trunnions

Trunnion is a cylindrical protrusion used as a mounting and pivot point for a rigid body. A trunnion provides a bearing surface and a fixed axis around which the body can rotate, while supporting the load and maintaining alignment.

In firearms and naval artillery, trunnions are the cylindrical pins on the sides of a cannon or gun barrel that rest in the carriage or mounting. They serve as the hinge line for elevation and traverse, allowing the barrel to tilt for aiming.

In machinery, trunnions appear at the ends of rotating drums, such as ball mills, rotary kilns, and conveyors. The drum is supported on trunnion bearings, which consist of end-mounted trunnion shafts and allied bearings that carry the weight and permit smooth rotation. Trunnions reduce lateral movement and help align the drum with the drive components. Depending on the design, trunnions may be integral with the drum or connected via end housings, and lubrication is normally provided by a continuous sealing arrangement.

In general engineering practice, trunnions function as a simple form of journal bearing, distributing load over a cylindrical surface and allowing rotation about a fixed axis. They may be designed to accommodate axial movement on thermal expansion or contraction, and can be hardened for wear resistance in heavy-duty applications.