Oh wait, it's in the TFS. Guess what function of the ring is no longer needed if friction is eliminated? Good thing you posted AC.
They plan to reduce/eliminate friction between the piston head and cylinder walls , the link between the piston head and the piston rod still needs to be lubricated which is what the gp was pointing out that they didnt consider or didnt mention in the article.
maybe you should read the comment you are replying to.
Do not meddle in the affairs of troff, for it is subtle and quick to anger.