This simple one piece 3D printed pendulum support design can be mounted to a ring stand using a right angle clamp holder. It is marked to read +/- 40 degree angles. The shape of the pendulum support mates with the "v" in the clamp to self-align the pendulum in the vertical plane. Using an electrical binding post allows easy length adjustment. This also works well with a photogate mounted to the ring stand below for accurate period measurements.
Print time at medium speed and 35% fill is about 4 hrs. I recommend placing a tongue depressor or piece rubber between pendulum support and thumb screw because over tightening (and I know this from experience) can break the support. The binding post was obtained from Radio Shack (2740662 $3.49 for a 2pk) but you may be able scavenge one from old electronic equipment. You may have to run a file through the slot before installing post. I also added a #10 nylon washer from Lowe's (139065 $.56 for a 4pk) to prevent the string from wrapping when the binder is tightened.
Pendulum 2 is an improved version incorporating a Vernier force sensor rod to eliminate any breaking of the pendulum support. It also allows for raised text which when colored with a Sharpie improves readability.