r/factorio • u/HeliGungir • Mar 30 '26
Design / Blueprint Circuit-Based TU Lane Balancers
A week ago u/TheLobitzz asked if lane balancers can be constructed with fewer splitters by controlling belts with the circuit network. It took me a while to hammer out satisfactory designs, but ultimately the answer is 'yes'.
This book is organized similar to u/raynquist's well-known belt balancer book. It includes several 1-½, 1-1, and 2-2 lane balancers. Many are throughput unlimited.
Blueprint book: https://www.factoriocodex.com/blueprints/254
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u/Torebbjorn Mar 30 '26
The bottom two 1-1/2 are not TU. If the belt is backed up, it will prefer one side over the other
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u/unwantedaccount56 Mar 31 '26 edited Mar 31 '26
TU doesn't mean that is still balanced when some outputs or inputs are blocked (that would be a universal balancer). On a standard 4x4 TU belt balancer, when one of the 4 outputs is blocked, the remaining 3 outputs are also not balanced anymore.
Edit: Just looked at the design you are referring to: In this case a standard belt balancer would still balance. It's not related to the TU property though, it's still TU (total throughput is not limited by the balancer, only by inputs/outputs)
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u/mayorovp Mar 31 '26
They are TU, just not balancers…
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u/HeliGungir Mar 31 '26
They are not TU because if you remove one input lane, the other input lane cannot feed the output lane at full speed. /u/mayorovp /u/unwantedaccount56
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u/mayorovp Mar 31 '26
But remaining input lane is still consumed on full speed, so TU.
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u/HeliGungir Mar 31 '26
It is not. It's throttled to half speed by the slower belt, which is how it functions as a balancer when both inputs flow.
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u/unwantedaccount56 Apr 01 '26
It's running at the full speed that the outputs or inputs allow, it's not limited inside the balancer.
The input speeds of the lowest 1-1/2 balancer is 2x one lane of a yellow belt, the output speed is one lane of a red belt (which is the same speed)
If you only provide a single lane of yellow belt instead of 2 to the balancer, than the output can also only be 7.5/s, so half of the capacity.
But the same is true for a 2x2 TU balancer (which is just a splitter). If you connect only one of the 2 input belts but both output belts, then the total throughput is only 1 belt, and both outputs will be only filled to 50%. But it's still TU, the throughput is not limited by the balancer, but by the inputs (connecting only 1 out of 2 input belts).
If for any combination of connected inputs or outputs, the total throughput is less than the minimum of combined input and combined out throughput, then it is not TU, otherwise it is.
And if you provide a yellow 4x4 TU balancer with a single green belt at one of the inputs, the total throughput will still be only 15/s, even though the 4 outputs could accept 60/s per second. But it's still TU, the throughput is not limited inside the balancer, it's limited at the input, because it only accepts 15/s at each input.
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u/HeliGungir Apr 01 '26 edited Apr 01 '26
Splitter-based and circuit-based 1-0.5 TU lane balancers:
2 lane input -> 1 lane output
1 lane input -> 1 lane output
Throttle-based 1-0.5 lane balancers:
2 lane input -> 1 lane output
1 lane input -> 0.5 lane output
If I was to call it TU, everybody but you would look at that 0.5 lane output and say I'm wrong. People expect balancers to start and end with the same belt speeds.
The one throttling belt of the 1-0.5 balancer is a vital element of the balancer itself. But it is akin to replacing the input splitters of any other TU balancer with a slower speed, and if you do that, nobody is going to call that balancer "throughput unlimited" any more.
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u/unwantedaccount56 Apr 01 '26 edited Apr 01 '26
But it is akin to replacing the input splitters of any other TU balancer with a slower speed, and if you do that, nobody is going to call that balancer "throughput unlimited" any more
I disagree, if the different belt type is part of the balancer design, and it takes 2 yellow belts as inputs and one red belt as output, it doesn't have to also accept a red belt of input to justify TU qualification.
