I have completed the Y and Z axes now of my OverlapStrap. I was originally planning to only use one Z axis motor and use one of the syncroflex belts that I bought for the Mendel to drive the two lead screws. But when I saw the price of the cheapest aluminium timing pulleys that I could find, I decided it was cheaper and simpler just to use two stepper motors for the Z axis instead
At this stage I also intend to drive the Y and X axis using lead screws. This required some modifications to the reprap firmware. Annoyingly there are preferences in the reprap software for features that don’t exist. I am a strong believer of YAGNI and also think that Green Code is a violation of this principle, so I was a bit annoyed to find both of these practices employed in the reprap code. Anyway, once I got over it and realised that the software preference for steps/mm had no effect on the hardcoded steps/mm defined in the configuration.h of the reprap firmware I was able to change it and upload the new firmware.
I have a feeling that such a low steps/mm setting will lead to printing problems when overlapstrap is complete, however I have a plan to mitigate these problems. I intend to bootstrap some basic parts using the leadscrews and then upgrade overlapstrap to a belt drive version using these parts. I will need to print a belt splitter jig, and some drive pulleys.