After a busy July, I’m back 
A “Capacitor” gear bit always starts centered. If it holds two balls balanced on it (“charge”), then it is 1; otherwise 0.
Obviously, the charge can be released by another ball. A register of connected capacitors will release their charges simultaneously. This enables fast calculations using multiple balls at once, instead of one at a time.
Here is an adder, which adds a 3 bit capacitor register to a traditional 4 bit register. In this example 7+3=10.
This is probably as close as one can get to how a real computer adds.
Can we do better? A 4 bit capacitor register is a bit problematic. With some values, one ball isn’t powerful enough to release the charge (due to friction and the imperfect connection of the cogs.)
The solution is to hit the register with two balls simultaneously! This can be done using one of my other ball release mechanisms. The one with the most reliable timing is two connected gear bits, both with a ball inserted inside the pointy part to add weight to the top. This can hold a single ball.
In this video I calculate 15+15=30:
