In incubators holding a thousand eggs or less, the egg trays slide into a rigid cradle, and the whole cradle rotates backwards and forwards on a central spindle. Rotation is achieved by means of an electric motor, suitably geared down, and connected to the central spindle wither with camshafts of a belt and pulley. A time clock initiates the turning, and limit switches turn off the motor when the desired angle of tilt has been reached. In incubators holding thousands of eggs, the rows of trays are in pairs, and the cradles are not rigid, but hinged. Movement of a central rod up and down, tilts the trays.
Control is by a similar time clock and limits switch.
The central rod is usually moved by a rack and pinion, whole banks of trays being connected to one large geared motor and a common shaft. About the Author During the years since the last edition, the natural habitat has been eroded at a far greater rate than ever envisaged. The collection of wild specimens to replace captive losses has virtually ceased due to public pressure and some countries now forbid this practice. Several reintroduction projects, from captive stock, are underway. It is imperative that a wider diversity of bird and reptile propagation be mastered to ensure the survival of the ailing populations.