After improving the workshops and facilities, including a second roundhouse in 1847, he persuaded the directors that the railway should build its own engines. New building began in 1851 with passenger engines to the "Jenny Lind" pattern, and more standard goods. He then produced a large "single" with six-foot six-inch driving wheels. Throughout its existence the Midland never became fully self-sufficient, usually having its locos built by private contractors to its own designs. Initially there was some resistance on the part of Sharp Stewart and Stephenson, who quoted over-long delivery times, so that Kirtley had to accept the maker's own designs. These were good enough, however, that Fowler built some more to a similar pattern. In 1861 he built four banking engines for the Lickey Incline with four-foot drivers instead of the usual five feet. Kirtley's first was a rebuilt but he went on to build six for use to King's Cross, then 15 more.