I added a PTO Hydraulic pump, resevoir, and valve to my JD 4100 to run a hydraulic-powered trencher that I borrowed. It was designed to mount on a Toro Dingo, so I also made an adapter to mount it on my FEL and/or 3-point. Worked great.
As another responder pointed out, you really need to creep along the ground, keeping pace with the cutting of the trencher, so a hydrostatic transmission is almost mandatory.
The hydraulic drive gave a nice feleing of indestructability when hitting rocks and roots - the pressure relief would just let it gracefully stall if it was really hung up. A mechanical-drive trencher would have to have a slip clutch or sheer-pins. The ability to hydraulicly reverse the trencher to clear rocks that wedged in the chain feed was also useful. I am not sure if a PTO-powered trencher would have reverse.
I know that both the Toro Dingo and Mini-Bobcat attachments are available for rental in many places, so I wonder if such an adapter would have any commercial value as a product?
- Rick