reversers

Reversers are mechanisms or devices that reverse the direction of a system's operation or the flow of energy, power, or momentum. They are found in transport technologies, machinery, and power systems, where changing direction or providing reverse thrust is required during operation or at shutdown.

In aviation, thrust reversers are installed on many jet engines to help decelerate an aircraft after landing. They redirect the engine's bypass air forward or block and deflect exhaust, creating reverse thrust and increased drag. Deployment is coordinated with braking and typically is inhibited at high speeds or for takeoff.

In marine propulsion, reversing gear or reversers switch a ship's propeller to run astern. The gear changes the direction of the propeller shaft, often with a clutch and hydraulic or electric control, allowing forward and reverse movement and sometimes reverse thrust for maneuvering in ports.

Rail and traction systems use reversers to set direction of travel. In electric or diesel-electric locomotives, a reversing device controls the polarity or phase of current to traction motors, enabling forward or reverse motion and influencing starting torque and speed range, governed by control systems.

Industrial reversers appear in cranes, hoists, winches, conveyors, and other machinery. Reversing gear or drum drives change the motion of lines or belts, enabling winding, unwinding, loading, or unloading operations. These systems may be manual, hydraulic, or electrically powered and include safety interlocks.

Design considerations for reversers include reliability, wear, alignment, and safe engagement and stowage. Fail-safes and maintenance regimes are common, given that incorrect reversal can cause overload, loss of control, or damage to equipment or personnel.