Herb,
My "tire machine" is actually a shallow plywood box that sits atop a Black & Decker Workmate. For security, the box has hefty metal brackets that allow me to bolt it to my 12-ft long workbench. The top of the box has a round cutout to allow the brake disc to fit inside and in the center is the 5/8" all-thread rod. My main concern in not buying a No-Mar or HF tire machine was the loss of floor space - I wanted something that broke down easily and could be stored under a bench or along a wall.
I've had the homemade machine for several years but recently bought a No-Mar Mount/Demount bar and to make it work I needed a center post so I created an inverted L that uses the jack handle of my HF floor jack as the post. The upright also holds the bead breaker. The long beam of the bead breaker was actually part of a bike lifter I'd made during my desert racing days when dinosaurs still roamed the earth. Previously I was using a clamshell type of bead breaker and it worked well but it was a tedious process - now I can break the bead in about 20 seconds! Another criteria I had was a good working height as all of the tire changes that I've seen would required that I stoop over so my back would be screaming bloody murder after about 30-minutes - this determined the height of the box that sits atop the Workmate.
I've added a few photos to My Album so you can see my homemade tire machine.