Here's a strange gearbox which creates 2 outputs, which alternate in turning half a revolution. The uncommon pieces for this include 3 yellow gears, 3 red gears, 2 blue gears, a motor, and a light grey rod (cannot be substituted for other colours). An industrial ruler is optional. This will get very fidgety.
Sorry for blurred pictures (zoom out the page if needed).
To build one with 4 outputs, make 3 of these and add lots of extra gears.
Step 1: The Base
This is the bottom layer. Not much yet.
Step 2: The Shifting Rod
This is the most difficult part of the machine, and you will probably continue to fidget this after completion. It is important you use a light grey rod as this reduces the ability of gears sliding out of place. I have added some lengths that worked for me.
Step 3: The Outputs
Here are 2 gears which mesh (separately) with the yellow gears from the previous step. The dark grey connectors (purple in the pictures) will be substituted for outputs upon completion of the gearbox.
Step 4: Combining Everything So Far
Now you will combine the previous 3 steps. Start with the first 2 (base + shifting rod) then add the outputs. I suggest adding each output separately then adding the blue rod.
Step 5: Stationary Rod
This rod contains 2 blue gears: one attaches to the motor's axle and the other to the shifting rod.
Step 6: Top Layer Part 1
This bit is partially aesthetics but also supports the outputs. Furthermore, it contains ratchets that stop the outputs from using their momentum. Upon completion, experiment not using them.
Step 7: Top Layer Part 2
This supports the shifting rod.
Step 8: Stationary Rod Support
This stops the stationary rod from skipping teeth.
Step 9: Shifts Shifting Rod
This attaches to a crankshaft that pushes the red gear from the shifting rod either direction. It slides into the base.
Step 10: Side Supports
This structure will support the motor's axle.
Step 11: Motor's Axle
This axle (including its crankshaft) will attach to the motor, the stationary rod, and the 'Shifts Shifting rod'.
Step 12: Connecting Motor's Axle
So far there are 5 connections to make. Make sure the yellow gear meshes with the blue gear.
Step 13: Last Bit of Scaffold
This will support the motor and the motor's axle.
Step 14: Done!
Add a motor and you're complete... almost.
The shifting rod requires lots of attention, so you will have to do lots of fidgeting with the yellow gears. If you keep the ratchets, make sure the motor switches on the right way.
Contact me when you turn this into something great (bonus brownie points if it's a ball lift).