[2.0.73] FluidWagonPrototype::tank_spacing does nothing

[protocol_1903]

Title, the tank_spacing property on fluid wagons doesn't seem to do anything. I got a bug report that describes an issue with 2-port fluid wagons. Since the tank_spacing property is new, I tried that out to fix it. It seems to fix the issue, but as far as I can tell it doesn't do anything else.

All of the screenshots were taken after rebuilding the setup from scratch. pYAE+dependencies used, tested on the "Advanced fluid wagon"

spacing = 0.1

07-30-2026, 18-27-09.png (110.19 KiB) Viewed 378 times

spacing = 0.5

07-30-2026, 18-28-25.png (103.62 KiB) Viewed 378 times

spacing = 2

07-30-2026, 18-29-32.png (117.1 KiB) Viewed 378 times

spacing = 8

07-30-2026, 18-32-13.png (117.35 KiB) Viewed 378 times

[boskid]

Thanks for the report. This is Not a bug.

Realistically the tank_spacing becomes meaningful only when fluid wagon has at least 3 tanks and since you are showing fluid wagon with 2 tanks, you will not see any behavior changes. There are 2 sets of tank spacing: one is visual related to valves (https://lua-api.factorio.com/latest/pro ... horizontal, https://lua-api.factorio.com/latest/pro ... n_vertical) and one is logical related to selecting tank to connect to (https://lua-api.factorio.com/latest/pro ... nk_spacing) as i did not want to rely on visual valve positioning when pump selects which valve a pump should connect to since there is projection involved. When a fluid wagon has 2 tanks, you effectively have "front tank" (when pump is more forward than fluid wagon position) and "back tank" (when pump is more backwards than fluid wagon position) and no amount of tweaking this parameter will change anything as the transition is always in the center. If a fluid wagon has at least 3 tanks, this value will have meaningful impact on pumps as this value will set the distance between 2 thresholds, first on the boundary of tanks 1-2 and second on the boundary of tanks 2-3.

-- edit:

Wait a second, in the report title you are refering to version 2.0.73. In that version there was no "tank_spacing" as this property was added in 2.1. This makes your report completly invalid.

[protocol_1903]

Thanks for the report. This is Not a bug.

Realistically the tank_spacing becomes meaningful only when fluid wagon has at least 3 tanks and since you are showing fluid wagon with 2 tanks, you will not see any behavior changes. There are 2 sets of tank spacing: one is visual related to valves (https://lua-api.factorio.com/latest/pro ... horizontal, https://lua-api.factorio.com/latest/pro ... n_vertical) and one is logical related to selecting tank to connect to (https://lua-api.factorio.com/latest/pro ... nk_spacing) as i did not want to rely on visual valve positioning when pump selects which valve a pump should connect to since there is projection involved. When a fluid wagon has 2 tanks, you effectively have "front tank" (when pump is more forward than fluid wagon position) and "back tank" (when pump is more backwards than fluid wagon position) and no amount of tweaking this parameter will change anything as the transition is always in the center. If a fluid wagon has at least 3 tanks, this value will have meaningful impact on pumps as this value will set the distance between 2 thresholds, first on the boundary of tanks 1-2 and second on the boundary of tanks 2-3.

Thanks, that makes sense. Does setting the value relate at all to how it 'fixes' the bug mentioned, where tanks do not connect? Or does it do functionally nothing?

Wait a second, in the report title you are refering to version 2.0.73. In that version there was no "tank_spacing" as this property was added in 2.1. This makes your report completly invalid.

I meant 2.1.13 i swear

[boskid]

Does setting the value relate at all to how it 'fixes' the bug mentioned, where tanks do not connect? Or does it do functionally nothing?

It defaults to 2, however if you specify this value manually it will just trigger usual "prototypes changed" loading mode where various structures are rebuilt and this may fix the pump in the same way as loading save while holding Ctrl to force prototypes changed mode manually.

[protocol_1903]

It defaults to 2, however if you specify this value manually it will just trigger usual "prototypes changed" loading mode where various structures are rebuilt and this may fix the pump in the same way as loading save while holding Ctrl to force prototypes changed mode manually.

Would the generic prototypes changing also rebuild those structures, or does one of a few related prototypes need to be updated for fluid wagons/pumps to update?