The Hickman C-2 engine conversion is a WWI surplus Lawrance A-3 engine modified to have a double-throw crankshaft to improve the vibrational problems of the original Lawrance version. This Lawrance engine, as described in Herschel Smith's book (S), had a single-throw crankshaft with the pistons perfectly opposed. This configuration resulted in the pistons both moving in the same direction at the same time and causing excessive oscillatory lateral loads. Orville Hickman built a new double-throw crankshaft, extended the length of the connecting rods, and bent the latter to match the new crankshaft throws. Hickman published conversion plans and details in the "1931 Flying and Glider Manual", an annual supplement of the popular "Modern Mechanix and Inventions" magazine of that time. Reprints of the "1929-1933 Manuals" are available from the EAA. Jim Warnock, in his excellent article "A Study of the Lawrance A-3 (C-2) Two-Cylinder Opposed Engine & Some of the Aircraft it Powered" (AAHS Sp 2006, pp.6-16), discusses the Hickman Conversion with respect to an earlier conversion, which C.J. Brukner of Waco Aircraft said had been made to the A-3 used in the Waco Cootie I monoplane and Cootie II biplane of 1919-1920.
O-150 -- {4.0 / 6.0 / 150.8 } / {101.6 / 152.4 / 2471}
2cyl; Hickman C-2 Conversion; 28hp@1450rpm; 1930-1935; Wt = 128#; TC = none.
Single-ignition engine. This conversion of the Lawrance A-3 engine had a two-throw crankshaft with the pistons perfectly opposed, as described above.
AAHS Sp 2006, pp.6-16; aerofiles.com (applications); S.
Applications: (US) See AAHS article and aerofiles.com via a Search.