After seeing the (almost) final design for the neck, I decided to change the mechanism for the lower neck pivot. It was originally a timing belt (GT2 3mm) but due to the space constraints, I changed it to a ANSI 25 roller chain and sprocket.
This should allow me to put in a larger diameter sprocket at the neck pivot than what I had with the timing belt. This configuration coupled with one or two step down sprockets should give me enough torque to move the neck and head assemblies.
At the moment, I am pretty much finished with the neck sections outside of the body, so now I will work on the mechanisms to drive the lower and upper pivots of the necks. They will both be powered by stepper motors for now. The lower pivot will have a counterspring for assistance but I don't know if I have room to add a counterspring for the upper pivot.
One last thing: Once Revision A is complete, I'll go back and virtually assemble WALL-E piece by piece to make sure I have the tools and clearance to assemble the components properly. During this time I will also take a look at the BOM and see if we can make small modifications in order to use the same fasteners as much as possible to minimize costs. I'll make some final changes and then I will start creating a Revision B for production with assembly drawings and whatnot.
Alright, time for a little break and then I'll get started on the two stepper motors and their mounts/linkages.