Eccentric

A device applied to the truck wheels of top carriages and beds of mortars in sea-coast artillery to give either rolling or sliding friction at will. The wheels turn on axle-arms which project eccentrically from the ends of an axle pa ing through both cheeks; when the axle is turned the axle-arms carry the wheels up or down; when at the lowest point the weight of the carriage is borne by the wheels, and the system moves on rolling friction; the wheels are then said to be in gear ; when out of gear , or at their highest points, the wheels do not touch the rails or platform plates, but the cheeks rest on them, and the carriage moves upon sliding friction. A similar device is attached to the cha is near the pintle to enable it to be readily traversed when in gear , and give it stability when out of gear .