propulsion power of bidirectional trains

[JohnyDL]

I don't know if anyone's considered this but push trains are less stable that pull trains irl, try pushing a pencil or section of chain/rope along your desk vs pulling it for an example of this. The push trains should provide less power and as speed increases pushing locomotive relative strength needs to be reduced to maintain stability and prevent derailment. however as breaks a locomotive at the rear of the train has a more sustainable breaking stability if you want to model the pushing train in factorio maybe both these factors need to be considered, a train with rear locomotives may not be any faster but should be able to maintain speed for longer.

[Optera]

I don't know if anyone's considered this but push trains are less stable that pull trains irl, try pushing a pencil or section of chain/rope along your desk vs pulling it for an example of this. The push trains should provide less power and as speed increases pushing locomotive relative strength needs to be reduced to maintain stability and prevent derailment. however as breaks a locomotive at the rear of the train has a more sustainable breaking stability if you want to model the pushing train in factorio maybe both these factors need to be considered, a train with rear locomotives may not be any faster but should be able to maintain speed for longer.

That really depends on couplings.
A lot of passenger trains in Austria, Switzerland and Germany are push-pull trains with only one locomotive, sometimes even smack in the middle which works just fine most of the time.

Instability really comes into play on mountain railways like the Semmeringbahn. Until a few years ago the ÖBB had the locomotive on their Railjets facing Vienna and push trains up the steep Lower Austria side. The ride was surprisingly rough and you really felt every rail joint.
After they turned the trains around with locomotives facing Graz so they pull trains up the ride is now almost as smooth as on straight tracks.

Mus using a Schaku don't experience such behaviour.

[JohnyDL]

actually I was more thinking about the japanese bullet trains that go at the 150km/h+ range of the factorio trains, they're set up with all cars as locomotives in effect (every wheel is a driver wheel) but still they're set up so that the front car provides more power than the rear ones and the rear ones more breaking force.

There are other things that effect stability but when you're at speed not coming off the track by applying extra lateral force than necessary on corners is an issue, pulling wagons tends to fight any momentum out of the curve where as pushing them increases momentum through the curve and to balance this you need banked rails something that is on the bullet train but clearly something not in factorio

The locomotive can go at 250km/h speeds and does a turning circle of what 10m radius doesn't take a genius to look at the math there and say it should fly off the track it's got to weigh about 24 tonnes and has a huge amount of momentum attached even dropping it to 130km/h you need to apply 1MN of force in the space of 3 seconds applying that as a pull is relatively easy, applying that as a push with the rails doing all of the newton's 3rd law without the train tipping gotta say that's not something I'd want to be standing near

[Tekky]

May I point (again) to the basic thought of why I think this distinction is good:
If you have a map of about 1000 tiles size, the bidirectional trains is a very good idea: They save you a lot of space, it is much easier to handle them. But if you go above that size, let's say your map is 5000x5000, well, then you should ask you if double-sided trains are still THAT good idea.

It's a simple decision the player needs to make, like the decision between steel- and electric-furnace.

Generally, I agree with you that it is good if certain possibilities have both advantages and disadvantages, so that, based on the situation, the player must decide which solution is best for the situation at hand.

However, in this case, I don't think that this is appropriate. As has been pointed out in this thread, the current disadvantages of bi-directional trains are very unrealistic. This unrealistic need to build loops breaks game immersion for me and for most people who are familiar with modern railroads. In my opinion, the added gameplay value mentioned above is not sufficient to justify breaking game immersion by having this very unrealistic behavior of trains.

Additionally, rather than completely banning trains from running without a locomotive at it's front, there could be an option in the train timetable to specity a timetable entry as a shunt manovure. Trains cold then run in reverse, without a locomotive at the front, but at a vastly reduced speed. This would be handy for a mainly one-direction train network where the occasional station needs a train to reverse out of a station, shunting into a separate reversing siding.

I really like that idea.

Also, this suggestion would be, in my opinion, a good way to give the player more control over the train's pathfinder.

