Mendel Y-belt tensioner.

cults3d

This is a replacement clamp for the Y-axis drive belt. It allows the belt tension to be fine tuned without removing the bed. One end of the belt is clamped to the Y chassis "squashed frog" with the standard clamp. After threading the belt around the motor and pulleys, the other end passes under the gap in the new clamp, loops back over the top of the clamp and is held down with the cap. The whole thing is held the carriage with 2 3mm cap screws and nylocks just like the old bracket. The ram is placed into the loop where the belt doubles back. A 4mm cap screw goes through the back of the clamp and pushes the ram forward. By turning the cap screw, you can change the tension on the belt. This design might work just fine without the ram and be a little easier to assemble. I haven't tried it.