Eureqa doesn't help in this regard. As the OP said, you will eventually find a giant model that is a brilliant fit for the data. What you need is some notion of regularization. To answer your comment, it doesn't deal with overfitting.
So for double pendulum it came back with like 8 equations, one of which was conservation of momentum (not actually accurate, but as close as you can get with that number of terms), and one of which was conservation of energy (actually accurate, but a bit more complicated).