First mass counting from which end? The masses are accelerated by each other as there are rigid rods between them.
The lack of friction and the perfectly rigid coupling between the joints might be what makes it seem lacking reality. If we'd extend the chain with more links, the motion of the outermost mass would become more and more unpredictable due to extreme acceleration.
Of course I might have made a mistake somewhere, but I checked that energy is conserved between the frames of the animation (excluding minor energy drift due to the numerical integration).
