Train Sim World: CSX Heavy Haul

Train Sim World: CSX Heavy Haul

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pschlik Mar 29, 2017 @ 1:09pm
The Throttle Problem
Updated with release of Rapid Transit-bit of a rewrite to include new details I've learned over time.
TL;DR: The way electric motors are handled in TSW leads to an effect somewhat like the throttle has a built in cruise control which does not happen in real life, which is making driving diesel electric trains more annoying than it really should be.

Of all TSW's current, and extremely long standing bugs (this was reported over a year ago, and has been fixed in new [but not old] content already!),...the one I understand the reason behind the least is what I'm calling 'the throttle problem' but could be the 'cruise control effect' as comes up plenty as well; it's just a messed up setup with the power curves of the motors and throttle. Worst of all, the throttle and power curves were things that were (mostly) correctly modeled in TS1...but TSW somehow did it worse than TS1 did.

Anyway: the problem itself. I'm going to be referring to the SD40-2 here, but all the diesel electric locomotives do this, just at different speeds.

So, in current TSW, each throttle notch acts not only as the control for the level of power, but also also as the control of the maximum speed of the motors. The technical side of that is voltage-which I'll explain more on later. For example, notch 1 is pretty low power, and the maximum speed is set prettly low too; 23 mph. So you'll go up to 19 mph, then the amps will start dropping faster than normal as the motor nears what it thinks is its voltage limit, going down to 0 amps at 23 mph.
That's how it is like a cruise control; each notch of power has its own cruise speed in the physics. Increase the throttle, the power is increased AND the max speed of the motors is increased up to 29 mph, so you can accelerate once more. Drop the throttle to notch 1 again and the motors will be going too fast for the max speed setting, so you get 0 amps once more.

So what's the deal with voltage? Well, (DC, that is; AC ones are bit funkier) motors are nice and easy to work with; the power of a motor is equal to the voltage (speed) multipled by the amperage (torque). On a diesel electric locomotive, the throttle only controls the power (in an indirect way), and the motors use an amperage based on what speed the motor is already at to reach the constant power level. However, motors have a voltage limit before things stop working and the motor loses the ability to make the amount of torque expected. Get close to that limit, and the torque of the motor will drop, causing the power of the motor overall to drop. Exceed that voltage limit, and the power of the motor will drop to 0 (no amps, no torque).
So that sounds like what TSW does is pretty accurate to a motor hitting its voltage limit, right? Well, motors have a constant voltage limit. No matter what power you stick in, the motor will reach its limits at the same voltage, and therefore the same speed. TSW has the voltage limit connected to the throttle setting on the diesel electrics, rather than it being a constant number. And that's just not realistic.

The practical downside of this wole thing is that you get a lot less control of how much torque the train is making. You might think that having an easy 'set throttle, reach speed' system would be nice, but it frequently forces you into very strange speeds that don't correspond to speed limits while also forcing you to often apply far too much power compared to what's needed. In real life, you would probably drive an HST up to 125 mph in notch 5, then leave it in notch 3 or 4 to maintain 125 mph. In TSW, notch 5's max speed is around 140 mph, but notch 4s max speed is around 120 mph. To stay at 125 mph, you have to alternate between 1000 amps in notch 5 (too much torque) to 0 amps in noth 4 (too little torque). You either get too much power or not enough; there is no in between.


This bug needs to be fixed for all the routes, not just Rapid Transit and the ACS-64. Even though it is "playable," it's not one of those 'I can live with that, I guess' things; it is something that is pathetic to fix in one route, but then leave it alone everywhere else. This should be a universal fix, not a route by route fix.

Oh yeah, don't get me started on dynamic brakes.
Last edited by pschlik; Mar 19 @ 5:34pm
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Showing 1-15 of 425 comments
Paul Mar 29, 2017 @ 1:40pm 
So what you're saying is....we've been playing in Baby Mode the entire time? I thought it was strange that it stays at the same speed and the amps drop to zero, but then again I don't know much about locomotives, so I thought whatever. Now I understand. Turns out it applies fake cruise control.

What the hell, Dovetail? We need an official statement on this. For a supposedly "next-gen" simulator, this is absolutely pathetic.

