My gearing is using a home built double-curved bolt drive. It consists of two 1/4” x 20 threaded rods bent along a curved section of steel with a radius of 11.43”. Turning against these rods is a 1/4” x 20 section of rod that serves as drive worm gear. It is designed to use a one r.p.m. motor. The design was adapted form articles in the January (p.26) and July (p.100) 1989 issues of Sky & Telescope.......So I'm not just 'wacking on a motor' & hoping for the best.
[see photo's of my setup]