Yeah, it'll want to ring like crazy. Try making a form tool with a rounded end instead of a square one. It will allow you to enter more gradually, reducing the risk of vibration. Make sure it's very well supported. Try reducing the speed and increasing feed.Hi Jeroen,
How did you bored grooves for the o rings?
I find it quite difficult to bore it in square shape.
Same problem here .I found that PDF that was posted by Jeroen is missing 2 rods.
One connects to tumbler plate on one end and to crank on another.
Second one connects to crank on one end and to displacer rod end on another.
Most important property of those rods are their length. Did anyone figured it out?