A Thingiverse user broke one of the arms of his Gravitrax hammer.
Sh#t happens... So, if it happened to you as well, here are replacement arms.
There are two versions. One as a single piece, the other one split in half so it is easier to print without support. Just glue the two pieces together.
Little bit of sanding may be required, just so it turns more smoothly.
Print at the highest resolution your printer can handle.
More models can be found at MyMiniFactory.