France or the Habsburg emperors, were able to expand their territories and maintain a tighter control over the land they already occupied. With the potential threat of their land and castles being seized, the nobility began to pay their taxes and more closely follow their ruler’s mandates. With siege guns mounted on trunnions, stronger and larger states were formed, but because of this, struggles between neighboring governments with consolidated power began to ensue and would continue to plague Europe for the next few centuries. Usages In dams A common floodgate used in dams and canal locks is the Tainter gate. This gate opens and closes by pivoting on a trunnion which extends into the mass of the dam or lock. The Tainter gate is used in water control dams and locks worldwide. The Upper Mississippi River basin alone has 321 Tainter gates, and the Columbia River basin has 195. In vehicles In older cars, the trunnion is part of the suspension and either allows free movement of the rear wheel hub in relation to the chassis or allows the front wheel hub to rotate with the steering. On many cars (such as those made by the Triumph) the trunnion is machined from a brass or bronze casting and is prone to failure if not greased properly. American Motors recommended lubrication of its pre-packed front suspension trunnions using a sodium base grease every or three years. It later incorporated molded rubber "Clevebloc" bushings on the upper trunnion to seal out dirt and retain silicone lubricant for the life of the car. In aviation, the term refers to the structural component that attaches the undercarriage or landing gear to the airframe. For aircraft equipped with retractable landing gear, the trunnion is pivoted to permit rotation of the entire gear assembly. In heavy equipment, such as a bulldozer, the term refers to the protrusions on the vehicle frame on which the blade frame attaches and hinges allowing vertical movement. In Chevrolet GMC C/K pickup trucks, the term refers to the tailgate attachment points. Rather than using conventional tailgate hinges, trunnions are used to permit quick toolless removal and installation of the pickup tailgate. In axles, the term refers to the type of suspension used on a multi-axle configurations. It is a "short axle pivoted at or near its mid-point about a horizontal axis transverse to its own centerline, normally used in pairs in