Dave Butler wrote:
Hi, I'm not TC, but you might try looking over http://www.enginehistory.org/
for a couple papers on crank dampers. Specifically I am thinking about
a story on the design of the P&W R2800 crankshaft that covers the various
modes of crank bending (which the counterweights are supposed to minimize).
Lycoming engines have dampers if their model number is "complex"
like O-540-J1BD and don't have 'em if it's simple like O-360-A4A.

The damper rolls around the inside of the hole in the crank counterweight.
Sometimes the plate on the outside moves too. That's the gist of the article.
When the holes get gummed up from oil coking the dampers don't move anymore
and you can have problems.
--
Aaron Coolidge