Based on the plan in the previous post, I have completed and tested the spiral cam drive. First, I cut to size some aluminum round stock on the lathe, and drilled a 3/4-inch hole through, also on the lathe, for the Acme rod. This became my blank.
Next, I wrote a program to generate GCode to mill the spiral cam out of the blank. I went through several iterations, improving the efficiency each time. It still takes about 20 minutes to mill the spiral cam. And here is the inevitable CNC porn:
I drilled and tapped a hole radially into the cam, drilled a set hole radially into the Acme rod, and attached the cam to the rod. Here's the installation showing how the bearing rides on the cam surface:
And here are some videos showing the mechanism in action, driving 12 rods. Four of the rods have extra-strength springs so this is the equivalent of 16 rods. The action is incredibly smooth, and doesn't take much force.
I also tested stringing fishing line between two modules, and that worked perfectly. I still need to work on getting the length of the string just right, since I can't adjust the spacing between modules for a given string length.
NextFab is closed for two weeks for the winter solstice holidays, and this also ends this phase of investigation. The next phase, to be started in January, is making a cylindrical gear to rotate the drive, and then putting together a single bit slice module. When those tasks are completed, I will have enough proof that I can complete the 16-bit ALU, which means that I can start a Kickstarter project. I hope to complete the bit slice module by the end of February.