## propulsion power of bidirectional trains

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Tekky
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### propulsion power of bidirectional trains

##### TL;DR
Locomotives facing the opposite direction should contribute to the propulsion power of the train.

##### What ?
Currently, a train in Factorio is only propulsed by all locomotives facing the direction the train is going. For example, if you have a bidirectional train with one locomotive on each end facing opposite directions, only one locomotive will pull the train while the other locomotive will be doing nothing, other than making the train slower due to its additional weight.

I am suggesting that all locomotives should contribute to the propulsion power of the train, even the ones that are facing the opposite direction.

##### Why ?
In reality, a modern bidirectional train with a locomotive on both ends will normally be propulsed by both locomotives. One locomotive will pull the train and the other will push the train, so that the total propulsion power of the train will be the sum of the power of both locomotives.

Therefore, in reality, bidirectional trains with 2 locomotives have no disadvantage compared to a unidirectional train with an equal number of locomotives. In Factorio, however, bidirectional trains only have half the power of a unidirectional train with an equal number of locomotives, because, in Factorio, locomotives must be facing the "correct" direction in order to contribute to the propulsion power of the train. Due to this, bidirectional trains have a major disadvantage in Factorio, which they do not have in reality.

As a consequence of this "nerfing" of bidirectional trains in Factorio, they are not very popular. Players often build unidirectional trains instead, because that is the only way to get the full power out of all locomotives. However, using unidirectional trains also requires that the player builds track loops everywhere, which would not be required for bidirectional trains.

Personally, I do not like the need to build track loops everywhere, because, in reality, they are unnecessary, for the reasons described above. In reality, virtually all trains are bidirectional. Even trains with only one locomotive are effectively bidirectional in reality, because the locomotive would simply detach itself from one end of the train and attach itself to the other end, if the train must change direction. This is possible because modern locomotives are symmetrical, i.e. they can drive equally well in both directions.

Of course, a locomotive automatically detaching itself and reattaching itself to the other end of the train would be too much work to implement in Factorio. (EDIT: Meanwhile, a mod which allows exactly this has been created for Factorio.)Therefore, I am not proposing that Factorio should attempt to imitate reality in every aspect.

However, I do believe that, in Factorio, a bidirectional train with at least one locomotive on each end should have the full amount of power of all of its locomotives at its disposal, no matter in which direction it is driving.

##### Extension of the suggestion
If this suggestion were implemented, it would no longer make sense for locomotives to have a front and a rear, since they could drive in both directions equally well. In that respect, locomotives would be symmetrical. Therefore, it would also make sense to also change the graphics of locomotives to make them symmetrical.

This would also be realistic, since most modern locomotives are symmetrical.

EDIT: Updated my original post with the suggestion template.
Last edited by Tekky on Wed Mar 06, 2019 5:17 pm, edited 8 times in total.

orzelek
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### Re: traction of bidirectional trains

Afaik certain %-age of train power is applied when going backwards.
There is an entry in train engine for this:

Code: Select all

``reversing_power_modifier``
I'm not sure how it is exactly used but it can be modded.

Optera
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### Re: traction of bidirectional trains

reversing_power_modifier only affects manually driven trains.
It would be nice if it also added to automatic trains.

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### Re: traction of bidirectional trains

the mentioned tag decides how much power is applied when the player runs the train in reverse.

unfortunately, no power is added in automatic mode if an engine runs backwards.

in my opinion, it should add to the total power.
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Tekky
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### Re: traction of bidirectional trains

Yes, I agree that at least the backwards power of locomotives facing the "wrong" direction should be added to the total power of a train, instead of them contributing no power at all.

However, I still believe that, in vanilla, it would be better (and also more realistic) if locomotives were symmetrical. This would not only solve the issue described above, but also several other issues, such as the issue described in this thread.

Even if locomotives were symmetrical, it would still be possible to prevent trains being able to drive backwards in automatic mode, by simply not placing a locomotive on both ends of the train. Also trains can be prevented to drive backwards on certain track segments by making these segments unidirectional using signals.

torne
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### Re: traction of bidirectional trains

Tekky wrote:Even if locomotives were symmetrical, it would still be possible to prevent trains being able to drive backwards in automatic mode, by simply not placing a locomotive on both ends of the train.
That's not how it currently works - the locomotive doesn't have to be at the front, having "pusher" trains works fine (and save space at stations, since you need fewer straight track pieces). So, if you made locomotives symmetrical, then there wouldn't be any way to prevent them driving backward without disallowing existing working configurations.

