These first experiments had been distinctly unsuccessful, as had previous attempts dating back several decades to build "portable railways" for agricultural use. Thus, at what was known as the Duffield Bank Railway, Heywood developed what he called the "minimum gauge railway". He settled on as the optimum, his previous line having proved to be too small to carry people in a stable manner. Built on a steep hillside, the line was an ideal testing ground and, to gain the adhesion for steep gradients and the ability to negotiate small radius curves, he built six-coupled locomotives with what he called his "radiating axle."
