How about some sort of a paddle wheel thingy on top of the bucket. The part falls into the top compartment, which renders the wheel out of balance, so then it rolls over and drops the part into the bucket (filled with water). Supposedly, if you kill off the initial energy the part acquires in free fall, then there won't be enough energy regained as it descends from almost zero speed at the top of the bucket.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)