[Zanthra]

Currently as things stand right now in Factorio, a train in automatic mode will only be powered by locomotives facing in the direction of travel, all other locomotives contribute nothing to acceleration, but continue to produce friction. On the other hand, a train with locomotives facing each direction can choose a path either direction to get to it's next destination. It does not matter where in the train these locomotives are. The forward facing locomotive can be at the back of the train, and push the train all the way to it's destination.

In manual mode things are a bit strange. There is a property that allows 60% (in the base game) of the locomotive power to apply in reverse, but this only works if there are no locomotives facing the other direction. A two locomotive train with both forward has 100% power forward and 60% power backwards in manual mode, but if one is facing forwards and the other is facing backwards, it's only 50% of the total power in either direction.

I did post this topic: viewtopic.php?f=28&t=57438 on the modding interface requests forum to allow this to be changed by a mod, but as I discovered the oddities of the current system, I felt less and less that this was a result of a thought out set of specifications for how the devs wanted trains to work, and rather was the side effects of a basic set of rule to get trains to work that simply has not been looked at or adjusted since it was implemented.

The major questions are, should rear facing locomotives provide power to trains in automatic mode? If so, how much power? I feel that the power reduction when manually driving trains in reverse was a matter of controllability rather than it being too powerful.

Also, if they can provide reverse power in automatic mode, should trains with only one locomotive, or with all locomotives facing one direction attempt to path backwards to reach their next destination, or should that be available as a toggle per train?

In terms of balance I think the only big impact would be that, adding reversing power to trains would make terminal stations which are a little easier to build closer to RORO stations in terms of train performance, but I don't see that as a large problem as they have other advantages already. I am in support of 100% reverse power in automatic and optional reverse pathing per train.

[bobingabout]

There is actually a big train topic somewhere, you probably should have posted in that, I'm sure the topics will be merged...


but the general consensus is basically that if the power exists, it should be used. In terms of the base game, where you have 60% reverse power, 1 forward facing and 1 rear facing locomotive should provide 160% in both directions, not just the 100% of each head.

[bobucles]

IRL Locomotives simply don't care which way they're pointing, and it makes sense. Changing a train's direction is hard, but changing a train's thrust is easy. The only real real reason a locomotive's direction matters is A) for aerodynamics and B) Crumple zones*.


* FYI you're the crumple zone.

[mrvn]

IRL Locomotives simply don't care which way they're pointing, and it makes sense. Changing a train's direction is hard, but changing a train's thrust is easy. The only real real reason a locomotive's direction matters is A) for aerodynamics and B) Crumple zones*.


* FYI you're the crumple zone.

That wasn't always the case.

[bobucles]

That wasn't always the case.

It's a good thing we aren't dealing with trains from the early 1900's then.

[Engimage]

The topic was called Propulsion power of bidirectional trains. Pretty big one

[bobingabout]

Yeah, Diesel and Electric locomotives pretty much don't care what direction you drive them. But steam locomotives were a bit different. A Tender engine was typically designed to go forward faster than backwards (reverser only going to 30 for reverse, where it goes to 60 or 70 in forward), but tank engines were designed to go backwards with as much power as forward.

[Zanthra]

I did find the topic you are referring to in Ideas and Suggestions: viewtopic.php?f=6&t=40644&hilit=bidirectional+trains

If it's reasonable to merge it I don't mind.

I wonder if the train code that controls this stuff may be scary to mess with. With trains as beloved as they are, changing it could create a whole new set of side effects and oddities that players would have to learn.

[Koub]

If it's reasonable to merge it I don't mind.

So nice of you, you just made my day
[Koub] Merged into older similar suggestion

[mrvn]

Additionally, rather than completely banning trains from running without a locomotive at it's front, there could be an option in the train timetable to specity a timetable entry as a shunt manovure. Trains cold then run in reverse, without a locomotive at the front, but at a vastly reduced speed. This would be handy for a mainly one-direction train network where the occasional station needs a train to reverse out of a station, shunting into a separate reversing siding.

