That is the basic layout. I originally used a fixed collet at the top but had trouble with wire fatigue so I suspended the collet below a pin and jewel pivot. I will have to find a way to post some pictures.
The slab is on grade so nothing more than some reinforcement mesh in the concrete and the pivot is bolted to a pair of large wood beams. The pivot arrangement might be the problem however. I had not considered this before because all of the arrangements I had found constrained pendulum...
The floor is a concrete slab and the pivot is bolted to the ridge beam of a cathedral ceiling. Not many places I can get 6 or 7 meters vertical but I will try moving it further out into the room. You also made me think to check that the base is exactly level. I will report back after trying...
The drive is a coil in the center of the pendulum base with a hall effect proximity sensor in the center. The coil is controlled be a timing circuit. The bob has a mild steel disk in the bottom. As the bob passes over the sensor the coil is depowered and remains off until the bob approaches...
I have completed a bottom driven pendulum that seems to have a preference to swing E/W. It is a 10kg bob on a 6M wire. The pivot is a tungsten carbide pin resting on a watch jewel. No matter how I start it it precesses at exactly the correct rate for 32 degrees latitude then stalls when it...