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How to line up balls single file

From The Great Ball Contraption Wiki

Balls arrive from the previous module randomly distributed in your 8x8-stud in basket. But it's much easier to handle them if they arrive in a single row. How does one make that transition? The first idea that occurs to most people is to use a funnel, or simply to narrow the ball path from eight studs wide to two studs wide. This works fine if balls arrive one at a time, but in this case, you don't need a funnel. It only takes two balls arriving together to jam this. To keep things rolling, you have to provide some kind of agitator to constantly clear the jams. There are more robust methods.

Skimming off the Edge[edit]

Skimming off the lower edge using a rubber wheel

A mechanism sweeps balls off the edge of the pile. This mechanism can be combined with a drop or lift mechanism as well to take advantage of two separation methods.

  • Pros: Often simple to implement. Can move a lot of balls quickly.
  • Cons: Not immune to funnel-like jamming.


Catch and Release by akiyuki picks, lifts, and drops

Here a grab picks balls out of the pile.

  • Pros: Looks impressive. Can control ball flow rate.
  • Cons: The grab mechanism can be complex. It is prone to jamming unless precautions are taken.

Dropping Balls Down[edit]

The Witch by pg5200 stirs balls out a hole in the cauldron

Balls drop through a slot. To be effective, usually the slot must move underneath the balls, or the balls must be passed over the slot. Surprisingly robust.

  • Pros: Can control ball flow rate. Not prone to jamming.
  • Cons: Balls end up lower than when they started.

Pushing Balls Up[edit]

Akiyuki lifts balls four at a time into his cleaner

A mechanism pushes one or more balls up out of the tray then (usually) down a ramp for further processing. Kawaguchi Akiyuki uses this method frequently.

  • Pros: This method almost never jams. The lifter is usually simple.
  • Cons: It's minor, but you can't lift directly out of your 8x8 in basket, because the in basket can't be taller than 10 bricks according to the GBC standard.

General Principle[edit]

You may notice a general tendency with these methods. While a funnel keeps the balls rolling in their original direction, these other methods change the direction of flow by roughly 90 degrees (up, down, or to the side). So if these specific methods don't work for your application, think about applying this direction change principle in a new way.