Sex differences in the behaviour of African elephants

A railway car side bearing combining in a unitary structure a bottom member and a top member with an elastomeric pad compressed between them, and means definitely limiting the movements of the bottom and top members toward and away from each other irrespective of their association with the car truck and body. The unit is adapted to be mounted on a car truck bolster and to engage a car body bolster but is not to be attached to the body bolster.