I'm writing a vehicle physics engine and am using an RK4 integrator which I wrote. But I am having huge problems with angular motion. Long story short I thing it might be to do with the fact that I'm integrating from accelerations. So I'm re-writing the integrator using momentum. However I'm very sketchy about momentum and how to handle it. Anyone know where I can see some good demos of a momentum based RK4, or perhaps anyone interested in having a look at my code to see if they can help? Cheers.