Tutorial:Main bus
The concept of a Main Bus is to put the most used and useful ingredients in a central spot to use for assembling machines. This is a good measure to combat "spaghetti factories" as it forces someone to plan a structured layout and move everything to use items from the bus. Which is also a downside as there are more belts used and therefore more room for belt-buffer and everything is less compact.
Whether one uses a bus is often decided before starting a map or when first building an array of furnaces.
A bus often starts at the smelting of iron, copper and steel and then over time and distance gains more and more different items. When one doe snot build enough smelting to saturate a belt or splits it into more then this can be called a "fake"-bus as it can not carry the amount it leads to believe it can. This can be done to reserve room for later expansion, blueprint-ghosts are a good usage for that as they don't allow the belt to be filled with non-usable items.
The direction of a bus, being horizontal or vertical depends on personal preference and how one likes to work on the production that splits off it, which can almost always be expanded for greater use later on. The orientation of and how wide the players monitor is also plays a role in this decision. A corner is not unheard of but very unusual and is often only necessary when a lake appears that is not planned for.
Content
What items one puts on a bus is personal preference. Some items are a good candidate to be built "on-site" meaning not carried by the bus but rather made where they are needed. A good example for this are copper cables as they consume more space on a belt than in form of copper plates.
Here are some things people have put on their bus in the past:
- Several belts of Iron plates usually a multiple of four as that is the length one underground belt can go underneath of.
- Some belts of Copper plates as well, usually less than Iron plates, as of 0.15 a lot less.
- Iron gears are seen on some buses as of 0.15 as they are denser than Iron plates (taking up half as much room) and see usage in a lot of recipes.
- Electronic circuits and later on even
- Advanced circuits though that may not be necessary as they just get used up quickly in other steps and aren't used in that many products.
- Steel plates.
- Processing units are rarely seen on a bus as they are used in even less recipes and also are mainly used as an intermediate product.
Some people like to have fluids part of their bus which could include:
- Sulfuric acid for processing units.
- Water for concrete.
- Lubricant for express transport belt.
Limitations
Having all possible items on a bus results in a huge wide bus with a lot of belt-buffer for expensive items and standing belts of output-items that wont get used in another process. These items are often just put into chests for personal use rather than on a bus.
When logistic robots are available one might not even need a bus any more and can just fly everything in where it is needed. This may happen at a later stage in the game up to which a bus is a very good tool to reduce clutter. But robots have their own difficulties and require a lot more ressources and knowledge of the game.
For very large amounts of items railways may be a better alternative that can not only carry large amounts of ore but also the intermediate and end-products. This can lead to designs of a base consisting of only train-stations with small logistic networks without any belts.
One reddit post mentions the use of cargo wagons as a means to increase throughput and reduce the size of a bus.
Split-off
When one wants to use the items on their bus one could directly take items off the bus as if it is just a belt, though that would mean an extremely long bus and useless lengths off other belts. This is sometimes done to get Items crafted into a chest for personal use like pipe which only uses Iron plates.
The Idea is that one wants to draw from every belt (and lane even) equally to not have too few items at the current planned production and not have empty and at the same time standing belts of items. That way at every step along the bus a few items are split off and used up and when the production comes to a stop the items go on to be used by the next production.
The following are 2 designs for a split-off off a 2-wide bus (by reddit user /u/unique_2).
Putting a lane-balancer after a split-off is not necessary most of the time as the rest moves on if the belt has no draw or if only one lane is used. If there is enough input for the item to saturate a whole belt then putting a lane-balancer in wont help to get more items later on. Putting a lane-balancer after an inherently balanced build that produces the item is also not necessary as then half of the production pauses and the other half fills the moving lane to saturation. The following is a split-off off a 4-wide bus.
The following are two designs for a split-off off a 4-wide bus that feature an in-line lane-balancer(by reddit user /u/moomaka).
See Also
TODO:
look at https://steamcommunity.com/sharedfiles/filedetails/?id=754378586
and https://www.reddit.com/r/factorio/comments/5vpf4h/what_belongs_in_the_main_bus_and_what_doesnt/
also look at youtube videos on the topic