double outline
1.Optimum design for double-horse head beam pumping unit with rear horse head′s outline of spiral of Archimedes
2.The optimum design method is utilized to design 12-5-48HB double-horse head beam pumping unit with rear horse head ′s outline of spiral of Archimedes, and the optimum result is analyzed and compared with double-horse head beam pumping unit with rear horse head ′s outline of three-section circular arc and beam pumping unit.

