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After building the very complicated Brass marble lifting mechanism, I decided I needed a break and would do a very simple new project. Here is a link to the Brass marble lifting mechanism.

I chose another simple project from the Building Wooden Machines book, a pyramid roller ball mechanism.

The idea of the model is to show kids [or adults] how the rotation of the balls is impacted by what layer they are on.

Once I got started on this new project, I ran into all kinds of unexpected problems…........

The first issue is that the pattern in the book is wrong, because it has the center distance between the 1.5" diameter balls at 1- 55/64" or 1.8 inches. This did not work because the big balls hit each other!! Common sense says if the 2nd layer of balls has a 2.0 inch diameter, then the small balls should be at 2.0 inches.

The 2nd issue was the difficulty of drilling straight holes for the 6.5 inches across the base for the 1/4" dowels. I did my best, but had to "wallow out' the holes to get the 1/4" dowel to fit right.

The 3rd issue was drilling 1/4" diameter holes in the 9 balls with 1.5" diameter. If you have too much run-out, the balls hit their openings and will not turn. Figured out how to get my old 1939 wood lathe to drill good holes using the chuck and a bit in the tailstock.

The 4th issue was with Sketchup. My balls used up way to much computer memory and slowed the program way down. I figured out the secret to make balls with small file sizes…......and converted this to a Youtube video to help others.

I made a YouTube video of the model in action. You can use this link to watch the short video.

Too see all my Trials & Tribulations on this project, see my woodworking web site.

I should know by now there is no such thing as a "simple project" in woodworking :)




· Registered
4,582 Posts
Neat little design. Just think as you solve the problems you learn what works and incorporate that into your next build. Great job

· Registered
1,403 Posts
Looks like a simple, plan…. still seems challengingly complicated. Nice work getting it done.