The second version of my pendulum pell has a smaller steel ball. I also used a piece of water pipe instead of fence post. The problem with the fence post is that it is galvanized, making impossible to weld safely.
For the holes I went with a 1/4” drill bit. Over-sizing the holes wasn’t necessary, as the pipe reamer added any necessary clearance.
The welds aren’t great, but thus far they seem to be holding up much better than the epoxy I used in the previous version.
The candle plate I used for a cap was hard to accurately drill and slipped either further during welding. Next time I think I’m just going to use a screw-on pipe fitting, which should reduce the first problem and eliminate the second.
Another problem is attacking the thrusting ring to the bottom. Binding wire is too weak and even the largest split-ring I could find is too easily bent out of shape. For the next version I should try getting some 1/8” rod, looping it into a small circle, and weld it closed.