Using combinators to control trains / stations

[Bill B]

My problem is, I have 4 locations where my trains drop off iron ore for processing, but I have 12 trains doing it.
I want to keep my trains parked in a remote stacker until a station is clear. not sure how to set up combinators to make this work.
Any help or videos on how to do this would be appreciated

[Yoyobuae]

Put the stacker right next to the stations.

If you still insist on setting up the stacker away from the drop-off stations, then place a "Park" stations where the stacker is located and add these "Park" stations into the train schedule. This is effectively the same thing as "put the stacker right next to the stations".

Trains at each "Park" station would only set off once the respective drop-off station becomes free. This can be achieved by running a circuit wire from each drop-off station to each corresponding "Park" station, no combinators needed.

[Bill B]

Capture.PNG (65.75 KiB) Viewed 1693 times

attached is a photo of what is happening....
Trains are going to 4 locations and jamming up the track....

[astroshak]

Personally, under those circumstances as described in the op, I would have the four drop off stations have their own individual names, and their own sets of three trains. Have the trains sit at the drop off station until empty, and have the pickup locations turn on when there is enough ore to fill a train. Make small stackers before the drop offs (for the other two trains there) to sit in while full waiting for their shot at the drop off station.

[SoShootMe]

attached is a photo of what is happening....
Trains are going to 4 locations and jamming up the track....

One simple approach is to have only chain signals between the stacker and the train stops, apart from the signal at the start of the block containing the stops, which must be a regular signal. This way, trains can only leave the stacker if the block containing the stop they are heading to is unoccupied. This will always work but the further the stacker is from the stops, the more throughput will be limited. This is because at any given time, only as many trains can be in the blocks covered by chain signals as there are different routes.

Another simple approach is to have a dedicated line that is the only way to get from the stacker to the stops, with regular signals a train-length apart so trains queue up. The front of the queue should be near the stops and have a chain signal, with (as above) regular signals at the start of the blocks containing the stops.

If you can't do either of those, I think the only reliable approach (other than mods) is to count trains. It looks like 76305 is a general solution using this idea, but I've not tried it.

[MassiveDynamic]

Also, your trains are too long for your signaling. ALL trains should be shorter than your shortest gap in signals. Put another way, ALL gaps in signals should be long enough to allow your longest train to wait without blocking any intersection.

[Zavian]

Clarifying what MassiveDynamic said.

You can have signals spaced closer than the length of your longest train without it causing problems (indeed most rail networks will have lots of small gaps signalled with chain signals within junctions). You just need to make sure that after the first regular signal at the exit to every junction you have a gap large enough to fit your longest train.

My first step for solving the problem in the OP, would be to make the exit(s) from the stacker a (set of) dedicated rail line(s). That way trains leaving the stacker would not clog the mainline.

BTW been there, built that kind of massive smelting array. Decided it wasn't a scalable approach, and now I avoid building such large centralised smelting at the megabase scale. (I do still build it at smaller scales). (And even at the megabase scale I don't need four track railways. With the right base design you can get by with just normal dual track railways upto at least 1500 sci/min).

[Bill B]

Thanks for all the suggestions and pointers. This is what I have come up with as my fix. Works the way I wanted..

Capture.PNG (60.18 KiB) Viewed 1574 times