Eccentric Cam

Drescription

Cams with complex profiles can be complicated to manufacture, particularly with the type of equipment available in the school workshop. However, if all that is required is to produce a single up and down motion for every revolution on the cam, a circular cam rotating about a point offset from its centre (i.e. eccentric), will often suffice.

Features and Applications

An Eccentric Cam would normally provide the follower with Simple Harmonic Motion - (this can be defined as the projection of a point on the diameter of a circle as it precesses around it with constant angular velocity).

Note: They can be modelled, in wooden mechanical toys for example, by drilling a Plyor MDF disc off-centre and gluing it on to a rotating Dowel.

Note that the cam follower need not just move up and down in a reciprocating motion, but it can be a lever as shown, which will produce oscillating motion.

Animations

Examples from Nguyen Duc Thang's YouTube Channel 2100 Animated Mechanical Mechanisms

Eccentric Driven Pump - the red arrows indicate the rotation direction of the eccentric shaft and the

fluid moving direction. The front half of the case is removed.

DT Online Buyers' Guide

Cam profiles (i.e. the shape of the outer edge of the cam against which the Follower engages) can be drawn as a Displacement Diagram using Drawing Instruments or CAD software.

Cams for models can be made simply by drilling an MDF or Ply Disc off-centre to make an Eccentric Cam or by mounting a disc at an angle to a dowel axle to make a Swashplate.

The use of Cams can most easily be explored using Contruction Kits such as those listed below.

Click top left to enlarge


Engino "STEM Mechanics" Cams and Cranks Set	Engino "STEM Mechanics" Levers and Linkages Set	Fischertechnik 536622 - Mechanic & Static 2	Engino Mechanisms Set	Engino Gears Set