Iron Plain Bearing

Accession Number1986.008.1922

VesselNuestra Señora de Atocha or Santa Margarita (1622)

Datecirca 1620

DescriptionA circular, iron object comes from the wreck of the 1622 galleon Nuestra Señora de Atocha. It is thought that it is a plain bearing, used to reduce friction between a rotating shaft or spinning wheel and a support member. Similarly designed objects called “coaks” are found mounted in the wooden sheaves of blocks to prevent the wheel-like piece from wearing as it turned on the pin. Considering that this Atocha piece has an inside diameter of 14.2 centimeters, it was for something much larger than a pulley or sheave. Instead, it is thought that this object was a bearing fixed in a cannon carriage wheel to fit over the axle so as to prevent wear between the two pieces. The exterior of this iron piece tapers slightly: one end has an outside diameter of 16.9 centimeters; the other 16.5 centimeters. Three evenly spaced, angular “ears” project outward, and they would have prevented the bearing from spinning within the body that held it.