This is about the only new contribution in your post, and is what I was about to write (even slightly better).

Making path finding work as expected is, as I understand it, the only reason locomotives don't go backwards by default. Your suggestion would improve the game without breaking many people's games, with the exception of trains currently running without a locomotive at the front.

Clearly pathing is not a problem or bidirectional trains wouldn't work.

The other issue I've had with bidirectional trains is that they can end up turning around unexpectedly. This is fine when the cargo is uniform/symmetric but not for all trains. Being able to specify that the train must in some cases enter a station a certain way around would therefore be useful.

In summary, please:

• let engines apply power backwards in automatic mode (possibly full power, possibly less as when manually driven)
• by default only allow a train to find a path to a station when it has an engine at the front pointing in that direction (or possibly anywhere in the train); if there is an engine at both ends this allows pathing in both directions
• allow items in the schedule to be made a "shunting manoeuvre", meaning do pathing in both directions (possibly restrict speed when there isn't an engine at the front)
• allow items in the schedule to have an enforced direction forwards/backwards, even when pathing in both directions is otherwise allowed (this requires identifying the "front" of a bidirectional train)

The (initial) topic of this thread is point 1. The backward driving power of a locomotive should work in automatic mode too. With the default 60% backward power bidirectional trains would still be slower than unidirectional but you can mod that. Vanilla locomotives are optimized to go forward. Build your own if you want same speed both ways.

Point 2 is already how the game work. Yes, don't change that. It would break everyones train network.

Point 3: Not really on topic. But maybe this should be an option in the train stop: "Allow backwards driving trains".

Point 4: I think this would cause more confusion than it solves. Build your trains palindrom if you can't handle trains going either way. Trains look the same going both ways and there really is nothing to make the "front" anything special for a bidirectional train. It would be an arbitrary attribute that would be hard to see and control. What happens when you turn the "front" locomotive around? What when you join two trains end to end? Which "front" stays the "front"?


In conclusion I would like to add one more point to the initial request:

When pathing first path in the direction the train has more power. If more locomotives faces one way than the other tan (with those 60% backwards power) the train will have a prefered direction. The pathing should consider that even if more locomotives face backwards to the internal forward direction.

[Barhandar]

I'd like to add that modern locomotives are only sideless because they're electric and electric motors don't care which direction to rotate in. Even fuel-using ones merely generate electricity onboard instead of taking it from the grid, and purely mechanical locomotives are much slower due to gearing being unable to take the loads.

Factorio's locomotives don't have eccentric shaft required for most mechanical transmission, though. Either they use non-shafted transmission, in which case slowdown in reverse is expected, or they run on diesel-hydraulic which, similarly to diesel-electric, doesn't seem to have a preferred direction. Diesel-hydraulics are used in Germany, for freight in particular, but not much elsewhere.

[Zanthra]

Additionally, rather than completely banning trains from running without a locomotive at it's front, there could be an option in the train timetable to specity a timetable entry as a shunt manovure. Trains cold then run in reverse, without a locomotive at the front, but at a vastly reduced speed. This would be handy for a mainly one-direction train network where the occasional station needs a train to reverse out of a station, shunting into a separate reversing siding.

This is about the only new contribution in your post, and is what I was about to write (even slightly better).

Making path finding work as expected is, as I understand it, the only reason locomotives don't go backwards by default. Your suggestion would improve the game without breaking many people's games, with the exception of trains currently running without a locomotive at the front.

Clearly pathing is not a problem or bidirectional trains wouldn't work.

The other issue I've had with bidirectional trains is that they can end up turning around unexpectedly. This is fine when the cargo is uniform/symmetric but not for all trains. Being able to specify that the train must in some cases enter a station a certain way around would therefore be useful.

