Showroom Belt driven linear actuator

Here is a shortened version of where I'm currently at with the 5mm pitch belt and a 3:1 pulley system. I'm currently planning to use the same 3" by 1.5" series 15 extrusion I was before but now I'll mount the carriage on the wide side on a pair of 12mm rails.

I think I've successfully managed to balance all the forces being applied as shown in the attached PDF. The ability to transfer motor torque to actuator force with perfect efficiency (in static conditions) was part of appeal of this approach for me over either screw or crank based designs. I hope it will help enable a powerful and responsive actuator but the overall performance of any actuator is also going to be influenced by many other factors.

I want to clean up a couple of things before I locate standoffs and can then try simulating the forces on the carriage in use. I'm still not certain of the best way to connect the round shaft to the carriage without creating a complex to machine part. I was using machine key before as it seemed strong but it also required key-ways to be machined in the round shaft. Threaded shafts are available off the shelf so a solution using them may be better overall.

when do you plan to build the first actuator ?