My son and I put together the z-axis today. Watching a 4 year old use a hack saw was amusing – I kept it safe and he felt like it was the best thing in the whole world.
The elevator is supported by 4 screws, using flanged nuts connected by L shaped aluminum extrusions. The screws float between the upper and lower cross beams – RC car bearings prevent them from binding. Sprockets and chain from Electric gold mine tie it together.  In order to tension the chain, I added an additional sprocket which I can move along another crossbar.  I designed the z-axis so that I can replace the print surface.Â
Looking good 😀
And yes, i imagine a 4 year old with a hack saw would have been entertaining 😀