Tekky
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### Re: traction of bidirectional trains

Meanwhile, in this thread, a mod has been created that allows for automatic coupling and decoupling of locomotives from trains. This opens up many new possibilities.

I also believe that this mod demonstrates the necessity for my idea that locomotives should be symmetrical. In the official video demonstration of that mod by the mod author, he has to simulate a symmetrical locomotive by placing two locomotives facing opposite directions next to each other, which is very ugly and also makes the train sluggish, because only one locomotive will be able to provide power to the train in automatic mode.
Tekky wrote:Even if locomotives were symmetrical, it would still be possible to prevent trains being able to drive backwards in automatic mode, by simply not placing a locomotive on both ends of the train.
After seeing the demonstration video of the mod described above, I no longer consider it appropriate that only trains with a locomotive on both ends should be bidirecitonal, i.e. able to drive forwards and backwards. All trains should be bidirectional. For example, a single locomotive at the back of the train should be able to push the train into a siding, in order to decouple its cargo wagons in that siding.

steinio
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### Re: traction of bidirectional trains

Maybe anyone could make a mod which cuts the vanilla loco in half and the back part is a reverse loco.

So the big picture looks like one loco
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Tekky
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### Re: traction of bidirectional trains

steinio wrote:Maybe anyone could make a mod which cuts the vanilla loco in half and the back part is a reverse loco.
Yes, it would be possible to create the graphics for a symmetrical locomotive and for a mod to increase the reversing power of a locomotive to 100%, so that, in manual mode, the locomotive will be able to drive just as fast forwards as backwards (although the current controls would be confusing when driving backwards, since the user cannot see when he is driving backwards).

However, the main problem I see is that it would not be possible for a mod to allow for a locomotive to drive backwards in automatic mode. As far as I can tell, this behavior is hard-coded in the Factorio executable file and the modding API does not allow for a mod to change this. Although, since I am rather unfamiliar with the modding API, I may be wrong.

impetus maximus
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### Re: propulsion power of bidirectional trains

i think a locomotive facing backwards should have the same power as one facing forwards when the forward facing train is 'driving'.
i really hope this gets adopted in vanilla!

PacifyerGrey
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### Re: propulsion power of bidirectional trains

I will vote for locomotives adding power in reverse mode. But the actual locomotive direction should limit train movement directions in auto mode. I mean if the train has only locomotives facing one side is should move only that way in auto mode and should reverse only if it has locomotives facing both directions.

impetus maximus
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### Re: propulsion power of bidirectional trains

PacifyerGrey wrote:I will vote for locomotives adding power in reverse mode. But the actual locomotive direction should limit train movement directions in auto mode. I mean if the train has only locomotives facing one side is should move only that way in auto mode and should reverse only if it has locomotives facing both directions.
agreed

Hannu
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### Re: propulsion power of bidirectional trains

impetus maximus wrote:
PacifyerGrey wrote:I will vote for locomotives adding power in reverse mode. But the actual locomotive direction should limit train movement directions in auto mode. I mean if the train has only locomotives facing one side is should move only that way in auto mode and should reverse only if it has locomotives facing both directions.
agreed
In my opinion it should work so that train runs automatically only to the directions where locomotive is first but direction of locomotive(s) should not effect. If you want to have bidirectional train put the locomotive on both ends.

There is no need to change graphics. Many, if not the most of, diesel locomotives have asymmetric body but their wheels and transmission are symmetric.

Tekky
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### Re: propulsion power of bidirectional trains

Hannu wrote:In my opinion it should work so that train runs automatically only to the directions where locomotive is first but direction of locomotive(s) should not effect. If you want to have bidirectional train put the locomotive on both ends.
Two days ago, I would have fully agreed with you. However, after watching this official demonstration video of this mod, which allows automatic coupling and decoupling of train wagons, I now consider it important for trains with only one locomotive to also be able to drive backwards, in order to pick up cargo out of a siding.

