EXARC Journal (May 2020)
The Vertical Olive Crushing Mill as a Machine and its Energy Balance - A Preliminary Approach
Abstract
The vertical crushing mill turns the olives into pulp by combining the rotational and rolling motion of a heavy upright stone wheel that moves with continuous contact along a circular horizontal trajectory on a stationary base which forms the system's frame of reference. It was devised during the Hellenistic period and served as one of the most important and impressive means of production in the pre-industrial olive mills of Crete and the Mediterranean in general, until more advanced mill types gradually started replacing it from the mid-19th century onwards. Although there is a rich bibliography historically and from a technical point of view, there seems to be a relative knowledge gap from the aspect of the physical quantities that regulate its movement and affect its productive capacity. The paper examines this type of mill from the aspect of a complete machine, according to the ideas of F. Rouleaux (1875), whose approach is still regarded to be fundamental in the field of kinematic analysis and machine theory in general. The use of animal power is considered indifferent to this theory. A generic kinematic diagram for this specific mill type was composed, according to the rules of modern mechanical analysis. The diagram describes the kinematic pairs and defines its degrees of kinematic freedom. On the other hand, by examining the mill's actual function, the specific forms of energy involved in its operation were determined. The energy balance and mechanical efficiency of the mill were expressed as a factor of these energy forms. Also, by making use of a few but essential data, there was an attempt to estimate roughly the productive capacity of this type of mill. Although it can only be tested by experiment, it is suggested that this subtype of mola olearia was a machine with relatively high mechanical efficiency but very low productive capacity per time unit, mainly because of its underdeveloped feed mechanism.