:steamfacepalm::steamsad:
Last edited by Paul; Mar 29, 2017 @ 1:43pm
pschlik Mar 29, 2017 @ 1:58pm 
Originally posted by Paul:
So what you're saying is....we've been playing in Baby Mode the entire time? I thought it was strange that it stays at the same speed and the amps drop to zero, but then again I don't know much about locomotives, so I thought whatever. Now I understand. Turns out it applies fake cruise control.

What the hell, Dovetail? We need an official statement on this. For a supposedly "next-gen" simulator, this is absolutely pathetic.

:steamfacepalm::steamsad:
Basically, yes, it is baby mode. Not as baby mode as it could be (would be even more baby mode if notch 2 was 15 mph and not 18 mph) but still trying way too hard to make it "easier" at the expense of realism.
GeneralGeldenhuys Mar 29, 2017 @ 2:10pm 
Yep, this killed the "realism" of this game and I don't think the locomotive is suppose to do that at all. Looking at the videos how people drive and where I was on an actual locomotive is completely different.

I was on the Class 35 (Transnet Freight Rail) and the train driver could coast the locomotive happily at 60km/h in notch 2 (1-8 notches) and the locomotive output around 80-100 amps. That locomotive looks similar to the U30B diesels from General Electric. The Class 35 has a low amp traction motors. Highest amps it can go is 600 amps.

The fact that you have to drive in notch 4 and it shows 0 amps around 45mph doesn't make sense at all. The amps falls gradually, but not to 0.
paweuek Mar 29, 2017 @ 8:11pm 
Thanks for bringing this up and for detailed description of the problem! I also thought that something here is really messed up...it's indeed sooo annoying. I hope it'll be fixed soon!
stephen dedalus Mar 29, 2017 @ 11:43pm 
I had the feeling that something was bugged (nothing like this cruise control thingy happens in Run8), so thank you for nailing it. Devs please remove the extra and/or make it optional!
Kyrah Abattoir Mar 30, 2017 @ 12:37am 
I'm not sure that i agree with the OP's statement.

Acceleration at a given power output is a factor of the current speed, long story short, the faster you go, the more power is spent maintaining your speed and the less is available to increase speed.

Once your acceleration strength drops below the slow down caused by the train's rolling resistance, you stop accelerating.

I did notice that rolling resistance feels a lot stronger in TSW than in TS, which one is the right one? i don't know.
GeneralGeldenhuys Mar 30, 2017 @ 12:55am 
Originally posted by Kyrah Abattoir:
I'm not sure that i agree with the OP's statement.

Acceleration at a given power output is a factor of the current speed, long story short, the faster you go, the more power is spent maintaining your speed and the less is available to increase speed.

Once your acceleration strength drops below the slow down caused by the train's rolling resistance, you stop accelerating.

I did notice that rolling resistance feels a lot stronger in TSW than in TS, which one is the right one? i don't know.

There is a difference between theory and reality. These locomotives are diesel-eletric, meaning the desiel engine spins a generator creating current. The amps are not behaving like it does on a real diesel-electric locomotive. It should behave closely to TSxx.

The fact the amps drop to 0 implies to me the locomotive have a "cruise control" as the OP described it. It should never drop to 0 in any given circumstances. The amps will continue to drop, but slower as the amps getting lower. It seems the game drop the amps linearly and not exponentially, like it should on a real diesel-electric locomotive.

The engineering behind this is the generator creates a voltage and current. The voltage of the generator is always higher than of the traction motors. The difference between the voltage of the traction motors and generator will dictate the amps flowing. As you accelerate, the traction motors build up a voltage, due to the coil fields (I'm not sure if it is eddy fields or franklin). That is why the amps drop, but the traction motors voltage will never exceed that of the generator, otherwise you will have a runaway engine and the amps going into the negative. The generator will aways build up a capacitance in itself, thus creating a higher than usual voltage.

In layman terms, if you want more amps, you have to increase the voltage of the generator. That is what they do on the Class 86 and 87 with the tap changer.
Phazon88 Mar 30, 2017 @ 2:57am 
Yeah the throttles are just weird in this game coming from TS2017. Probably my main pet peeve at the moment apart from the performance issues.
wato Mar 30, 2017 @ 5:56am 
Originally posted by Kyrah Abattoir:
I'm not sure that i agree with the OP's statement.

I do. It's not realistic the way it's configured right now.