Don't you agree that, in the demonstration video, it is very ugly to have to place two locomotives right next to each other, just to imitate a bidirectional locomotive?

Also, because you suggest that a bidirectional train must always have a locomotive on both ends, it would not be possible for a train to drop all of its cargo wagons in a siding, without also detaching one of its locomotives. Therefore, I believe it should be possible for a train with a single locomotive to drive backwards into a siding, in order to drop all of its cargo wagons there. This is also what happens most of the time in reality.

However, I do agree that it would look stupid if it were possible for a train without a locomotive at the front to drive at a speed of 260 km/h (even if it is automatic and has no driver). Maybe trains should have a speed limit as long as they drive in a direction in which it has no locomotive at the front?

Optera
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### Re: propulsion power of bidirectional trains

Tekky wrote: However, I do agree that it would look stupid if it were possible for a train without a locomotive at the front to drive at a speed of 260 km/h (even if it is automatic and has no driver). Maybe trains should have a speed limit as long as they drive in a direction in which it has no locomotive at the front?
"Wendezüge", push-pull trains according to wiki, are rather common to central Europe. Although they are almost exclusively used for passenger services irl, completely automated systems like factorio's trains have no restrictions derived from a driver needing to see track and signals.

The only limiting factor is the design of the couplings and physics. If wagons where more aerodynamically shaped nothing would speak against trains with a locomotive sandwiched between unmotorized carriages to go over 200kmph.

PS: The most efficient train would consist only of motorized carriages with no locomotive. Would be a pain to discern between loading burnable items into cargo or fuel slots, so they really ought to be electric.

orzelek
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### Re: propulsion power of bidirectional trains

Optera wrote:
Tekky wrote: However, I do agree that it would look stupid if it were possible for a train without a locomotive at the front to drive at a speed of 260 km/h (even if it is automatic and has no driver). Maybe trains should have a speed limit as long as they drive in a direction in which it has no locomotive at the front?
"Wendezüge", push-pull trains according to wiki, are rather common to central Europe. Although they are almost exclusively used for passenger services irl, completely automated systems like factorio's trains have no restrictions derived from a driver needing to see track and signals.

The only limiting factor is the design of the couplings and physics. If wagons where more aerodynamically shaped nothing would speak against trains with a locomotive sandwiched between unmotorized carriages to go over 200kmph.

PS: The most efficient train would consist only of motorized carriages with no locomotive. Would be a pain to discern between loading burnable items into cargo or fuel slots, so they really ought to be electric.
There are no cargo MTU's in real world AFAIK but it would be cool to have them in Factorio.
Or at least actual electric locomotives without need to cheat and recharge them by script.

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### Re: propulsion power of bidirectional trains

I think this is the reference thread for this idea:
viewtopic.php?f=5&t=35806 RoRo vs Terminus (was Loop vs 2-headed train network)

Please read before continuing discussion or continue discussion there.
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Optera
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### Re: propulsion power of bidirectional trains

orzelek wrote: There are no cargo MTU's in real world AFAIK but it would be cool to have them in Factorio.
I was sure I've read about a cargo subway using MUs years ago. Perhaps it was only a concept never realized.
ssilk wrote:I think this is the reference thread for this idea:
viewtopic.php?f=5&t=35806 RoRo vs Terminus (was Loop vs 2-headed train network)

Please read before continuing discussion or continue discussion there.
Are you sure a thread about RoRo vs Terminus station design is applicable? Apart from Terminus necessitating bidirectional trains there's no overlap to reasons why it makes no sense for factorio to only have uni-directional automatic locomotives.

Also that thread somehow derailed into a debate about junction designs.

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### Re: propulsion power of bidirectional trains

Page 3ff. is in my eyes useful.
viewtopic.php?f=5&t=35806&start=40
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### Re: propulsion power of bidirectional trains

Tekky wrote:Don't you agree that, in the demonstration video, it is very ugly to have to place two locomotives right next to each other, just to imitate a bidirectional locomotive?
Nice switching work. Maybe I have to try that mod. I did not take it into account. If switching will be possible, then of course locomotive should be able to push trains automatically. It could happen at limited speed in limited area like in real world.

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