Here's a project I completed a few decades ago. I got tired from moving a rather large utility trailer around by hand, so put together his handy device. Power is supplied by a small HF 12 VDC winch, converted to chain drive by adding a sprocket to the cable spool. In/out reversing switch that came with the winch provides for reversing directions. Triangular design with split frame facilitates easy chain tensioning by sliding motor. Wheel is stolen off of a wheel borrow. Black pipe for handle. Easily moved the trailer with a full load of firewood.