Originally posted by Kyrah Abattoir:
Acceleration at a given power output is a factor of the current speed, long story short, the faster you go, the more power is spent maintaining your speed and the less is available to increase speed.

Correct, as you state, due to:

Originally posted by Kyrah Abattoir:
Once your acceleration strength drops below the slow down caused by the train's rolling resistance, you stop accelerating.

However, the problem with TSW is that each notch of the throttle seems to produce power only up to a certain speed and then suddenly stops producing power.
Realistically, the power would remain constant regardless of the train's speed. Thus, acceleration would decrease gradually (proportional to 1/speed) until the forces are balanced, i.e., tractive effort equals the resistances.

See also http://steamcommunity.com/app/530070/discussions/0/133259956020607312/#c133259956023180536
Last edited by wato; Mar 30, 2017 @ 5:57am
pschlik Mar 30, 2017 @ 1:49pm 
All the detailed explanation here is right. The amps do decrease as speed increases, but they should never hit 0 so long as the throttle is on and the locomotive is not significantly above its maximum speed.
StratPlayer62 Mar 30, 2017 @ 8:30pm 
The amp meter never drops to 0 unless the you are going downhill on a steep enough grade to maintain or increase your speed, or you just reduced the throttle and are slowing down, which would put no load at all on the motor. If you let the speed level off you will see the amp meter fluctuates depending on how much load is being places on the motors, just like a motor does in real life. I'd love to hear from someone who actually drives American Locomotives on how the throttle works instead of a lot of assumptions.
Last edited by StratPlayer62; Mar 30, 2017 @ 8:32pm
GeneralGeldenhuys Mar 30, 2017 @ 10:53pm 
Originally posted by StratPlayer62:
The amp meter never drops to 0 unless the you are going downhill on a steep enough grade to maintain or increase your speed, or you just reduced the throttle and are slowing down, which would put no load at all on the motor. If you let the speed level off you will see the amp meter fluctuates depending on how much load is being places on the motors, just like a motor does in real life. I'd love to hear from someone who actually drives American Locomotives on how the throttle works instead of a lot of assumptions.

I was on an actual American diesel, but not the specific model SD40-2. We imported a lot of GM and GE diesels in South African in the 70's. Your description is accurate about what happens with the ammeter. It drops exponentially and not linearly. So it never reaches zero under notch 1-5. TSxx is the more correct on how this should behave.

What I also don't know about TSW is, do the locomotive have a continuous rating and peak rating for its traction motors? When you start off in notch 6-8 with the amps close in the red or in the red themselves, then the traction motors will start to heat up and the amps will drop slowly, even when the diesel is not moving.

The best way to test this is to turn the brakes on and the handbrake, set the loco in notch 8 withouth itself being able to move and see if the amps drop slowly.
u4ia Apr 19, 2017 @ 5:29pm 
Amps don't drop slowly as traction motors heat up, they're inductive loads (mostly). Even if they do, the load regulator will increase traction alternator excitation to make up for the lost load because it's a constant-kilowatt machine (as amps rise voltage will fall, and vice-versa). Amps will only drop off as locomotive speed increases or Performance Control (AKA power matching) kicks in at very low speeds with the throttle in position 8. You should also always get amps unless the train's near the maximum permissible speed. There's also no forward transition at ~21MPH on the current EMDs (varied slightly to prevent the whole consist from making transition at the same time, it would rip the train apart. Also no backward transition at ~18MPH like it should be) TSW doesn't do it right at all, coming from a real-world (albeit former) engineer in the US. A very neat sim indeed, just not accurate yet.
Last edited by u4ia; Apr 19, 2017 @ 5:32pm
bigbadvuk Apr 20, 2017 @ 10:31am 
It seems more like design decision then a classical bug. However, i agree Ts2017 had MUCH better throttle feeling. I also expected TSW to go and move things to next level but it seems atm we are going backwards in certain areas.

I hope this will be addressed in some of futrue patches.
Austin Apr 20, 2017 @ 12:39pm 
I agree with the OP. More to the point, in another thread there's a link to comments from a real-life engineer which says more or less exactly the same thing.

The brakes are also wrong, but they have been looking at that - but more needs to be done if it's ever going to be anything like a "sim" and not just a pretty arcade game.

And yes, as regards throttle behaviour, TS2017 was better.
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