Friction
Mechanical contact, be it in bearings or between cogs, generates friction. Friction is subdivided into several categories:
-Â Solid friction: Solid matter rubs on solid matter, no lubricant between contact surfaces.
-Â Mixed friction: Although there is lubricant between the friction surfaces, they still have mechanical contact.
-Â Hydrodynamic friction: A lubricating film separates the materials preventing mechanical contact between the friction surfaces.
Every effort is made to reduce friction to a minimum. As a rule, the least friction is generated by hydrodynamic friction.