Currently fluid-wagons on a train can only be accessed by running through LuaTrain.carriages and filtering out locos and cargo-wagons.
LuaTrain should contain a shortcut luaTrain.fluid-wagons similar to http://lua-api.factorio.com/latest/LuaT ... rgo_wagons
[0.15.2] add LuaTrain.fluid_wagons
Re: [0.15.2] add LuaTrain.fluid_wagons
Added for the next version of 0.15.
If you want to get ahold of me I'm almost always on Discord.