Crankcams

Crankcams are a class of mechanical devices in which a rotating crank drives a cam surface that acts on a follower to produce a controlled, nonuniform motion. By integrating the crank and cam into a single compact geometry, crankcams aim to realize specific lift or displacement profiles without requiring a separate camshaft and timing mechanism.

How they work can be described as a coordinated interaction between crank rotation and a cam profile. The crank provides a primary rotary input, while the attached or adjacent cam surface influences the follower’s position as the mechanism turns. Depending on the design, the cam profile may be formed on an eccentric portion of the crank, or on a disk and gear arrangement that cooperates with a follower. This arrangement yields a predetermined displacement versus angle relationship, which can be tuned by altering the cam shape, follower type, and mounting geometry.

Design considerations for crankcams include the choice of follower (roller, flat, or another contact surface), bearing supports, material selection, and tolerance control, as well as the synchronization between crank angle and follower motion. Variants may employ single or multiple lobes, and can be optimized for smoothness, stiffness, and load capacity. Crankcams are often contrasted with conventional separate cams and camshafts, offering potential benefits in compactness or manufacturing in certain applications, while presenting challenges in stress distribution and maintenance.

Applications span small engines, precision actuators, and specialized machinery where a compact actuator with a predetermined motion profile is advantageous. While the broader use of crankcams has diminished with advances in programmable actuators and modular cam systems, the concept remains relevant in niche implementations requiring integrated crank-to-cam motion.

See also: camshaft, crankshaft, follower, eccentric cam, valve timing mechanisms.