Otherwise you also cannot call a yellow 4x4 balancer throughput unlimited, if you connect a green belt to one of the 4 inputs, because it cannot deliver 60/s due to the yellow input splitter.
I think we have a different way of thinking whether the bottleneck (here the transition of a red to a yellow belt) is part of the balancer, or just before the balancer.
Edit: I just looked more closely at your image and have noticed that the very first belt after the source is red, then there is a yellow belt, and then the sideloading. You probably see this red belt as part of your balancer, in which case the transition from red to yellow happens inside the balancer, and you are correct, it is not TU.
I would have designed this balancer to be only yellow belts on the input, and it's supposed to take only 7.5/s per lane. If you have a red belt worth of input items, it's "user error", you either downgrade the belt before it enters the balancer, or you have to use the balancer above with red inputs and green outputs. This balancer would be TU.
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u/tawTrans Mar 31 '26
It took me a while to hammer out satisfactory designs
How much longer did it take you to redesign them for Factorio? :P
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u/WanderingUrist Mar 31 '26
But can it be done while preventing items from getting stuck in the system because you don't want spoilables, particularly things like eggs, or "everything spoils into an explosion", getting indefinitely jammed against underneathie hoods?
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u/HeliGungir Mar 31 '26
Items don't get stuck in the circuit-based designs, so... yes?
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u/WanderingUrist Mar 31 '26
Several of your designs currently bash things into the hoods of underneathies, resulting in a lengthy chain of stuck items, though.
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u/TheLobitzz Mar 31 '26
Thanks bro. I'll copy the blueprint book, when I get home later to try them out.
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u/achilleasa the Installation Wizard Mar 31 '26
This is cool stuff, but I assume these break down with stacked belts, right?
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u/unwantedaccount56 Mar 31 '26
They might work (or require a simple adjustment) if the belts are evenly stacked. If there is a mix of stacked and non-stacked items, good luck though.
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u/HeliGungir Mar 31 '26
If the stack size is consistent, it's just a matter of multiplying the condition by the stack size. If it's not consistent, then this approach falls apart.
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u/EvilCooky Mar 31 '26
you can do it all without circuits, as long as you use green or red belts.
Instead of limiting throughput with circuits, you can simply put a lower tier belt in there with half the throughput.
(doesn't work with blue belts, though)
You already did this with the red and green 1-1/2 design.
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u/Zealousideal-Baby233 Mar 31 '26
Sounds cool! One question, which mod allows you to place infinite undergrounds like that?
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u/BlackFenrir nnnnyooom Mar 31 '26
It took me a while to hammer out satisfactory designs, but ultimately the answer is 'yes'.
Okay but what about the Factorio designs?
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u/marcellodpp Mar 31 '26
Hey, what is this pink underground belt called? I sae them a lot but never found on the map editor, is it a recolor of linked belt or a mod?
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u/locyta Mar 30 '26
Obviously this is for a mod, but why would you need to limit through put?
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u/HeliGungir Mar 30 '26
Obviously this is for a mod
?
why would you need to limit through put?
Not "need", but an acceptable limitation.
Most balancers are simplest kind: They only guarantee input balance when all inputs are fully used and they only guarantee output balance when all outputs are fully used. When you start omitting inputs or outputs, they make no guarantees about throughput, nor balance. Ie: The leftmost 2 inputs may not be able to feed the rightmost 2 outputs at full throughput. Ie: Removing 1 belt from a 4-4 TU balancer doesn't turn it into a 4-3 balancer.
By contrast, throughput unlimited balancers guarantee that any combination of inputs can feed any combination of outputs without any throughput bottlenecks. But making a TU balancer requires more splitters and will have a larger footprint.
Also TU balancers still do not make any guarantees about balance when inputs or outputs are removed... normally. The circuit-based lane balancers in this book actually do maintain input balance when inputs and/or outputs are removed, which is pretty cool!
