A pure rolling double steel ball collision experiment is carried out on a wide

and narrow horizontal rails，and it is found that it is significantly different from the double

steel ball collision experiment in sliding motion; the reason is that the collision of the pure

rolling double steel ball is the frontal and tangential collision at the colli- sion point. The

two types of collisions obey different dynamic laws; after a collision，the motion state of the two

steel balls is no longer pure rolling. To return to pure rolling，each steel ball must pass through

the interaction between it- self and the guide rail. The effect is to go through a self-adjusting

stage; the energy loss in the self-adjusting stage is related to the rolling radius of the steel

ball and the deviation of its immediate state from pure rolling.