Hi Brian,

The first model is just lots of spheres,

I started with a large sphere for the internal rad,
I then added a small sphere, snapping on the int of the outside of the large sphere.



I cut off the top of the small sphere, then boolean away the large sphere (I made copy of large sphere to clipboard so I could paste back for later booleans), which left me with:-



I then made circular array of the cut sphere:-



I then placed a sphere at the int of 2 of the spheres:-



I then pasted back the large sphere to boolean away from the new small sphere:-



Then back to making array, then just repeated that until I got to the bottom (where I wanted the base to be). Then made boolean union of all the spheres, then added a base.

That is basically it.

I hope I have made it understandable?

- Steve