In summary, please:

• let engines apply power backwards in automatic mode (possibly full power, possibly less as when manually driven)
• by default only allow a train to find a path to a station when it has an engine at the front pointing in that direction (or possibly anywhere in the train); if there is an engine at both ends this allows pathing in both directions
• allow items in the schedule to be made a "shunting manoeuvre", meaning do pathing in both directions (possibly restrict speed when there isn't an engine at the front)
• allow items in the schedule to have an enforced direction forwards/backwards, even when pathing in both directions is otherwise allowed (this requires identifying the "front" of a bidirectional train)

The (initial) topic of this thread is point 1. The backward driving power of a locomotive should work in automatic mode too. With the default 60% backward power bidirectional trains would still be slower than unidirectional but you can mod that. Vanilla locomotives are optimized to go forward. Build your own if you want same speed both ways.

Point 2 is already how the game work. Yes, don't change that. It would break everyones train network.

Point 3: Not really on topic. But maybe this should be an option in the train stop: "Allow backwards driving trains".

Point 4: I think this would cause more confusion than it solves. Build your trains palindrom if you can't handle trains going either way. Trains look the same going both ways and there really is nothing to make the "front" anything special for a bidirectional train. It would be an arbitrary attribute that would be hard to see and control. What happens when you turn the "front" locomotive around? What when you join two trains end to end? Which "front" stays the "front"?


In conclusion I would like to add one more point to the initial request:

When pathing first path in the direction the train has more power. If more locomotives faces one way than the other tan (with those 60% backwards power) the train will have a prefered direction. The pathing should consider that even if more locomotives face backwards to the internal forward direction.

In response to Pont 2 there: Currently, the game does not care if there is a locomotive at the front of a train. It only cares that there is a locomotive on the train somewhere that faces in that direction. This makes it possible in factorio to have a network of pusher trains already, with cargo wagons at the "front". It might be reasoanble to change that trains can only operate in automatic mode if there is a locomotive at the front, with the argument that only the locomotives have the equipment to detect and use train stops and rail signals. Then you could also potentially add a "Control Cargo Wagon" with a slightly different look, but with the ability to carry cargo and operate the train in that direction to lead a pusher train for expanded choices of train layouts, but also for aesthetic reasons.

[Tekky]

In response to Pont 2 there: Currently, the game does not care if there is a locomotive at the front of a train. It only cares that there is a locomotive on the train somewhere that faces in that direction. This makes it possible in factorio to have a network of pusher trains already, with cargo wagons at the "front". It might be reasoanble to change that trains can only operate in automatic mode if there is a locomotive at the front, with the argument that only the locomotives have the equipment to detect and use train stops and rail signals.

I fully agree with this, in principle. The only problem I see with this are shunting maneuvers, i.e. if you want to automatically couple or uncouple carriages, for example by using this mod. For shunting maneuvers, it is necessary for a single locomotive to be able to go (at least very slowly) backwards. Therefore, I still think that the following solution from page 2 of this thread would be best:

Additionally, rather than completely banning trains from running without a locomotive at it's front, there could be an option in the train timetable to specity a timetable entry as a shunt manovure. Trains cold then run in reverse, without a locomotive at the front, but at a vastly reduced speed. This would be handy for a mainly one-direction train network where the occasional station needs a train to reverse out of a station, shunting into a separate reversing siding.

[JaJe]

Hello,
Right now if you place 2 locomotives on both sides, only a locomotive push the force while the other is just an extra weight to carry. I'd like to see the other locomotive pushing backward to increase the acceleration.

Of course the best would have been if a single locomotive can travel backwards but I guess it's not going to happen anytime soon.

[ikarikeiji]

For passenger only use it would make sense to add a DMU, which would be symmetric and could be driven in either direction with the same speed/acceleration.

For anything else I can't really see backward driving locomotives happening.

[Tekky]

I have made exactly the same suggestions two years ago in the following thread:

viewtopic.php?f=6&t=40644 propulsion power of bidirectional trains

EDIT: Meanwhile, the threads have been merged. Therefore, my above link now points to the current thread.