This presentation will draw heavily on the Working Group 138 report, Mechanical and Electrical Engineering Lessons Learned from Navigation Structures. Four different types of linkages are commonly used to drive miter gates. Three of these linkages are closely related and consist of a sector gear and sector arm with a strut connecting the sector arm to the gate. These three linkages are referred to as the Panama Canal, Ohio River, and Modified Ohio River linkages. The original Panama Locks used the Panama Canal linkage. The fourth type of linkage is the direct connected cylinder. The direct connected cylinder consists of a hydraulic cylinder with its shell (or body) supported in the miter gate machinery recess by a trunnion and cardanic ring assembly (or gimbal) and its rod connected directly to the miter gate with a spherical bearing type clevis. The direct connected cylinder has become the most common type of miter gate drive for new construction and retrofits. This is because of a cost advantage in the fabrication, installation, and maintenance of these systems. The Panama Canal and related linkages offered some advantages that should be considered. One is that the linkage can be electrically or hydraulically driven. Another advantage is that the geometry of the linkages inherently decelerates the motion of the gate as it approaches fully open or closed. This advantage is useful when the motion of the gate is controlled by the input of a human operator. Also, shock absorption can be incorporated into the strut. Miter gates are now often controlled by electronic control systems with varying degrees of automation. The control of drives with direct connected cylinders can be programmed to automatically decelerate the gate as it approaches opened or closed position. The direct connected cylinder can also be a linear mechanical actuator within certain stroke and gate size limitations.
Advances in hydraulic power systems for miter gates have allowed for increased reliability and maintainability through compact hydraulic drive units and self-contained hydraulic that can be quickly and easily exchanged for maintenance with a spare. Also, environmentally acceptable hydraulic fluids and lubricants are available which are high quality and can have a long life if properly maintained.