I’m several iterations into my Y axis tensioner.  I think this newest version is a pretty good improvement.  I’m now on version 7 – and have put each part in its own file.  Here’s some information about the revisions:

• The first printable version, #5 still used a single captive nut and bolt system.  The nut had to be a certain minimum distance from the center of the pulley axle in order to allow the pulley to turn freely.  However, this minimum distance also meant that the edge of the captive nut was too close to the edge of the stage – which wouldn’t allow the piece to be tightened.
• Thus, I revised the piece so that it uses two captive nut/bolt parts – one on each side of the pulley.  This allows me to set the captive nut back far enough that it leave room for the piece to be tightened without running into the pulley.
• I discovered that I had forgotten to measure one of the pieces of wood properly and ended up with a 3mm gap for the edge of the Y stage, rather than a 5mm gap.

I’ve printed up version 7, but haven’t had occasion to disassemble the Y stage yet.  The next time I do I’m installing this tensioner.  Time to design the X stage tensioner!