During the design process, initially there is rapid progress and the design changes very noticeably. As time goes on the rate of change decreases and there comes a point where it's ok to actually build the mechanism.

Using 3D software such as Fusion 360, we can model the mechanism with incredible ease and view it as an animation to check that components mesh with each other properly and don't bump into each other either. I think that currently the design is at about 95% 'finished' and I aim to create the first prototype at 98%, so there's a bit more work to go in Fusion 360: