easy Adjustable and reusable belt tensioner for prusa y carriage

a very fast and easy way to solve the loose belt problem on on the y carriage of my prusa reprap printer.

what you need:
1x m8x45 bolt(i used m8x60)
3x m8 nuts
2x 8x30 washers
2x 8x15 washers
1x 608zz