Hubometer

A hubometer (from hub, center of a wheel; -ometer, measure of) or hubodometer, is a device mounted on the axle of any land vehicle to measure the distance traveled by a vehicle based on the rotations of the wheel hub.

The whole device rotates with the wheel, except for an eccentrically mounted weight on an internal shaft. This remains pointing downwards and drives the counting mechanism as the body of the hubometer rotates around it.