This unloader uses 1 underground blue belt for extra length (could use a quality red belt) and one belt that is 1 tier lower to carry half a belt. You can make the blue underground belt the same as the rest of the main belts if you are using blue or higher as your main belts.
It will unload 4 full belts from each side while using the thinest profile that I could get to work.
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(extra details)
The requester chest will grab Rocket Fuel and Nuclear Fuel if you have it and use that instead of the coal, that should be placed on the virtically running belt(red underground is just long enough to reach to the next rank of stations).
The combinator next to the large power pole acts as a number of trains limit by sending a signal for how many trains can enter the train stacker buffer to a station just before the train stacker and using that signal as the train limit. I found that if I just set the limit on this station multiple trains could head for the same lane and cause a jam even with open spots in the buffer. By adding a station just before it they pick a lane just before the train stacker instead of miles away when they head to the unloader.
You can also remove the unloading stuff from above the rail to get a single side unloader as all the smarts are on the lower side.
Re: Slim 1-4 Train Unloader
Posted: Sat Jul 18, 2026 1:52 pm
by Tertius
Train unloaders are among the earliest published builds for Factorio. Your design has the issue that it requires a blue underground belt, which becomes available only somewhere mid-game. Not early game as red belts. And when you get blue belts, you want blue belt output and no red belt output, and your setup cannot be upgraded since it relies on belt braiding.
However, it just happened that with the upcoming 2.1 release, a 6-chest unloader with red belts to the right side of the train becomes available (was already possible to the left side, or with 4 chests in general). Notice the selected inserter, which has to be flipped to the other belt lane so there are 3 inserters contributing to each output belt lane. Copy and mirror and you want corresponding unloading for the left side if you need.
Slightly easier and more uniform is a 4 chest unloader as shown in the center.
Really balanced and even unload across all chests is only accomplished with the bottom example. The bottom has also the advantage that you're able to directly downgrade and upgrade to every belt type (need to slightly move the underground belts for yellow belt 4 tile underground).
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To take full advantage from the new inserter flipping functionality, you can also do this:
(if you don't use the blueprint, check every inserter that you flip it so every belt lane gets the same amount of contributing inserters)
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I did not realise that you could select which side an inserter uses with 2.1, with that I should be able to shrink a few other things.
I was not looking at 4 chest unloaders, just 6. My blueprint can be upgraded to output 4 Blue belts or 4 Turbo belts by matching the blue underground to the top tier and making the slow belts 1 tier lower (the blueprint book included the upgrade for Blue belts). Having said that your 6 chest unloader would also work with 1 blue underground belt without switching inserter sides and is simpler which would make it better.
Your one would also be doable with a single upgraded red belt and mine needs a longer run to replace the red belt without switching the inserter.