=KyoJRQ8IVT8

Yeah sometimes it's a bit strange.
For example, the SD70ACE feels so much more powerful than the Dash9s. I don't know if this is accurate, but it feels strange.
Another observation is that I had a AI consist on Cajon going upwards a not very steep grade: about 50 cars (mixed), 5 Dash9s at the head and Dash9, Dash9, SD40-2 at the end.
And this idiot of an AI train drove with about 15 mph although the limit was 45 or something.

That's pretty much what I'm talking about. That many locos for 50 cars? I know it's an AI train in real life only two locomotives at the most would probably be running, but I believe RW is set to use the power of all the locomotives in the consist and really it shouldn't take that many to move that number of cars up Cajon Pass.

[Trainguy76]

The case of the AI is that they are running at a set speed, so even if you have 1 locomotive, It will reach that speed. I happen to think that the locomotives are underpowered, because I can get up Soldier Summit with a loaded coal train on notch 3 with 3 locomotives.

PS. All loco's behind the player loco in a consist have the same power as the player loco, last I checked.

[Toripony]

A subject dear to my heart......

Striving for the realism that I know well on the C&O, I have fussed and discussed this topic several times over a couple of years. I believe (but can't prove) that some of the physics were improved over time because early in my experimenting with RW I setup the train I see drive by the house daily and gave it a try. I FLEW up the mountain (as we call it; it's only 0.6%) like I didn't have a train. Working on someone's suggestions, I have tinkered with loco and car weights this past year. Then, after understanding the scales they are using in RW, I did some calculations and determined that the weight settings for those units are about right. At least, the ones they have in there now for the SD40-2s and the Coal Hopper are about right.

So, I've put together "that train" again... 4 SD40-2 heads and 100 loaded cars and did a few runs. I am finding that it is now surprisingly realistic! Of course, I've never driven a locomotive, but I have seen hundreds (thousands?) stop and go here in 40+ years and the behavior I am experiencing feels exactly like the real thing looks. That's good enough for me. From a dead stop in snowy weather anything over 25% throttle on a 0.1% grade spins out up until making 10 mph. After 5-6 miles I am up to speed, around 35 mph and my power levels off with the load at about 75% throttle. That's what the engineers around here have mentioned as typical and it is what I hear coming from their exhausts. I usually hear them push the throttle up (full?) as they go by here because the grade increase is just ahead.

I started out with RailSimulator and came online with the same question you just asked... for 22 cars with 4 heads, I guessed I should be going a lot faster. I wonder (am not sure why) if for some reason, trying to gauge the realism of power/behavior on steep grades like the B-SB doesn't appear valid???

Tori

[ATSF3814]

PS. All loco's behind the player loco in a consist have the same power as the player loco, last I checked.

I didn't know about that. Thanks. I guess that explains why having an SD40-2 ahead of ES44s or Dash 9s seems to diminish the train's power.

You made a good point in your post Tori. Maybe it isn't the physics for the locomotives and railcars that seems to be off, perhaps it's the physics for the gradients themselves.

[Shortliner]

RSC.com has actually done pretty well with cars that you can have "loaded" or "unloaded". However, cars like the Box cars or tank cars, you can't "load" or "unload" them, and I hope that's something RSC.com fixes in the future.

[arizonachris]

I understand what you're saying but how long were the trains that all those locomotives you saw were hauling?

I couldn't say for certain, but some of the Intermodals I have seen must be 100+ cars. Going east, they are usually loaded, and up a 2.2% grade, that takes horsepower. Tail end loco's could also be a (very small?) power move, too. I dunno, I'll that the game as it is.

[mapitts]

This is something that's just been irking me for a while. I personally don't think they have the pulling power of some of the locomotives right. Like in some of the scenarios when you have 3 or 4 SD40-2s pulling only 20 freight cars up Cajon Pass and they're struggling even at full throttle? It just doesn't seem right to me especially after watching several youtube videos.

Here's one with a single CN SD40-2W handling 100+ freight cars all by itself. Even if they're all empty, that's pretty impressive:

It is not a matter of horsepower at low speeds, it is a matter of tractive effort. All of the horsepower you see in a lashup, is for speed. A MP-15 can easily move 50 -60 cars or more on a flat track. That is only 3K horsepower, but 120K LBS. T.E. @ 7 MPH. As speed increases, T.E. decreases. As a close rule of thumb here is a little formula to help figure out tractive effort of a lashup at any given speed; Horsepower of locomotive(s) X 308 / MPH. There are other formulas to figure out other things as well. Flat rolling resistance, resistance on a grade, etc. Another thing that kills tractive effort is a curve. That is one reason they developed self steering trucks. The thing about 3 or 4 SD40-2's pulling 25 or so cars at WOT @ 20mph on a 2% grade is that they are also pulling their weight as well.

[mapitts]

Another couple of formulas I forgot to mention. One is 5 pounds drawbar force per ton on flat rail. The other is 20 pounds per ton per % of grade PLUS the 5 pounds flat rolling resistance. Drawbar force is different from tractive effort. Tractive effort is limited by adhesion, the amount of weight that the locomotive can actually put to the ground for pulling. On DC locomotives, the factor of adhesion is about 25% of the weight of the locomotive. On an AC locomotive with steerable trucks it is somewhere between 35% - 45%. Tractive effort is what the locomotive (s) can put to the rail as traction. Drawbar force is what the locomotive (s) can actually use to pull the train.