Start by building a sturdy table. This table top is a 3'x3' square of 3/4" thick plywood. The legs are 1½" x 1½" square and about 37" long, with triangular braces cut from 1½" x 8"x 12" wooden pieces. The legs are splayed out slightly to give the table strength, and to allow the rotary pendulum to swing without hitting a leg. Tip: screw and/or glue the braces to the legs first, and then cut their tops together at a slight angle with a table or circular saw. Adjust the leg lengths to give a table-top height of about 37".