I wanted to try making a concrete clock with my modules. 

I started by designing an interior mold printed in 3d

The outside of the mold is made of wood panel.

I poured the concrete in two stages.

Everything seemed to be going well...

But removing the cylindrical parts was complicated. I had to bump them out. Result: big cracks!

I'm thinking of redesigning the cylinders to give them a conical shape. Maybe also add more fiber to the concrete...