This is the normal way of using Kangaroo with the timer, to see the movement on screen:

However, if you want to produce and save an animation, you can do this:

The 'NOT' component (found in Math>Boolean) means that when the slider is at 0, the input to SimulationReset will be True, and for any other value it will be False.

When you then animate the slider in the usual way by right clicking it, the first frame will reset the simulation, and every subsequent frame will be another iteration of the physical system. Note that with this setup there is no need for a timer component. Also, the upper limit of the slider is unimportant - however many frames you choose in the animate dialogue will be the number of physical iterations. To speed up or slow down the simulation, change the number of subiterations in Kangaroo settings.

This can also be combined with Giulio's 'renderanimation' script, if you want the result to be properly rendered, not just Grasshopper preview.

The sequence of images produced can then be easily assembled into a video or animation using a free software like VirtualDub.