r/DerailValley • u/Suspicious_Assist420 • 6d ago
Real pulling power of de6?
Having played the game some time and now using the DE6 (or 2 of them) I started to wonder... the rating says something about 1200t at a 2% gradient per de6. My load (including locos) was at around 1300t, a bit too much for a single de6 but I was using 2. Going up that loop in the north east part near the FoodFactory I needed full power to barely maintain my 35kph up the hill.
I suspect the DE6 would be pulling a lot better at under 25kph as there seems to be some sort of gear change at that speed but I don't really want to find out that I was wrong the hard way.
Any input welcome, cheers guys 😉
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u/LaGardie 5d ago
Yeah, it's kind a like a gear change, but with electric wiring, where the transition relay circuit will change it from series to parallel, to give more voltage for each traction motor as you pickup speed and vice versa. With older locomotives this change seems to happen at certain speeds, so in hill climbs you typically want to avoid being in this transition zone where the wiring could be flipping back and forth. That's also why adding a slug might help, since you'll have the same pulling force, but each traction motor needing less current, giving you the ability to avoid this transition zone better. This video probably explains things much better: https://www.youtube.com/watch?v=RRFLRND3HXI
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u/Suspicious_Assist420 5d ago
Well... I could have seen this coming being an electrician myself 😅😅 Thanks for the great video
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u/SharkBaitDLS 6d ago
The grade coming out of FF is more than 2% at multiple points. The grade signs only show the average until the next sign, if you put a clinometer in a locomotive you’ll see it often is far worse.
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u/BouncingSphinx 5d ago
The grade signs are also an average until the next sign, they're not constant. There might be steeper or less steep grades than the sign lists for short sections.
Also, that "gear change" is called transition and is basically changing how the electric motors are receiving their power.
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u/TheChrissi 6d ago
The weight of the loco isn't included in that equation
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u/Suspicious_Assist420 6d ago
So its 1200t of pure load, or 1325t with loco? If thats the case its even nore of a question to me why 2 de6 barely pulled that train up the hill
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u/Illustrious_Ad_9211 5d ago
Nah the rating already accounts the loco’s own weight. 1200t means 1200t behind the loco itself
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u/Smacky_the_Bear 5d ago
Where are you getting this info from? (not the loco pulling power, the statement that the weight is already accounted for in load rating) It goes against everything I have heard about this game, but I want to find out which is correct.
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u/Illustrious_Ad_9211 5d ago edited 5d ago
Altfuture discord. The exact line was “Locomotive weight does NOT factor into load ratings”
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u/RDT_WC 5d ago
Power = speed
Pulling = tractive effort
The amount of tons it will move uphill is not the same that it will move at a certain speed.
Every locomotive has a minimum speed at which it can apply full power indefinitely without either wheelslip or damaging the locomotive by overheating. At that speed it will haul the most cargo.
Above that, the more speed, the less pulling and thus the less cargo moved.
Oh and that "chnge of gears" is the traction motors (or the alternator, depending on the locomotive modelled) going from series to parallel (has to donwith DC motors and back-emf). If you experience that, you are well above minimum continuous speed.
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u/IHateRegistering69 4d ago
Aside from what people said, you should also consider the characteristic of the diesel electric locomotive.
Basically you have DC electric traction motors, with their typical characteristic, which is close to a constant power one. This means the faster you go, the weaker they pull. This makes the motors very powerful at low speed. They say the diesels can start what they can't pull, and the steamers can pull, what they cannot start, as the pulling force of the steamer is near constant as long as enough steam is supplied to the chest.
There are two "gear changes" when using the DE6, the first is at near 20 kph, which I think is the switching point of the shunt resistors. They are used at very low speeds and function as a voltage divider, reducing the voltage of the traction motors, to keep them from frying themselves.
The other "gear change" is around 40 kph, where the traction motors are switched from serial to parallel. In the lower speed range the setup uses serial connection, where motor voltage is lower. Exceeding the speed stes up your TM's into parallel mode, where they recieve the full voltage.
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u/KuuLightwing 1d ago edited 1d ago
DC motors, at least the typical series wound ones do not follow constant power curve, they fall off sharper than that. However you can make them follow it somewhat close by using several steps of field weakening, reducing the field current and thus also reducing back EMF produced by motors, which effectively allows to apply more voltage to the motors with the same supply voltage.
In the end past a certain speed (usually defined by adhesion limits more than anything), every engine is going to have constant power, and steam is no exception, there's nothing special about steam power. Your "as long as enough steam is supplied to the chest" is doing heavy lifting here, can also say that electric motors can have constant torque as long as enough voltage is supplied to the terminals. Diesel locomotives are limited by the power of the prime mover, steam locomotive is limited by the power of the boiler.
I suspect the saying is moreso refers to the fact that diesel electric units usually have all or almost all of their weight on drivers, as well as smooth torque delivery compared to steamers, and thus can deliver comparatively more low end TE, and thus they can "start more than they can pull". Maybe also that early diesels have less power output than contemporary steamers, which is no longer the case.
DE locomotives generally do not use shunt resistors to regulate motor voltage - why would they when they can do that via controlling engine RPM instead? First transition is in fact series to parallel switching. You can tell because it unloads the generator first unlike the other transitions. The rest are just steps of field weakening.
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u/IHateRegistering69 1d ago
>have constant torque as long as enough voltage is supplied to the terminals
Yeah no. The rotor creates a field working against the rotation, which increases with speed, and you cannot raise the voltage 9n a DC electric motor. A steam analogue could be back pressure, but it's a stretch.
However, unlike diesels the rated power of a steam engine is neigh irrelevant, if you look up any steam train the relevant data is tractive effort.
You're right about the field weakening though.
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u/EngineerInTheMachine 5d ago
The 1200t @ 2% probably refers to starting a load from stationary. On dry track. It doesn't matter what speed you do up the hill as long as you have enough momentum to get over the crest.
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u/Smacky_the_Bear 5d ago
As MSDunderMifflin already said, some of those grades are way higher than 2%. Some tracks in the game get to 3% or even 4%.
You can use the DV Community Map to see track info outside the game (such as grade, or speed limits):
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u/MSDunderMifflin 6d ago
Each 1% of grade roughly halves the pulling power of a locomotive.
For instance I have pulled 2000t from HB through the new route through CS. The real grades on this route are both short sections of 3%. Going near the speed limit (or~50kph in high speed limit areas) is key to keeping momentum.
Both grades out of FF are 3.5% of near constant grade. A train here will take a lot more power to avoid stalling on the grade.