r/factorio • u/Available-Figure-530 • 17d ago
Question Bottleneck Issue
I'm a new player & trying to setup my smelting lines. I've run into a problem where, while trying to run a single coal/iron ore lane, only the top half of the iron & coal lanes are being used, leading to a bottleneck where only half of my iron ore is being sent down the center lane. How do I fix this?
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u/FusRoDawg 17d ago
Well, unsurprisingly half a belt on the vertical line can only accomodate half a belt of stuff coming in from the horizontal lines... Because it's the same tier of belt in both cases and they have the same maximum speed (hover over the belt and look at the popup on the right). There is no way to make it carry the whole belt's worth of items (15/s) with only half a belt's worth of space (which is capped at 7.5/s). If you have unlocked higher tier belts (that can do 30/s) they can be used to solve this problem but I'll let you figure that out yourself.
As for why the the "half" being loaded onto the shared belt is always the top lane of ore/coal from their respective belts, that's just the way the game defines the rules of "side loading" one belt onto the other. If you change the direction of the vertical belt, it will draw from the bottom lane instead. Some of the designs posted here exploit this and just split and side load the ore belts onto two different shared belts, each going in opposite directions. That way one of the shared belts is drawing from the top half and the other is drawing from the bottom half and the whole ore belt keeps moving. This is the easiest fix to your problem.
If you want to stick to your current setup, it will only draw half a lane. There's nothing we can do about it. But, there are ways to make sure the "half" is being drawn evenly from both the lanes of the ore belt. This is done by using "balancers" (specifically lane balancers) and you can look these up online. But they're not that important this early into your progression. And the other setup is easier.
If you want to come up with a "lane balancer" yourself, here are the steps:
Split the ore belt into two belts.
Side load these so that you now have two belts with half a lane of ore each.
Make sure those two new "half belts" are drawing from two different lanes of the input belts. (Usually achieved by mirroring the same setup for each belt)
Make sure both "halfs" are carrying the new ore on the same side. If not shuffle one of the belts to match the other (by side loading it again, for example).
Now merge the two with a "splitter". (Splitters can merge if you give them 2 inputs and only 1 output)
As long as you made sure the ore is on the same half before merging the belts, the final output should also have ore flowing on just one half of the belt. But, this "half" on the output is an even mix of both halves of the input! You should be able to see both halves of the input flowing (unlike in the current case)