If you're talking about the "over center" principle, it's a mechanical device which conserves and redirects the force placed upon a lever or spring attached to a cam such that a movement "over center" (point of no return) is converted to a further automatic (not requiring further effort) movement of the lever. Common examples: the Southgate ejector mech in AyA doubleguns, opening mech of common jacknife, the toggle lock mech of the sliding breech in the Charlin double shotgun. All over center devices have in common resistance to motion in both directions of the toggle or lever.
To illustrate the possibilities of the over-center principle, an authority on French sliding breech shotguns has stated that the sliding breech of a Charlin cannot open on firing despite the absence of a locking mechanism other than the position of the toggle relative to the cam when totally housed in the breechblock body.
Last edited by rabbit; 10/15/12 04:39 PM.
