To Grav

You're right! I also got the negative acceleration at r=rmax/20. The problem is one I fixed about 10 years back and forgot. The center ring mass is a circle, and the rods must be placed at the centroids of triangles that make up the circle to properly represent the circle. So for the first speed location the rods radius is 2*dr/3 and the rod location is asymptotic to rs(i)-dr/2 at large radii. I use the following:

rr(i) = (rs(i)-dr) + (rs(i)-dr/3)/(rs(i)-dr/2) * dr/2

Try again using this and the original data, and accuracy can be improved later.

Good work, Ken Nicholson