What is Tainter gate?

The Tainter gate is a type of radial arm floodgate used in dams and canal locks to control water flow. It is named for Wisconsin structural engineer Jeremiah Burnham Tainter.

A side view of a Tainter gate resembles a slice of pie with the curved part of the piece facing the source or upper pool of water and the tip pointing toward the destination or lower pool. The curved face or skinplate of the gate takes the form of a wedge section of cylinder. The straight sides of the pie shape, the trunnion arms, extend back from each end of the cylinder section and meet at a trunnion which serves as a pivot point when the gate rotates.

Pressure forces on a submerged body act perpendicular to the body's surface. The design of the Tainter gate results in every pressure force acting through the centre of the imaginary circle of which the gate is a section, so that all resulting pressure force acts through the pivot point of the gate, making construction and design easier.

When a Tainter gate is closed, water bears on the convex side. When the gate is rotated, the rush of water passing under the gate helps to open and close the gate. The rounded face, long radial arms and bearings allow it to close with less effort than a flat gate. Tainter gates are usually controlled from above with a chain/gearbox/electric motor assembly.