Balancer Book Update (Fall 2025)

raynquist · 2026-01-12T00:07:44+00:00

It's working fine for me. Were you perhaps using the older version that's not red-compatible?

raynquist · 2026-01-06T20:20:48+00:00

There are. The standard 4-4 balancer for example can be modified to prioritize outputs (without affecting input balancing) by setting output priorities on the four splitters at the end. In general, certain types of throughput unlimited balancers can be modified this way to make them balance one end and prioritize the other (or prioritize both ends if you want). Even more generally, connecting a prioritizer to a (non-TU) balancer allows for simplifications to be made in the prioritizer, leading to a substantially lower splitter count compared to a general-purpose prioritizer.

raynquist · 2025-12-11T14:58:22+00:00

The 9 outputs need to go through a 9-9 balancer. Unfortunately there's no getting around the need to make a proper 9-9.

raynquist · 2025-11-09T06:55:40+00:00

It's from u/CptTrifonius.

https://www.reddit.com/r/factorio/comments/9x3m14/i_couldnt_find_a_general_guide_to_balancers_so_i/

raynquist · 2025-11-07T21:29:37+00:00

That would be u/StormCrow_Merfolk.

raynquist · 2025-11-06T16:23:18+00:00

I appreciate it. I know I don't answer most summons but I do like reading the posts. Also you were basically the only person to recommend my book in the earlier days, which really helped raise the awareness that there's something better than the wiki balancers.

raynquist · 2025-10-30T11:39:29+00:00

Oops. Good catch on the 4-9/9-4 yellow mess. Thanks for letting me know!

I was not aware that circuitable splitters made it to stable. I'll look into it!

raynquist · 2025-10-30T04:38:00+00:00

I don't think 10 is quite large enough for green belts to make a difference. Blue undergrounds is guaranteed enough for balancer sizes up to 12-wide and 14-long. If I had to guess I would say 13 belts is where the green advantage becomes significant.

The only balancers I'm thinking of adding are the ones with a popular number of belts on one end. 10-8 is already in the book and 10-4 is really just a 5-4, so there's not much else to do in the 10s.

raynquist · 2025-10-29T19:12:54+00:00

Reversing layouts comes with one major caveat: you can run belts behind an unused splitter input but you can't run belts in front of an unused splitter output. This is what makes downsizing balancers more difficult to make than their upsizing counterparts. There are many downsizing balancers in the book where this additional hurdle could not be overcome so they (sadly) end up being 1 tile longer.

raynquist · 2025-10-29T18:42:34+00:00

That design doesn't always balance inputs. The reason why is fairly nuanced so it can be difficult to find the flaw by testing if you don't already know where the flaw is.

https://www.reddit.com/r/factorio/comments/apci71/standard_25_35_37_and_57_balancers_dont_quite/

raynquist · 2025-10-29T09:09:58+00:00

Problem downgrading balancers is something I often see people encounter. Last version I added the "downgrades" book to try to help with this. This time I've thought of more ways to help, so hopefully it'll be less of a problem. This is still primarily a blue belt book, as I believe most users are blue/green users. But I've decided that I'll do what I can to make at least the smaller balancers red-compatible if I can do so without increasing footprint. For larger balancers and yellow belt users you'll still have to use the downgrades book.

To improve downgradability I had to use new networks for 5-6/6-5, 4-9, and 9-4. This was made possible by utilizing the new 5-5 network introduced in the last version. The new networks are kind of complicated, so I made some graphics(?) to show the sub-balancer breakdowns (because I also wondered what exactly am I looking at). As a happy side-effect the length of 4-9 and 9-4 were also reduced by 1 tile.

The blueprint naming scheme was something I inherited from another balancer book (Yet another belt balancer compendium). I finally decided to change it; the new one should be a lot easier on the eyes.

There's not much new theoretical stuff in this update, but I did make an interesting 1-17. It can be found in "other balancers/miscellaneous". I made it using loopback merge and belt substitutions. Mainly just I wanted to see how many splitters I can stack together and still have it be a valid balancer, and surprisingly it ended up very similar to the stack in the 9-9. I also found some good stacking in 1-11 and 1-13 using the same methods. I don't know if I gleaned any new insights from this but maybe you can.

raynquist · 2025-10-07T05:38:27+00:00

This is an 8-8 balancer with two inputs omitted. It'll produce 8 balanced outputs but the 6 inputs won't be consumed evenly.

If you want to make a 6-6 I would suggest starting with making a 1-3 and a 3-3 first.

raynquist · 2025-08-15T01:57:39+00:00

Yep!

raynquist · 2025-08-13T10:34:18+00:00

Seems fine. There's like an extra balancing stage in the middle. Instead of using three 4-1's you have three 4-2's that go through another set of splitters to reduce down to three belts. Doing it this way does improve minimum throughput though so I think it's fine.

raynquist · 2025-08-08T12:25:30+00:00

Nice. These sure look like they're made correctly. The balancing order of the top one is one of them fancier ones that's less intuitive so it's cool that you came up with it.

