I don’t know if this will be any help to anyone, but I just put this on thingiverse based off roselea’s design. I moved the holes, redid the sprocket hole so on my printer with no scaling it fits the sprocket perfectly with 0 play, and added a slot for a tape measure to sit in, slightly offset so that the inner side of the L thingy on the tape will be perfectly centered on the spindle. I was having a hell of a time measuring my motor distance on a 12’ beam that is really high!
Should really help measure motor distance accuretly. I am printing 2 so i can measure to the slot on the other end too, so long as i turn the second print 180 degrees before putting it on the sprocket, it should be 100% accurate. Shame my eyes not that accurate 