I still have brochures from the now-defunct company called Sperber which made several nice dual engine mills and sold them with the heads on them. I wanted one BAD in the early 1980s. I put them in a folder and would pull them out and wish for one back when I had no money for 'nuttin' as a young married man. (Still married to the same one, but have a little more money when I can keep it.)
That was the first such contraption I ever saw. They were nice with a winch/chain arrangement for the depth adjustment, but had round rails. (Round won't scrape away the chips on the surface of your previous cut, so not so good.) You do need to reasonably match your engines, but, think about it. When you hit the wood both engines go under load and become contributing partners, just like two men pulling a rope by steadily leaning on it. One man may weigh 190 and the other 205, but once they are both leaning and pulling steadily, the difference in their combined pulling does not interfere with the effect on the rope. In this case, it's just a chain, instead of a rope and the men are two engines pulling.
(Was that as clear as mud?) My men are REEEAL MEN. Two Stihl 090s.
Phil L.