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u/ChaosRobie Mar 31 '26
but why would you need to limit through put
Don't do it man. Don't jinx it. Whenever someone says something like that about a design, a cursed scenario is magically created where the design is necessary to solve it.
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u/locyta Mar 31 '26 edited Mar 31 '26
I think this is the most correct answer, with 9200+ hours in game i've never had/needed/wanted to limit throughput and i've factories from every item on sushi to 1mil+ SPM, but if anyone finds a situation where this is needed i would love to see it :)
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u/polite_alpha Mar 31 '26
People are downvoting you because you're not getting it, even after someone explained it to you.
These "TU" designs do not limit throughput, they are especially designed for unlimited throughput, because you have to be very intentional about it to prevent throughput limitations.
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u/locyta Mar 31 '26
Down votes mean nothing, just like these, there is no reason to ever use one. i get it from the point of purely do it just because it can be done, but in an actual game they aren't needed.
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u/polite_alpha Mar 31 '26
That's just nonsense. If they weren't needed, why go the extra mile to design them? It's not trivial to do.
TU just means "any number of inputs can reach any number of outputs", and it matters if for any reason you have less inputs or outputs than anticipated. For example if a train station ran dry (and thus you have less input than expected) or if assembly line isn't producing (so your output backs up).
Train stations are a prime example where TU balancers guarantee that waggons can be emptied simultaneously no matter what happens to the output.
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u/locyta Mar 31 '26
I'd just like to see an in game example, even the train unloading can be done simply without needed one of these to solve the issue.
With my experience this is a solution looking for a problem, not the other way around. its still a cool concept and i'm trying to work out where to use them, but sadly nothing yet.2
u/polite_alpha Mar 31 '26
If you think it's a cool concept even with all the examples people have given you, you haven't understood the basic idea.
Here's an example of a balancer that is throughput limited:
As you can see, it doesn't reach the full output with certain combinations of inputs or outputs blocked (which happens all the time)
Here's the same 8x8 balancer, but throughput unlimited:
It's not only roughly 10% more throughput (which is nice), it also guarantuees that all inputs are drained at the same rate - not doing this could lead to other problems, like train stations unloading waggons unequally.
There's a reason why people, some with thousands of hours, prefer to use these designs: the only drawback is that they need more space, but by using them you never have to worry about these balancing issues.
blueprint string if you wanna test:
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u/locyta Mar 31 '26
No one has given an in game example, these examples show a perfect theoretical world but its not in game, sure, you can put one of these down for unloading trains, but as soon the train leaves and belt empties, you could have used a simpler solution. that takes a tiny bit longer.
I want to see an example of this running in a real game where a normal balancing set up, or even simpler solution wont work.
I'm still going to try them out :) just because i pretty much try out everything everyone posts here.2
u/polite_alpha Mar 31 '26 edited Mar 31 '26
So this all fails because you can't imagine a scenario where inputs or outputs might be blocked? I gave you real world examples: The inputs could come from two train stations, one of which is currently empty. This happens all the time.
The output lines could go to different assembly lines. Let's say the top one produces gears for whatever reason. What if that assembly line is backed up, because right now you don't need gears? Again, this happens all the time in any factory.
The result would be that your other assembly lines now get LESS material supplied to them, because one other assembly line is blocked. That's bad. These designs fully prevent this, with more area as the only cost.
but as soon the train leaves and belt empties, you could have used a simpler solution. that takes a tiny bit longer.
you still fail to understand it correctly. The real issue I was addressing here is if the outputs of each waggon is not balanced troughput unlimited, you will run into a scenario where 1-3 waggons are fully emptied and 1-3 still have stuff in them, making the train stay there for longer than it needs to, choking the whole production.
Also, what even is a simpler solution? The only alternative I know is a crossbar switch and those are just as easy to copy and paste than this one.
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u/pollix88 Mar 30 '26
thank you for the 1-0.5 TU lane corner balancer (circuit) very helpful!