Perhaps a door that rotates to open?

I am designing the lower Y-Rail mount a well as the lower assembly of the Big Dip. I think it is most sensible to figure out the dipping system and then figure out the lower assembly.

One thing I’m interested in is having the paint containers open and close at the time of dipping. This will allow longer runs, add charisma and still allow hot swapping and filling of the paint containers.

There are two problems I’m wrestling with for this:

1. How to have the little doors open as the brush comes down
2. What containers to use for the paint/ink?

The best idea I have so far is from Michael Grant who suggested the doors work like a VHS tape. Something comes in contact with the door which opens it.

This could entail a post coming down along side the brush which contacts a button or lever and opens the door.