Without friction, locomotive wheels cannot "grasp" the track or transmit power through belts. However, excessive friction during movement can generate heat, leading to expansion and mechanical failures, especially bearings. If friction is severe, problems can occur.

　　Friction issues with bearings:

　　The manufacturer of the bearing seat introduces that friction depends on the smoothness of the contact surface between the bearing and the machine tool. If the two surfaces are rough, greater force is required for the two surfaces to move towards each other. However, friction only decreases to a certain extent with smoothness. Due to the increased electrostatic attraction between its atoms, the friction between two smooth surfaces does not actually increase depending on the surface area of contact between moving objects or the relative velocity of objects (within a certain range).

　　However, it depends on the magnitude of the force that puts these things together. When an object moves on a horizontal plane, it will press down on the surface with a force equal to its weight, which is the force of gravity. The increase in weight leads to an increase in the resistance to relative motion provided to the contact surface.

　　It is worth noting that the friction coefficient of the bearing seat manufacturer is the quotient obtained by dividing the force required to move an object to another object at a certain speed by the weight of the body. For example, if a force of 20 Newtons is needed to move an object weighing 100 Newtons to another horizontal body at a constant speed, the friction coefficient between these two materials is 20/100 or 0.2. Different materials come into contact and produce different results. For example, if a piece of wood is pushed onto the surface of wood, steel, and plastic, different resistance will be felt, and different friction coefficients must be calculated for each pair of different materials.