Is a triple pendulum with a significantly heavy end-mass supposed to spaz around? Using the Euler-Lagrange formula in Mathematica, I've found (and simulated here) a triple pendulum system with arbitrary masses and lengths. The rods are massless (so no moment of inertia's), and I've generalized the state equations in terms of angular coordinates. There is no friction. There's a sanity check in the simulation: The total energy is quite constant. When you make the end mass very heavy though (and decrease the time-step to compensate for the numerical stiffness), the system has a very odd twitching, oscillating behavior. Is this correct? Has this phenomenon been seen elsewhere, on other simulations? Some links would be appreciated. I tried googling "behavior of triple pendulum with heavy end-mass", but nothing came up. Go to that link, set "Mass 3" to 100 or so, and "steps per frame" to 1000 or so to see what I mean.