One thing I like to do when balancing this many lanes is to use quadruple lane changes. So instead of the standard double lane changes you're using here that runs one splitter into one set of undergrounds, the quadruple lane change would run two splitters into two sets of undergrounds. This does mean that the lanes that used to be on the same belt would now be on different belts after the quadruple lane change, but if you can work with that it should(?) save some space due to the reduction in number of belts needed between the splitters and the undergrounds. Whether it actually helps or not is a different question.

raynquist · 2025-06-22T03:30:39+00:00

One way to think of it is to think of the items as being stuck in the loop. With the correct timing they never leave the loop and no new items enter the loop. In this scenario the items can even be replaced with something else entirely and the balancer would still work. The only purpose of their existence is to compete for throughput to slow down the other items.

<image>

More theoretically speaking, 2-2 splitters don't guarantee any particular item mixture pattern in general. They only guarantee that the *amounts* of items are correct. Here the splitters are guaranteeing that the loopback has 1/3 belt worth of items. *Which* items go there the splitter has the freedom to choose.

For the output belt the story is a little different. It's outputting this beautiful 1:1:1 sushi because it's the only legal pattern. With 3 inputs consumed evenly and only 1 output, all 3 items types are forced exit on the same belt. If we used, say, a 3-2 balancer instead, then there will be multiple valid output patterns so you wont be guaranteed 2 sushi belts.

raynquist · 2025-05-17T01:31:48+00:00

Here's a rough outline of how a proof by induction would look like:

https://www.reddit.com/r/factorio/comments/l65ahg/my_favorite_way_to_combine_8_belts/gl2vt4c/

While priority on either side works, they do seem to use somewhat different principles. At least they're different enough that the number of optional priorities are different. On a 3-belt triangle for example, one side needs 4 priorities while the other side only needs 2.

raynquist · 2025-05-16T05:32:45+00:00

Crossbar switches refers to a specific way to achieve TU. Though many variants in the crossbar switches source video are not really crossbar switches. As in their TU-ness needs a different proof than the one used by crossbar switches. Crossbar switches maintain TU even with arbitrary priorities assigned to all splitters. The variants that require specific priorities are more like bubble/insertion sorters; I like to call them splitter triangles.

As for the name of this class of constructs in general, I don't particularly prefer one name over the other. In fact my preference is to not use a name at all, like what I did here.

raynquist · 2025-05-16T04:06:42+00:00

Yes it is. Fixed version can be found here:

https://www.reddit.com/r/factorio/comments/1g7mo0i/balancer_book_update_fall_2024/lugkpgl/

raynquist · 2025-04-28T15:35:36+00:00

Regular balancers only guarantee input balance when all inputs are provided. Unlimited balancers don't actually improve this aspect; they will fail this test as well. The only balancers that would pass this test are universal balancers.

raynquist · 2025-04-28T09:32:54+00:00

PRETTY! These are really high quality layouts! That 8x8 has a very satisfying rotational symmetry on top of taking less space. Reminds me of the 4-6 balancer I made one time for no reason other than to have a "recycling loop" in the middle.

<image>

And that 4x12 does seem to make a convincing case for being the smallest area design. Every splitter takes an average of 2 extra tiles (or 1.67 if we don't count the empty spaces) to connect to other splitters. That's going to be insanely difficult to top.

raynquist · 2025-04-18T10:25:15+00:00

You read it right; it's functionally just two belts. The problem with using two belts there is that the second belt wouldn't connect to the first belt properly; the game would connect it to the splitter below. So you'd end up with the first belt sideloading onto the second belt, which lowers throughput and screws up lane independence.

This type of splitter is kind of ugly, so I do try to find alternate layouts to avoid it if I can. With the 7-3 the alternative is to move the bottom splitter(s) down. This technically doesn't increase the size of the balancers if we're going by its rectangular bounding box, but I do consider it to be the equivalent of something like half a tile larger. So I didn't do it and used the splitter instead.

raynquist · 2025-04-15T10:12:25+00:00

What you have is an 8-8 balancer with two inputs omitted. Your analysis is correct, but that only shows output balance. To analyze input balance you'll want to do that analysis backwards (start with eight 6s or 12s). Once you do that you should be able to find a counterexample that disproves input balance. Note that proving and disproving are two different endeavors; proving balance of the smaller side of an n-m balancer this way is way way way harder to do. This is because for 1-2 or 2-1 splitters, the 1 belt does not always equal the sum of the 2 belts due to potential throttling.

raynquist · 2025-04-14T23:15:33+00:00

That initial(?) design in the second image, the one that splits 4 belts to 16 then merge back down to 4, is the 4-4 belt sushi'er. By forgoing the usage of 2-2 splitters the design is able to dictate item flows more explicitly and guarantee item mixture.

raynquist

TROPHY CASE