updated the bp string in OPAnson wrote:just add the unloader for the first position and you can almost keep the original description
"A depot able to service any vanilla train composition of length 4 or lower"
That's what I meant. 5 locomotive types would only need 2 additional arithmetic combinators.edit: on reading what i just wrote, i got an idea to halve the number of combinators. instead of "engine1 * 1 = diesel engine", etc six times, i can simply do "engine1 + engine2 = diesel engine", etc three times (connecting all three outputs just like i did before with six outputs). any ideas for reducing that even more ?
To automatically cycle out old fuel type you have a low tech and an overly complicated option.btw: i also chained one constant combinator to all requester chests and set all requester chests to "Mode of Operation: set requests". by only changing the value in that single constant combinator, i now can reprogram the whole system to fuel trains with one or more other types of fuel, eg when i have too much wood, or when i start working with oil, using solid fuel or rocket fuel, or with some mods even burning alien artifacts. the only problem i noticed when changing the fuel type is on trains that have only one fuel slot or that useup all their fuel slots for long roundtrips since they start refueling with the new type only when the last unit of the old fuel is used up, and that almost always isn't good enough to go back to the depot in time (worst when switching from wood and/or for longer distances)
low tech:
Add an active provider chest with filter inserter set to old fuel type next to every locomotive spot in the depot.
overly complicated:
Construct a override logic for the binary decoder so it empties locomotives when you change fuel type.
The potential problem here is inserters fill fuel slots from left to right, but also empty in that order.